@ARTICLE{Oakley2007, title = {Uncertainty in prior elicitations: a nonparametric approach}, author = {Oakley, J. E. and O'Hagan, A.}, journal = {Biometrika}, year = {2007}, volume = {94}, number = {2}, pages = {427--441}, month = jun, } @ARTICLE{Lal2008, title = {Soils and sustainable agriculture. A review}, author = {Lal, R.}, journal = {Agronomy for Sustainable Development}, year = {2008}, volume = {28}, number = {1}, pages = {57--64}, publisher = {Edp Sciences S A, 17, Ave Du Hoggar, Pa Courtaboeuf, Bp 112, F-91944 Les Ulis Cedex A, France}, abstract = {Enhancing food production and supporting civil/engineering structures have been the principal foci of soil science research during most of the 19th and the first seven or eight decades of the 20th century. Demands on soil resources during the 21st century and beyond include: (i) increasing agronomic production to meet the food needs of additional 3.5 billion people that will reside in developing countries along with likely shift in food habits from plant-based to animal-based diet, (ii) producing ligno-cellulosic biomass through establishment of energy plantations on agriculturally surplus/marginal soils or other specifically identified lands, (iii) converting degraded/desertified soils to restorative land use for enhancing biodiversity and improving the environment, (iv) sequestering carbon in terrestrial ( soil and trees) and aquatic ecosystems to off-set industrial emissions and stabilize the atmospheric abundance of CO2 and other greenhouse gases, ( v) developing farming/cropping systems which improve water use effciency and minimize risks of water pollution, contamination and eutrophication, and ( vi) creating reserves for species preservation, recreation and enhancing aesthetic value of soil resources. Realization of these multifarious soil functions necessitate establishment of inter-disciplinary approach with close linkages between soil scientists and chemists, physicists, geologists, hydrologists, climatologists, biologists, system engineers ( nano technologists), computer scientists and information technologists, economists, social scientists and molecular geneticists dealing with human, animal and microbial processes. While advancing the study of basic principles and processes, soil scientists must also reach out to other disciplines to address the global issues of the 21st century and beyond.}, keywords = {water-resources, carbon, crop, population, biofuels, sustainable agriculture, soil functions, food security, climate change, biofuels, water resources, waste management}, doi = {10.1051/agro:2007025}, ISSN = {1774-0746}, } @ARTICLE{Kiers2008, title = {{Agriculture at a crossroads}}, author = {Kiers, E. T. and Leakey, R. R. B. and Izac, A. M. and Heinemann, J. A. and Rosenthal, E. and Nathan, D. and Jiggins, J.}, journal = {Science}, year = {2008}, volume = {320}, number = {5874}, pages = {320--321}, publisher = {Amer Assoc Advancement Science, 1200 New York Ave, Nw, Washington, Dc 20005 USA}, keywords = {africa, impact, world}, doi = {10.1126/science.1158390}, ISSN = {0036-8075}, } @article{Metropolis1953, author = {Nicholas Metropolis and Arianna W. Rosenbluth and Marshall N. Rosenbluth and Augusta H. Teller and Edward Teller}, collaboration = {}, title = {Equation of State Calculations by Fast Computing Machines}, publisher = {AIP}, year = {1953}, journal = {The Journal of Chemical Physics}, volume = {21}, number = {6}, pages = {1087-1092}, url = {http://link.aip.org/link/?JCP/21/1087/1}, doi = {10.1063/1.1699114} } @ARTICLE{Larssen2007, title = {Impact of time series data on calibration and prediction uncertainty for a deterministic hydrogeochemical model}, author = {Larssen, T. and Hogasen, T. and Cosby, B. J.}, journal = {Ecological Modelling}, year = {2007}, volume = {207}, number = {1}, pages = {22--33}, month = sep, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {Model calibration is fundamental in applications of deterministic process-based models. Uncertainty in model predictions depends much on the input data and observations available for model calibration. Here we explored how model predictions (forecasts) and their uncertainties vary with the length of time series data used in calibration. As an example we used the hydrogeochemical model MAGIC and data from Birkenes, a small catchment in southern Norway, to simulate future water chemistry under a scenario of reduced acid deposition. A Bayesian approach with a Markov Chain Monte Carlo (MCMC) technique was used to calibrate the model to different lengths of observed data (4-29 years) and to estimate the prediction uncertainty each calibration. The results show that the difference between modelled and observed water chemistry (calibration goodness of fit) in general decreases with increasing length of the time series used in calibration. However, there are considerable differences for different time series of the same length. The results also show that the uncertainties in predicted future acid neutralizing capacity were lowest (i.e. the distribution peak narrowest) when using the longest time series for calibration. As for calibration success, there were considerable differences between the future distributions (prediction uncertainty) for the different calibrations.}, keywords = {acid deposition, parameter-estimation, catchment model, water, acidification, performance, length, magic, acidification modelling, recovery, markov chain monte carlo, model calibration, data availability, time series data}, ISSN = {0304-3800}, } @ARTICLE{Larssen2006, title = {Forecasting acidification effects using a {Bayesian} calibration and uncertainty propagation approach}, author = {Larssen, T. and Huseby, R. B. and Cosby, B. J. and Host, G. and Hogasen, T. and Aldrin, M.}, journal = {Environmental Science \& Technology}, year = {2006}, volume = {40}, number = {24}, pages = {7841--7847}, month = dec, publisher = {Amer Chemical Soc, 1155 16th St, Nw, Washington, Dc 20036 USA}, abstract = {We present a statistical framework for model calibration and uncertainty estimation for complex deterministic models. A Bayesian approach is used to combine data from observations, the deterministic model, and prior parameter distributions to obtain forecast distributions. A case study is presented in which the statistical framework is applied using the hydrogeochemical model (MAGIC) for an assessment of recovery from acidification of soils and surface waters at a long-term study site in Norway under different future acid deposition conditions. The water quality parameters are coupled with a simple doseresponse model for trout population health. Uncertainties in model output parameters are estimated and forecast results are presented as probability distributions for future water chemistry and as probability distributions of future healthy trout populations. The forecast results are examined for three different scenarios of future acid deposition corresponding to three different emissions control strategies for Europe. Despite the explicit consideration of uncertainties propagated into the future forecasts, there are clear differences among the scenarios. The case study illustrates how inclusion of uncertainties in model predictions can strengthen the inferences drawn from model results in support of decision making and assessments.}, keywords = {acid deposition, surface waters, model, recovery, future}, ISSN = {0013-936X}, } @ARTICLE{Tremblay2004, title = {Comparison of parameter estimation methods for crop models}, author = {Tremblay, M. and Wallach, D.}, journal = {Agronomie}, year = {2004}, volume = {24}, number = {6}, pages = {351--365}, month = {Sep-nov}, publisher = {E D P Sciences, 17, Ave Du Hoggar, Pa Courtaboeuf, Bp 112, F-91944 Les Ulis Cedex A, France}, abstract = {Crop models are important tools in agronomic research, a major use being to make predictions. A proper parameter estimation method is necessary to ensure accurate predictions. Until now studies have focused on the application of a particular estimation method and few comparisons of different methods are available. In this paper, we compare several parameter estimation methods, related, on the one hand, to model selection, and on the other, to ridge regression based on an analogy to a Bayesian approach. The different methods are applied to a simplified crop model derived from the STICS model, using simulated data. The criteria for comparison are prediction error and errors in the parameter estimates. Among the methods of model comparison a version of the Schwarz criterion, corrected for small samples and with maximum and minimum bounds for each parameter, is the preferred method. Ridge regression is found to be superior to this best method of model selection.}, keywords = {identifiability analysis, hydrological models, bayesian-approach, small samples, calibration, regression, selection, catchment, uncertainty, predictions, parameter estimation, crop model, model selection methods, ridge regression}, ISSN = {0249-5627}, } @ARTICLE{Lo2005, title = {Quantifying and reducing uncertainty in life cycle assessment using the {Bayesian Monte Carlo method}}, author = {Lo, S. C. and Ma, H. W. and Lo, S. L.}, journal = {Science of the Total Environment}, year = {2005}, volume = {340}, number = {1}, pages = {23--33}, month = mar, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {The traditional life cycle assessment (LCA) does not perform quantitative uncertainty analysis. However, without characterizing the associated uncertainty, the reliability of assessment results cannot be understood or ascertained. In this study, the Bayesian method, in combination with the Monte Carlo technique, is used to quantify and update the uncertainty in LCA results. A case study of applying the method to comparison of alternative waste treatment options in terms of global warming potential due to greenhouse gas emissions is presented. In the case study, the prior distributions of the parameters used for estimating emission inventory and environmental impact in LCA were based on the expert judgment from the intergovernmental panel on climate change (IPCC) guideline and were subsequently updated using the likelihood distributions resulting from both national statistic and site-specific data. The posterior uncertainty distribution of the LCA results was generated using Monte Carlo simulations with posterior parameter probability distributions. The results indicated that the incorporation of quantitative uncertainty analysis into LCA revealed more information than the deterministic LCA method, and the resulting decision may thus be different. In addition, in combination with the Monte Carlo simulation, calculations of correlation coefficients facilitated the identification of important parameters that had major influence to LCA results. Finally, by using national statistic data and site-specific information to update the prior uncertainty distribution, the resultant uncertainty associated with the LCA results could be reduced. A better informed decision can therefore be made based on the clearer and more complete comparison of options. (c) 2004 Elsevier B.V. All rights reserved.}, keywords = {greenhouse-gas emissions, solid-waste management, model uncertainty, quality model, inventory, paper, water, lca, bayesian monte carlo simulation, life cycle assessment, probabilistic uncertainty analysis, coefficients of variation}, ISSN = {0048-9697}, } @ARTICLE{Gallagher2007, title = {Parameter estimation and uncertainty analysis for a watershed model}, author = {Gallagher, M. and Doherty, J.}, journal = {Environmental Modelling \& Software}, year = {2007}, volume = {22}, number = {7}, pages = {1000--1020}, month = jul, publisher = {Elsevier Sci Ltd, the Boulevard, Langford Lane, Kidlington, Oxford Ox5 1gb, Oxon, England}, abstract = {Where numerical models are employed as an aid to environmental management, the uncertainty associated with predictions made by such models must be assessed. A number of different methods are available to make such an assessment. This paper explores the use of three such methods, and compares their performance when used in conjunction with a lumped parameter model for surface water flow (HSPF) in a large watershed.}, keywords = {rainfall-runoff models, shuffled complex evolution, groundwater-flow model, monte-carlo methods, bayesian-approach, metropolis algorithm, prediction intervals, catchment models, markov- chains, calibration, uncertainty analysis, parameter estimation, mathematical modeling, markov chain monte carlo, model calibration}, ISSN = {1364-8152}, } @ARTICLE{Dowd2003, title = {A {Bayesian} approach to the ecosystem inverse problem}, author = {Dowd, M. and Meyer, R.}, journal = {Ecological Modelling}, year = {2003}, volume = {168}, number = {1}, pages = {39--55}, month = oct, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {This study investigates a probabilistic approach for the inverse problem associated with blending time-dependent ecosystem models and observations. The goal is to combine prior information, in the form of ecological dynamics and substantive knowledge about uncertain parameters, with available measurements. Posterior estimates of both the time-varying ecological state variables and the model parameters are obtained, along with their uncertainty. Ecological models of interacting populations are considered in the context of a nonlinear, non-Gaussian state space model. This comprises a nonlinear stochastic difference equation for the ecological dynamics, and an observation equation which relates the model state to the measurements. Complex error processes are readily incorporated. The posterior probability density function provides a complete solution to the inverse problem. Bayes' theorem allows one to obtain this posterior density through synthesis of the prior information and the observations. To illustrate this Bayesian inverse method, these ideas are applied to a simple ecosystem box model concerned with predicting the seasonal co-evolution of a population of grazing shellfish and its two food sources: plankton and detritus. Observations of shellfish biomass over time are available. Lognormal system noise was incorporated into the ecosystem equations at all time steps. Ingestion and respiration parameters for shellfish growth are considered as uncertain quantities described by beta distributions. Stochastic simulation was carried out and provided predictions of the model state with uncertainty estimates. The Bayesian inverse method was then used to assimilate the additional information contained in the observations. Posterior probability density functions for the parameters and time-varying ecological state were computed using Markov Chain Monte Carlo methods. The ecological dynamics spread the measurement information to all state variables and parameters, even those not directly observed. Probabilistic state estimates are refined in comparison to those from the stochastic simulation. It is concluded that this Bayesian approach appears promising as a framework for ecosystem inverse problems, but requires careful control of the dimensionality for practical applications. (C) 2003 Elsevier B.V. All rights reserved.}, keywords = {monte-carlo methods, data assimilation, population-dynamics, mytilus- edulis, time-series, model, systems, uncertainty, lagoon, distributions, bayesian statistics, inverse methods, marine ecosystem models, shellfish growth, data assimilation}, ISSN = {0304-3800}, } @ARTICLE{Brooks1998, title = {{Convergence assessment techniques for Markov chain Monte Carlo}}, author = {Brooks, S. P. and Roberts, G. O.}, journal = {Statistics and Computing}, year = {1998}, volume = {8}, number = {4}, pages = {319--335}, month = dec, publisher = {Kluwer Academic Publ, Spuiboulevard 50, Po Box 17, 3300 Aa Dordrecht, Netherlands}, abstract = {MCMC methods have effectively revolutionised the field of Bayesian statistics over the past few years. Such methods provide invaluable tools to overcome problems with analytic intractability inherent in adopting the Bayesian approach to statistical modelling.}, keywords = {run length control, gibbs sampler, stochastic relaxation, geometric- convergence, bayesian-inference, simulation output, algorithms, distributions, models, rates, mcmc, gibbs sampler, metropolis hastings, convergence rate}, ISSN = {0960-3174}, } @ARTICLE{Brooks1998, title = {{Markov chain Monte Carlo method and its application}}, author = {Brooks, S. P.}, journal = {Journal of the Royal Statistical Society Series D-the Statistician}, year = {1998}, volume = {47}, number = {1}, pages = {69--100}, publisher = {Blackwell Publ Ltd, 108 Cowley Rd, Oxford Ox4 1jf, Oxon, England}, abstract = {The Markov chain Monte Carlo (MCMC) method, as a computer-intensive statistical tool, has enjoyed an enormous upsurge in interest over the last few years. This paper provides a simple, comprehensive and tutorial review of some of the most common areas of research in this field. We begin by discussing how MCMC algorithms can be constructed from standard building- blocks to produce Markov chains with the desired stationary distribution. We also motivate and discuss more complex ideas that have been proposed in the literature, such as continuous time and dimension jumping methods. We discuss some implementational issues associated with MCMC methods. We take a look at the arguments for and against multiple replications, consider how long chains should be run for and how id determine suitable starting points. We also take a look at graphical models and how graphical approaches can be used to simplify MCMC implementation. Finally, we present a couple of examples, which we use as case-studies to highlight some of the points made earlier in the text. In particular, we use a simple changepoint model to illustrate how to tackle a typical Bayesian modelling problem via the MCMC method, before using mixture model problems to provide illustrations of good sampler output and of the implementation of a reversible jump MCMC algorithm.}, keywords = {gibbs sampler, stochastic relaxation, geometric-convergence, bayesian computation, models, distributions, inference, simulation, hastings, rates, bayesian statistics, gibbs sampler, metropolis-hastings updating, simulation, software}, ISSN = {0039-0526}, } @ARTICLE{Naud2007, title = {Application of an interacting particle filter to improve nitrogen nutrition index predictions for winter wheat}, author = {Naud, C. and Makowski, D. and Jeuffroy, M. H.}, journal = {Ecological Modelling}, year = {2007}, volume = {207}, number = {2--4}, pages = {251--263}, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {Dynamic crop models predict several state variables at a daily time step and thus provide useful information for optimizing agricultural techniques. But the prediction errors of these models are often large due to uncertainties in parameters, initial state values, and equations. Monte Carlo sequential methods, like the interacting particle filter [Del Moral, 1996. Nonlinear filtering: interacting particle solution. Markov Process. Relat. Fields 2, 555-580], can be used to update the state variable values predicted by nonlinear dynamic models from a set of measurements and thus reduce the prediction errors. An interesting feature of these methods is that they do not require a linearization of the original nonlinear model. Up to now, these methods have never been applied to complex dynamic crop models. In this paper, the interacting particle filter was used to update the Azodyn model, a dynamic winter wheat crop model, at 10 or 11 dates, from biomass and nitrogen uptake measurements, and to predict a variable of practical interest, the nitrogen nutrition index. We showed that the implementation of this method can reduce the root mean squared error by 66.7-79.7\% for the nitrogen nutrition index, but that the filter is highly sensitive to the assumptions made about the probability distribution of the model errors. We also showed that the particle filter gives stable results with 10,000 Monte Carlo simulations and that this number of simulations can be performed in a very reasonable calculation time. (C) 2007 Elsevier B.V. All rights reserved.}, keywords = {extended kalman filter, parameter-estimation, chlorophyll meter, state estimation, generic model, crop models, stics, systems, water, fertilization, data assimilation, dynamic crop model, interacting particle filter, nitrogen nutrition index, sensitivity analysis}, doi = {10.1016/j.ecolmodel.2007.05.003}, ISSN = {0304-3800}, } @ARTICLE{Lawrie2007, title = {Reducing model complexity via output sensitivity}, author = {Lawrie, J. and Hearne, J.}, journal = {Ecological Modelling}, year = {2007}, volume = {207}, number = {2--4}, pages = {137--144}, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {Ecosystem models help us understand the mechanisms that influence ecosystem health indicators. However, if they are too complex, these mechanisms can be difficult to identify. On the other hand, if they are too simple the mechanisms may be distorted or even absent. Determining an appropriate level of model complexity is therefore desirable. This paper introduces two model simplification methods that are based on the sensitivity of performance measures to model rates and components. The first method identifies rates that have little influence on the performance measures and subsequently eliminates them. The second identifies, for a given performance measure, state variables that can be made constant. The methods can be implemented automatically, so that familiarity with the model is not required a priori. Demonstrating with a biogeochemical model of Port Phillip Bay, Australia, we find that significant reduction in model complexity is possible, including reductions in model order. Also, the process of implementing the methods reveals insights into the system that were not obvious beforehand. (C) 2007 Elsevier B.V All rights reserved}, keywords = {simulation-models, domain knowledge, uncertainty, ecosystems, systems, large ecosystem models, complexity, eliminating rates, simplifying state equations, model order reduction}, doi = {10.1016/j.ecolmodel.2007.04.013}, ISSN = {0304-3800}, } @ARTICLE{Radtke2006, title = {{A Bayesian strategy for combining predictions from empirical and process-based models}}, author = {Radtke, P. J. and Robinson, A. P.}, journal = {Ecological Modelling}, year = {2006}, volume = {190}, number = {3--4}, pages = {287--298}, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {We present a strategy for using an empirical forest growth model to reduce uncertainty in predictions made with a physiological process-based forest ecosystem model. The uncertainty reduction is carried out via Bayesian melding, in which information from prior knowledge and a deterministic computer model is conditioned on a likelihood function. We used predictions from an empirical forest growth model G-HAT in place of field observations of aboveground net primary productivity (ANPP) in a deciduous temperate forest ecosystem. Using Bayesian melding, priors for the inputs of the process-based forest ecosystem PnET-II were propagated through the model, and likelihoods for the PnET-II output ANPP were calculated using the G-HAT predictions. Posterior distributions for ANPP and many PnET-II inputs obtained using the G-HAT predictions largely matched posteriors obtained using field data. Since empirical growth models are often more readily available than extensive field data sets, the method represents a potential gain in efficiency for reducing the uncertainty of process-based model predictions when reliable empirical models are available but high-quality data are not. (c) 2005 Elsevier B.V. All rights reserved.}, keywords = {net primary production, forest ecosystem model, deciduous forests, climate-change, loblolly-pine, united-states, growth-model, regional-scale, water yield, productivity, bayesian melding, bayesian synthesis, ecosystem modeling, forest growth and yield modeling, likelihood, sampling importance resampling}, doi = {10.1016/j.ecolmodel.2005.04.021}, ISSN = {0304-3800}, } @ARTICLE{Ricciuto2008, title = {{Causes of interannual variability in ecosystem-atmosphere {CO$_2$} exchange in a northern Wisconsin forest using a Bayesian model calibration}}, author = {Ricciuto, D. M. and Butler, M. P. and Davis, K. J. and Cook, B. D. and Bakwin, P. S. and Andrews, A. and Teclaw, R. M.}, journal = {Agricultural and Forest Meteorology}, year = {2008}, volume = {148}, number = {2}, pages = {309--327}, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {Variability in fluxes of CO2 observed at the WLEF tall tower in northern Wisconsin was analyzed for the years 1997-2004. During this time, the WLEF region was a source of CO2 to the atmosphere averaging 120 g C m(-2) year(-1), with a range of interannual variability of 140 g C m(-2) year(-1). Random uncertainty in annual sums of net ecosystem exchange (NEE) due to turbulent variability and gap-filling was estimated to be 15-20 g C m(-2) year(-1). Although magnitudes of NEE sums were affected systematically by the choice of friction velocity (u*) threshold, this choice had little effect on interannual variability of annual sums. The WLEF region was, on average, a source of carbon from 1997 to 2004 regardless of the u* threshold applied. Interannually, daytime NEE sums varied more than nighttime NEE sums, and spring and summer NEE sums varied more than autumn and winter NEE sums. Interannual variations in seasonal sums of daytime, nighttime and total NEE were often strongly correlated with changes in soil moisture and soil temperature. Standard nonlinear gap-filling regression models of respiration and gross ecosystem productivity were extended to incorporate the effects of soil moisture and phenology and combined into a single model of NEE. The Markov Chain Monte Carlo (MCMC) data assimilation technique was performed using observed WLEF NEE to derive full probability density functions (PDFs) of time-invariant model parameters. Prior values had little effect on posterior parameter PDFs, but significant differences in parameter PDFs occurred depending on whether daytime NEE, nighttime NEE, or total NEE data were used. This simple model was moderately successful in producing statistically significant correlations with interannual variations in annual and growing season NEE sums, but was generally unsuccessful in spring and autumn. In all cases, the model underestimated the degree of variability in NEE sums. (C) 2007 Elsevier B.V. All rights reserved.}, keywords = {carbon-dioxide fluxes, mixed hardwood forest, soil-water content, eddy covariance, tall tower, long-term, deciduous forest, climate- change, spatial variability, net primary, carbon cycle, eddy covariance, respiration, ecosystems, managed and natural}, doi = {10.1016/j.agrformet.2007.08.007}, ISSN = {0168-1923}, } @ARTICLE{Brus2008, title = {{Bayesian Maximum Entropy prediction of soil categories using a traditional soil map as soft information}}, author = {Brus, D. J. and Bogaert, P. and Heuvelink, G. B. M.}, journal = {European Journal of Soil Science}, year = {2008}, volume = {59}, number = {2}, pages = {166--177}, publisher = {Blackwell Publishing, 9600 Garsington Rd, Oxford Ox4 2zg, Oxon, England}, abstract = {Bayesian Maximum Entropy was used to estimate the probabilities of occurrence of soil categories in the Netherlands, and to simulate realizations from the associated multi-point pdf. Besides the hard observations (H) of the categories at 8369 locations, the soil map of the Netherlands 1:50 000 was used as soft information (S). The category with the maximum estimated probability was used as the predicted category. The quality of the resulting BME(HS)-map was compared with that of the BME(H)-map obtained by using only the hard data in BME- estimation, and with the existing soil map. Validation with a probability sample showed that the use of the soft information in BME-estimation leads to a considerable and significant increase of map purity by 15\%. This increase of map purity was due to the high purity of the existing soil map (71.3\%). The purity of the BME(HS) was only slightly larger than that of the existing soil map. This was due to the small correlation length of the soil categories. The theoretical purity of the BME-maps overestimated the actual map purity, which can be partly explained by the biased estimates of the one-point bivariate probabilities of hard and soft categories of the same label. Part of the hard data is collected to describe characteristic soil profiles of the map units which explains the bias. Therefore, care must be taken when using the purposively selected data in soil information systems for calibrating the probability model. It is concluded that BME is a valuable method for spatial prediction and simulation of soil categories when the number of categories is rather small (say < 10). For larger numbers of categories, the computational burden becomes prohibitive, and large samples are needed for calibration of the probability model.}, keywords = {spatial prediction, variables}, doi = {10.1111/j.1365-2389.2007.00981.x}, ISSN = {1351-0754}, } @ARTICLE{Heuvelink1998, title = {Uncertainty analysis in environmental modelling under a change of spatial scale}, author = {Heuvelink, G. B. M.}, journal = {Nutrient Cycling in Agroecosystems}, year = {1998}, volume = {50}, number = {1--3}, pages = {255--264}, publisher = {Kluwer Academic Publ, Spuiboulevard 50, Po Box 17, 3300 Aa Dordrecht, Netherlands}, abstract = {Although environmental processes at large scales are to a great degree the resultant of processes at smaller scales, models representing these processes can vary considerably from scale to scale. There are three main reasons for this. Firstly, different processes dominate at different scales, and so different processes are ignored in the simplification step of the model development. Secondly, input data are often absent or of a much lower quality at larger scales, which results in a tendency to use simpler, empirical models at the larger scale. Third, the support of the inputs and outputs of a model changes with change of scale, and this affects the relationships between them. Given these reasons for using different models at different scales, application of a model developed at a specific scale to a larger scale should be treated with care. Instead, models should be modified to suit the larger scale, and for this purpose uncertainty analyses can be extremely helpful. If upscaling disturbed the balance between the contributions of input and model error to the output error, then an uncertainty analysis will show this. Uncertainty analysis will also show how to restore the balance. In practice, application of uncertainty analysis is severely hampered by difficulties in the assessment of input and model error. Knowledge of the short distance spatial variability is of paramount importance to input error assessment with a change of support, but current geographical databases rarely convey this type of information. Model error can only be estimated reliably by validation, but this is not easy because the support of model predictions and validation measurements is usually not the same.}, keywords = {monte-carlo simulation, error propagation, groundwater-flow, soil, calibration, variability, prediction, systems, future, environmental modelling, geostatistics, uncertainty analysis, upscaling, change of support, error balance, validation}, ISSN = {1385-1314}, } @ARTICLE{Qian2003, title = {{On Monte Carlo methods for Bayesian inference}}, author = {Qian, S. S. and Stow, C. A. and Borsuk, M. E.}, journal = {Ecological Modelling}, year = {2003}, volume = {159}, number = {2--3}, pages = {269--277}, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {Bayesian methods are experiencing increased use for probabilistic ecological modelling. Most Bayesian inference requires the numerical approximation of analytically intractable integrals. Two methods based on Monte Carlo simulation have appeared in the ecological/environmental modelling literature, Though they sound similar, the Bayesian Monte Carlo (BMC) and Markov Chain Monte Carlo (MCMC) methods are very different in their efficiency and effectiveness in providing useful approximations for accurate inference in Bayesian applications. We compare these two methods using a low-dimensional biochemical oxygen demand decay model as an example. We demonstrate that the BMC is extremely inefficient because the prior parameter distribution, from which the Monte Carlo sample is drawn, is often a poor surrogate for the posterior parameter distribution, particularly if the parameters are highly correlated. In contrast, MCMC generates a chain that converges, in distribution, on the posterior parameter distribution, that can be regarded as a sample from the posterior distribution. The inefficiency of the BMC can lead to marginal posterior parameter distributions that appear irregular and may be highly misleading because the important region of the posterior distribution may never be sampled. We also point out that a priori specification of the model error variance can strongly influence the estimation of the principal model parameters. Although the BMC does not require that the model error variance be specified, most published applications have treated this variance as a known constant. Finally, we note that most published BMC applications have chosen a uniform prior distribution, making the BMC more similar to a likelihood-based inference rather than a Bayesian method because the posterior is unaffected by the prior. Though other prior distributions could be applied, the treatment of Monte Carlo samples with any other choice of prior distribution has not been discussed in the BMC literature. (C) 2002 Elsevier Science B.V. All rights reserved.}, keywords = {uncertainty analysis, quality model, gibbs sampler, simulations, biochemical oxygen demand, mcmc, uncertainty analysis, winbugs}, ISSN = {0304-3800}, } @ARTICLE{Klepper1994, title = {{A Method for Robust-calibration of Ecological Models Under Different Types of Uncertainty}}, author = {Klepper, O. and Hendrix, E. M. T.}, journal = {Ecological Modelling}, year = {AUG 1994}, volume = {74}, number = {3--4}, pages = {161--182}, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {This paper is concerned with the inverse problem in ecological modelling: how to update information (if any) on parameter uncertainty by using the information on the actual system. In the probabilistic (Bayesian) context this implies estimating the posterior probability distribution of the parameters on the basis of prior information and the probability distribution of measurements. In other contexts the procedure may result in a set or a possibility distribution (fuzzy representation) in parameter space. Although the solution to the inverse problem is apparently straightforward, to be practical it requires either fairly restrictive assumptions or it makes large computational demands. The paper presents an algorithm to solve the inverse problem in various contexts which is generally applicable and computationally efficient. The method is illustrated on various test functions and an actual case study. For calibration problems with a moderate number of dimensions (or: higher-dimensional problems that can be reduced to these) the new algorithm provides a robust and relatively efficient way to characterize posterior parameter distributions or sets. The algorithm requires a number of function evaluations proportional to the logarithm of the search volume, while for conventional random search this number increases proportional to search volume itself. For inherently high dimensional problems the present approach is still relatively efficient, but slow in absolute numbers of function evaluations.}, keywords = {parameter uncertainty, propagation, intervals, ecosystem, regions, example, search, calibration, parameter uncertainty}, ISSN = {0304-3800}, } @ARTICLE{Hong2005, title = {{Bayesian estimation of input parameters of a nitrogen cycle model applied to a forested reference watershed, Hubbard Brook Watershed Six}}, author = {Hong, B. G. and Strawderman, R. L. and Swaney, D. P. and Weinstein, D. A.}, journal = {Water Resources Research}, year = {2005}, volume = {41}, number = {3}, publisher = {Amer Geophysical Union, 2000 Florida Ave Nw, Washington, Dc 20009 USA}, abstract = {We present a Bayesian parameter estimation technique for improving estimates of simulation model input parameters and apply the technique to the nitrogen cycle model SINIC, which has been used to simulate the streamflow and streamflow nitrate flux at Hubbard Brook Watershed 6, New Hampshire, during the 1964-1994 period. Uncertainty in initial estimates of model input parameters was incorporated by replacing each estimate with a probability distribution of values, or ''prior'' distribution, usually centered at the initial estimate and having a large variance. These prior distributions were then ``updated'' by incorporating available data on model output variables, producing a ''posterior'' probability distribution of parameter values. Several key parameters used for calculating the N mineralization rate were identified as controlling the predicted nitrate export from this watershed. The level of uncertainty in these parameters was substantially reduced by incorporating the observations on streamflow and streamflow nitrate flux. The posterior distribution of predicted yearly streamflow nitrate flux shifted from year to year, with relatively large uncertainties in years with high streamflow nitrate flux.}, keywords = {northern hardwood forest, testing ecological models, fine-root dynamics, atmospheric deposition, uncertainty, ecosystem, soil, responses, methodology, simulation}, doi = {10.1029/2004WR003551}, ISSN = {0043-1397}, } @ARTICLE{Wikle1998, title = {{Hierarchical Bayesian space-time models}}, author = {Wikle, C. K. and Berliner, L. M. and Cressie, N.}, journal = {Environmental and Ecological Statistics}, year = {1998}, volume = {5}, number = {2}, pages = {117--154}, publisher = {Kluwer Academic Publ, Spuiboulevard 50, Po Box 17, 3300 Aa Dordrecht, Netherlands}, abstract = {Space-time data are ubiquitous in the environmental sciences. Often, as is the case with atmospheric and oceanographic processes, these data contain many different scales of spatial and temporal variability. Such data are often non-stationary in space and time and may involve many observation/prediction locations. These factors can limit the effectiveness of traditional spacetime statistical models and methods. In this article, we propose the use of hierarchical space-time models to achieve more flexible models and methods for the analysis of environmental data distributed in space and time. The first stage of the hierarchical model specifies a measurement-error process for the observational data in terms of some 'state' process. The second stage allows for site-specific time series models for this state variable. This stage includes large-scale (e.g. seasonal) variability plus a space-time dynamic process for the 'anomalies'. Much of our interest is with this anomaly process. In the third stage, the parameters of these time series models, which are distributed in space, are themselves given a joint distribution with spatial dependence (Markov random fields). The Bayesian formulation is completed in the last two stages by specifying priors on parameters. We implement the model in a Markov chain Monte Carlo framework and apply it to an atmospheric data set of monthly maximum temperature.}, keywords = {atmospheric science, dynamical systems, environmental studies, gibbs sampling, markov random field, mcmc, non-stationarity, temperature}, ISSN = {1352-8505}, } @ARTICLE{Wikle2007, title = {{A Bayesian tutorial for data assimilation}}, author = {Wikle, C. K. and Berliner, L. M.}, journal = {Physica D-nonlinear Phenomena}, year = {2007}, volume = {230}, number = {1--2}, pages = {1--16}, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {Data assimilation is the process by which observational data are fused with scientific information. The Bayesian paradigm provides a coherent probabilistic approach for combining information, and thus is an appropriate framework for data assimilation. Viewing data assimilation as a problem in Bayesian statistics is not new. However, the field of Bayesian statistics is rapidly evolving and new approaches for model construction and sampling have been utilized recently in a wide variety of disciplines to combine information. This article includes a brief introduction to Bayesian methods. Paying particular attention to data assimilation, we review linkages to optimal interpolation, kriging, Kalman filtering, smoothing, and variational analysis. Discussion is provided concerning Monte Carlo methods for implementing Bayesian analysis, including importance sampling, particle filtering, ensemble Kalman filtering, and Markov chain Monte Carlo sampling. Finally, hierarchical Bayesian modeling is reviewed. We indicate how this approach can be used to incorporate significant physically based prior information into statistical models, thereby accounting for uncertainty. The approach is illustrated in a simplified advection-diffusion model. (c) 2006 Elsevier B.V. All rights reserved.}, keywords = {quasi-geostrophic model, ensemble kalman filter, prediction, bayes, ensemble kalman filter, importance sampling, kriging, markov chain monte carlo, particle filter}, doi = {10.1016/j.physd.2006.09.017}, ISSN = {0167-2789}, } @ARTICLE{Wikle2003, title = {{Hierarchical Bayesian models for predicting the spread of ecological processes}}, author = {Wikle, C. K.}, journal = {Ecology}, year = {2003}, volume = {84}, number = {6}, pages = {1382--1394}, publisher = {Ecological Soc Amer, 1707 H St Nw, Ste 400, Washington, Dc 20006-3915 USA}, abstract = {There is increasing interest in predicting ecological processes. Methods to accomplish such predictions must account for uncertainties in observation, sampling, models, and parameters. Statistical methods for spatiotemporal processes are powerful, yet difficult to implement in complicated high-dimensional settings. However, recent advances in hierarchical formulations for such processes can be utilized for ecological prediction. These formulations are able to account for the various sources of uncertainty and can incorporate scientific judgment in a probabilistically consistent manner. In particular, analytical diffusion models can serve as motivation for the hierarchical model for invasive species. We demonstrate by example that such a framework can be utilized to predict, spatially and temporally, the relative population abundance of House Finches over the, eastern United States.}, keywords = {breeding bird survey, space, dynamics, bayesian models, carpodacus mexicanus, diffusion, forecast, hierarchical models, house finch, invasive species, state space, uncertainty}, ISSN = {0012-9658}, } @ARTICLE{Wikle2003, title = {Hierarchical models in environmental science}, author = {Wikle, C. K.}, journal = {International Statistical Review}, year = {2003}, volume = {71}, number = {2}, pages = {181--199}, publisher = {Int Statistical Inst, 428 Prinses Beatrixlaan, 2270 Az Voorburg, Netherlands}, abstract = {Environmental systems are complicated. They include very intricate spatio-temporal processes, interacting on a wide variety of scales. There is increasingly vast amounts of data for such processes from geographical information systems, remote sensing platforms, monitoring networks, and computer models. In addition, often there is a great variety of scientific knowledge available for such systems, from partial differential equations based on first principles to panel surveys. It is argued that it is not generally adequate to consider such processes from a joint perspective. Instead, the processes often must be considered as a coherently linked system of conditional models. This paper provides a brief overview of hierarchical approaches applied to environmental processes. The key elements of such models can be considered in three general stages, the data stage, process stage, and parameter stage. In each stage, complicated dependence structure is mitigated by conditioning. For example, the data stage can incorporate measurement errors as well as multiple datasets with varying supports. The process and parameter stages can allow spatial and spatio-temporal processes as well as the direct inclusion of scientific knowledge. The paper concludes with a discussion of some outstanding problems in hierarchical modelling of environmental systems, including the need for new collaboration approaches.}, keywords = {stationary covariance functions, markov random-fields, space-time models, statistical-analysis, kalman filter, prediction, systems, interpolation, exposure, disease, bayesian, car, change of support, climate, co-kriging, conditional, convolution, dynamic, markov random field, mcmc, ozone, pde, spatial, spatio-temporal, spectral}, ISSN = {0306-7734}, } @ARTICLE{Wikle2001, title = {{Spatiotemporal hierarchical Bayesian modeling: Tropical ocean surface winds}}, author = {Wikle, C. K. and Milliff, R. F. and Nychka, D. and Berliner, L. M.}, journal = {Journal of the American Statistical Association}, year = {2001}, volume = {96}, number = {454}, pages = {382--397}, publisher = {Amer Statistical Assoc, 1429 Duke St, Alexandria, Va 22314 USA}, abstract = {Spatiotemporal processes are ubiquitous in the environmental and physical sciences. This is certainly true of atmospheric and oceanic processes, which typically exhibit many different scales of spatial and temporal variability. The complexity of these processes and the large number of observation/prediction locations preclude the use of traditional covariance-based spatiotemporal statistical methods. Alternatively, we focus on conditionally specified (i.e., hierarchical) spatiotemporal models. These methods offer several advantages over traditional approaches. Primarily, physical and dynamical constraints can be easily incorporated into the conditional formulation, so that the series of relatively simple yet physically realistic conditional models leads to a much more complicated spatiotemporal covariance structure than can be specified directly. Furthermore, by making use of the sparse structure inherent in the hierarchical approach, as well as multiresolution (wavelet) bases, the models can be computed with very large datasets. This modeling approach was necessitated by a scientifically meaningful problem in the geosciences. Satellite-derived wind estimates have high spatial resolution but limited global coverage. In contrast, wind fields provided by the major weather centers provide complete coverage but have low spatial resolution. The god is to combine these data in a manner that incorporates the space-time dynamics inherent in the surface wind field. This is an essential task to enable meteorological research, because no complete high-resolution surface wind datasets exist over the world oceans. High-resolution datasets of this type are crucial for improving our understanding of global air-sea interactions affecting climate and tropical disturbances, and for driving large-scale ocean circulation models.}, keywords = {scatterometer winds, wavenumber spectra, space, sensitivity, temperature, resolution, turbulence, climate, combining information, conjugate gradient algorithm, dynamical model, fractal process, gibbs sampling, numerical model, ocean model, satellite data, turbulence, wavelets}, ISSN = {0162-1459}, } @ARTICLE{Wikle2005, title = {Combining information across spatial scales}, author = {Wikle, C. K. and Berliner, L. M.}, journal = {Technometrics}, year = {2005}, volume = {47}, number = {1}, pages = {80--91}, publisher = {Amer Statistical Assoc, 1429 Duke St, Alexandria, Va 22314 USA}, abstract = {Spatial and spatiotemporal processes in the physical. environmental. and biological sciences often exhibit complicated and diverse patterns across different space-time scales. Both scientific understanding and observational data vary in form and content across scales. We develop and examine a Bayesian hierarchical framework by which the combination of such information sources can be accomplished. Our approach is targeted to settings in which various special spatial scales arise. These scales may be dictated by the data collection methods, availability of prior information, and/or goals of the analysis. The approach restricts to a few essential scales. Hence we avoid the challenging problem of constructing a model that can be used at all scales. This means that we can provide inferences only at the preselected special scales. However, problems involving special scales are sufficiently common to justify the trade-off between our comparatively simple modeling and analysis strategy with the formidable task of forming models valid at all scales. Specifically. our approach is based on a simple idea of conditioning the spatially continuous process on an areal average of the process at some resolution of interest. In addition, the data at prescribed resolutions are then conditioned on this areal-averaged true process. These conditioning arguments fit nicely into the hierarchical Bayesian framework. The methodology is demonstrated for the spatial prediction of an important quantity known as streamfunction based on wind information from satellite observations and weather center, computer model output.}, keywords = {air-sea interaction, labrador sea, bayes, change of support, hierarchical, poisson equation, spatiotemporal, streamfunction, wind}, doi = {10.1198/004017004000000572}, ISSN = {0040-1706}, } @ARTICLE{Wikle2007, title = {A {Bayesian} tutorial for data assimilation}, author = {Wikle, C. K. and Berliner, L. M.}, journal = {Physica D-nonlinear Phenomena}, year = {2007}, volume = {230}, number = {1--2}, pages = {1--16}, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {Data assimilation is the process by which observational data are fused with scientific information. The Bayesian paradigm provides a coherent probabilistic approach for combining information, and thus is an appropriate framework for data assimilation. Viewing data assimilation as a problem in Bayesian statistics is not new. However, the field of Bayesian statistics is rapidly evolving and new approaches for model construction and sampling have been utilized recently in a wide variety of disciplines to combine information. This article includes a brief introduction to Bayesian methods. Paying particular attention to data assimilation, we review linkages to optimal interpolation, kriging, Kalman filtering, smoothing, and variational analysis. Discussion is provided concerning Monte Carlo methods for implementing Bayesian analysis, including importance sampling, particle filtering, ensemble Kalman filtering, and Markov chain Monte Carlo sampling. Finally, hierarchical Bayesian modeling is reviewed. We indicate how this approach can be used to incorporate significant physically based prior information into statistical models, thereby accounting for uncertainty. The approach is illustrated in a simplified advection-diffusion model. (c) 2006 Elsevier B.V. All rights reserved.}, keywords = {quasi-geostrophic model, ensemble kalman filter, prediction, bayes, ensemble kalman filter, importance sampling, kriging, markov chain monte carlo, particle filter}, doi = {10.1016/j.physd.2006.09.017}, ISSN = {0167-2789}, } @ARTICLE{Xu2007, title = {Estimation of parameterized spatio-temporal dynamic models}, author = {Xu, K. and Wikle, C. K.}, journal = {Journal of Statistical Planning and Inference}, year = {2007}, volume = {137}, number = {2}, pages = {567--588}, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {Spatio-temporal processes are often high-dimensional, exhibiting complicated variability across space and time. Traditional state-space model approaches to such processes in the presence of uncertain data have been shown to be useful. However, estimation of state-space models in this context is often problematic since parameter vectors and matrices are of high dimension and can have complicated dependence structures. We propose a spatio-temporal dynamic model formulation with parameter matrices restricted based on prior scientific knowledge and/or common spatial models. Estimation is carried out via the expectation-maximization (EM) algorithm or general EM algorithm. Several parameterization strategies are proposed and analytical or computational closed form EM update equations are derived for each. We apply the methodology to a model based on an advection-diffusion partial differential equation in a simulation study and also to a dimension-reduced model for a Palmer Drought Severity Index (PDSI) data set. (c) 2006 Elsevier B.V. All rights reserved.}, keywords = {stationary covariance functions, maximum-likelihood-estimation, space- time models, kalman filter, dynamic, em algorithm, general em, state-space, time series, spatial, spatio-temporal}, doi = {10.1016/j.jspi.2005.12.005}, ISSN = {0378-3758}, } @ARTICLE{Kuczera1998, title = {{Monte Carlo assessment of parameter uncertainty in conceptual catchment models: the Metropolis algorithm}}, author = {Kuczera, G. and Parent, E.}, journal = {Journal of Hydrology}, year = {1998}, volume = {211}, number = {1--4}, pages = {69--85}, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {Two Monte Carlo-based approaches for assessing parameter uncertainty in complex hydrologic models are considered. The first, known as importance sampling, has been implemented in the generalised likelihood uncertainty estimation (GLUE) framework of Beven and Binley. The second, known as the Metropolis algorithm, differs from importance sampling in that it uses a random walk that adapts to the true probability distribution describing parameter uncertainty. Three case studies are used to investigate and illustrate these Monte Carlo approaches. The first considers a simple water balance model for which exact results are known. It is shown that importance sampling is inferior to Metropolis sampling. Unless a large number of random samples are drawn, importance sampling can produce seriously misleading results. The second and third case studies consider more complex catchment models to illustrate the insights the Metropolis algorithm can offer. They demonstrate assessment of parameter uncertainty in the presence of bimodality, evaluation of the significance of split-sample tests, use of prior information and the assessment of confidence limits on hydrologic responses not used in calibration. When compared with the capabilities of traditional inference based on first-order approximation, the Metropolis algorithm provides a quantum advance in our capability to deal with parameter uncertainty in hydrologic models. (C) 1998 Elsevier Science B.V. All rights reserved.}, keywords = {prediction, eutrophication, bayesian inference, conceptual catchment models, importance sampling, markov chain monte carlo sampling, parameter uncertainty, rainfall-runoff models}, ISSN = {0022-1694}, } @incollection{IB-GueHouMakLau06, author = {Martine Gu\'erif and Vianney Houl\`es and David Makowski and Claire Lauvernet}, title = {Data assimilation and parameter estimation for precision agriculture using the crop model {STICS}}, booktitle = {Working with dynamic crop models: evaluating, analyzing, parameterizing and using them}, editor = {Daniel Wallach and David Makowski and James W. Jones}, publisher = {Elsevier}, chapter = 17, month = avr, year = {2006} } @ARTICLE{Harmon1997, title = {{A Markov chain Monte Carlo method for estimation and assimilation into models}}, author = {Harmon, R. and Challenor, P.}, journal = {Ecological Modelling}, year = {1997}, volume = {101}, number = {1}, pages = {41--59}, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {The arrival of satellite-borne ocean colour sensors means that there will soon be a wealth of observations of the surface concentration of chlorophyll in the worlds oceans. These observations can be used to improve our understanding of the oceanic ecosystem if the appropriate data assimilation techniques are available to combine them with an ecosystem model. In this paper we explore a novel method, based on Bayes Theorem and a Monte Carlo Markov Chain algorithm, of estimating a subset of the parameters in a seven compartment ecosystem model. The model describes the flows of nitrogen amongst phytoplankton, zooplankton, nitrate, bacteria, ammonium, dissolved organic nitrogen and detritus. We first generate synthetic observations from the model and then, in three separate experiments, try to recover subsets of the model parameters from clean and noisy versions of these. Bayes Theorem allows us to combine both prior information on the parameter values and the observations to generate a posterior probability density function of the parameters. The Metropolis- Hastings algorithm then allows us to produce Markov chains that sample this posterior probability density function and recover the parameter means, variances and standard errors. We find that the technique is very successful in recovering information on a small number of parameters but that the time required to solve the model makes it impractical to find second order properties of more than about ten of the model parameters. (C) 1997 Elsevier Science B.V.}, keywords = {optimization, dynamics, station, data assimilation, parameter estimation, oceanic ecosystem model}, ISSN = {0304-3800}, } @ARTICLE{Makowski2002, title = {Using a {B}ayesian approach to parameter estimation; comparison of the {GLUE} and {MCMC} methods}, author = {Makowski, D. and Wallach, D. and Tremblay, M.}, journal = {Agronomie}, year = {2002}, volume = {22}, number = {2}, pages = {191--203}, publisher = {E D P Sciences, 7, Ave Du Hoggar, Parc D Activites Courtaboeuf, Bp 112, F-91944 Les Ulis Cedexa, France}, abstract = {The Bayesian approach allows one to estimate model parameters from prior expert knowledge about parameter values and from experimental data. The purpose of this paper is to compare the performances of two Bayesian methods, namely the Metropolis- Hastings algorithm and the Generalized Likelihood Uncertainty Estimation method (GLUE). These two methods are applied to a non-linear model that includes 22 parameters. This model has the main features of an agronomic model. The two Bayesian methods give similar results. The parameter estimates obtained with the two methods have similar properties. Both methods improve strongly the accuracy of model predictions even when only few data samples are available for estimating the parameters. However, the values of mean squared error of prediction of the model are slightly higher with the GLUE method than with the Metropolis-Hastings algorithm. The performances of the methods are sensitive to the prior assumptions made about parameter values.}, keywords = {applied nitrogen, models, calibration, responses, bayes, markov chain monte carlo, parameter estimation, parameter uncertainty}, doi = {10.1051/agro:2002007}, ISSN = {0249-5627}, } @ARTICLE{VanOijen2005, title = {Bayesian calibration of process-based forest models: bridging the gap between models and data}, author = {Van Oijen, M. and Rougier, J. and Smith, R.}, journal = {Tree Physiology}, year = {2005}, volume = {25}, number = {7}, pages = {915--927}, publisher = {Heron Publishing, 202, 3994 Shelbourne St, Victoria, Bc V8n 3e2, Canada}, abstract = {Process-based forest models generally have many parameters, multiple outputs of interest and a small underlying empirical database. These characteristics hamper parameterization. Bayesian calibration offers a solution to the calibration problem because it applies to models of any type or size. It provides parameter estimates, with measures of uncertainty and correlation among the parameters. The procedure begins by quantifying the uncertainty about parameter values in the form of a prior probability distribution. Then data on the output variables are used to update the parameter distribution by means of Bayes' Theorem. This yields a posterior calibrated distribution for the parameters, which can be summarized in the form of a mean vector and variance matrix. The predictive uncertainty of the model can be quantified by running it with different parameter settings, sampled from the posterior distribution. In a further step, one may evaluate the posterior probability of the model itself (rather than that of the parameters) and compare that against the probability of other models, to aid in model selection or improvement.}, keywords = {mathematical-models, decision-making, growth data, uncertainty, inference, predictions, ecosystems, parameters, systems, markov chain monte carlo, tree measurement, parameterization, uncertainty}, ISSN = {0829-318X}, } @ARTICLE{Svensson2008, title = {{Bayesian calibration of a model describing carbon, water and heat fluxes for a Swedish boreal forest stand}}, author = {Svensson, M. and Jansson, P. E. and Gustafsson, D. and Kleja, D. B. and Langvall, O. and Lindroth, A.}, journal = {Ecological Modelling}, year = {2008}, volume = {213}, number = {3--4}, pages = {331--344}, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {This study quantified major fluxes of carbon (C), heat and water, including uncertainty estimates, in a boreal forest in northern Sweden, using a process-based model (Coup-Model) and Bayesian calibration methodology. Coupled C, water and heat fluxes were described together with estimated uncertainties for all major components of the simulated C budget. Simulated mean gross primary production was 641 +/- 74 gC m(-2) yr(-1), total ecosystem respiration 570 +/- 55 gC m(-2)yr(-1) and net ecosystem productivity 71 +/- 37gCm(-2)yr(-1). Most high- resolution measurements were well described but some interesting exceptions arose between model and measurements, e.g. latent heat flux was overestimated and field layer (understory) root litter production underestimated. Bayesian calibration reduced the assumed prior parameter ranges in 30 of 33 parameters, thus reducing the uncertainty in the estimates. There was a high degree of couplings between different sub- models and processes in the model, highlighting the importance of considering parameters not as singularities but in clusters. (C) 2008 Elsevier B.V. All rights reserved.}, keywords = {net primary production, ecosystems, climate, balance, vapor, carbon budget, coupmodel, markov chain monte carlo simulation, process-based model, uncertainty estimate}, doi = {10.1016/j.ecolmodel.2008.01.001}, ISSN = {0304-3800}, } @article{Klemedtsson2007, abstract = {Abstract\ \ Depending on the balance between sink and source processes for C, drained organic forest soil ecosystems can be in balance or act as net sinks or sources of CO2 to the atmosphere. In order to study the effect of groundwater level and soil temperature on C-flux, the CoupModel was calibrated (climate data, groundwater levels, soil CO2 flux, net ecosystem fluxes of CO2-exchange, sensible heat flux and latent heat flux, forest production etc.) for a drained forest in Sweden. Bayesian calibration techniques were used to elucidate how different parameters and variables were interlinked in C-circulation. The calibrated model reproduced abiotic and biotic variables reasonably well except for root respiration, which was largely underestimated. Bayesian calibration reduced the uncertainties in the model and highlighted the fact that calibrations should be performed with a high number of parameters instead of specific parameter values.}, author = {Klemedtsson, Leif and Jansson, Per-Erik and Gustafsson, David and Karlberg, Louise and Weslien, Per and von Arnold, Karin and Ernfors, Maria and Langvall, Ola and Lindroth, Anders }, citeulike-article-id = {2801993}, doi = {10.1007/s10533-007-9169-0}, journal = {Biogeochemistry}, year = {2007}, keywords = {bayes}, posted-at = {2008-05-15 16:22:34}, priority = {2}, title = {Bayesian calibration method used to elucidate carbon turnover in forest on drained organic soil}, url = {http://dx.doi.org/10.1007/s10533-007-9169-0} } @article{Gelman1992, abstract = {The Gibbs sampler, the algorithm of Metropolis and similar iterative simulation methods are potentially very helpful for summarizing multivariate distributions. Used naively, however, iterative simulation can give misleading answers. Our methods are simple and generally applicable to the output of any iterative simulation; they are designed for researchers primarily interested in the science underlying the data and models they are analyzing, rather than for researchers interested in the probability theory underlying the iterative simulations themselves. Our recommended strategy is to use several independent sequences, with starting points sampled from an overdispersed distribution. At each step of the iterative simulation, we obtain, for each univariate estimand of interest, a distributional estimate and an estimate of how much sharper the distributional estimate might become if the simulations were continued indefinitely. Because our focus is on applied inference for Bayesian posterior distributions in real problems, which often tend toward normality after transformations and marginalization, we derive our results as normal-theory approximations to exact Bayesian inference, conditional on the observed simulations. The methods are illustrated on a random-effects mixture model applied to experimental measurements of reaction times of normal and schizophrenic patients.}, author = {Gelman, Andrew and Rubin, Donald B. }, citeulike-article-id = {1911404}, journal = {Statistical Science}, keywords = {mcmc, statistics}, number = {4}, pages = {457--472}, posted-at = {2008-01-22 06:44:59}, priority = {2}, title = {Inference from Iterative Simulation Using Multiple Sequences}, url = {http://www.jstor.org/stable/2246093}, volume = {7}, year = {1992} } @ARTICLE{Rnews2006, AUTHOR = {Martyn Plummer and Nicky Best and Kate Cowles and Karen Vines}, TITLE = {{CODA}: Convergence Diagnosis and Output Analysis for {MCMC}}, JOURNAL = {R News}, YEAR = {2006}, VOLUME = 6, NUMBER = 1, PAGES = {7--11}, MONTH = {March}, URL = {http://CRAN.R-project.org/doc/Rnews/}, PDF = {http://CRAN.R-project.org/doc/Rnews/Rnews_2006-1.pdf} } @Manual{R, title = {R: A Language and Environment for Statistical Computing}, author = {{R Development Core Team}}, organization = {R Foundation for Statistical Computing}, address = {Vienna, Austria}, year = {2008}, note = {{ISBN} 3-900051-07-0}, url = {http://www.R-project.org} } @incollection{Smith1996, author={Smith, J.U. and Smith, P. and Addiscott, T.M.}, year={1996}, title={Quantitative methods to evaluate and compare soil organic matter ({SOM}) models}, publisher={Springer-Verlag, Heidelberg}, booktitle={Evaluation of soil organic matter models using existing long-term datasets}, series={1}, volume={38}, editor={Powlson, D.S. and Smith, P. and Smith, J.U. Editors}, pages={183--202}, } @ARTICLE{Kass1995, title = {Bayes Factors}, author = {Kass, R. E. and Raftery, A. E.}, journal = {Journal of the American Statistical Association}, year = {1995}, volume = {90}, number = {430}, pages = {773--795}, publisher = {Amer Statist Assn, 1429 Duke St, Alexandria, Va 22314}, abstract = {In a 1935 paper and in his book Theory of Probability, Jeffreys developed a methodology for quantifying the evidence in favor of a scientific theory. The centerpiece was a number, now called the Bayes factor, which is the posterior odds of the null hypothesis when the prior probability on the null is one- half. Although there has been much discussion of Bayesian hypothesis testing in the context of criticism of P-values, less attention has been given to the Bayes factor as a practical tool of applied statistics. In this article we review and discuss the uses of Bayes factors in the context of five scientific applications in genetics, sports, ecology, sociology, and psychology.}, keywords = {vague prior information, monte-carlo integration, model selection, change-point, posterior distributions, regression variables, exponential family, irish education, poisson-process, gibbs sampler, bayesian hypothesis tests, big, importance sampling, laplace method, markov chain monte carlo, model selection, monte carlo integration, posterior model probabilities, posterior odds, quadrature, schwarz criterion, sensitivity analysis, strength of evidence}, ISSN = {0162-1459}, } @ARTICLE{Clark2005, title = {Why environmental scientists are becoming Bayesians}, author = {Clark, J. S.}, journal = {Ecology Letters}, year = {2005}, volume = {8}, number = {1}, pages = {2--14}, publisher = {Blackwell Publishing Ltd, 9600 Garsington Rd, Oxford Ox4 2dg, Oxon, England}, abstract = {Advances in computational statistics provide a general framework for the high-dimensional models typically needed for ecological inference and prediction. Hierarchical Bayes (HB) represents a modelling structure with capacity to exploit diverse sources of information, to accommodate influences that are unknown (or unknowable), and to draw inference on large numbers of latent variables and parameters that describe complex relationships. Here I summarize the structure of HB and provide examples for common spatiotemporal problems. The flexible framework means that parameters, variables and latent variables can represent broader classes of model elements than are treated in traditional models. Inference and prediction depend on two types of stochasticity, including (1) uncertainty, which describes our knowledge of fixed quantities, it applies to all 'unobservables' (latent variables and parameters), and it declines asymptotically with sample size, and (2) variability, which applies to fluctuations that are not explained by deterministic processes and does not decline asymptotically with sample size. Examples demonstrate how different sources of stochasticity impact inference and prediction and how allowance for stochastic influences can guide research.}, keywords = {ecological applications, models, uncertainty, variability, management, inference, patterns, forests, long, data modelling, gibbs sampler, hierarchical bayes, inference, mcmc, models, prediction}, doi = {10.1111/j.1461-0248.2004.00702.x}, ISSN = {1461-023X}, } @incollection{Gabrielle2006c, author = {Gabrielle, B.}, title = {Sensitivity and uncertainty analysis of a static denitrification model}, booktitle = {Working with dynamic crop models: evaluating, analyzing, parameterizing and using them}, editor = {Daniel Wallach and David Makowski and James W. Jones}, publisher = {Elsevier}, chapter = {14}, month = {avr}, year = {2006} } @incollection{Makowski2006, author = {Makowski, D. and Hillier, J. and Wallach, D. and Andrieu, B. and Jeuffroy, M. H.}, title = {Parameter estimation for crop models}, booktitle = {Working with dynamic crop models: evaluating, analyzing, parameterizing and using them}, editor = {Daniel Wallach and David Makowski and James W. Jones}, publisher = {Elsevier}, chapter = {4}, month = {avr}, year = {2006} } @incollection{Monod2006, author = {Monod, H. and Naud, C. and Makowski, D.}, title = {Uncertainty and sensitivity analysis for crop models}, booktitle = {Working with dynamic crop models: evaluating, analyzing, parameterizing and using them}, editor = {Daniel Wallach and David Makowski and James W. Jones}, publisher = {Elsevier}, chapter = {3}, month = {avr}, year = {2006} } @ARTICLE{TUBIELLO1995, title = {Interactions of {CO$_$2}, Temperature and Management-practices - Simulations With a Modified Version of {CERES}-wheat}, author = {Tubiello, F. N. and Rosenzweig, C. and Volk, T.}, journal = {Agricultural Systems}, year = {1995}, volume = {49}, number = {2}, pages = {135--152}, publisher = {Elsevier Sci Ltd, the Boulevard, Langford Lane, Kidlington, Oxford, Oxon, England Ox5 1gb}, abstract = {A new growth subroutine was developed for CERES-Wheat, a computer model of wheat (Triticum aestivum) growth and development. The new subroutine simulates canopy photosynthetic response to CO2 concentrations and light levels, and includes the effects of temperature on canopy light-use effciency. Its performance was compared to the original CERES-Wheat V-2.10 in 30 different cases. Biomass and yield predictions of the two models were well correlated (correlation coefficient r > 0.95). As an application, summer growth of spring wheat was simulated at one site. Modeled crop responses to higher mean temperatures, different amounts of minimum and maximum warming, and doubled CO2 concentrations were compared to observations. The importance of irrigation and nitrogen fertilization in modulating the wheat crop climatic responses were also analyzed. Specifically, in agreement with observations, rainfed crops were found to be more sensitive to CO2 increases than irrigated ones. On the other hand, low nitrogen applications depressed the ability of the wheat crop to respond positively to CO2 increases. In general, the positive effects of high CO2 grain yield were found to be almost completely counterbalanced by the negative effects of high temperatures. Depending on how temperature minima and maxima were increased, yield changes averaged across management practices ranged from -4\% to 8\%.}, keywords = {carbon-dioxide, plant-growth, leaf-area, yield, crop, photosynthesis, productivity, enrichment, climate}, ISSN = {0308-521X}, } @ARTICLE{Xiong2007, title = {Modelling China's potential maize production at regional scale under climate change}, author = {Xiong, W. and Matthews, R. and Holman, I. and Lin, E. and Xu, Y. L.}, journal = {Climatic Change}, year = {2007}, volume = {85}, number = {3--4}, pages = {433--451}, publisher = {Springer, Van Godewijckstraat 30, 3311 Gz Dordrecht, Netherlands}, abstract = {With the continuing warming due to greenhouse gases concentration, it is important to examine the potential impacts on regional crop production spatially and temporally. We assessed China's potential maize production at 50 x 50 km grid scale under climate change scenarios using modelling approach. Two climate changes scenarios (A2 and B2) and three time slices (2011-2040, 2041-2070, 2071-2100) produced by the PRECIS Regional Climate Model were used. Rain-fed and irrigated maize yields were simulated with the CERES-Maize model, with present optimum management practices. The model was run for 30 years of baseline climate and three time slices for the two climate change scenarios, without and with simulation of direct CO2 fertilization effects. Crop simulation results under climate change scenarios varied considerably between regions and years. Without the CO2 fertilization effect, China's maize production was predicted to suffer a negative effect under both A2 and B2 scenarios for all time slices, with greatest production decreases in today's major maize planting areas. When the CO2 fertilization effect is taken into account, production was predicted to increase for rain-fed maize but decrease for irrigated maize, under both A2 and B2 scenarios for most time periods.}, keywords = {air co2 enrichment, crop/soil simulation-model, assess methane emissions, crop-growth-model, elevated co2, united-states, integrated assessment, carbon-dioxide, change impacts, winter- wheat}, doi = {10.1007/s10584-007-9284-x}, ISSN = {0165-0009}, } @ARTICLE{Gabrielle1995, title = {Analysis and Field-evaluation of the {CERES} Models Water-balance Component}, author = {Gabrielle, B. and Menasseri, S. and Houot, S.}, journal = {Soil Science Society of America Journal}, year = {1995}, volume = {59}, number = {5}, pages = {1403--1412}, publisher = {Soil Sci Soc Amer, 677 South Segoe Road, Madison, Wi 53711}, abstract = {The soil water status partly determines the N losses from soil-crop systems, With the ultimate objective of estimating N losses, the capacity-based water balance module of the Ceres models was tested against field data collected from various pedoclimatic regimes in France, A process-oriented analysis of initial simulation results for a loamy soil prompted introduction of Darcy's law in the drainage and capillary rise parts of the model, As a result, a more accurate prediction of the soil water storage and surface water content was achieved. This was confirmed by comparing model output against independent data from bare or maize (Zea mays L.)-cropped conditions and for silt loam or sandy loam soils, For a 1-yr period, the mean square error between modeled and measured water storages was in the range 1.9 to 3 cm(2) water for the modified model, in contrast with 4 to 12 cm(2) using the original model (which performed best on well-drained soils). A unidimensional sensitivity analysis was conducted with regard to the three new parameters introduced in the revised model: the saturated hydraulic conductivity and two texture-dependent constants used in simple analytical representations of the moisture retention and hydraulic conductivity curves. The sensitivity analysis proved that this more physical approach in capacity-based models required less rigorous parameterization than mechanistic models. Moreover, the accuracy of the simulations performed with the modified model fell within the experimental error in the measurements.}, keywords = {denitrification}, ISSN = {0361-5995}, } @ARTICLE{Adegoke2007, title = {Observational and modeling studies of the impacts of agriculture-related land use change on planetary boundary layer processes in the central {US}}, author = {Adegoke, J. O. and Pielke, R. and Carleton, A. M.}, journal = {Agricultural and Forest Meteorology}, year = {2007}, volume = {142}, number = {2}, pages = {203--215}, month = feb, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {The impact of agricultural land use change on atmospheric boundary layer processes, the associated feedbacks and their regional scale impacts, are examined with particular emphasis on the central United States. Specifically, the role of contrasting forested and agricultural land covers in the initiation and subsequent evolution of summertime cloud patterns in the U.S. Midwest; and the impact of agricultural practices, including irrigation, on the surface climate of the U.S. High Plains are discussed in detail. Satellite-based observational results of previous work summarized in this paper indicate that the timing and intensity of cloud development appears to be influenced by both synoptic flow regimes and agricultural land use type. For example, under conditions characterized by high I pressure with surface winds generally less than 5 m s(-1), peak cloud development occurred almost two hours earlier over cropland than over the forest or boundary locations in Michigan. Cloud masses were also considerably taller over cropland in the mid- afternoon than over forest and land cover transition zones. The modeling results discussed here for a model domain centered over Nebraska indicate significant differences in the surface energy fluxes between the irrigated (control) and non-irrigated (dry) simulations. Surface latent heat flux was higher by 36\% and dewpoint temperature higher by 2.3 degrees C in the control simulation. Also, surface sensible heat flux of the control simulation was 15\% less and the near-ground (2 m) temperature was 1.2 degrees C less compared to dry run, indicating irrigation-induced surface cooling effect. Recent investigations on crop-climate interactions in which crop and ecological models were coupled to regional climate models show that incorporating important perturbations such as prolonged droughts and the resulting changes in soil and plant nutrient conditions remains one of the biggest challenges in developing effective and realistic ecological-climate integrated modeling systems. (c) 2006 Elsevier B.V. All rights reserved.}, keywords = {3-dimensional atmospheric simulations, warm-season precipitation, central united-states, regional climate, deep convection, soil- moisture, north-america, great-plains, potential impacts, irrigated areas, crop-climate interactions, convective clouds, regional climate modeling, agricultural land use}, ISSN = {0168-1923}, } @ARTICLE{Betts2007, title = {Biogeophysical effects of land use on climate: Model simulations of radiative forcing and large-scale temperature change}, author = {Betts, R. A. and Falloon, P. D. and Goldewijk, K. K. and Ramankutty, N.}, journal = {Agricultural and Forest Meteorology}, year = {2007}, volume = {142}, number = {2}, pages = {216--233}, month = feb, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {Changes in land cover affect climate through the surface energy and moisture budgets. Here we assess the importance of these biogeophysical effects for present-day climate, and quantify the radiative forcing of historical climate change by land use change for comparison with radiative forcings due to anthropogenic changes in greenhouse gases and aerosols. We also discuss the implications of biogeophysical effects for the use of forestry as a tool for mitigating climate change through carbon sequestration. Our model results suggest that since most historical deforestation has taken place in temperate regions where the main climatic effect is an increase in surface albedo, the dominant biogeophysical effect of past land cover change has been a cooling. The northern mid-latitude agricultural regions are simulated to be approximately 1-2 K cooler in winter and spring in comparison with their previously forested state. This conflicts with the suggestion that land use change is responsible for the warming observed over the 20th century. The increase in albedo by 1750 is simulated to exert a negative radiative forcing of approximately -2 W m(-2) locally over Europe, China and India, suggesting a potential anthropogenic influence on climate before fossil fuel burning began. The present-day global mean radiative forcing by anthropogenic surface albedo change relative to the natural state is simulated to be -0.2 W m(-2), which is comparable with the estimated forcings relative to pre-industrial times by stratospheric and tropospheric ozone, N2O, the halocarbons, and the direct effect of anthropogenic aerosols. In cold regions, afforestation or reforestation would decrease the surface albedo and induce a positive radiative forcing (warming) which could partly or completely offset the negative forcing (cooling) due to carbon sequestration. This suggests that carbon sink plantations could be less effective than expected at reducing warming, and could even cause further warming. However, we note that reforestation (or avoided deforestation) in tropical regions could exert a double cooling effect through carbon sequestration and increased evaporation and cloud cover. (c) 2006 Published by Elsevier B.V.}, keywords = {boreal forest, carbon-sequestration, greenhouse gases, gcm simulation, surface albedo, cover, impact, sensitivity, atmosphere, vegetation, land use, climate change, biogeophysical effects, radiative forcing, surface albedo}, ISSN = {0168-1923}, } @ARTICLE{Betts2007a, title = {Impact of agriculture, forest and cloud feedback on the surface energy budget in {BOREAS}}, author = {Betts, A. K. and Desjardins, R. L. and Worth, D.}, journal = {Agricultural and Forest Meteorology}, year = {2007}, volume = {142}, number = {2}, pages = {156--169}, month = feb, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {We explore the impact of agriculture, forest and cloud feedback on the surface energy budget using data obtained using a research aircraft, mesonet towers and model data. The forest has an order of magnitude larger roughness length, a lower albedo, a much smaller seasonal cycle in surface Bowen ratio (BR) and a weak mid-summer maximum of CO2 uptake compared to agricultural areas, which have much smaller BR and much higher mid-summer CO2 uptake, but a net CO2 release and much reduced evaporation in spring and fall. Higher surface temperatures and the higher albedo over agricultural land reduce R-net near local noon in the warm season by about 50 W m(-2) in comparison with the adjacent boreal forest. The annual averaged R-net derived from 2 years of tower data, is 14 W m(-2) less over grass sites than over forest sites. A reanalysis time-series for the BOREAS southern study area shows the coupling on daily timescales between the surface energy partition, the mean boundary layer depth, the cloud field and the long-wave and short-wave radiation fields. The albedo of the cloud field, the cloud short-wave forcing at the surface, varies over the range 0.1-0.8 with decreasing surface BR, and plays a major role in the surface energy budget. We estimate that this cloud feedback may increase albedo by 0.13 and reduce R-net by 25 W m(-2) in summer over agricultural land. (c) 2006 Elsevier B.V. All rights reserved.}, keywords = {climate-vegetation system, soil-moisture, flux measurements, aircraft, albedo, model, precipitation, temperature, variability, circulation, surface energy balance, land-cover change, agriculture, boreal forest, cloud feedback}, ISSN = {0168-1923}, } @ARTICLE{Desjardins2007, title = {The contribution of agriculture to the state of climate: Workshop summary and recommendations}, author = {Desjardins, R. L. and Sivakumar, M. V. K. and de Kimpe, C.}, journal = {Agricultural and Forest Meteorology}, year = {2007}, volume = {142}, number = {2}, pages = {314--324}, month = feb, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {An international workshop to discuss the contribution of agriculture to climate was held in Ottawa, Canada, from 27 to 30 September 2004. It was organized under the auspices of the World Meteorological Organization (WMO), Environment Canada and Agriculture and Agri-Food Canada (AAFC). Topics included the development of agriculture, land use change, the interactions between physiological properties of vegetation, ecosystem physical properties and climate, the impact of agriculture on weather and climate, interactive mechanisms resulting from human activities, the acquisition of relevant greenhouse gas (GHG) emission data, and the promotion/adoption of management practices to reduce the impact of agriculture on the environment. It was demonstrated that important biophysical forcing with significant climate feedback exist as a result of agriculture-related land use change. It was concluded that biogeochemical forcing is usually considered but that biophysical impacts are not well characterized, and few studies have included both of these aspects. For example, human disturbances of the earth's surface that affect the energy budget might be as important climatologically as GHG emissions arising from land disturbance. It was suggested that current GHG mitigation practices should be reassessed to account for both the biogeochemical and the biogeophysical forcing, and that there are significant opportunities and risks that occur in the complex interactions between agriculture and the environment. Workshop recommendations on how to minimize the impact of agriculture on climate were developed for the scientific community, funding agencies, and the agricultural community. (c) 2006 Elsevier B.V. All rights reserved.}, keywords = {development of agriculture, land use, physiological properties}, ISSN = {0168-1923}, } @ARTICLE{Gameda2007, title = {Climatic trends associated with summerfallow in the Canadian Prairies}, author = {Gameda, S. and Qian, B. and Campbell, C. A. and Desjardins, R. L.}, journal = {Agricultural and Forest Meteorology}, year = {2007}, volume = {142}, number = {2}, pages = {170--185}, month = feb, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {The Canadian Prairies have undergone important land use changes over the past 150 years. Beginning in the early 20th century, a significant portion of agricultural land was under surnmerfallow primarily to conserve soil moisture. The area under fallow grew to over 11 Mha, which constitute about 25\% of Canada's cultivated land, and mostly remained at that level until 1975, subsequent to which improved land management practices led to significant reductions in areas under summerfallow. By 2001 surnmerfallow area had been reduced to 5.4 Mha, and future projections expect it to fall to 3.5 Mha. Numerous modeling studies and observations have shown that land use change can have a significant impact on regional and local climate. In the Canadian Prairies, these effects would likely be seen during the mid-June to mid-July period, when agricultural crops undergo rapid foliar expansion and substantial transpiration, thus contributing to significantly higher latent heat fluxes. Observations of 1976-2000 climate trends in the black, dark brown and brown soil zones of the Canadian Prairies showed that there have been substantial reductions in maximum temperature (1.7 degrees C decade(-1)), diurnal temperature range (1.1 degrees C decade(-1)) and solar radiation (1.2 MJ m(-2) decade(-1)), as well as a corresponding increase in precipitation (10.3 mm decade(-1)) during the mid- June to July period. These findings are in opposition to trends that would be expected from climate change from an enhanced greenhouse effect, and suggest that there is substantial correspondence between reductions in surnmerfallow and changes in climate in the agricultural regions of the Canadian Prairies. (c) 2006 Elsevier B.V. All rights reserved.}, keywords = {land-use, deep convection, united-states, vegetation, temperature, variability, impact, canadian prairies, summerfallow, land use, land use change, climate}, ISSN = {0168-1923}, } @ARTICLE{Hutchinson2007, title = {Some perspectives on carbon sequestration in agriculture}, author = {Hutchinson, J. J. and Campbell, C. A. and Desjardins, R. L.}, journal = {Agricultural and Forest Meteorology}, year = {2007}, volume = {142}, number = {2}, pages = {288--302}, month = feb, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {One of the main options for greenhouse gas (GHG) mitigation identified by the IPCC is the sequestration of carbon in soils. Since the breaking of agricultural land in most regions, the carbon stocks have been depleted to such an extent, that they now represent a potential sink for CO, removal from the atmosphere. Improved management will however, be required to increase the inputs of organic matter in the top soil and/or decrease decomposition rates. In this paper we use data from selected regions to explore the global potential for carbon sequestration in arable soils. While realising that C sequestration is not limited to the selected regions, we have, however, focussed our review on two regions: (i) Canadian Prairies and (ii) The Tropics. In temperate regions, management changes for an increase in C involve increase in cropping frequency (reducing bare fallow), increasing use of forages in crop rotations, reducing tillage intensity and frequency, better crop residue management, and adopting agroforestry. In the tropics, agroforestry remains the primary method by which sequestration rates may be significantly increased. Increases in soil C may be achieved through improved fertility of cropland/pasture; on extensive systems with shifting cultivation cropped fallows and cover crops may be beneficial, and adopting agro forestry or foresting marginal cropland is also an alternative. In addition, in the tropics it is imperative to reduce the clearing of forests for conversion to cropland. Some regional analyses of soil C sequestration and sequestration potential have been performed, mainly for temperate industrialized North America where the majority of research pertaining to C sequestration has been carried out. More research is needed, especially for the Tropics, to more accurately capture the impact of region-specific interactions between climate, soil, and management of resources on C sequestration, which are lost in global level assessments. By itself, C sequestration in agricultural soils can make only modest contributions (3-6\% of fossil fuel contributions) to mitigation of overall greenhouse gas emissions. However, effective mitigation policies will not be based on any single 'magic bullet' solutions, but rather on many modest reductions which are economically efficient and which confer additional benefits to society. In this context, soil C sequestration is a significant mitigation option. (c) 2006 Elsevier B.V. All rights reserved.}, keywords = {greenhouse-gas emissions, soil organic-carbon, crop rotations, southwestern saskatchewan, canadian agriculture, black chernozem, brown chernozem, great-plains, management, impact, carbon sequestration, mitigation options, canadian prairies, tropics, tillage, fertilizer effects, cropping frequency}, ISSN = {0168-1923}, } @ARTICLE{Motha2007, title = {Development of an agricultural weather policy}, author = {Motha, R. P.}, journal = {Agricultural and Forest Meteorology}, year = {2007}, volume = {142}, number = {2}, pages = {303--313}, month = feb, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {Climate is one of the most important factors determining the sustainability of agricultural production systems. More emphasis must be placed on understanding the influence of changing climate conditions on sustainable agricultural systems, given the increasing limitations of the natural resource base. Agrometeorologists can play a leading role in bridging the gaps between the diverse multi-disciplinary fields of science, by reaching out to farmers, extension service personnel, and the agricultural business community. The farming community must cope with issues of climate variability and climate change, and, the challenge for agricultural meteorologists is to develop a coordinated national agricultural weather policy to assist agriculture as it deals with these issues. Agricultural weather policy must be formulated so that proactive long-term preparedness activities are strengthened to ensure agricultural sustainability and to preserve natural resources. Preparedness must be the essential foundation of an agricultural weather policy that builds upon mitigation measures and adaptation strategies to cope with climate variability and climate change as it affects agriculture, forestry, rangelands, and fisheries. (c) 2006 Elsevier B.V. All rights reserved.}, keywords = {sustainable agriculture, climate variability, climate change, agricultural weather policy}, ISSN = {0168-1923}, } @ARTICLE{Pielke2007, title = {A new paradigm for assessing the role of agriculture in the climate system and in climate change}, author = {Pielke, R. A. and Adegoke, J. O. and Chase, T. N. and Marshall, C. H. and Matsui, T. and Niyogi, D.}, journal = {Agricultural and Forest Meteorology}, year = {2007}, volume = {142}, number = {2}, pages = {234--254}, month = feb, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {This paper discusses the diverse climate forcings that impact agricultural systems, and contrasts the current paradigm of using global models downscaled to agricultural areas (a top- down approach) with a new paradigm that first assesses the vulnerability of agricultural activities to the spectrum of environmental risk including climate (a bottom-up approach). To illustrate the wide spectrum of climate forcings, regional climate forcings are presented including land-use/land-cover change and the influence of aerosols on radiative and biogeochemical fluxes and cloud/precipitation processes, as well as how these effects can be teleconnected globally. Examples are presented of the vulnerability perspective, along with a small survey of the perceived drought impacts in a local area, in which a wide range of impacts for the same precipitation deficits are found. This example illustrates why agricultural assessments of risk to climate change and variability and of other environmental risks should start with a bottom-up perspective. (c) 2006 Elsevier B.V. All rights reserved.}, keywords = {land-cover change, regional climate, carbon-cycle, atmospheric circulation, irrigated areas, impact, vegetation, aerosols, florida, clouds, climate change, climate models, climate impacts, ecosystems, managed and natural, mesoscale atmospheric circulations, agroforestry}, ISSN = {0168-1923}, } @ARTICLE{Raddatz2007, title = {Evidence for the influence of agriculture on weather and climate through the transformation and management of vegetation: Illustrated by examples from the Canadian Prairies}, author = {Raddatz, R. L.}, journal = {Agricultural and Forest Meteorology}, year = {2007}, volume = {142}, number = {2}, pages = {186--202}, month = feb, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {This paper lists selected observational and modeling studies which provide evidence that agriculture, through the transformation and management of vegetation, has had, and continues to have, an impact upon the weather and climate on the local, regional and global scales. The influence of agriculture on weather and climate, through the alteration of the physiological properties of the land cover, is illustrated by examples from the cropped grassland of the Canadian Prairies.}, keywords = {land-cover change, general-circulation model, soil-moisture, mesoscale circulations, regional climate, deep convection, united-states, great-plains, amazonian deforestation, temperature records, land-surface forcing, local effects, regional hydrologic cycle, tele-connections}, ISSN = {0168-1923}, } @ARTICLE{Sivakumar2007, title = {Interactions between climate and desertification}, author = {Sivakumar, M. V. K.}, journal = {Agricultural and Forest Meteorology}, year = {2007}, volume = {142}, number = {2}, pages = {143--155}, month = feb, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {Deserts are known to mankind, but the term desertification has always been an elusive concept. It is now defined in the United Nations Convention to Combat Desertification (UNCCD) as land degradation in the drylands (land failing within arid, semi- arid and dry sub-humid areas) resulting from various factors, including climatic variations and human activities. This definition, which is now being used worldwide to describe desertification and its impacts, leads to the need to consider carefully the two-way interactions between climate and desertification. Dramatic changes in agricultural practices during the last several decades are one of the main driving forces for land degradation in the drylands and examples of land degradation are given for several regions around the world. The effects of desertification on climate have been described mainly in terms of changes in land use and land cover leading to land degradation; overgrazing; biomass burning and atmospheric emissions; agriculture's contribution to air pollution; forest and woodland clearing and accelerated wind erosion; anthropogenic land disturbances and wind erosion; and the impact of irrigated agriculture on surface conditions in drylands. It is equally important to consider the impact of dryland climates on soils and vegetation and the impact of climate change on desertification. It is important to adopt uniform criteria and methods to assess desertification and encourage monitoring of dryland degradation in all the regions around the world. To better understand the interactions between climate and desertification, it is also important to identify the sources and sinks of dryland carbon, aerosols and trace gases in drylands. (c) 2006 Elsevier B.V. All rights reserved.}, keywords = {land-use change, soil organic-matter, tropical deforestation, global climate, sahel drought, carbon, impacts, african, surface, emissions, land degradation, land use and land cover changes, overgrazing, biomass burning and atmospheric emissions, air pollution, forest and woodland clearing, wind erosion, climate change}, ISSN = {0168-1923}, } @ARTICLE{Stigter2007, title = {From basic agrometeorological science to agrometeorological services and information for agricultural decision makers: A simple conceptual and diagnostic framework}, author = {Stigter, C. J.}, journal = {Agricultural and Forest Meteorology}, year = {2007}, volume = {142}, number = {2}, pages = {91--95}, month = feb, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, keywords = {climate variability, northern nigeria, policy-making, needs}, ISSN = {0168-1923}, } @ARTICLE{Salinger2007, title = {Agriculture's influence on climate during the Holocene}, author = {Salinger, M. J.}, journal = {Agricultural and Forest Meteorology}, year = {2007}, volume = {142}, number = {2}, pages = {96--102}, month = feb, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {This paper summarizes the variations of trace gas behaviour and climate during the Holocene (approximately the last 10,000 years), with reference to the last four ice age cycles. The industrial era, commonly regarded as commencing during the 18th century, is one noted when atmospheric greenhouse gas increases due to burning of fossil fuels and land use changes have been attributed to increases in global average near-surface temperatures, particularly in the latter part of the 20th century. However, analysis by Ruddiman has noted that in the Holocene during the period of civil society, the changes in atmospheric greenhouse gases have been anomalous compared with the geological record of the last 400,000 years. During this period, both carbon dioxide (CO2) and methane (CH4) increased, probably as a result of the introduction of agrarian agriculture and land clearing in Eurasia. These, and other land use changes because of agrarian rural activities, may have caused a subtle forcing of climate, preventing climate cooling which might have been expected because of natural forcing. If future evidence supports the Ruddiman hypothesis, then agricultural and forestry activities during the period of civil society may have been exerting an influence on climate for, at least, the last 8000 years. (c) 2006 Elsevier B.V. All rights reserved.}, keywords = {vostok ice, antarctica, forcings, climate, climate change, agriculture, atmospheric greenhouse gases, holocene, industrial era}, ISSN = {0168-1923}, } @ARTICLE{Verge2007, title = {Agricultural production, greenhouse gas emissions and mitigation potential}, author = {Verge, X. P. C. and De Kimpe, C. and Desjardins, R. L.}, journal = {Agricultural and Forest Meteorology}, year = {2007}, volume = {142}, number = {2}, pages = {255--269}, month = feb, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {During the next three decades, Asia will remain the largest food consumer (increasing from 40 to 55\% of the global consumption between 2000 and 2015) and the largest source of greenhouse gas (GHG) from agriculture (about 50\% of the total emissions). The growth of food demand in Africa and South America will cause substantial increase in GHG emissions by the agri-food sector, unless improved management systems are adopted. The higher food consumption rate (kJ person(-1) day(-1)) around the world is primarily a result of improved crop production and higher percentage of animal products in diet. The latter will, however, result in more CH4 emissions. The growing use of N fertilizers is also a concern. The part not taken up by crops (more than 50\%) is either lost through leaching or released to the atmosphere as N gases including nitrous oxide. Between 2000 and 2030, the total GHG emissions are expected to increase by about 50\%, with further impact on weather and climate. Mitigation techniques such as improved feed quality for a better digestibility, improved manure management, greater N use efficiency, better water management of rice paddies and/or by increasing the role of agro-forestry in agriculture, have to be considered in order to minimize the impact of agriculture on climate. (c) 2006 Elsevier B.V. All rights reserved.}, keywords = {methane, management, fields, soils, greenhouse gas, climate, population growth, food consumption, mitigation practices, regional associations}, ISSN = {0168-1923}, } @ARTICLE{Wang2007, title = {Impact of climate variations on surface albedo of a temperate grassland}, author = {Wang, S. S. and Davidson, A.}, journal = {Agricultural and Forest Meteorology}, year = {2007}, volume = {142}, number = {2}, pages = {133--142}, month = feb, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {Albedo controls surface energy balance and affects the microclimate conditions of ecosystems. Changes in albedo could induce significant changes in climate. Anthropogenic and natural factors, such as land cover and land use change, could result in the albedo change of land surfaces. In this study, we used Moderate Imaging Spectroradiometer (MODIS) data and climate station observations to investigate the albedo patterns of a temperate grassland (Grasslands National Park, Canada) and its changes due to the impact of climate variations. Our study focuses on 3 years of data (2001-2003), each of which had a different climatic regime. In 2001, precipitation fell well below its historical mean, and drought severely affected agricultural production over the GNP region. In 2002, annual precipitation was well above its historical mean, although most of the precipitation fell in the late growing season and drought conditions still occurred in the early growing season of the year. In 2003, annual precipitation was slightly lower than its historical mean, but more precipitation fell in the early growing season. MODIS and climate station observations suggest (a) during the winter-to-summer and summer-to-winter transitional periods, air temperature plays an important role in determining the surface albedo by controlling snow absence and presence; (b) in the winter season, the amount of precipitation (snow) greatly affects the surface albedo, of this ecosystem; (c) in the growing season, ecosystem water conditions can significantly alter the surface albedo of the semiarid grassland through their impact on plant growth and ecosystem conditions. These results show that surface albedo changes of this temperate grassland highly respond to climate variations. The results of this study have a number of implications in weather forecasting, climate change, and ecosystem studies. Our results stress the importance of (a) accurately simulating snow coverage fractions in regions where snow cover tends to exist throughout a long winter season, and thus, has a large influence on surface albedo; (b) accurately simulating temperatures during seasonal transitional periods ( winter-summer or summer-winter) since they determine the dates that snow covers the land surface and, in turn, strongly impact on simulations of surface albedo; (c) explicitly linking the impacts of climate change with variations on surface albedo, and the feedbacks of the albedo response to the physical climate system, in the climate model projections. (c) 2006 Elsevier B.V. All rights reserved.}, keywords = {reflectance distribution function, boreal aspen forest, bidirectional reflectance, july circulation, carbon dynamics, energy- exchange, land, modis, north, algorithm, albedo, grassland, climate change impact}, ISSN = {0168-1923}, } @ARTICLE{Ziska2007, title = {Predicting the impact of changing {CO$_2$} on crop yields: some thoughts on food}, author = {Ziska, L. H. and Bunce, J. A.}, journal = {New Phytologist}, year = {2007}, volume = {175}, number = {4}, pages = {607--617}, publisher = {Blackwell Publishing, 9600 Garsington Rd, Oxford Ox4 2dq, Oxon, England}, abstract = {Recent breakthroughs in CO2 fumigation methods using free-air CO2 enrichment (FACE) technology have prompted comparisons between FACE experiments and 'enclosure studies' with respect to quantification of the effects of projected atmospheric CO2 concentrations on crop yields. On the basis of one such comparison, it was argued that model projections of future food supply (some of which are based on older enclosure data) may have significantly overestimated the positive effect of elevated CO2 concentration on crop yields and, by extension, food security. However, in the comparison, no effort was made to differentiate 'enclosure study' methodologies with respect to maintaining projected CO2 concentration or to consider other climatic changes (e.g. warming) that could impact crop yields. In this review, we demonstrate that relative yield stimulations in response to future CO2 concentrations obtained using a number of enclosure methodologies are quantitatively consistent with FACE results for three crops of global importance: rice (Oryza sativa), soybean (Glycine max) and wheat (Triticum aestivum). We suggest, that instead of focusing on methodological disparities per se, improved projections of future food supply could be achieved by better characterization of the biotic/abiotic uncertainties associated with projected changes in CO2 and climate and incorporation of these uncertainties into current crop models.}, keywords = {elevated carbon-dioxide, rice oryza-sativa, soybean glycine-max, ultraviolet-b radiation, triticum-aestivum l., atmospheric co2, seed yield, enrichment face, climate-change, c-4 weed, carbon, crops, elevated co2, food security, rice, soybean, wheat}, ISSN = {0028-646X}, } @book{IPCC2007WorkingGroup1, abstract = {The Climate Change 2007 volumes of the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) provide the most comprehensive and balanced assessment of climate change available. This IPCC Working Group I report brings us completely up-to-date on the full range of scientific aspects of climate change. Written by the world's leading experts, the IPCC volumes will again prove to be invaluable for researchers, students, and policymakers, and will form the standard reference works for policy decisions for government and industry worldwide.}, author = {Intergovernmental~panel~on~climate~change}, citeulike-article-id = {1277492}, howpublished = {Paperback}, isbn = {0521705967}, keywords = {climate\_change, ipcc}, month = {July}, posted-at = {2007-05-04 16:25:14}, priority = {2}, publisher = {Cambridge University Press}, title = {Climate Change 2007 - The Physical Science Basis: Working Group I Contribution to the Fourth Assessment Report of the IPCC (Climate Change 2007)}, url = {http://www.amazon.ca/exec/obidos/redirect?tag=citeulike09-20\&path=ASIN/0521705967}, year = {2007} } @book{IPCC2007WorkingGroup2, abstract = {The Climate Change 2007 volumes of the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) provide the most comprehensive and balanced assessment of climate change available. This IPCC Working Group II volume brings us completely up-to-date on the vulnerability of socio-economic and natural systems to climate change. Written by the world's leading experts, the IPCC volumes will again prove to be invaluable for researchers, students, and policymakers, and will form the standard reference works for policy decisions for government and industry worldwide.}, author = {Intergovernmental~panel~on~climate~change}, citeulike-article-id = {1277490}, howpublished = {Paperback}, isbn = {0521705975}, keywords = {adaptation, change\_response, climate\_change, ipcc, vulnerability}, month = {September}, posted-at = {2007-05-04 16:24:39}, priority = {2}, publisher = {Cambridge University Press}, title = {Climate Change 2007 - Impacts, Adaptation and Vulnerability: Working Group II contribution to the Fourth Assessment Report of the IPCC (Climate Change 2007)}, url = {http://www.amazon.ca/exec/obidos/redirect?tag=citeulike09-20\&path=ASIN/0521705975}, year = {2007} } @book{IPCC2007WorkingGroup3, abstract = {The Climate Change 2007 volumes of the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) provide the most comprehensive and balanced assessment of climate change available. This IPCC Working Group III volume is a state-of-the-art assessment of the scientific, technical, environmental, economic, and social aspects of the mitigation of climate change. Written by the world's leading experts, the IPCC volumes will again prove to be invaluable for researchers, students, and policymakers, and will form the standard reference works for policy decisions for government and industry worldwide.}, author = {Intergovernmental~panel~on~climate~change}, citeulike-article-id = {1277489}, howpublished = {Hardcover}, isbn = {0521880114}, keywords = {climate\_change, ipcc, mitigation}, month = {October}, posted-at = {2007-05-04 16:23:56}, priority = {2}, publisher = {Cambridge University Press}, title = {Climate Change 2007 - Mitigation of Climate Change: Working Group III contribution to the Fourth Assessment Report of the IPCC}, url = {http://www.amazon.ca/exec/obidos/redirect?tag=citeulike09-20\&path=ASIN/0521880114}, year = {2007} } @book{Agri_IPCC2007WorkingGroup3, author= {Smith, P. and Martino, D. and Cai, Z. and Gwary, D. and Janzen, H. and Kumar, P. and McCarl, B. and Ogle, S. and O’Mara, F. and Rice, C. and Scholes, B. and Sirotenko, O.}, year={2007}, title={ Agriculture. In Climate Change 2007: Mitigation. Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, [B. Metz, O.R. Davidson, P.R. Bosch, R. Dave, L.A. Meyer (eds)]}, publisher={Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA} } @incollection{IPCC2001WorkingGroup2, abstract = {{This Working Group II volume brings us completely up-to-date on the vulnerability of socio-economic and natural systems to climate change.}}, author = {Mccarthy, James J. }, citeulike-article-id = {297638}, howpublished = {Paperback}, isbn = {0521015006}, keywords = {adaption, change, climate, impact, ipcc}, month = {July}, posted-at = {2005-08-18 16:02:17}, priority = {0}, publisher = {{Cambridge University Press}}, title = {Climate Change 2001: Impacts, Adaptation, and Vulnerability : Contribution of Working Group II to the Third Assessment Report of the Intergovernmental Panel on Climate Change}, url = {http://www.amazon.ca/exec/obidos/redirect?tag=citeulike09-20\&path=ASIN/0521015006}, year = {2001} } @book{IPCC2006Guidelines, author = {IPCC}, year = {2006}, publisher = {{Published: IGES, Japan}}, title = {2006 IPCC Guidelines for National Greenhouse Gas Inventories, Prepared by the National Greenhouse Gas Inventories Programme, Eggleston H.S., Buendia L., Miwa K., Ngara T. and Tanabe K. (eds)}, } @Article{Lehuger2007, AUTHOR = {Lehuger, S. and Gabrielle, B. and Larmanou, E. and Laville, P. and Cellier, P. and Loubet, B.}, TITLE = {Predicting the global warming potential of agro-ecosystems}, JOURNAL = {Biogeosciences Discussions}, VOLUME = {4}, YEAR = {2007}, NUMBER = {2}, PAGES = {1059--1092}, URL = {http://www.biogeosciences-discuss.net/4/1059/2007/}, ISSN = {1810-6277} } @ARTICLE{Parton1998, title = {{DAYCENT} and its land surface submodel: description and testing}, author = {Parton, W. J. and Hartman, M. and Ojima, D. and Schimel, D.}, journal = {Global and Planetary Change}, year = {1998}, volume = {19}, number = {1--4}, pages = {35--48}, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {A land surface submodel was developed for the daily version of the CENTURY ecosystem model (DAYCENT). The goal of DAYCENT to simulate soil N2O, NOx, and CH4 fluxes for terrestrial ecosystems determined the structure and processes represented in the land surface model. The land surface model was set up to simulate daily dynamics of soil water and temperature from a multi-layered soil system (0-1, 1-4, 4-15, 15-30 cm, etc.) and included surface runoff and above field capacity soil water dynamics during intense rainfall events and snowmelt into frozen soils. The comparison of the simulated soil water content (0-10 cm) with observed data from four sites was quite favorable (squared correlation coefficient-gamma(2) = 0.87, 0.65, 0.86 and 0.58) and the simulated results were comparable for the soil temperature model (r(2) = 0.92 and 0.95 for minimum and maximum 10 cm soil temperatures). Detailed soil water and temperature data during snowmelt time periods and following rainfall events are needed to fully evaluate the performance of the water flow model. (C) 1998 Elsevier Science B.V. All rights reserved.}, keywords = {shortgrass steppe, model, nitrification, worldwide, dynamics, impact, soil water, ecological models, soil temperature, latent heat flux, daycent, water flow, trace gas flux}, ISSN = {0921-8181}, } @BOOK{Jones1986, title={{CERES-N} Maize: a simulation model of maize growth and development}, author={Jones, C. A. and Kiniry, J. R.}, year={1986}, publisher={Texas A\&M University Press, College Statio, Temple, TX}, } @ARTICLE{Maag1999, title = {Effect of temperature and water on gaseous emissions from soils treated with animal slurry}, author = {Maag, M. and Vinther, F. P.}, journal = {Soil Science Society of America Journal}, year = {1999}, volume = {63}, number = {4}, pages = {858--865}, month = {Jul-aug}, publisher = {Soil Sci Soc Amer, 677 South Segoe Road, Madison, Wi 53711 USA}, abstract = {Microbial respiration and denitrification are greatly affected by abiotic factors, but they are difficult to assess in natural environments. Under controlled conditions the interactions between temperature and soil water content on microbial respiration, N2O production, and denitrification in soil amended with animal slurries were studied. The effects of the abiotic factors on the biological processes mere monitored for 8 wk in repacked soil cores amended with pig or cattle slurry. The soil cores were incubated at 43, 57, and 72\% water-filled pore space (WFPS) and at 10, 15, and 20 degrees C with or without addition of 10\% acetylene, The amount of N2O Lost at 72\% WFPS corresponded to 8 to 22\% of the slurry's NH4+ content, but to only 0.01 to 0.9\% at 43 to 57\% WFPS. Denitrification losses at 72\% WFPS accounted for 17 to 58\% of the slurry's NH4+ content, but for only 0.01 to 1.2\% at 43 to 57\% WFPS. The amount of available C accounted for by denitrification was 8 to 16\% of total respiration at 72\% WFPS, but only 0.03 to 0.4\% at 43 to 57\% WFPS. Both N2O production and denitrification peal;ed earlier in the cattle-slurry treated soil than in the pig- slurry treated soil, whereas the total N loss was greatest from the latter. Neither amendments nor soil water contents seemed to affect the Q(10)-values for the CO2 production, resulting in values between 1.6 and 1.6. At 72\% WFPS, N2O production and denitrification had Q(10)-values ranging between 3.3 and 5.4. High temperatures enhanced both aerobic respiration and denitrification, and aerobic respiration further enhanced denitrification by consuming oxygen, resulting in strong sensitivity of denitrification to temperature.}, keywords = {nitrous-oxide reduction, volatile fatty-acids, denitrification activity, concurrent observation, acetylene inhibition, organic materials, cropped sandy, n-2 fixation, nitrification, nitrate}, ISSN = {0361-5995}, } @ARTICLE{Metay2007, title = {{N$_2$O} and {CH$_4$} emissions from soils under conventional and no-till management practices in Goiania (Cerrados, Brazil)}, author = {Metay, A. and Oliver, R. and Scopel, E. and Douzet, J. M. and Alves Moreira, J. A. and Maraux, F. and Feigl, B. J. and Feller, C.}, journal = {Geoderma}, year = {2007}, volume = {141}, number = {1}, pages = {78--88}, month = sep, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {Nitrous oxide (N2O) and methane (CH4) are important greenhouse gases (GHG) produced respectively by the naturally occurring microbial processes of incomplete denitrification or nitrification and methanogenesis. Tillage practices and climate affect the release of GHGs. No tillage (DMC) systems may increase CO2-C fixation in soil but also N2O and CH4 emissions. The aim of this article is to question whether the positive effect of a DMC system observed on carbon storage for the topsoil layer in Cerrado soils is offset or not by the N2O and/or CH4 emissions. Two 5-year-old systems, tillage (disc on the first 15 cm called offset: OFF) and a direct-sowing mulch- based crop system (DMC) with an additional cover crop were studied during a cropping cycle. N2O and CH4 fluxes are determined using a closed-chamber, N2O and CO2 concentrations are measured at 3 depths (10-, 20- and 30 cm). No significant difference between treatments was observed for both gases (for emissions and concentrations). Soil NO contents increase from surface to depth (30 cm) and range from 300 ppbv to 3 ppm for both treatments. Total annual estimated emissions of N2O range from 31 to 35 g N2O-N ha(-1) year(-1) for DMC and OFF respectively which is low and corresponds only to 0.03\% of he total N-fertilizer applied. Monthly means N2O emissions were strongly correlated to monthly means of N2O content at 10 cm depth (R-2 = -0.66) and seem to increase exponentially with monthly mean Water Filled Pore Space WFPS (0-10 cm layer) (R-2 = 0.33). CH4 fluxes were very low as well: both treatment act as source of CH4 (245 and 403 g CH4-C ha(-1) year(-1) for DMC and OFF respectively. On a CO-C equivalent basis these results correspond to 4.1 and 4.7 kg CO2-C ha(-1) year(-1) for NO and to 1.9 and 3.1 kg CO2-C ha(-1) year(-1) for CH4 for DMC and OFF respectively. As a result, the carbon sequestration balance taking into account the CO2, CH4 and N2O on a CO2-C equivalent basis is in favour of DMC treatment considering that this treatment increases carbon storage originated from CO-C for the topsoil (0-10 cm) layer (350 kg C ha(-1) year(-1)) in comparison with OFF treatment. (C) 2007 Elsevier B.V. All rights reserved.}, keywords = {nitrous-oxide emissions, tropical agricultural soils, temperate forest soils, land-use change, nitric-oxide, biogeochemical controls, eastern amazonia, carbon-dioxide, humid tropics, costa-rica, no tillage, ch4, n2o, soil c sequestration, cerrado, brazil}, ISSN = {0016-7061}, } @ARTICLE{Calanca2007, title = {Simulating the fluxes of {CO$_2$} and {N$_2$O} in European grasslands with the Pasture Simulation Model (PaSim)}, author = {Calanca, P. and Vuichard, N. and Campbell, C. and Viovy, N. and Cozic, A. and Fuhrer, J. and Soussana, J. F.}, journal = {Agriculture Ecosystems \& Environment}, year = {2007}, volume = {121}, number = {1}, pages = {164--174}, month = jun, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {A mechanistic model of grassland dynamics is used to simulate fluxes of carbon dioxide (CO2) and nitrous oxide (N2O) in European grasslands. The simulations refer to five sites belonging to a monitoring network setup within the framework of the European Union project GREENGRASS. Simulated gross primary productivity ranges from 0.4 to 1.9 kg C m(-2) year(-1) depending on environmental conditions and management. Ecosystem respiration is calculated in the order of 0.7-1.5 kg C m(-2) year(-1), resulting in a net CO2 uptake of about 0.3 kg C m(-2) year(-1), in reasonable agreement with observations. Linear relationships between ecosystem respiration and gross primary productivity, as well as between net primary productivity and annual precipitation are indicated by the simulations. Annual emissions of NO are predicted in the range of 1-5 kg N ha(-1) year(-1), a factor of 2-10 higher than observed. This is caused by an overestimation of the background fluxes. On the other hand, the model fails to faithfully reproduce timing, duration and magnitude of peak emissions triggered by the application of mineral and organic fertilizers and by rain events. (c) 2006 Elsevier B.V. All rights reserved.}, keywords = {nitrous-oxide, agricultural soils, denitrification, nitrification, emissions, exchange, systems, carbon, daily and annual co2 and n2o fluxes, grassland ecosystem modelling, gross primary productivity, net primary productivity, ecosystem respiration, net ecosystem exchange, nitrification and denitrification, background n2o flux, peak n2o emissions}, ISSN = {0167-8809}, } @ARTICLE{Mathieu2006, title = {Quantifying the contribution of nitrification and denitrification to the nitrous oxide flux using {N}-15 tracers}, author = {Mathieu, O. and H\'enault, C. and Leveque, J. and Baujard, E. and Milloux, M. J. and Andreux, F.}, journal = {Environmental Pollution}, year = {2006}, volume = {144}, number = {3}, pages = {933--940}, month = dec, publisher = {Elsevier Sci Ltd, the Boulevard, Langford Lane, Kidlington, Oxford Ox5 1gb, Oxon, England}, abstract = {Microbial transformations of nittification and denitrification are the main sources of nitrous oxide (N2O) from soils. Relative contributions of both processes to N2O emissions were estimated on an agricultural soil using N-15 isotope tracers ((NH4+)-N-15 or (NO3-)-N-15), for a 10-day batch experiment. Under unsaturated and saturated conditions, both processes were significantly involved in N2O production. Under unsaturated conditions, 60\% of N-N2O came from nitrification, while denitfification contributed around 85-90\% under saturated conditions. Estimated nitrification rates were not significantly different whatever the soil moisture content, whereas the proportion of nitrified N emitted as N2O changed from 0.13 to 2.32\%. In coherence with previous studies, we interpreted this high value as resulting from the decrease in O-2 availability through the increase in soil moisture content. It thus appears that, under limiting aeration conditions, some values for N2O emissions through nitrification could be underestimated. (c) 2006 Elsevier Ltd. All rights reserved.}, keywords = {barometric process separation, n transformation rates, agricultural soils, n2o production, nitric-oxide, emissions, moisture, forest, mineralization, temperature, nitrification, denitrification, nitrous oxide, n-15 tracer, soil moisture content}, ISSN = {0269-7491}, } @ARTICLE{del2006, title = {{N$_2$O} and {NO} emissions from different {N} sources and under a range of soil water contents}, author = {del Prado, A. and Merino, P. and Estavillo, J. M. and Pinto, M. and Gonzalez-Murua, C.}, journal = {Nutrient Cycling in Agroecosystems}, year = {2006}, volume = {74}, number = {3}, pages = {229--243}, month = mar, publisher = {Springer, Van Godewijckstraat 30, 3311 Gz Dordrecht, Netherlands}, abstract = {Emissions of nitrous oxide (N2O) and nitric oxide (NO) have been identified as one of the most important sources of atmospheric pollution from grasslands. Soils are major sources for the production of N2O and NO, which are by-products or intermediate products of microbial nitrification and denitrification processes. Some studies have tried to evaluate the importance of denitrification or nitrification in the formation of N2O or NO but there are few that have considered emissions of both gases as affected by a wide range of different factors. In this study, the importance of a number of factors (soil moisture, fertiliser type and temperature) was determined for N2O and NO emissions. Nitrous oxide and NO evolution in time and the possibility of using the ratio NO:N2O as an indicator for the processes involved were also explored. Dinitrogen (ND and ammonia (NH3) emissions were estimated and a mass balance for N fluxes was performed. Nitrous oxide and NO were produced by nitrification and denitrification in soils fertilised with NH4+ and by denitrification in soils fertilised with NO3-. Water content in the soil was the most important factor affecting N2O and NO emissions. Our N2O and NO data were fitted to quadratic (r = 0.8) and negative exponential (r = 0.7) equations, respectively. A long lag phase was observed for the N2O emitted from soils fertilised with NO3- (denitrification), which was not observed for the soils fertilised with NH4+ (nitrification) and was possibly due to a greater inhibiting effect of low temperatures on microbial activity controlling denitrification rather than on nitrification. The use of the NO:N2O ratio as a possible indicator of denitrification or nitrification in the formation of N2O and NO was discounted for soils fertilised with NO3-. The N mass balance indicated that about 50 kg N ha(-1) was immobilised by microorganisms and/or taken up by plant roots, and that most of the losses ocurred in wet soils (WFPS > 60\%) as N-2 and NH3 losses (> 55\%).}, keywords = {nitrous-oxide emissions, filled pore-space, nitric-oxide, agricultural soils, grassland soil, fertilizer application, mitigation options, field conditions, clay soil, denitrification, denitrification, fertiliser type, nitric oxide, nitrification, nitrous oxide, (wfps) water filled pore space}, ISSN = {1385-1314}, } @ARTICLE{Liu2007, title = {Dinitrogen and {N$_2$O} emissions in arable soils: Effect of tillage, {N} source and soil moisture}, author = {Liu, X. J. J. and Mosier, A. R. and Halvorson, A. D. and Reule, C. A. and Zhang, F. S.}, journal = {Soil Biology \& Biochemistry}, year = {2007}, volume = {39}, number = {9}, pages = {2362--2370}, month = sep, publisher = {Pergamon-elsevier Science Ltd, the Boulevard, Langford Lane, Kidlington, Oxford Ox5 1gb, England}, abstract = {A laboratory investigation was performed to compare the fluxes of dinitrogen (N-2), N2O and carbon dioxide (CO2) from no-till (NT) and conventional till (CT) soils under the same water, mineral nitrogen and temperature status. Intact soil cores (0-10 cm) were incubated for 2 weeks at 25 degrees C at either 75\% or 60\% water-filled pore space (WFPS) with N-15-labeled fertilizers (100 mg N kg(-1) soil). Gas and soil samples were collected at 1-4 day intervals during the incubation period. The N2O and CO2 fluxes were measured by a gas chromatography (GC) system while total N-2 and N2O losses and their N-15 mole fractions in the soil mineral N pool were determined by a mass spectrometer. The daily accumulative fluxes of N-2 and N2O were significantly affected by tillage, N source and soil moisture. We observed higher (P < 0.05) fluxes of N-2+N2O, N2O and CO2 from the NT soils than from the CT soils. Compared with the addition of nitrate (NOD, the addition of ammonium (NH4+) enhanced the emissions of these N and C gases in the CT and NT soils, but the effect of NH4+ on the N-2 and/or N2O fluxes was evident only at 60\% WFPS, indicating that nitrification and subsequent denitrification contributed largely to the gaseous N losses and N2O emission under the lower moisture condition. Total and fertilizer-induced emissions of N-2 and/or N2O were higher (P < 0.05) at 75\% WFPS than with 60\% WFPS, while CO2 fluxes were not influenced by the two moisture levels. These laboratory results indicate that there is greater potential for N2O loss from NT soils than CT soils. Avoiding wet soil conditions (> 60\% WFPS) and applying a NO3 form of N fertilizer would reduce potential N2O emissions from arable soils. (c) 2007 Elsevier Ltd. All rights reserved.}, keywords = {nitrous-oxide emissions, filled pore-space, northeastern colorado, mass-spectrometry, cropping systems, long-term, denitrification, nitrification, field, fluxes, no-till, wfps, (sn)-s-15-labeled fertilizer, denitrification, nitrification, nitrous oxide emission}, ISSN = {0038-0717}, } @ARTICLE{Grant2006, title = {Modeling the effects of fertilizer application rate on nitrous oxide emissions}, author = {Grant, R. F. and Pattey, E. and Goddard, T. W. and Kryzanowski, L. M. and Puurveen, H.}, journal = {Soil Science Society of America Journal}, year = {2006}, volume = {70}, number = {1}, pages = {235--248}, month = {Jan-feb}, publisher = {Soil Sci Soc Amer, 677 South Segoe Road, Madison, Wi 53711 USA}, abstract = {The attribution of N2O emission factors to N inputs from chemical fertilizers requires an understanding of bow those inputs affect the biological processes from which these emissions are generated. We propose a detailed model of soil N transformations as part of the ecosystem model ecosys for use in attributing N2O emission factors to fertilizer use. In this model, the key biological processes-mineralization, immobilization, nitrification, denitrification, root, and mycorrhizal uptake - controlling the generation of N2O were coupled with the key physical processes-convection, diffusion, volatilization, dissolution-controlling the transport of the gaseous reactants and products of these biological processes. Physical processes controlling gaseous transport and solubility caused large temporal variation in the generation and emission of N2O in the model. This variation limited the suitability of discontinuous surface flux chambers measurements used to test modeled N2O emissions. Continuous flux measurements using micrometeorological techniques were better suited to the temporal scales at which variation in N2O emission occurred and at which motel testing needed to be conducted. In a temperate., humid climate, modeled N2O emissions rose nonlinearly with fertilizer application rate once this rate exceeded the crop and soil uptake capacities for added N. These capacities were partly determined by history of fertilizer use, so that the relationship between N2O emissions and carrent N inputs depended on earlier N inputs. A scheme is proposed in which N2O emission factors rise nonlinearly with fertilizer N inputs that exceed crop plus soil N uptake capacities.}, keywords = {temporal variation, simulation-model, soil compaction, n-fertilization, n2o emissions, root-growth, trace gas, water, evolution, fields}, ISSN = {0361-5995}, } @ARTICLE{Hofstra2005, title = {Denitrification in agricultural soils: Summarizing published data and estimating global annual rates}, author = {Hofstra, N. and Bouwman, A. F.}, journal = {Nutrient Cycling in Agroecosystems}, year = {2005}, volume = {72}, number = {3}, pages = {267--278}, month = jul, publisher = {Springer, Van Godewijckstraat 30, 3311 Gz Dordrecht, Netherlands}, abstract = {Information taken from 336 measurements of denitrification in agricultural soils was summarized to assess the influence on denitrification of several factors related to soil, climate, agricultural management and the measurement techniques. The data set is summarized by calculating means and medians and balanced median values (with correction for unbalanced features) for all factor classes in the data set, and by developing a summary model to calculate global denitrification rates for a 0.5 by 0.5 degree resolution. Our results suggest that agricultural fields with high nitrogen application rates and poor soil drainage show higher denitrification values than those with lower nitrogen application rate and good soil drainage. The data also indicate that conditions in wetland rice systems are more prone to denitrification than those in upland cropping and grassland systems. Large uncertainties in the results are caused by differences between the measurement techniques and lack of long-term measurements covering the range of environmental and management conditions found in global agricultural fields.}, keywords = {nitrous-oxide, fertilized fields, emissions, n2o, nitrification, no, volatilization, variability, atmosphere, acetylene, agriculture, animal manure, denitrification, fertilizer, model, nitrogen}, ISSN = {1385-1314}, } @ARTICLE{LiY2005, title = {Comparison of three modeling approaches for simulating denitrification and nitrous oxide emissions from loam-textured arable soils}, author = {Li, Y. and Chen, D. L. and Zhang, Y. M. and Edis, R. and Ding, H.}, journal = {Global Biogeochemical Cycles}, year = {2005}, volume = {19}, number = {3}, publisher = {Amer Geophysical Union, 2000 Florida Ave Nw, Washington, Dc 20009 USA}, abstract = {[1] Soil denitrification fluxes and nitrous oxide (N2O) emissions from the soil surface simulated by a Water and Nitrogen Management Model (WNMM), with three different gas modules, are compared to measurement data sets from two irrigated wheat-maize systems at two locations in the North China Plain (NCP) ( 2 years of measurement at the Luancheng site and 1 year of measurement at the Fengqiu site). The three gas modules are the WNMM gas module, the DAYCENT gas module, and the DNDC gas module. The term gas module used in this paper refers to the model component which simulates N2O emission from the processes of soil nitrification and denitrification. Soil water, temperature, organic matter decomposition, other nitrogen (N) transformations, such as mineralization and immobilization, and crop growth are simulated by the WNMM platform. For the 2-year data set from Luancheng, the three gas modules generate similar soil mineral N dynamics in the 0 - 20 cm topsoil. The daily time step, simply structured WNMM gas module consistently performs the best among the three gas modules for predicting soil denitrification fluxes (R-2 = 0.28, n = 39, p = 0.0006) and N2O emissions (R-2 = 0.45, n = 36, p < 0.0001). Up to 73, 43, and 22\% of total N2O emissions are nitrification-induced as simulated by the DNDC, DAYCENT, and WNMM gas modules respectively, in this well-drained loam soil during the 2-year simulation. When applied to the 1-year data set at the Fengqiu site, the WNMM gas module consistently performs better in estimating N2O emissions (R-2 = 0.54, n = 35, p < 0.0001) compared to the other two modules. Simulations using the DNDC and DAYCENT gas modules explain over 40\% of the temporal variation of N2O emission from the soil. Further testing on different soils and different agroecosystems is needed to confirm the superior performance of the WNMM gas module observed in this simulation study.}, keywords = {trace gas emissions, n2o emissions, nitrifier denitrification, mechanistic model, generalized-model, nitrification, evolution, n-2, system}, ISSN = {0886-6236}, } @ARTICLE{Li2000, title = {Modeling trace gas emissions from agricultural ecosystems}, author = {Li, C. S.}, journal = {Nutrient Cycling in Agroecosystems}, year = {2000}, volume = {58}, number = {1}, pages = {259--276}, month = nov, publisher = {Kluwer Academic Publ, Spuiboulevard 50, Po Box 17, 3300 Aa Dordrecht, Netherlands}, abstract = {A computer simulation model was developed for predicting trace gas emissions from agricultural ecosystems. The denitrification- decomposition (DNDC) model consists of two components. The first component, consisting of the soil climate, crop growth, and decomposition submodels, predicts soil temperature, moisture, pH, Eh, and substrate concentration profiles based on ecological drivers (e.g., climate, soil, vegetation, and anthropogenic activity). The second component, consisting of the nitrification, denitrification, and fermentation submodels, predicts NH3, NO, N2O, and CH4 fluxes based on the soil environmental variables. Classical laws of physics, chemistry, or biology or empirical equations generated from laboratory observations were used in the model to parameterize each specific reaction. The entire model links trace gas emissions to basic ecological drivers. Through validation against data sets of NO, N2O, CH4, and NH3 emissions measured at four agricultural sites, the model showed its ability to capture patterns and magnitudes of trace gas emissions.}, keywords = {nitrous-oxide emissions, nitric-oxide, rice paddies, field- measurements, united-states, atmospheric ammonia, compensation point, methane oxidation, microbial-growth, gaseous exchange, agroecosystem, trace gas, modeling}, ISSN = {1385-1314}, } @ARTICLE{Conen2000, title = {Predicting {N$_2$O} emissions from agricultural land through related soil parameters}, author = {Conen, F. and Dobbie, K. E. and Smith, K. A.}, journal = {Global Change Biology}, year = {2000}, volume = {6}, number = {4}, pages = {417--426}, month = apr, publisher = {Blackwell Science Ltd, P O Box 88, Osney Mead, Oxford Ox2 0ne, Oxon, England}, abstract = {An empirical model of nitrous oxide emission from agricultural soils has been developed. It is based on the relationship between N2O and three soil parameters - soil mineral N (ammonium plus nitrate) content in the topsoil, soil water-filled pore space and soil temperature - determined in a study on a fertilized grassland in 1992 and 1993. The model gave a satisfactory prediction of seasonal fluxes in other seasons when fluxes were much higher, and also from other grassland sites and from cereal and oilseed rape crops, over a wide flux range (<1 to >20 kg N2O-N ha(-1) y(-1)). However, the model underestimated emissions from potato and broccoli crops; possible reasons for this are discussed. This modelling approach, based as it is on well-established and widely used soil measurements, has the potential to provide flux estimates from a much wider range of agricultural sites than would be possible by direct measurement of N2O emissions.}, keywords = {nitrous-oxide emissions, water-content, denitrification, grassland, model, nitrate, fluxes, nitrification, temperature, field, agricultural soil, modelling, nitrogen, nitrous oxide, soil water, temperature}, ISSN = {1354-1013}, } @ARTICLE{Frolking1998, title = {Comparison of {N$_2$O} emissions from soils at three temperate agricultural sites: simulations of year-round measurements by four models}, author = {Frolking, S. E. and Mosier, A. R. and Ojima, D. S. and Li, C. and Parton, W. J. and Potter, C. S. and Priesack, E. and Stenger, R. and Haberbosch, C. and Dorsch, P. and Flessa, H. and Smith, K. A.}, journal = {Nutrient Cycling in Agroecosystems}, year = {1998}, volume = {52}, number = {2}, pages = {77--105}, month = oct, publisher = {Kluwer Academic Publ, Spuiboulevard 50, Po Box 17, 3300 Aa Dordrecht, Netherlands}, abstract = {Nitrous oxide (N2O) flux simulations by four models were compared with year-round field measurements from five temperate agricultural sites in three countries. The field sites included an unfertilized, semi-arid rangeland with low N2O fluxes in eastern Colorado, USA; two fertilizer treatments (urea and nitrate) on a fertilized grass ley cut for silage in Scotland; and two fertilized, cultivated crop fields in Germany where N2O loss during the winter was quite high. The models used were daily trace gas versions of the CENTURY model, DNDC, ExpertN, and the NASA-Ames version of the CASA model. These models included similar components (soil physics, decomposition, plant growth, and nitrogen transformations), but in some cases used very different algorithms for these processes. All models generated similar results for the general cycling of nitrogen through the agro-ecosystems, but simulated nitrogen trace gas fluxes were quite different. In most cases the simulated N2O fluxes were within a factor of about 2 of the observed annual fluxes, but even when models produced similar N2O fluxes they often produced very different estimates of gaseous N loss as nitric oxide (NO), dinitrogen (N-2), and ammonia (NH3). Accurate simulation of soil moisture appears to be a key requirement for reliable simulation of N2O emissions. All models simulated the general pattern of low background fluxes with high fluxes following fertilization at the Scottish sites, but they could not (or were not designed to) accurately capture the observed effects of different fertilizer types on N2O flux. None of the models were able to reliably generate large pulses of N2O during brief winter thaws that were observed at the two German sites. All models except DNDC simulated very low N2O fluxes for the dry site in Colorado. The US Trace Cas Network (TRAGNET) has provided a mechanism for this model and site intercomparison. Additional intercomparisons are needed with these and other models and additional data sets; these should include both tropical agro-ecosystems and new agricultural management techniques designed for sustainability.}, keywords = {nitrogen-oxide emissions, freeze-thaw cycles, rainfall events, denitrification, nitrification, evolution, fluxes, carbon, sensitivity, grassland, models, n2o, nitrogen cycle, nitrous oxide, temperate agro-ecosystems, tragnet}, ISSN = {1385-1314}, } @ARTICLE{Freney1997, title = {Emission of nitrous oxide from soils used for agriculture}, author = {Freney, J. R.}, journal = {Nutrient Cycling in Agroecosystems}, year = {1997}, volume = {49}, number = {1}, pages = {1--6}, publisher = {Kluwer Academic Publ, Spuiboulevard 50, Po Box 17, 3300 Aa Dordrecht, Netherlands}, abstract = {Nitrous oxide is emitted into the atmosphere as a result of biomass burning, and biological processes in soils. Biomass burning is not only an instantaneous source of nitrous oxide, but it results in a longer term enhancement of the biogenic production of this gas. Measurements of nitrous oxide emissions from soils before and after a controlled burn showed that significantly more nitrous oxide was exhaled after the burn. The current belief is that 90\% of the emissions come from soils. Nitrous oxide is formed in soils during the microbiological processes nitrification and denitrification. Because nitrous oxide is a gas it can escape from soil during these transformations. Nitrous oxide production is controlled by temperature, pH, water holding capacity of the soil, irrigation practices, fertilizer rate, tillage practice, soil type, oxygen concentration, availability of carbon, vegetation, land use practices and use of chemicals. Nitrous oxide emissions from agricultural soils are increased by the addition of fertilizer nitrogen and by the growth of legumes to fix atmospheric nitrogen. A recent analysis suggests that emissions of nitrous oxide from fertilized soils are not related to the type of fertilizer nitrogen applied and emissions can be calculated from the amount of nitrogen applied. Legumes also contribute to nitrous oxide emission in a number of ways, viz. atmospheric nitrogen fixed by legumes can be nitrified and denitrified in the same way as fertilizer nitrogen, thus providing a source of nitrous oxide, and symbiotically living Rhizobia in root nodules are able to denitrify and produce nitrous oxide. Conversion of tropical forests to crop production and pasture has a significant effect on the emission of nitrous oxide. Emissions of nitrous oxide increased by about a factor of two when a forest in central Brazil was clear cut, and pasture soils in the same area produced three times as much nitrous oxide as adjacent forest soils. Studies on temperate and tropical rice fields show that less than 0.1\% of the applied nitrogen is emitted as nitrous oxide if the soils are flooded for a number of days before fertilizer application. However, if mineral nitrogen is present in the soil before flooding it will serve as a source of nitrous oxide during wetting and drying cycles before permanent flooding. Thus dry seeded rice can be a source of considerable nitrous oxide. There are also indirect contributions to nitrous oxide emission through volatilization of ammonia and emission of nitric oxides into the atmosphere, and their redistribution over the landscape through wet and dry deposition. In general nitrous oxide emissions can be decreased by management practices which optimize the crop's natural ability to compete with processes whereby plant available nitrogen is lost from the soil-plant system. If these options were implemented they would also result in increased productivity and reduced inputs.}, keywords = {coated calcium carbide, flooded rice fields, ammonia volatilization, nitrification inhibitors, fertilizer nitrogen, anhydrous ammonia, irrigated wheat, denitrification, n2o, nitrapyrin, biomass burning, n-fertilizer, n2o}, ISSN = {1385-1314}, } @ARTICLE{Jambert1997, title = {Quantification of {N}-losses as {NH$_3$}, {NO}, {N$_2$O} and {N$_2$} from fertilized maize fields in {Southwestern France}}, author = {Jambert, C. and Serca, D. and Delmas, R.}, journal = {Nutrient Cycling in Agroecosystems}, year = {1997}, volume = {48}, number = {1}, pages = {91--104}, publisher = {Kluwer Academic Publ, Spuiboulevard 50, Po Box 17, 3300 Aa Dordrecht, Netherlands}, abstract = {Emissions of nitrogen compounds (NO, NH3, N2O and N-2) from heavily fertilized (280 kg(N) ha(-1)) and irrigated maize fields were studied over an annual cultivation cycle in southwestern France. NO and N2O emissions were measured by chamber techniques throughout the year. During fertilization and maize growth periods, chamber measurements were intensified and complemented by flux-gradient micrometeorological measurements of NOx and NH3. The two methods used, Bowen ratio and a simplified aerodynamical techniques, agree quite well and quantify NOx and NH3 flux variations during the period of intense emission which followed fertilizer application. Over a yearly cycle, nitrogen loss in the form of NH3, NO and N2O were calculated using micrometeorological flux measurements and emission algorithms calibrated with field data (chambers). The soil denitrification potential represented by the ratio N2O/(N2O+N-2) was measured in the laboratory to calculate potential total gaseous nitrogen loss. Taking into account all uncertainties, the total N loss into the atmosphere represents 30 to 110 kg(N) ha(-1) with about less than 1\% as NH3, 40\% as NO, 14\% as N2O and 46\% as N-2. This is in agreement with the agronomic nitrogen budget based on the N fertilizer input and soil furniture and, on the N-output by crops and crop residues, which displays a net imbalance of 50 to 100 kg(N) ha(-1).}, keywords = {atmospheric surface-layer, nitrogen-oxide emissions, profile relationships, soils, forest, fluxes, ozone, agroecosystem, ammonia, denitrification, fertilizer, gaseous emissions, nitric oxide, nitrification, nitrogen budget, nitrous oxide}, ISSN = {1385-1314}, } @ARTICLE{Beheydt2007, title = {Validation of {DNDC} for 22 long-term {N$_2$O} field emission measurements}, author = {Beheydt, D. and Boeckx, P. and Sleutel, S. and Li, C. S. and Van Cleemput, O.}, journal = {Atmospheric Environment}, year = {2007}, volume = {41}, number = {29}, pages = {6196--6211}, month = sep, publisher = {Pergamon-elsevier Science Ltd, the Boulevard, Langford Lane, Kidlington, Oxford Ox5 1gb, England}, abstract = {Twenty-two long-term measurements of direct N2O emissions from soils in an intensive agricultural area were used for the validation of the process-based DNDC model (version 8.3P). Model simulations were evaluated for temporal patterns of N2O. NH4+, NO3- and water-filled pore space (WFPS) and total N2O emissions. Several soil and crop input parameter adjustments to the model were evaluated but only the recalculation of the WFPS at wilting point and at field capacity, using pedotransfer functions, resulted in a clear improvement of the simulated variables (WFPS in all cases, N2O in some cases). Therefore, only this adjustment was made to DNDC 8.3P. This change, however, resulted for some cases (both cropland and grassland) in retardation of nitrate leaching and to a lesser extent of NH4+ to the deeper soil layers. The goodness of fit of the simulated temporal pattern of N2O varied considerably between sites. The total simulated N2O emissions from cropland showed a good agreement with the measurements, although there was a systematic overestimation of 7.4 kg N2O-N ha(-1). Grassland soils, in contrast, gave a low agreement between total simulated and measured N2O losses. On the basis of all measured data a regional emission factor of 3.16 with a 95\% confidence interval of -0.89 to 7.21 could be calculated. DNDC simulations resulted in an emission factor of 6.49 with a 95\% confidence interval of 4.04-8.93. The overall outcome of the N2O emission measurements and DNDC simulations were compared with several empirical regression models, which may be applicable for a temperate climate system. All of the tested regression models showed reliable results up to a N2O emission of 10 kg N2O-N ha(-1). Higher emissions, however, were systematically underestimated. Though DNDC both under- and overestimated specific sites, the general agreement, over the whole range between measurements and simulations of total N2O losses (simulations = 0.82 x meas. + 6.2), was better than for the different regression models. (c) 2007 Elsevier Ltd. All rights reserved.}, keywords = {nitrous-oxide emissions, gas emissions, nitrifier denitrification, spatial variability, agricultural soils, rainfall events, no emissions, forest soils, ch4 fluxes, model, process-based model, regression model, nitrous oxide emission, agriculture, greenhouse gas}, ISSN = {1352-2310}, } @ARTICLE{Rizhiya2007, title = {Earthworm activity as a determinant for {N$_2$O} emission from crop residue}, author = {Rizhiya, E. and Bertora, C. and van Vliet, P. C. J. and Kuikman, P. J. and Faber, J. H. and van Groenigen, J. W.}, journal = {Soil Biology \& Biochemistry}, year = {2007}, volume = {39}, number = {8}, pages = {2058--2069}, month = aug, publisher = {Pergamon-elsevier Science Ltd, the Boulevard, Langford Lane, Kidlington, Oxford Ox5 1gb, England}, abstract = {Earthworm activity may have an effect on nitrous oxide (N2O) emissions from crop residue. However, the importance of this effect and its main controlling variables are largely unknown. The main objective of this study was to determine under which conditions and to what extent earthworm activity impacts N2O emissions from grass residue. For this purpose we initiated a 90-day (experiment I) and a 50-day (experiment II) laboratory mesocosm experiment using a Typic Fluvaquent pasture soil with silt loam texture. In all treatments, residue was applied, and emissions of NO and carbon dioxide (CO2) were measured. In experiment I the residue was applied on top of the soil surface and we tested (a) the effects of the anecic earthworm species Aporrectodea longa (Ude) vs. the epigeic species Lumbricus rubellus (Hoffmeister) and (b) interactions between earthworm activity and bulk density (1.06 vs. 1.61 g cm(-3)). In experiment II we tested the effect of L. rubellus after residue was artificially incorporated in the soil. In experiment 1, N2O emissions in the presence of earthworms significantly increased from 55.7 to 789.1 mu g N2O-N kg(-1) soil (L. rubellus; p < 0.001) or to 227.2 mu g N2O-N kg(-1) soil (A. longa, p < 0.05). This effect was not dependent on bulk density. However, if the residue was incorporated into the soil (experiment II) the earthworm effect disappeared and emissions were higher (1064.2 mu g N2O-N kg(-1) soil). At the end of the experiment and after removal of earthworms, a drying/wetting and freezing/thawing cycle resulted in significantly higher emissions of NO and CO2 from soil with prior presence of L. rubellus. Soil with prior presence of L. rubellus also had higher potential denitrification. We conclude that the main effect of earthworm activity on N2O emissions is through mixing residue into the soil, switching residue decomposition from an aerobic and low denitrification pathway to one with significant denitrification and NO production. Furthermore, A. longa activity resulted in more stable soil organic matter than L. rubellus. (c) 2007 Elsevier Ltd. All rights reserved.}, keywords = {nitrous-oxide emission, soil organic-matter, denitrifying bacteria, denitrification rates, aporrectodea-turgida, lumbricus- terrestris, octolasion-tyrtaeum, agricultural soils, carbon, management, greenhouse gases, nitrous oxide, emission factor, earthworm ecological groups, residue application, bulk density}, ISSN = {0038-0717}, } @ARTICLE{Levy2007, title = {Simulation of fluxes of greenhouse gases from European grasslands using the {DNDC} model}, author = {Levy, P. E. and Mobbs, D. C. and Jones, S. K. and Milne, R. and Campbell, C. and Sutton, M. A.}, journal = {Agriculture Ecosystems \& Environment}, year = {2007}, volume = {121}, number = {1}, pages = {186--192}, month = jun, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {Agricultural management of grasslands results in sequestration and emission of greenhouse gases (GHGs, particularly CO2, N2O and CH4). Here, we used a process-based model (DNDC) to estimate the fluxes of the major GHGs from grasslands at 0.5 degrees resolution across Europe, and combined these to produce a spatially explicit estimate of the total global warming potential (GWP, expressed in CO2 equivalents). The DNDC model [Li, C., Frolking, S., Crocker, G.J., Grace, P.R., Klir, J., Korchens, M., Poulton, P.R., 1997. Simulating trends in soil organic carbon in long-term experiments using the DNDC model. Geoderma 81, 45-60] simulates carbon and nitrogen cycling in agroecosystems at a sub-daily time step and consists of four interacting submodels: soil and climate (including water flow and leaching), plant growth, decomposition, and denitrification. Input data sets for grassland area, climate, nitrogen deposition, and soil properties were collated. The typical current grassland management regime was established for ten biogeographical regions on the basis of questionnaires sent to national experts, and used to derive model input data. A 20- year simulation was carried out using DNDC for each site. Simple estimates of methane emissions from grazing livestock were made according to the IPCC Tier 1 method. Most grassland areas are net sources for GHGs in terms of total global warming potential-the beneficial effect of sequestering carbon in soil is outweighed by the emissions of N2O from soil and (predominantly) CH4 emissions from livestock. The net effect of European grasslands on GWP (emission of 23 Tg C year(-1)) corresponds to a 2.5\% increase on the EU-15 fossil fuel CO2 emissions (907 Tg C year(-1)). (c) 2006 Elsevier B.V. All rights reserved.}, keywords = {carbon, n2o, emissions, ch4, carbon dioxide, nitrous oxide, methane, global warming potential, grassland management, livestock emissions}, ISSN = {0167-8809}, } @ARTICLE{Pattey2007, title = {Tools for quantifying {N$_2$O} emissions from agroecosystems}, author = {Pattey, E. and Edwards, G. C. and Desjardins, R. L. and Pennock, D. J. and Smith, W. and Grant, B. and MacPherson, J. I.}, journal = {Agricultural and Forest Meteorology}, year = {2007}, volume = {142}, number = {2}, pages = {103--119}, month = feb, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {The importance of constraining the global budget of nitrous oxide (N2O) has been well established. The current global estimate of the contribution of N2O to total anthropogenic greenhouse gas emissions from agriculture is about 69\%. Considerable progress has been made over the past few years in developing tools for quantifying the emissions from agricultural sources, at the local and field scale (i.e., chamber and tower-based measurements) as well as at the landscape and regional levels (i.e., aircraft-based measurement and modelling). However, aggregating these emissions over space and time remains a challenge because of the high degree of temporal and spatial variability. Emissions of N2O in temperate climate are largely event driven, e.g., in Eastern Canada, large emissions are observed right after snowmelt. The average emissions during the snowmelt period vary considerably, reflecting the influence of many controlling factors. Cumulative emissions reported here range from 0.05 kg N2O-N ha(-1) in Western Canada to 1.26 kg N2O-N ha-1 in Eastern Canada, values that reflect differences in climatic zones and fertilizer management practices. This paper describes the tools for refining the global N2O budget and provides examples of measurements at various scales. Tower- based and aircraft measurement platforms provide good data for quantifying the variability associated with the measurements. Chamber-based methods lack the temporal and spatial resolution required to follow the event driven nature of N2O fluxes but provide valuable information for evaluating management practices. The model DeNitrification and DeComposition is an example of a technique to estimate N2O emissions when no data is available. Crown Copyright (c) 2006 Published by Elsevier B.V. All rights reserved.}, keywords = {nitrous-oxide emissions, tunable diode-laser, relaxed eddy- accumulation, greenhouse-gas fluxes, agricultural fields, spring thaw, micrometeorological measurements, interannual variations, generalized-model, parkland region, flux measurement tools, modelling, snowmelt n2o release}, ISSN = {0168-1923}, } @ARTICLE{Ludwig2001, title = {Soil-air exchange of nitric oxide: An overview of processes, dnvironmental vactors, and modeling studies}, author = {Ludwig, J. and Meixner, F. X. and Vogel, B. and Forstner, J.}, journal = {Biogeochemistry}, year = {2001}, volume = {52}, number = {3}, pages = {225--257}, month = feb, publisher = {Kluwer Academic Publ, Spuiboulevard 50, Po Box 17, 3300 Aa Dordrecht, Netherlands}, abstract = {Terrestrial ecosystems with their main elements soil and plants may act, in principle, as both source and sink for atmospheric nitric oxide (NO). The net exchange between ecosystems and the atmosphere, however, is globally dominated by biogenic emissions of NO from soils. Consequently the soil-air exchange of NO is the focus of the following overview. Particular emphasis is placed on the major processes that are responsible for NO production in soils (nitrification, denitrification) and their regulation by environmental factors (nitrogen availability, soil water content, soil temperature, ambient NO concentration). It is shown that interactions of these factors are a major reason for the broad range that exists in published data on NO fluxes. This variability makes it difficult to predict the magnitude of NO fluxes on relevant spatial and temporal scales. To overcome the problem various generalization procedures for scaling up in space and time have been developed, and the potential and limitations of the different approaches is discussed.}, keywords = {vertical concentration profiles, southern african savanna, biogenic nox emissions, dry tropical forest, nitrous-oxide, field- measurements, agricultural soils, trace gases, nitrosomonas- europaea, microbial-production, biogenic no emission, influencing factors, land-use, modeling, upscaling}, ISSN = {0168-2563}, } @ARTICLE{Roelandt2005, title = {Estimating annual {N$_2$O} emissions from agricultural soils in temperate climates}, author = {Roelandt, C. and van Wesemael, B. and Rounsevell, M.}, journal = {Global Change Biology}, year = {2005}, volume = {11}, number = {10}, pages = {1701--1711}, month = oct, publisher = {Blackwell Publishing, 9600 Garsington Rd, Oxford Ox4 2dq, Oxon, England}, abstract = {The Kyoto protocol requires countries to provide national inventories for a list of greenhouse gases including N2O. A standard methodology proposed by the Intergovernmental Panel on Climate Change (IPCC) estimates direct N2O emissions from soils as a constant fraction (1.25\%) of the nitrogen input. This approach is insensitive to environmental variability. A more dynamic approach is needed to establish reliable N2O emission inventories and to propose efficient mitigation strategies. The objective of this paper is to develop a model that allows the spatial and temporal variation in environmental conditions to be taken into account in national inventories of direct N2O emissions. Observed annual N2O emission rates are used to establish statistical relationships between N2O emissions, seasonal climate and nitrogen-fertilization rate. Two empirical models, MCROPS and MGRASS, were developed for croplands and grasslands. Validated with an independent data set, MCROPS shows that spring temperature and summer precipitation explain 35\% of the variance in annual N2O emissions from croplands. In MGRASS, nitrogen-fertilization rate and winter temperature explain 48\% of the variance in annual N2O emissions from grasslands. Using long-term climate observations (1900-2000), the sensitivity of the models with climate variability is estimated by comparing the year-to-year prediction of the model to the precision obtained during the validation process. MCROPS is able to capture interannual variability of N2O emissions from croplands. However, grassland emissions show very small interannual variations, which are too small to be detectable by MGRASS. MCROPS and MGRASS improve the statistical reliability of direct N2O emissions compared with the IPCC default methodology. Furthermore, the models can be used to estimate the effects of interannual variation in climate, climate change on direct N2O emissions from soils at the regional scale.}, keywords = {nitrous-oxide emissions, arable soils, long-term, n-fertilization, managed grasslands, temporal variation, ch4 fluxes, land-use, fields, crops, croplands, emission factors, empirical model, grasslands, greenhouse gas, nitrous oxide}, ISSN = {1354-1013}, } @ARTICLE{Wolf2000, title = {Different pathways of formation of {N$_2$O}, {N$_2$} and {NO} in black earth soil}, author = {Wolf, I. and Russow, R.}, journal = {Soil Biology \& Biochemistry}, year = {2000}, volume = {32}, number = {2}, pages = {229--239}, month = feb, publisher = {Pergamon-elsevier Science Ltd, the Boulevard, Langford Lane, Kidlington, Oxford Ox5 1gb, England}, abstract = {The use of N-15 tracer provides a suitable technique to investigate the processes of N transformation in soils and the origin of the environmentally relevant gaseous N compounds N2O and NO from nitrification and denitrification. incubation experiments with black earth soil under two different water contents are presented here. Nitrification and denitrification proceeded simultaneously, but the importance of these two microbial processes shifted depending on the water content of the soil. Under water-unsaturated conditions the microbial oxidation of NH4+ to NO3- predominated, but a reduction of NO3- also occurred. The emission of NO exceeded the emission of N2O by a factor of up to 20 at the beginning of the experiments. Under water-saturated conditions denitrification was the dominant process of N transformation in the soil. However, nitrification also occurred to a considerable extent. The emission of N2O was greater than under unsaturated conditions. The formation of NO could hardly be observed. N loss by molecular nitrogen from denitrification could be detected under saturated conditions. The N loss amounted to 60\% of NO3- and thereby the cumulative N ratio of N-2 to N2O was 3. Under either unsaturated or saturated conditions NO arose from NO2- or during the microbial oxidation of NH4+ to NO2-. However, N2O mainly formed from denitrification under both conditions. Furthermore, NO could not be observed as a precursor of N2O and the free NO2- could not be detected as a common N pool for the formation of N2O and NO. High emissions of NO could be a problem for the black earth soil in the semi-arid climate in central Germany, if there are large amounts of NH4+ in the soil after fertilisation. (C) 2000 Elsevier Science Ltd. All rights reserved.}, keywords = {nitric-oxide, nitrous-oxide, denitrification, nitrification, consumption, dinitrogen, samples, denitrification, di-nitrogen, nitrification, n-15, nitric oxide, nitrous oxide}, ISSN = {0038-0717}, } @ARTICLE{Khalil2004, title = {Nitrous oxide production by nitrification and denitrification in soil aggregates as affected by {O$_2$} concentration}, author = {Khalil, K. and Mary, B. and Renault, P.}, journal = {Soil Biology \& Biochemistry}, year = {2004}, volume = {36}, number = {4}, pages = {687--699}, month = apr, publisher = {Pergamon-elsevier Science Ltd, the Boulevard, Langford Lane, Kidlington, Oxford Ox5 1gb, England}, abstract = {Nitrous oxide emitted by soils can be produced either by denitrification in anoxic conditions or by nitrification in presence Of O-2. The relative importance of the two processes, particularly under varied partial pressures Of O-2, is not always known. This paper focuses on the influence of O-2 concentration on N2O production by nitrification and denitrification in an arable Orthic Luvisol. Soil aggregates (2-3 mm size), water unsaturated, received 116 mg N kg(-1) as ammonium sulphate labelled with N-15 and were incubated during 14 days at different O-2 partial pressures: 0, 0.35, 0.76, 1.5, 4.3 and 20.4 kPa. A N-15 tracing technique was used to quantify nitrification and denitrification rates. (N2O)-N-15 and N-15(2) were measured. Oxygen pressure appeared to strongly influence both nitrification and denitrification rates and also N2O emissions. Nitrification rates were reduced by a factor of 6-9 when O-2 decreased from 20.4 to 0.35 kPa. They were highly correlated with O-2 consumption rates. Denitrification mainly occurred in complete anoxic conditions. The proportion of N2O emitted by denitrification was estimated by two independent methods: one based on N-15 tracing using isotope composition of NH4, NO3 and N2O, the other based on the measurement of the (N2O)-N-15: N-15(2) ratio. The two methods gave close results. The highest N2O emissions were obtained under complete anoxic conditions and were due to denitrification. However, N2O emissions almost as important were obtained at day 14 with 1.5 kPa O-2 pressure, and they were due to nitrification. Nitrification was the main source of N2O at O-2 concentrations greater than 0.35 kPa. The amounts of N2O-N emitted by nitrification were linearly related to the amounts of N nitrified, but the slope of the regression was highly dependent on O-2 concentration: it varied from 0.16 to 1.48\% when O-2 concentration was reduced from 20.4 to 0.76 kPa. Emissions of N2O by nitrification may then be quite significant if nitrification occurs at a reduced O-2 concentration. (C) 2004 Elsevier Ltd. All rights reserved.}, keywords = {nitrosomonas-europaea, n2o production, heterotrophic nitrifiers, aerobic denitrification, agricultural soils, grassland soil, pore-space, no, emissions, ammonia, denitrification, nitrification, nitrous oxide, oxygen, n-15}, ISSN = {0038-0717}, } @ARTICLE{Rodrigo1997, title = {Modelling temperature and moisture effects on {C-N} transformations in soils: comparison of nine models}, author = {Rodrigo, A. and Recous, S. and Neel, C. and Mary, B.}, journal = {Ecological Modelling}, year = {1997}, volume = {102}, number = {2}, pages = {325--339}, month = oct, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {Most models designed to simulate carbon and nitrogen transformations in the soil have defined functions to describe the effects of temperature and water content on microbial processes. These functions are normally derived from soil incubation studies, but they could be one of the main differences among models, and their specific effect has yet to be studied. We have analysed different functions describing the effects of soil moisture, temperature and their interaction on microbial processes reported in the literature. Evolution of temperature (f(T)) and moisture (g(psi)) functions applied to N mineralisation in nine C-N simulation models (SOILN, MATHILD, SUNDIAL, TRITSIM, DAISY, NLEAP, NCSOIL, CANTIS and Kersbaum's), representing a wide range of those reviewed, were compared by using a daily data set of soil temperature (T) and water potential (Psi) obtained in the held in Northern France. Comparison between f(T) and g(psi) was realised using a common values of 'reference' temperature and moisture (T-ref and Psi(ref)), values at which f(T), and g(psi) are equal to 1 in all models. Large differences were observed among proposed f(T) especially when T-ref = 35 degrees C, which is much higher than the average temperature of data set examined (T = 11 degrees C). In this case, maximal relative differences between f(T) functions of studied models were around 325\%. The g(psi) functions reached similar maximum values at soil moisture near held capacity, except for NLEAP and NCSOIL models. In the dry range of soil moisture, the relative differences in g(psi) become higher. The combined effect of temperature and moisture product, f(T).g(psi), varied by a five-fold factor between models for T-ref= 35 degrees C and Psi(ref)= -50 kPa. (C) 1997 Elsevier Science B.V.}, keywords = {net nitrogen mineralization, winter-wheat, straw decomposition, organic-matter, water-content, root decomposition, field conditions, barley straw, clay soil, nitrification, temperature, moisture, nitrogen, carbon, mineralisation, models}, ISSN = {0304-3800}, } @ARTICLE{Howard1993, title = {{Relationships Between {CO$_2$} Evolution, Moisture-content and Temperature for a Range of Soil Types}}, author = {Howard, D. M. and Howard, P. J. A.}, journal = {Soil Biology \& Biochemistry}, year = {1993}, volume = {25}, number = {11}, pages = {1537--1546}, month = nov, publisher = {Pergamon-elsevier Science Ltd, the Boulevard, Langford Lane, Kidlington, Oxford, England Ox5 1gb}, abstract = {Soils were collected from two locations at six sites on each of eight soil types. After sieving, soil CO2 evolution was measured at three moisture contents and at 5, 10, 15 and 20-degrees-C. Our objectives were to (i) establish a regression model for the relationships between CO2 evolution, temperature and soil moisture content, and (ii) to investigate which aspects of this regression apply universally and which are specific to individual soil types. The same soil samples were used at the different temperatures, giving CO2 data which were repeated or longitudinal measurements. This experimental structure has implications for the covariance structure of the data.}, keywords = {humic acids, phanerochaete-chrysosporium, organic-matter, biodegradation, carbon}, ISSN = {0038-0717}, } @ARTICLE{Muller2004, title = {Nitrous oxide emissions from temperate grassland ecosystems in the Northern and Southern Hemispheres}, author = {Muller, C. and Sherlock, R. R.}, journal = {Global Biogeochemical Cycles}, year = {2004}, volume = {18}, number = {1}, publisher = {Amer Geophysical Union, 2000 Florida Ave Nw, Washington, Dc 20009 USA}, abstract = {[1] Nitrogen (N) fertilized or grazed grasslands in temperate regions of the Northern and Southern Hemisphere are important sources for atmospheric nitrous oxide (N2O). Following synthetic urine applications in a New Zealand grassland ecosystem, and ammonium (NH4+) and nitrate (NO3-) applications to a German grassland ecosystem, approximately 31, 16, and 5\%, respectively, of the total emitted N2O (N2Otot) was produced by nitrification (N2Onit) with the rest being produced by denitrification (N2Oden). Analyses of the combined data set showed that 75\% of all N2O emissions occurred above 60\% water filled porosity (WFPS) and that more than 80\% of all N2O emissions occurred at soil temperatures between 10degrees and 15degreesC. N2Oden emissions were associated with a WFPS value at around 80\% at relatively low NO3- concentrations, while N2Onit emissions only occurred at high NH4+ levels shortly after N application at soil temperatures around 10 degreesC. To increase the accuracy of predictions with simple mathematical models, such as the hole-in-the-pipe-model,'' long-term validation data sets are needed where driving variables are related to measured N2Onit and N2Oden data.}, keywords = {denitrification process, acetylene-inhibition, fertilized grassland, agricultural soils, field measurement, n2o production, animal urine, new-zealand, nitrification, pasture, grassland, nitrous oxide}, ISSN = {0886-6236}, } @ARTICLE{Liu2000, title = {Simulation of nitrous oxide and nitric oxide emissions from tropical primary forests in the Costa Rican Atlantic Zone}, author = {Liu, S. G. and Reiners, W. A. and Keller, M. and Schimel, D. S.}, journal = {Environmental Modelling \& Software}, year = {2000}, volume = {15}, number = {8}, pages = {727--743}, publisher = {Elsevier Sci Ltd, the Boulevard, Langford Lane, Kidlington, Oxford Ox5 1gb, Oxon, England}, abstract = {Nitrous oxide (N2O) and nitric oxide (NO) are important atmospheric trace gases participating in the regulation of global climate and environment. Predictive models on the emissions of N2O and NO emissions from soil into the atmosphere are required. We modified the CENTURY model (Soil Sui. Sec. Am. J., 51 (1987) 1173) to simulate the emissions of N2O and NO from tropical primary forests in the Atlantic Zone of Costa Rica at a monthly time step. Combined fluxes of N2O and NO were simulated as a function of gross N mineralization and water-filled pore space (WFPS). The coefficients for partitioning N2O from NO were derived from field measurements (Global Biogeochem. Cycles, 8 (1994) 399). The modified CENTURY was calibrated against observations of carbon stocks in various pools of forest ecosystems of the region, and measured WFPS and emission rates of N2O and NO from soil to the atmosphere.}, keywords = {colorado shortgrass steppe, trace-gas emissions, n2o production, rain- forest, wet forest, soil properties, pasture, model, denitrification, dynamics, century, nitrogen, mineralization, modeling, rainfall, wfps}, ISSN = {1364-8152}, } @ARTICLE{Schmidt2000, title = {Using a boundary line approach to analyze {N$_2$O} flux data from agricultural soils}, author = {Schmidt, U. and Thoni, H. and Kaupenjohann, M.}, journal = {Nutrient Cycling in Agroecosystems}, year = {2000}, volume = {57}, number = {2}, pages = {119--129}, month = jun, publisher = {Kluwer Academic Publ, Spuiboulevard 50, Po Box 17, 3300 Aa Dordrecht, Netherlands}, abstract = {Predicting the N2O flux from soils is difficult because of the complex interplay of the various processes involved. In this study a boundary line approach was used to apply results from mechanistic experiments to N2O flux data resulting from measurements on field scale in southern Germany. Boundary lines were fitted to the rim of the data points in scattergrams depicting readily obtainable soil variables against the measured N2O flux. The boundary Line approach is based on the hypothesis that this line depicts the functional dependency between the two variables. For determining these boundary lines a novel method was applied. The function best representing the relationship between the N2O flux and soil temperature had a maximum above 23 degrees C and the one between the N2O flux and the water filled pore space (WFPS, to represent water content) had a maximum at 72\% WFPS. In the range of 0-20 mg N kg(-1) the relationship between N2O flux and nitrate in the soil was best described by a linear function, whereas in the range of 0-35 mg N kg(-1) a Michaelis-Menten function was more appropriate. The boundary lines specified in this study are in agreement with existing theoretical concepts as well as experimental results obtained under controlled and field conditions as reported in the literature. Therefore, the boundary line approach can be used to improve empirical models for predicting the N2O flux in the field.}, keywords = {nitrous-oxide emissions, empirical-model, denitrification, nitrate, temperature, prediction, moisture, losses, system, oxygen, boundary line, field measurement, model, n2o flux}, ISSN = {1385-1314}, } @ARTICLE{Pihlatie2004, title = {Contribution of nitrification and denitrification to {N$_2$O} production in peat, clay and loamy sand soils under different soil moisture conditions}, author = {Pihlatie, M. and Syvasalo, E. and Simojoki, A. and Esala, M. and Regina, K.}, journal = {Nutrient Cycling in Agroecosystems}, year = {2004}, volume = {70}, number = {2}, pages = {135--141}, month = oct, publisher = {Kluwer Academic Publ, Van Godewijckstraat 30, 3311 Gz Dordrecht, Netherlands}, abstract = {Agricultural soils are a significant source of nitrous oxide (N2O). Since mitigation of greenhouse gas emissions is needed in all sectors of society, it is important to identify the processes producing N2O and the factors affecting the production rates in agricultural soils. This study aimed to elucidate the N2O production in peat, clay and loamy sand at four different soil moisture conditions (40, 60, 80 and 100\% Water Filled Pore Space). The acetylene inhibition technique was used to evaluate the contribution of nitrification to N2O production. Nitrous oxide production responded markedly to soil moisture in all three soils. The highest N2O production, measured at the wettest soils (100\% WFPS), was up to four orders of magnitude higher than that at the dry soils (40\% WFPS). In dry conditions N2O production decreased in the order of peat>clay>loamy sand, while in wet conditions the highest N2O production was measured in loamy sand, then in peat, and the lowest in clay soils. Nitrification was the dominant N2O producing process in all the soils at 60\% WFPS. In the sandy soil 70\% of the total N2O production originated from nitrification, while in the peat soil most of the total N2O production originated from denitrification. Data on processes producing N2O in agricultural soils are needed to develop process-based models that could reduce the uncertainty of the emission estimates in greenhouse gas inventories.}, keywords = {nitrous-oxide production, filled pore-space, nitric-oxide, emissions, acetylene, fluxes, fertilization, temperature, field, grassland, agricultural soils, denitrification, nitrification, nitrous oxide, soil moisture}, ISSN = {1385-1314}, } @ARTICLE{Saggar2004, title = {Modelling nitrous oxide emissions from dairy-grazed pastures}, author = {Saggar, S. and Andrew, R. M. and Tate, K. R. and Hedley, C. B. and Rodda, N. J. and Townsend, J. A.}, journal = {Nutrient Cycling in Agroecosystems}, year = {2004}, volume = {68}, number = {3}, pages = {243--255}, month = mar, publisher = {Kluwer Academic Publ, Van Godewijckstraat 30, 3311 Gz Dordrecht, Netherlands}, abstract = {Soil N2O emissions were measured during four seasons from two highly productive grass-clover dairy pastures to assess the influences of soil moisture, temperature, availability of N (NH4+ and NO3-) and soluble C on N2O emissions, and to use the emission data to validate and refine a simulation model (DNDC). The soils at these pasture sites (Karapoti fine sandy loam, and Tokomaru silt loam) differed in texture and drainage characteristics. Emission peaks for N2O coincided with rainfall events and high soil moisture content. Large inherent variations in N2O fluxes were observed throughout the year in both the ungrazed (control) and grazed pastures. Fluxes averaged 4.3 and 5.0 g N2O/ha/day for the two ungrazed sites. The N2O fluxes from the grazed sites were much higher than for the ungrazed sites, averaging 26.4 g N2O/ ha/day for the fine sandy loam soil, and 32.0 g N2O/ ha/day for the silt loam soil. Our results showed that excretal and fertiliser-N input, and water-filled pore space (WFPS) were the variables that most strongly regulated N2O fluxes. The DNDC model was modified to include the effects of day length on pasture growth, and of excretal-N inputs from grazing animals; the value of the WFPS threshold was also modified. The modified model 'NZ-DNDC' simulated effectively most of the WFPS and N2O emission pulses and trends from both the ungrazed and grazed pastures. The modified model fairly reproduced the real variability in underlying processes regulating N2O emissions and could be suitable for simulating N2O emissions from a range of New Zealand grazed pastures. The NZ-DNDC estimates of total yearly emissions of N2O from the grazed and ungrazed sites of both farms were within the uncertainty range of the measured emissions. The measured emissions changed with changes in soil moisture resulting from rainfall and were about 20\% higher in the poorly drained silt loam soil than in the well-drained sandy loam soil. The model accounts for these climatic variations in rainfall, and was also able to pick up differences in emissions resulting from differences in soil texture.}, keywords = {n2o emissions, new-zealand, spatial variability, ipcc methodology, rainfall events, soil driven, gas fluxes, land-use, denitrification, inventory, excretal inputs, grazed pastures, ipcc methodology, new zealand modified dndc, nitrous oxide, temperate grasslands}, ISSN = {1385-1314}, } @ARTICLE{Dobbie2001, title = {The effects of temperature, water-filled pore space and land use on {N$_2$O} emissions from an imperfectly drained gleysol}, author = {Dobbie, K. E. and Smith, K. A.}, journal = {European Journal of Soil Science}, year = {2001}, volume = {52}, number = {4}, pages = {667--673}, month = dec, publisher = {Blackwell Publishing Ltd, 9600 Garsington Rd, Oxford Ox4 2dg, Oxon, England}, abstract = {To investigate the effect of soil physical conditions and land use on emissions of nitrous oxide (N2O) to the atmosphere, soil cores of an imperfectly, drained gleysol were taken from adjacent fields under perennial ryegrass and winter wheat. The cores were fertilized with ammonium nitrate and incubated at three different temperatures and water-filled pore space (WFPS) values, and N2O emissions were measured by gas chromatography: Emissions showed a very large response to temperature. Apparent values of Q(10)(emission rate at (T+10)degreesC/emission rate at T degreesC) for the arable soil were about 50 for the 5-12 degreesC interval and 8.9 for 12-18 degreesC; the corresponding Q(10)s for the grassland soil were 3.7 and 2.3. Emissions from the grassland soil were always greater than those from the arable soil, although the ratio narrowed with increasing temperature. Changes in soil WFPS also had a profound effect on emissions. Those from the arable soil increased about 30-fold as the WFPS increased from 60 to 80\%, while that from the grassland soil increased 12-fold. This latter response was similar to earlier field measurements. The N2O emissions were considered to be produced primarily by denitrification. We concluded that the impacts of temperature and WFPS on emissions could both be explained on the basis of existing models relating increasing respiration or decreased oxygen diffusivity, or both, to the development of anaerobic zones within the soil.}, keywords = {nitrous-oxide emissions, modeling oxygen diffusion, aggregated soils, partial anaerobiosis, gas fluxes, denitrification, grassland, chambers, systems, budget}, ISSN = {1351-0754}, } @ARTICLE{Davidson2000, title = {Testing the hole-in-the-pipe model of nitric and nitrous oxide emissions from soils using the {TRAGNET} database}, author = {Davidson, E. A. and Verchot, L. V.}, journal = {Global Biogeochemical Cycles}, year = {2000}, volume = {14}, number = {4}, pages = {1035--1043}, month = dec, publisher = {Amer Geophysical Union, 2000 Florida Ave Nw, Washington, Dc 20009 USA}, abstract = {Because several soil properties and processes affect emissions of nitric oxide (NO) and nitrous oxide (N2O) from soils, it has been difficult to develop effective and robust algorithms to predict emissions of these gases in biogeochemical models. The conceptual "hole-in-the-pipe" (HIP) model has been used effectively to interpret results of numerous studies, but the ranges of climatic conditions and soil properties are often relatively narrow for each individual study. The Trace Gas Network (TRAGNET) database offers a unique opportunity to test the validity of one manifestation of the HIP model across a broad range of sites, including temperate and tropical climates, grasslands and forests, and native vegetation and agricultural crops. The logarithm of the sum of NO + N2O emissions was positively and significantly correlated with the logarithm of the sum of extractable soil NH,+ + NO3-. The logarithm of the ratio of NO:N2O emissions was negatively and significantly correlated with water-filled pore space (WFPS). These analyses confirm the applicability of the HIP model concept, that indices of soil N availability correlate with the sum of NO+N2O emissions, while soil water content is a strong and robust controller of the ratio of NO:N2O emissions. However, these parameterizations have only broad-brush accuracy because of unaccounted variation among studies in the soil depths where gas production occurs, where soil N and water are measured, and other factors. Although accurate predictions at individual sites may still require site-specific parameterization of these empirical functions, the parameterizations presented here, particularly the one for WFPS, may be appropriate for global biogeochemical modeling. Moreover, this integration of data sets demonstrates the broad ranging applicability of the HIP conceptual approach for understanding soil emissions of NO and N2O.}, keywords = {costa-rica, humid tropics, pasture, forest, n2o, denitrification, no, dynamics, water}, ISSN = {0886-6236}, } @ARTICLE{Kesik2005, title = {Inventories of {N$_2$O} and {NO} emissions from European forest soils}, author = {Kesik, M. and Ambus, P. and Baritz, R. and Bruggemann, N. B. and Butterbach-Bahl, K. and Damm, M. and Duyzer, J. and Horvath, L. and Kiese, R. and Kitzler, B. and Leip, A. and Li, C. and Pihlatie, M. and Pilegaard, K. and Seufert, G. and Simpson, D. and Skiba, U. and Smiatek, G. and Vesala, T. and Zechmeister-Boltenstern, S.}, journal = {Biogeosciences}, year = {2005}, volume = {2}, number = {4}, pages = {353--375}, publisher = {European Geosciences Union, Max-planck-str 13, 37191 Katlenburg-lindau, Germany}, abstract = {Forest soils are a significant source for the primary and secondary greenhouse gases N2O and NO. However, current estimates are still uncertain due to the still limited number of field measurements and the herein observed pronounced variability of N trace gas fluxes in space and time, which are due to the variation of environmental factors such as soil and vegetation properties or meteorological conditions. To overcome these problems we further developed a process-oriented model, the PnET-N-DNDC model, which simulates the N trace gas exchange on the basis of the processes involved in production, consumption and emission of N trace gases. This model was validated against field observations of N trace gas fluxes from 19 sites obtained within the EU project NOFRETETE, and shown to perform well for N2O (r(2) = 0.68, slope = 0.76) and NO (r(2) = 0.78, slope = 0.73). For the calculation of a European-wide emission inventory we linked the model to a detailed, regionally and temporally resolved database, comprising climatic properties (daily resolution), and soil parameters, and information on forest areas and types for the years 1990, 1995 and 2000. Our calculations show that N trace gas fluxes from forest soils may vary substantial from year to year and that distinct regional patterns can be observed. Our central estimate of NO emissions from forest soils in the EU amounts to 98.4, 84.9 and 99.2 kt N yr(-1) 1, using meteorology from 1990, 1995 and year 2000, respectively. This is < 1.0\% of pyrogenic NOx emissions. For N2O emissions the central estimates were 86.8, 77.6 and 81.6 kt N yr(-1), respectively, which is approx. 14.5\% of the source strength coming from agricultural soils. An extensive sensitivity analysis was conducted which showed a range in emissions from 44.4 to 254.0 kt N yr(-1) for NO and 50.7 to 96.9 kt N yr(-1) for N2O, for year 2000 meteorology.}, keywords = {nitrous-oxide emissions, trace gas fluxes, 3-year continuous record, process-oriented model, nitric-oxide, united-states, agricultural soils, saturated spruce, source strength, limed soil}, ISSN = {1726-4170}, } @ARTICLE{Saggar2007, title = {Modelling nitrous oxide emissions from grazed grasslands in New Zealand}, author = {Saggar, S. and Giltrap, D. L. and Li, C. and Tate, K. R.}, journal = {Agriculture Ecosystems \& Environment}, year = {2007}, volume = {119}, number = {1}, pages = {205--216}, month = feb, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {In sitit farm-scale measurements are a prerequisite for improving the accuracy of greenhouse gas inventories, and for developing and modifying the modelling approaches to quantify emissions. We describe here the changes made to the process-based model NZ- DNDC to allow us to simulate emissions of nitrous oxide (N2O) from typical New Zealand grazed grassland soils, and subsequent improvements to account for periodic changes in pasture growth, N input from animals, and water balance/soil moisture status. In grazed pastures, NO fluxes varied widely both spatially due to uneven excretal N inputs, and seasonally due to climatic conditions. The model was validated against field measurements from two dairy pastures with contrasting soils and from a sheep pasture. The model simulated effectively most of the soil water-filled pore-space (WFPS) and the general pulses and trends in NO emission from both the sheep- and dairy-grazed pastures, and also captured the observed effects of excretal and fertiliser N inputs. It also fairly reproduced the real variability in underlying processes regulating N2O emissions. A series of sensitivity tests conducted on NZ-DNDC showed the model predicted changes in pasture production and N2O emissions with changes in climate, soil properties, fertiliser management and grazing regimes. Pasture production was more sensitive to rainfall, temperature and initial soil carbon levels than to fertiliser additions, and stocking rate while NO emissions were strongly sensitive to rainfall, quantity and frequency of N inputs through both fertiliser and increased stocking rate, and initial soil carbon levels. (c) 2006 Elsevier B.V. All rights reserved.}, keywords = {rainfall events, n2o emissions, soil driven, pastures, management, phosphorus, evolution, sulfur, fate, excretal and fertiliser n inputs, dairy and sheep-grazed pastures, tpcc methodology, new zealand modified dndc, nitrous oxide emissions, temperate grasslands}, ISSN = {0167-8809}, } @ARTICLE{Dobbie2003, title = {Nitrous oxide emission factors for agricultural soils in Great Britain: the impact of soil water-filled pore space and other controlling variables}, author = {Dobbie, K. E. and Smith, K. A.}, journal = {Global Change Biology}, year = {2003}, volume = {9}, number = {2}, pages = {204--218}, month = feb, publisher = {Blackwell Publishing Ltd, 9600 Garsington Rd, Oxford Ox4 2dg, Oxon, England}, abstract = {Measurements were made of nitrous oxide (N-2 O) emissions from N-fertilised ungrazed grassland and arable land at sites widely distributed across Great Britain during 1999-2001. The closed static chamber method was used throughout. Emissions varied widely throughout the year at each site, and between sites. Daily fluxes up to 1200 g N-2 O-N ha (- 1) d (- 1) were recorded. The highest annual flux was 27.6 kg N-2 O-N ha (- 1) at a grassland site in Wales, whereas the lowest, 1.7 kg N-2 O-N ha (- 1) , occurred on a soil overlying chalk in southern England. The key factors affecting N-2 O emissions from agricultural soil were soil WFPS, temperature and soil NO3 (-) -N content. On grassland, rainfall (particularly around the time of N application), with its consequent effect on water- filled pore space (WFPS), was the main driving factor during the growing season. Annual emission factors (EFs), uncorrected for background emission, varied from 0.4 to 6.5\% of the nitrogen (N) applied, covering a similar range for grassland to that found previously for sites restricted to Scotland. Continued monitoring at a grassland reference site near Edinburgh showed that annual EFs vary greatly from year to year, even with similar management, and that several years' data are required to produce a robust mean EF. The overall distribution of EFs in this and previous studies was log- normal. The EFs for small-grain cereals (and oilseed rape) peaked at a much lower value than those for grassland, whereas the values for leafy vegetables and potato crops fitted well into the grassland distribution. These differences in EF between various types of crop should be taken into account when compiling regional or national N-2 O emission inventories.}, keywords = {global n2o budget, fertilizer application, n-fertilization, gas fluxes, grassland, denitrification, netherlands, temperature, evolution, rainfall, crops, emission factor, nitrous oxide, pore space, soils, water}, ISSN = {1354-1013}, } @ARTICLE{Chatskikh2005, title = {Simulation of effects of soils, climate and management on {N$_2$O} emission from grasslands}, author = {Chatskikh, D. and Olesen, J. and Berntsen, J. and Regina, K. and Yamulki, S.}, journal = {Biogeochemistry}, year = {2005}, volume = {76}, number = {3}, pages = {395--419}, month = dec, publisher = {Springer, Van Godewijckstraat 30, 3311 Gz Dordrecht, Netherlands}, abstract = {Nitrous oxide (N2O) is a potent greenhouse gas with a high contribution from agricultural soils and emissions that depend on soil type, climate, crops and management practices. The N2O emissions therefore need to be included as an integral part of environmental assessments of agricultural production systems. An algorithm for N2O production and emission from agricultural soils was developed and included in the FASSET whole-farm model. The model simulated carbon and nitrogen (N) turnover on a daily basis. Both nitrification and denitrification was included in the model as sources for N2O production, and the N2O emissions depended on soil microbial and physical conditions. The model was tested on experimental data of N2O emissions from grasslands in UK, Finland and Denmark, differing in climatic conditions, soil properties and management. The model simulated the general time course of N2O emissions and captured the observed effects of fertiliser and manure management on emissions. Scenario analyses for grazed and cut grasslands were conducted to evaluate the effects of soil texture, climatic conditions, grassland management and N fertilisation on N2O emissions. The soils varied from coarse sand to sandy loam and the climatic variation was taken to represent the climatic variation within Denmark. N fertiliser rates were varied from 0 to 500 kg N ha(-1). The simulated N2O emissions showed a non-linear response to increasing N rates with increasing emission factors at higher N rates. The simulated emissions increased with increasing soil clay contents. N2O emissions were slightly increased at higher temperatures, whereas increasing annual rainfall generally lead to decreasing emissions. Emissions were slightly higher from grazed grasslands compared with cut grasslands at similar rates of total N input (fertiliser and animal excreta). The results indicate higher emission factors and thus higher potentials for reducing N2O emissions for intensively grazed grasslands on fine textured soils than for extensive cut-based grasslands on sandy soils.}, keywords = {nitrous-oxide emissions, loamy sand soils, organic-matter, forest soils, agricultural soils, generalized-model, gas emissions, water-content, field-scale, term carbon, climate, grassland, greenhouse gas emissions, management, model, n2o, nitrous oxide, soil}, ISSN = {0168-2563}, } @ARTICLE{Schmidt2000, title = {Using a boundary line approach to analyze {N$_2$O} flux data from agricultural soils}, author = {Schmidt, U. and Thoni, H. and Kaupenjohann, M.}, journal = {Nutrient Cycling in Agroecosystems}, year = {2000}, volume = {57}, number = {2}, pages = {119--129}, month = jun, publisher = {Kluwer Academic Publ, Spuiboulevard 50, Po Box 17, 3300 Aa Dordrecht, Netherlands}, abstract = {Predicting the N2O flux from soils is difficult because of the complex interplay of the various processes involved. In this study a boundary line approach was used to apply results from mechanistic experiments to N2O flux data resulting from measurements on field scale in southern Germany. Boundary lines were fitted to the rim of the data points in scattergrams depicting readily obtainable soil variables against the measured N2O flux. The boundary Line approach is based on the hypothesis that this line depicts the functional dependency between the two variables. For determining these boundary lines a novel method was applied. The function best representing the relationship between the N2O flux and soil temperature had a maximum above 23 degrees C and the one between the N2O flux and the water filled pore space (WFPS, to represent water content) had a maximum at 72\% WFPS. In the range of 0-20 mg N kg(-1) the relationship between N2O flux and nitrate in the soil was best described by a linear function, whereas in the range of 0-35 mg N kg(-1) a Michaelis-Menten function was more appropriate. The boundary lines specified in this study are in agreement with existing theoretical concepts as well as experimental results obtained under controlled and field conditions as reported in the literature. Therefore, the boundary line approach can be used to improve empirical models for predicting the N2O flux in the field.}, keywords = {nitrous-oxide emissions, empirical-model, denitrification, nitrate, temperature, prediction, moisture, losses, system, oxygen, boundary line, field measurement, model, n2o flux}, ISSN = {1385-1314}, } @ARTICLE{Oorts2007, title = {Determinants of annual fluxes of {CO$_2$} and {N$_2$O} in long-term no-tillage and conventional tillage systems in northern France}, author = {Oorts, K. and Merckx, R. and Grehan, E. and Labreuche, J. and Nicolardot, B.}, journal = {Soil \& Tillage Research}, year = {2007}, volume = {95}, number = {1}, pages = {133--148}, month = sep, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {The greenhouse gases CO2 and N2O emissions were quantified in a long- term experiment in northern France, in which no-till (NT) and conventional tillage (CT) had been differentiated during 32 years in plots under a maize-wheat rotation. Continuous CO2 and periodical N2O soil emission measurements were performed during two periods: under maize cultivation (April 2003-July 2003) and during the fallow period after wheat harvest (August 2003-March 2004). In order to document the dynamics and importance of these emissions, soil organic C and mineral N, residue decomposition, soil potential for CO2 emission and climatic data were measured. CO2 emissions were significantly larger in NT on 53\% and in CT on 6\% of the days. From April to July 2003 and from November 2003 to March 2004, the cumulated CO2 emissions did not differ significantly between CT and NT. However, the cumulated CO2 emissions from August to November 2003 were considerably larger for NT than for CT. Over the entire 331 days of measurement, CT and NT emitted 3160 +/- 269 and 4064 +/- 138 kg CO2-C ha(-1) respectively. The differences in CO2 emissions in the two tillage systems resulted from the soil climatic conditions and the amounts and location of crop residues and SOM. A large proportion of the CO2 emissions in NTover the entire measurement period was probably due to the decomposition of old weathered residues. NT tended to emit more N2O than CTover the entire measurement period. However differences were statistically significant in only half of the cases due to important variability. N2O emissions were generally less than 5 g N ha(-1) day(-1), except for a few dates where emission increased up to 21 g N ha(-1) day(-1). These N2O fluxes represented 0.80 +/- 0.15 and 1.32 +/- 0.52 kg N2O-N ba(-1) year(-1) for CT and NT, respectively. Depending on the periods, a large part of the N2O emissions occurred was probably induced by nitrification, since soil conditions were not favorable for denitrification. Finally, for the period of measurement after 32 years of tillage treatments, the NT system emitted more greenhouses gases (CO2 and N2O) to the atmosphere on an annual basis than the CT system. (C) 2006 Elsevier B.V. All rights reserved.}, keywords = {nitrous-oxide emissions, carbon-dioxide fluxes, soil organic-matter, new-zealand, bare soil, management, rotations, evolution, dynamics, storage, soil tillage, co2 emission, n2o emission, effect of climatic conditions, crop residues, soil organic matter}, ISSN = {0167-1987}, } @ARTICLE{Granli1995, title = {Nitrous oxide ({N$_2$O}) emissions from soils in warm climates}, author = {Granli, T. and Bockman, O. C.}, journal = {Fertilizer Research}, year = {1995}, volume = {42}, number = {1}, pages = {159--163}, publisher = {Kluwer Academic Publ, Spuiboulevard 50, Po Box 17, 3300 Aa Dordrecht, Netherlands}, abstract = {N2O emission rates seem to be higher from soils in warm climates than from soils in temperate climates. Warm and moist conditions promote microbial processes that generate N2O. Clearance of tropical forests enhances N2O formation, but emission measurements from other agricultural operations in the tropics are few. Limiting fertilizer application to recommended rates applied at appropriate times and avoiding fallow land wherever practical serves to limit N2O emissions. More specific advice for agriculture in warm climates requires further studies.}, keywords = {tropical deforestation, atmosphere, forest, fluxes, ch4, nitrous oxide, tropical soils, agriculture, n availability, temperature, soil water content}, ISSN = {0167-1731}, } @ARTICLE{Liu2007, title = {Dinitrogen and {N$_2$O} emissions in arable soils: Effect of tillage, {N} source and soil moisture}, author = {Liu, X. J. J. and Mosier, A. R. and Halvorson, A. D. and Reule, C. A. and Zhang, F. S.}, journal = {Soil Biology \& Biochemistry}, year = {2007}, volume = {39}, number = {9}, pages = {2362--2370}, month = sep, publisher = {Pergamon-elsevier Science Ltd, the Boulevard, Langford Lane, Kidlington, Oxford Ox5 1gb, England}, abstract = {A laboratory investigation was performed to compare the fluxes of dinitrogen (N-2), N2O and carbon dioxide (CO2) from no-till (NT) and conventional till (CT) soils under the same water, mineral nitrogen and temperature status. Intact soil cores (0-10 cm) were incubated for 2 weeks at 25 degrees C at either 75\% or 60\% water-filled pore space (WFPS) with N-15-labeled fertilizers (100 mg N kg(-1) soil). Gas and soil samples were collected at 1-4 day intervals during the incubation period. The N2O and CO2 fluxes were measured by a gas chromatography (GC) system while total N-2 and N2O losses and their N-15 mole fractions in the soil mineral N pool were determined by a mass spectrometer. The daily accumulative fluxes of N-2 and N2O were significantly affected by tillage, N source and soil moisture. We observed higher (P < 0.05) fluxes of N-2+N2O, N2O and CO2 from the NT soils than from the CT soils. Compared with the addition of nitrate (NOD, the addition of ammonium (NH4+) enhanced the emissions of these N and C gases in the CT and NT soils, but the effect of NH4+ on the N-2 and/or N2O fluxes was evident only at 60\% WFPS, indicating that nitrification and subsequent denitrification contributed largely to the gaseous N losses and N2O emission under the lower moisture condition. Total and fertilizer-induced emissions of N-2 and/or N2O were higher (P < 0.05) at 75\% WFPS than with 60\% WFPS, while CO2 fluxes were not influenced by the two moisture levels. These laboratory results indicate that there is greater potential for N2O loss from NT soils than CT soils. Avoiding wet soil conditions (> 60\% WFPS) and applying a NO3 form of N fertilizer would reduce potential N2O emissions from arable soils. (c) 2007 Elsevier Ltd. All rights reserved.}, keywords = {nitrous-oxide emissions, filled pore-space, northeastern colorado, mass-spectrometry, cropping systems, long-term, denitrification, nitrification, field, fluxes, no-till, wfps, (sn)-s-15-labeled fertilizer, denitrification, nitrification, nitrous oxide emission}, ISSN = {0038-0717}, } @ARTICLE{Castaldi2000, title = {Responses of nitrous oxide, dinitrogen and carbon dioxide production and oxygen consumption to temperature in forest and agricultural light-textured soils determined by model experiment}, author = {Castaldi, S.}, journal = {Biology and Fertility of Soils}, year = {2000}, volume = {32}, number = {1}, pages = {67--72}, month = oct, publisher = {Springer-verlag, 175 Fifth Ave, New York, Ny 10010 USA}, abstract = {The experiment, carried out on a forest and arable light-textured soil, was designed to study the temperature response of autotrophic and heterotrophic N2O production and investigate how the N2O flux relates to soil respiration and O-2 consumption. Although N2O production seemed to be stimulated by a temperature increase in both soils, the relationship between production rate and temperature was different in the two soils. This seemed to depend on the different contribution of nitrification and denitrification to the overall N2O flux. In the forest soil, almost all N2O was derived from nitrification, and its production rate rose linearly from 2 degreesC to 40 degreesC. A stronger effect of temperature on N2O production was observed in the arable soil, apparently as a result of an incremental contribution of denitrification to the overall N2O flux with rising temperature. The soil respiration rate increased exponentially with temperature and was significantly correlated with N2O production. O-2 consumption stimulated denitrification in both soils. In the arable soil, N2O and N-2 production increased exponentially with decreasing O-2 concentration, though N2O was the main gas produced at any temperature. In the forest soil, only the N-2 flux was related exponentially to O-2 consumption and it outweighed the rate of N2O production only at >34 degreesC. Thus, it appears that in the forest soil, where nitrification was the main source of N2O, temperature affected the N2O flux less dramatically than in the arable soil, where a temperature increase strongly stimulated N2O production by enhancing favourable conditions for denitrification.}, keywords = {denitrification, inhibition, acetylene, zones, denitrification, nitrification, nitrous oxide, respiration, temperature}, ISSN = {0178-2762}, } @ARTICLE{Smith1997, title = {The potential for feedback effects induced by global warming on emissions of nitrous oxide by soils}, author = {Smith, K. A.}, journal = {Global Change Biology}, year = {1997}, volume = {3}, number = {4}, pages = {327--338}, month = aug, publisher = {Blackwell Science Ltd, P O Box 88, Osney Mead, Oxford, Oxon, England Ox2 0ne}, abstract = {About 65\% of all emissions of nitrous oxide, N2O, are from soils, and are caused by aerobic nitrification and anaerobic denitrification. Tropical forest soils are probably the most important single source, followed by cultivated soils. Emission rates in natural systems are related to the rate of N mineralization from organic matter, and N deposition; in agricultural systems they are related to the quantities of N used as fertilizers and, where relevant, to recent land use change. The global budget for N2O is not well balanced, and sources may still be underestimated. Direct evidence of a positive feedback of global warming on N2O emissions comes from studies of air in ice cores. One of the projected effects of future global warming is a lowering of water tables in northern peatlands; experiments suggest that this would lead to increased emissions, but that the effect on total emissions would be small. The results of many experiments with non- peatland soils indicate that the effect of temperature on soil emissions is generally positive, and that the rate of increase may be very steep when denitrification is the principal process involved. process-level modelling suggests that the reason is increased soil respiration, which causes an increase in anaerobic volume in which denitrification can take place, in addition to the increased denitrification rate per unit anaerobic volume brought about directly by the rise in temperature. These results imply that generally a positive feedback on emissions from soils is likely. However, in some environments, a large proportion of total annual emissions can occur during freeze-thaw cycles; such cycles may become more or less frequent, depending on the climatic zone, and this may result in either a positive or negative feedback effect due to global warming. Models of global and regional trends give very conflicting predictions of the direction and the magnitude of climatic impacts on fluxes, but the prediction of a positive feedback seems to be the more soundly based.}, keywords = {aggregated soils, partial anaerobiosis, rainfall events, carbon- dioxide, arable soils, water-table, ice core, denitrification, model, fluxes, denitrification, feedback, global warming, nitrification, nitrous oxide, soil, temperature}, ISSN = {1354-1013}, } @ARTICLE{Bateman2005, title = {Contributions of nitrification and denitrification to {N$_2$O} emissions from soils at different water-filled pore space}, author = {Bateman, E. J. and Baggs, E. M.}, journal = {Biology and Fertility of Soils}, year = {2005}, volume = {41}, number = {6}, pages = {379--388}, month = aug, publisher = {Springer, 233 Spring Street, New York, Ny 10013 USA}, abstract = {A combination of stable isotope and acetylene (0.01\% v/v) inhibition techniques were used for the first time to determine N2O production during denitrification, autotrophic nitrification and heterotrophic nitrification in a fertilised (200 kg N ha(-1)) silt loam soil at contrasting (20-70\%) water-filled pore space (WFPS). N-15-N2O emissions from (NH4NO3)-N-14-N-15 replicates were attributed to denitrification and N-15-N2O from (NH4NO3)-N-15-N-15 minus that from (NH4NO3)-N-14-N-15 replicates was attributed to nitrification and heterotrophic nitrification in the presence of acetylene, as there was no dissimilatory nitrate reduction to ammonium or immobilisation and remineralisation of N-15-NO3-. All of the N2O emitted at 70\% WFPS (31.6 mg N2O-N m(-2) over 24 days; 1.12 mu g N2O-N g dry soil(-1); 0.16\% of N applied) was produced during denitrification, but at 35-60\% WFPS nitrification was the main process producing N2O, accounting for 81\% of N-15-N2O emitted at 60\% WFPS, and 7.9 mu g N-15-N2O m(-2) (0.28 ng N-15-N2O g dry soil(-1)) was estimated to be emitted over 7 days during heterotrophic nitrification in the 50\% WFPS treatment and accounted for 20\% of N-15-N2O from this treatment. Denitrification was the predominant N2O-producing process at 20\% WFPS (2.6 mu g N-15-N2O m(-2) over 7 days; 0.09 ng N-15-N2O g dry soil(-1); 85\% of (15)pN-N2O from this treatment) and may have been due to the occurrence of aerobic denitrification at this WFPS. Our results demonstrate the usefulness of a combined stable isotope and acetylene approach to quantify N2O emissions from different processes and to show that several processes may contribute to N2O emission from agricultural soils depending on soil WFPS.}, keywords = {nitrous-oxide emissions, heterotrophic nitrification, nitrifier denitrification, nitrosomonas-europaea, alcaligenes-faecalis, nitrifying bacteria, agricultural soils, aggregated soils, pool dilution, no, denitrification, nitrification, nitrous oxide, soil water-filled pore space}, ISSN = {0178-2762}, } @ARTICLE{DelGrosso2000, title = {General model for {N$_2$O} and {N$_2$} gas emissions from soils due to dentrification}, author = {Del Grosso, S. J. and Parton, W. J. and Mosier, A. R. and Ojima, D. S. and Kulmala, A. E. and Phongpan, S.}, journal = {Global Biogeochemical Cycles}, year = {2000}, volume = {14}, number = {4}, pages = {1045--1060}, month = dec, publisher = {Amer Geophysical Union, 2000 Florida Ave Nw, Washington, Dc 20009 USA}, abstract = {Observations of N gas loss from incubations of intact and disturbed soil cores were used to model N2O and N-2 emissions from soil as a result of denitrification. The model assumes that denitrification rates are controlled by the availability in soil of NO3 (e(-) acceptor), labile C compounds (e(-) donor), and O-2 (competing e(-) acceptor). Heterotrophic soil respiration is used as a proxy for labile C availability while O-2 availability is a function of soil physical properties that influence gas diffusivity, soil WFPS, and O-2 demand. The potential for O-2 demand, as indicated by respiration rates, to contribute to soil anoxia varies inversely with a soil gas diffusivity coefficient which is regulated by soil porosity and pore size distribution. Model inputs include soil heterotrophic respiration rate, texture, NO3 concentration, and WFPS. The model selects the minimum of the NO3 and CO2 functions to establish a maximum potential denitrification rate for particular levels of e(-) acceptor and C substrate and accounts for limitation of O-2 availability to estimate daily N-2+N2O flux rates. The ratio of soil NO3 concentration to CO2 emission was found to reliably (r(2)=0.5) model the ratio of N-2 to N2O gases emitted from the intact cores after accounting for differences in gas diffusivity among the soils. The output of the ratio function is combined with the estimate of total N gas flux rate to infer N2O emission. The model performed well when comparing observed and simulated values of N2O flux rates with the data used for model building (r(2)=0.50) and when comparing observed and simulated N2O+N-2 gas emission rates from irrigated field soils used for model testing (r(2)=0.47).}, keywords = {nitrous-oxide emissions, shortgrass steppe, water content, denitrification, carbon, mineralization, nitrification, grassland, rates}, ISSN = {0886-6236}, } @ARTICLE{Parton2001, title = {Generalized model for {NO$_x$} and {N$_2$O} emissions from soils}, author = {Parton, W. J. and Holland, E. A. and Del Grosso, S. J. and Hartman, M. D. and Martin, R. E. and Mosier, A. R. and Ojima, D. S. and Schimel, D. S.}, journal = {Journal of Geophysical Research-atmospheres}, year = {2001}, volume = {106}, number = {15}, pages = {17403--17419}, month = aug, publisher = {Amer Geophysical Union, 2000 Florida Ave Nw, Washington, Dc 20009 USA}, abstract = {We describe a submodel to simulate NOx and N2O emissions from soils and present comparisons of simulated NOx and N2O fluxes from the DAYCENT ecosystem model with observations from different soils. The N gas flux submodel assumes that nitrification and denitrification both contribute to N2O and NOx emissions but that NOx emissions are due mainly to nitrification. N2O emissions from nitrification are calculated as a function of modeled soil NH4+ concentration, water-filled pore space (WFPS), temperature, pH, and texture. N2O emissions from denitrification are a function of soil NO3- concentration, WFPS, heterotrophic respiration, and texture. NOx emissions are calculated by multiplying total N2O emissions by a NOx:N2O equation which is calculated as a function of soil parameters (bulk density, field capacity, and WFPS) that influence gas diffusivity. The NOx submodel also simulates NOx emission pulses initiated by rain events onto dry soils. The DAYCENT model was tested by comparing observed and simulated parameters in grassland soils across a range of soil textures and fertility levels. Simulated values of soil temperature, WFPS (during the non-winter months), and NOx gas flux agreed reasonably well with measured values (r(2) = 0.79, 0.64, and 0.43, respectively). Winter season WFPS was poorly simulated (r(2) = 0.27). Although the correlation between simulated and observed N2O flux was poor on a daily basis (r(2)=0.02), DAYCENT was able to reproduce soil textural and treatment differences and the observed seasonal patterns of gas flux emissions with r(2) values of 0.26 and 0.27, for monthly and NOx flux rates, respectively.}, keywords = {colorado shortgrass steppe, nitrogen-oxide emissions, 3-year continuous record, beech forest ecosystem, trace-gas emissions, n-saturated spruce, land-use change, nitric-oxide, biogeochemical controls, tropospheric ozone}, ISSN = {0747-7309}, } @ARTICLE{Parton1996, title = {Generalized model for {N$_2$} and {N$_2$O} production from nitrification and denitrification}, author = {Parton, W. J. and Mosier, A. R. and Ojima, D. S. and Valentine, D. W. and Schimel, D. S. and Weier, K. and Kulmala, A. E.}, journal = {Global Biogeochemical Cycles}, year = {1996}, volume = {10}, number = {3}, pages = {401--412}, month = sep, publisher = {Amer Geophysical Union, 2000 Florida Ave Nw, Washington, Dc 20009}, abstract = {We describe a model of N-2 and N2O gas fluxes from nitrification and denitrification. The model was developed using laboratory denitrification gas flux data and field-observed N2O gas fluxes from different sites. Controls over nitrification N2O gas fluxes are soil texture, soil NH4, soil water-filled pore space, soil N turnover rate, soil pH, and soil temperature. Observed data suggest that nitrification N2O gas fluxes are proportional to soil N turnover and that soil NH4 levels only impact N2O gas fluxes with high levels of soil NH4 (>3 mu g N g(-1)). Total denitrification (N-2 plus N2O) gas fluxes are a function of soil heterotrophic respiration rates, soil NO3, soil water content, and soil texture. N-2:N2O ratio is a function of soil water content, soil NO3, and soil heterotrophic respiration rates. The denitrification model was developed using laboratory data [Weier et al., 1993] where soil water content, soil NO3, and soil C availability were varied using a full factorial design. The Weier's model simulated observed N-2 and N2O gas fluxes for different soils quite well with r(2) equal to 0.62 and 0.75, respectively. Comparison of simulated model results with field N2O data for several validation sites shows that the model results compare well with the observed data (r(2)=0.62). Winter denitrification events were poorly simulated by the model. This problem could have been caused by spatial and temporal variations in the observed soil water data and N2O fluxes. The model results and observed data suggest that approximately 14\% of the N2O fluxes for a shortgrass steppe are a result of denitrification and that this percentage ranged from 0\% to 59\% for different sites.}, keywords = {soil, oxide, nitrogen, simulation, grasslands, ammonium, moisture, methane, water}, ISSN = {0886-6236}, } @ARTICLE{Smith1998, title = {Effects of temperature, water content and nitrogen fertilisation on emissions of nitrous oxide by soils}, author = {Smith, K. A. and Thomson, P. E. and Clayton, H. and McTaggart, I. P. and Conen, F.}, journal = {Atmospheric Environment}, year = {1998}, volume = {32}, number = {19}, pages = {3301--3309}, month = oct, publisher = {Pergamon-elsevier Science Ltd, the Boulevard, Langford Lane, Kidlington, Oxford Ox5 1gb, England}, abstract = {Nitrous oxide emissions were measured from several grassland and arable soils in the field, and from two of these soils and a forest soil transferred in large monoliths to a greenhouse. The effects of fertiliser N additions and of soil water content and temperature were investigated. Emissions were in the order grazed grassland > grassland cut for conservation > potatoes > cereal crops, and generally were higher than those from temperate natural ecosystems. Based on these data, agricultural soils constitute the major soil source of N2O in the Y.K. The highest emission recorded was 8 kg N2O-N ha(-1) over 10 months, from a grazed grassland site. Emissions varied from year to year, depending particularly on rainfall at the time of fertilisation. When soil mineral N was not limiting, exponential relationships between N2O Aux and both water-filled pore space (WFPS) and temperature were observed. The Q(10) value for a sandy loam was 1.6, but ranged up to 12 for a clay loam soil at high WFPS. The high values were attributed to the increase in anaerobic zones where denitrification could take place, as respiratory demand for O-2 increased. A forest soil(peaty gley) showed an optimum water potential for N2O emission. Diurnal fluctuations in emissions were associated with diurnal cycles in soil temperature, but with varying time lags, which could be explained by the N2O being produced at different depths. (C) 1998 Elsevier Science Ltd. All rights reserved.}, keywords = {denitrification, anaerobiosis, fluxes, flux chamber, gas analysis, greenhouse effect, nitrous oxide, ozone layer, soil}, ISSN = {1352-2310}, } @ARTICLE{Muller1997, title = {Mechanistic model for nitrous oxide emission via nitrification and denitrification}, author = {Muller, C. and Sherlock, R. R. and Williams, P. H.}, journal = {Biology and Fertility of Soils}, year = {1997}, volume = {24}, number = {2}, pages = {231--238}, month = feb, publisher = {Springer Verlag, 175 Fifth Ave, New York, Ny 10010}, abstract = {Seasonal and annual N2O fluxes from urine-affected pasture were approximated with a mechanistic model based on Michaelis-Menten kinetics. The model combined the effects of soil nitrate-N, soil ammonium-N, soil temperature and soil moisture (all from the top 5 cm) to calculate N2O emissions from nitrification (F-nit) and denitrification (F-den), with total N2O emission being the sum Of the two (F-tot=F-nit+F-den), Best results were obtained when different kinetic parameters were used for periods of constant soil moisture conditions and after heavy rainfalls when a rapid change of the soil moisture status occurred. Modelled N2O emissions over a year were within the range of uncertainties of measured N2O emissions. Results indicate that the spatial variability of N2O emissions at times when all the model inupt variables were constant may be related to microorganism growth dynamics or enzyme production rates.}, keywords = {transient microsite models, soil, evolution, nitrate, rates, ph, temperature, fertilizer, n2o, mechanistic model, nitrification, denitrification, michaelis-menten kinetics, grassland, spatial variability}, ISSN = {0178-2762}, } @ARTICLE{Regina2004, title = {Fluxes of {N$_2$O} from farmed peat soils in Finland}, author = {Regina, K. and Syvasalo, E. and Hannukkala, A. and Esala, M.}, journal = {European Journal of Soil Science}, year = {2004}, volume = {55}, number = {3}, pages = {591--599}, month = sep, publisher = {Blackwell Publishing Ltd, 9600 Garsington Rd, Oxford Ox4 2dg, Oxon, England}, abstract = {Agricultural peat soils are important sources of nitrous oxide (N2O). Emissions of N2O were measured from field plots of grass, barley, potatoes and fallow on a peat field in northern Finland during 2000-2002 and in southern Finland in 1999-2002. In the north the mean annual fluxes of N2O (with their standard errors) during 2 years were 4.0 (+/-1.2), 13 (+/-3.0) and 4.4 (+/-0.8) kg N ha(-1) from the plots of grass, barley and fallow, respectively. In the north there were no significant thaw periods in the middle of winter. As a result, the thawing in the spring did not induce especially large N2O emissions. Emissions of N2O were larger in the south than in the north. In the southern peat field the mean annual fluxes during 3 years were 7.3 (+/-1.2), 15 (+/-2.6), 10 (+/-1.9) and 25 (+/-6.9) kg N2O-N ha(-1) for grass, barley, potato and fallow plots, respectively. Here, the largest single episodes of emission occurred during the spring thaw each year, following winter thaw events. An emission factor of 10.4 kg N2O-N ha(-1) year(-1) for the N2O emission from the decomposition of the peat results from these data if the effect of fertilization according to the IPCC default emission factor is omitted. The direct effect of adding N as fertilizer on N2O emissions was of minor importance. On average, 52\% of the annual N2O flux entered the atmosphere outside the cropping season (October- April) in the north and 55\% in the south. The larger N2O fluxes from the peat soil in the south might be due to the more humified status of the peat, more rapid mineralization and weather with more cycles of freezing and thawing in the winter.}, keywords = {nitrous-oxide emissions, greenhouse-gas emissions, organic soils, freeze-thaw, ch4, agriculture, grassland, crops, co2}, ISSN = {1351-0754}, } @ARTICLE{Parry1999, title = {Denitrification in pasture and cropped soil clods as affected by pore space structure}, author = {Parry, S. and Renault, P. and Chenu, C. and Lensi, R.}, journal = {Soil Biology \& Biochemistry}, year = {1999}, volume = {31}, number = {4}, pages = {493--501}, month = apr, publisher = {Pergamon-elsevier Science Ltd, the Boulevard, Langford Lane, Kidlington, Oxford Ox5 1gb, England}, abstract = {To assess the influence of the pore space structure and organic matter on denitrification, a comparative study was performed on clods in a soil under cropped and pasture managements. For each management, the potential denitrification rate was estimated. Denitrification under oxic conditions was also measured on 100 clods, which were saturated with KNO3 solution (4 g l(-1)). Size and density fractions of the soil were separated, and the C and N contents of their particulate organic matter were determined. Clod porosities were measured and the distributions of distances of any point within the clod to the nearest air- filled pore were estimated on 20 thin sections for each soil management. Potential denitrification rates were similar (105 x 10(-11) and 98 x 10(-11) mol N2O kg(-1) dry soil s(-1) for pasture and cropped soil, respectively). The mean denitrification rate under oxic conditions was only equal to 0.14\% of the potential denitrification rate for pasture, whereas it was about 2.1\% for cropped soil. The total and soluble organic C content was significantly higher in pasture than in cropped soil clods. The quantity or the quality of organic matter fractions did not explain the difference in denitrification activities. Even if macroporosity represented a small fraction of the total porosity in both soils, the differences in macropore distribution induced by soil management practices led to significantly different maximal distances between any clod point and the nearest air-filled pore (8 and 14 mm for pasture and cropped soils, respectively). Consequently, we demonstrated that the pore space structure appears to be the major factor explaining the difference in mean denitrification rates between pasture and cropped soil clods, while the distribution of particulate organic matter is suspected to be involved in the differences in denitrifying activity distribution between the clods of the two soils. (C) 1999 Elsevier Science Ltd. All rights reserved.}, keywords = {organic-matter, cultivated soils, size fractions, rates, anaerobiosis, grassland, porosity, profiles, density}, ISSN = {0038-0717}, } @ARTICLE{Parry2000, title = {Particulate organic matter as a source of variation in denitrification in clods of soil}, author = {Parry, S. and Renault, P. and Chadoeuf, J. and Chenu, C. and Lensi, R.}, journal = {European Journal of Soil Science}, year = {2000}, volume = {51}, number = {2}, pages = {271--281}, month = jun, publisher = {Blackwell Science Ltd, P O Box 88, Osney Mead, Oxford Ox2 0ne, Oxon, England}, abstract = {Existing mechanistic models of denitrification in clods of soil describe the anaerobic activity in the centres of the clods, but they neglect the role of particulate organic materials. We therefore studied the effect of particulate organic matter on denitrification in soil both under pasture and in arable cultivation. Clods were separated into two compartments: (i) particulate organic matter and adhering soil exceeding 200 mu m (coated POM), and (ii) the matrix (the rest of the soil). Potential denitrification and production of CO2 were then estimated on coated POM, matrix and unfractionated soil. The quantity and the quality of coated POM were assessed individually in 100 clods from the pasture and 100 from the arable land. The rate of potential denitrification was similar in unfractionated soil from these treatments. However, it was 70 times greater in the coated POM than in the matrix from the arable soil. Production of CO2 was nine times greater in the coated POM than in the matrix from the pasture soil and 33 times greater in the arable soils. These observations were the basis for a mechanistic model of denitrification, taking into account contributions from coated POM and the matrix. Denitrification rates in a computerized representation of clods from both pasture and arable soil had approximately the same distribution as experimental data both in the matrix and coated POM contributions in the cropped soil and in the matrix alone in the pasture soil. Coated particulate organic matter can explain more than half of the denitrification and most of the variation in denitrification when it increases microbial activity sufficiently and the soil structure limits the supply of O-2.}, keywords = {aggregated soils, rates, anaerobiosis, dynamics, bacteria, location, pasture}, ISSN = {1351-0754}, } @ARTICLE{Dambreville2008, title = {{N$_2$O} emission in maize-crops fertilized with pig slurry, matured pig manure or ammonium nitrate in {Brittany}}, author = {Dambreville, C. and Morvan, T. and Germon, J. C.}, journal = {Agriculture Ecosystems \& Environment}, year = {2008}, volume = {123}, number = {1}, pages = {201--210}, month = jan, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {N2O is a potent greenhouse gas and solutions have to be sought to reduce its emission from agriculture. This work evaluates N2O emission from maize-crop (Zea mays) fields submitted to different organic or mineral fertilizers (pig slurry, matured pig manure or ammonium nitrate) in Brittany (France). N2O emission was evaluated along a year in two experimental sites receiving 110 or 180 kg N ha(-1) as ammonium nitrate or pig slurry and 180 or 132 kg N ha(-1) as ammonium nitrate or matured pig manure at Champ Noel and Le Rheu experimental plots, respectively. N2O emission was evaluated by interpolation method of periodic fluxes on the field scale and by simulation with NOE algorithm using measured soil characteristics such as N content and gravimetric moisture and other soil biological properties determined in a previous study (potential denitrifying activity, N2O/[N2O + N-2] ratio during denitrification) or drawn from literature.}, keywords = {nitrous-oxide emissions, greenhouse-gas emissions, n fertilizer, grassland soil, end-products, hot-spots, denitrification, nitrification, fluxes, carbon, soil, organic fertilizer, ammonium nitrate, denitritication, n2o emission, simulation}, ISSN = {0167-8809}, } @Article{Vieten2008, AUTHOR = {Vieten, B. and Conen, F. and Seth, B. and Alewell, C.}, TITLE = {The fate of N$_{2}$O consumed in soils}, JOURNAL = {Biogeosciences}, VOLUME = {5}, YEAR = {2008}, NUMBER = {1}, PAGES = {129--132}, URL = {http://www.biogeosciences.net/5/129/2008/}, ISSN = {1726-4170} } @ARTICLE{Kesik2006, title = {Future scenarios of {N$_2$O} and {NO} emissions from European forest soils}, author = {Kesik, M. and Bruggemann, N. and Forkel, R. and Kiese, R. and Knoche, R. and Li, C. S. and Seufert, G. and Simpson, D. and Butterbach-Bahl, K.}, journal = {Journal of Geophysical Research-biogeosciences}, year = {2006}, volume = {111}, number = {2}, publisher = {Amer Geophysical Union, 2000 Florida Ave Nw, Washington, Dc 20009 USA}, abstract = {In this study we investigated possible feedbacks of predicted future climate change on forest soil NO and N2O emissions in Europe. For this we used two climate scenarios, one representing a 10- year period of present-day climate (1991-2000) and a 9-year period for future climate conditions (2031-2039). The climate scenarios were used to drive the GIS-coupled biogeochemical model Photosynthesis-Evapotranspiration-Model Denitrification- Decomposition-Model (PnET-N-DNDC), which has currently been tested for its predicting capability for soil N trace gas emissions for various sites across Europe. The model results show a complex, spatially differentiated pattern of changes in future N2O and NO emissions from the forest soils across Europe, which were driven by the combined effect of changes in precipitation and temperature. Overall, the model predicted that N2O emissions from the European forest soils will on average decrease by 6\%. This decrease was mainly due to the shift in N2O:N-2 ratio driven by enhanced denitrification. NO emissions were found to increase by 9\%. The increases in NO emissions were mainly due to increases in temperature. Only for the regions where soil moisture was predicted to markedly increase or suffer from water stress during the vegetation period, a reduction of NO emissions was simulated. The simulations show the possibility and feasibility for assessing climate change feedbacks on biogenic N trace gas emissions from soils at a regional scale.}, keywords = {nitrous-oxide emissions, climate-change scenarios, 3-year continuous record, process-oriented model, trace gas emissions, nitric- oxide, agricultural lands, saturated spruce, source strength, limed soil}, doi = {10.1029/2005JG000115}, ISSN = {0148-0227}, } @ARTICLE{Hergoualch2007, title = {Processes responsible for the nitrous oxide emission from a Costa Rican Andosol under a coffee agroforestry plantation}, author = {Hergoualc'h, K. and Skiba, U. and Harmand, J. M. and Oliver, R.}, journal = {Biology and Fertility of Soils}, year = {2007}, volume = {43}, number = {6}, pages = {787--795}, publisher = {Springer, 233 Spring Street, New York, Ny 10013 USA}, abstract = {We used the inhibitor acetylene (C2H2) at partial pressures of 10 Pa and 10 kPa to inhibit autotrophic nitrification and the reduction of nitrous oxide (N2O) to N-2, respectively. Soils (Andosol) from a Coffea arabica plantation shaded by Inga densiflora in Costa Rica were adjusted to 39, 58, 76 and 87\% water-filled pore space (WFPS) and incubated for 6 days in the absence or presence of C2H2. Soil respiration, nitrification rates and N2O emissions by both processes were measured in relation to soil moisture conditions. At all WFPS studied, rates of N2O and N-2 productions were small (4.8; 14.7; 23 and 239.6 ng N-N2O g(-1) d.w. d(-1) at 39, 58, 76 and 87\% WFPS, respectively), and despite a low soil pH (4.7), N2O was mainly produced by nitrification, which was responsible for 85, 91, 84 and 87\% of the total N2O emissions at 39, 58, 76 and 87\% WFPS, respectively. At the three smaller values of WFPS, a linear relationship was established between WFPS, soil respiration, nitrification and N2O released by nitrification; no N-2 was produced by denitrification. At more anaerobic conditions achieved by a WFPS of 87\%, a large rate of N2O production was measured during nitrification, and N-2 production accounted for 84\% of the gaseous N fluxes caused by denitrification.}, keywords = {no emissions, denitrification, nitrification, soils, n2o, n2o, denitrification, nitrification, coffea arabica, acetylene inhibition, water-filled pore space (wfps), costa rica}, doi = {10.1007/s00374-007-0168-z}, ISSN = {0178-2762}, } @ARTICLE{Henault1998, title = {Influence of different agricultural practices (type of crop, form of N-fertilizer) on soil nitrous oxide emissions}, author = {H\'enault, C. and Devis, X. and Lucas, J. L. and Germon, J. C.}, journal = {Biology and Fertility of Soils}, year = {1998}, volume = {27}, number = {3}, pages = {299--306}, publisher = {Springer Verlag, 175 Fifth Ave, New York, Ny 10010 USA}, abstract = {N2O emissions were periodically measured using the static chamber method over a 1-year period in a cultivated field subjected to different agricultural practices including the type of N fertilizer (NH4NO3, (NH4)(2)SO4: CO(NH2)(2) or KNO3 and the type of crop (rapeseed and winter wheat). N2O emissions exhibited the same seasonal pattern whatever the treatment, with emissions between 1.5 and 15 g N ha(-1) day(-1) during the autumn, 16-56 g N ha(-1) day(-1) in winter after a lengthy period of freezing, 0.5-70 g N ha(-1) day(-1) during the spring and lower emissions during the summer. The type of crop had little impact on the level of N2O emission. These emissions were a little higher under wheat during the autumn in relation to an higher soil NO3-, content, but the level of emissions was similar over a 7-month period (2163 and 2093 g N ha(-1) for rape, and wheat, respectively). The form of N fertilizer affected N2O emissions during the month following fertilizer application, with higher emissions in the case of NH4NO3 and (NH4)(2)SO4, and a different temporal pattern of emissions after CO(NH2)2 application. The proportion of applied N lost as N2O varied from 0.42\% to 0.55\% with the form of N applied, suggesting that controlling this agricultural factor would not be an efficient way of limiting N2O emissions under certain climatic and pedological situations.}, keywords = {denitrification, variability, landscape, forest, nitrous oxide emissions, soil chamber method, nitrogen fertilizer types, wheat, rapeseed crop}, ISSN = {0178-2762}, } @ARTICLE{Chatskikh2007, title = {Soil tillage enhanced {CO$_2$} and {N$_2$O} emissions from loamy sand soil under spring barley}, author = {Chatskikh, D. and Olesen, J. E.}, journal = {Soil \& Tillage Research}, year = {2007}, volume = {97}, number = {1}, pages = {5--18}, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {Soil tillage intensity can be expected to affect the greenhouse gas balance of arable cropping systems through effects on soil physics and biology affecting soil carbon storage and nitrous oxide (N2O) emissions. The effects of conventional tillage (CT) with ploughing to 20 cm, reduced tillage (RT) with harrowing to 8-10 cm and direct drilling (DD) on CO2 and N2O emissions from a loamy sand soil (8.1\% clay, 3.5\% organic matter) under spring barley undersown with ryegrass were measured by static chambers over a period of H 3 days in spring and summer 2004 in a tillage experiment established in 2002 at Foulum, Denmark. There was a high temporal and spatial variation in both CO2 and N2O emissions, which made the comparisons of treatment effects on emissions on single dates difficult. However, this variation was reduced when the measurements were corrected for diurnal variation in the emissions and when emissions were cumulated over a longer period. Both CO2 and N2O emissions decreased in the order CT > RT > DD. Compared with CT (40 kg C day(-1)) the cumulated CO2 emissions during the 91 days after tillage were 21 and 25\% lower for the RT and the DD treatments, respectively. The cumulated N2O emission from CT over the entire observation period (0.89 kg N ha(-1) or 7.9 g N day(-1)) was about twice that of DD. The N2O emissions were significantly higher for CT compared with DD and RT, even before tillage and the difference increased after tillage, but decreased after fertilisation. Spring barley dry matter grain yields were reduced by 14\% for RT and 27\% for DD compared to CT. Measurements of soil mineral nitrogen (N) at sowing showed no difference between the treatments, and could thus not explain the differences in N2O emissions and crop N uptake. It is likely that tillage affected CO2 emissions, N2O emissions and crop growth through different processes, where effects of soil compactness on root penetration and soil aeration and diffusivity on one side and soil organic matter turnover on the other side probably played key roles. (c) 2007 Elsevier B.V. All rights reserved.}, keywords = {nitrous-oxide emissions, long-term, agricultural soils, microbial activity, carbon mitigation, chamber methods, organic-carbon, winter barley, no-till, fluxes, nitrous oxide, carbon dioxide, greenhouse gas, direct drilling, reduced tillage, ploughing, crop growth}, doi = {10.1016/j.still.2007.08.004}, ISSN = {0167-1987}, } @ARTICLE{Phillips2008, title = {Denitrification in cropping systems at sub-zero soil temperatures. A review}, author = {Phillips, R. L.}, journal = {Agronomy for Sustainable Development}, year = {2008}, volume = {28}, number = {1}, pages = {87--93}, publisher = {Edp Sciences S A, 17, Ave Du Hoggar, Pa Courtaboeuf, Bp 112, F-91944 Les Ulis Cedex A, France}, abstract = {Nitrogen (N) in agricultural fertilizers is denitrified by soil bacteria when oxygen is limited, which effectively removes plant-available N from the soil to the atmosphere. Reported denitrification rates range from 0 to 239 kg N ha(-1) yr(-1), and, depending upon environmental conditions and management, may reduce the amount of N available for crop growth by 27\%. Denitrification in soils also results in emissions of nitrous oxide ( N2O), which is a recognized pollutant that contributes to stratospheric ozone destruction and radiative forcing in the troposphere. Practitioners of sustainable agronomy aim to improve plant N-use efficiency and reduce emissions of the greenhouse gases by synchronizing N application and plant nutritional requirements. However, it is difficult to predict denitrification rates during and after the growing season based on current knowledge. High rates are consistently reported in irrigated cropping systems following heavy applications of fertilizer-N, but few studies report denitrification during the dormant season. Denitrification in winter may represent a significant sink for fertilizer-N in cropping systems, but further research at sub-zero soil temperatures is needed. Here, the three factors required for microbial denitrification: limited O-2 availability, electron donors and electron acceptors, are reviewed based on soil research performed both above and below 0 degrees C. Gaps in the knowledge of denitrification rates in cropping systems, particularly when soils are frozen, are identified. Sustainable management of N in cropping systems such as greater N-use efficiency and lower greenhouse gas emissions could be advanced by greater understanding of denitrification in winter.}, keywords = {nitrous-oxide emissions, freeze-thaw cycles, manure-amended soil, filled pore-space, agricultural soils, organic-matter, n2o emissions, n-fertilization, arable soil, taiga soils, nitrous oxide, sub-zero temperatures, nitrogen, fertilizer}, doi = {10.1051/agro:2007045}, ISSN = {1774-0746}, } @ARTICLE{Heinen2006a, title = {Simplified denitrification models: Overview and properties}, author = {Heinen, M.}, journal = {Geoderma}, year = {2006}, volume = {133}, number = {3--4}, pages = {444--463}, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {This paper reviews simplified process models for denitrification. More than fifty models were considered. The majority of these (simple) models are based on potential denitrification-either measured as a soil's property or computed from organic C dynamics-or consider denittification as a first-order decay process. As it is generally accepted that environmental soil conditions affect the denitrification process, reduction functions are used. Although denitrification is truly driven by the non-availability of oxygen, most authors argue that oxygen dynamics in soil is hard to simulate (or to measure). Therefore, water content is used as a complementary for oxygen diffusion. The higher the water content, the less oxygen will be present. Other factors that influence denitrification are nitrate-nitrogen content, soil temperature and soil acidity (pH). The availability of easily decomposable organic carbon determines the value of potential denitrification or the first- order decay rate constant. Although there seems to be consensus about the mathematical formulation of the simple process model, the shapes of the reduction functions differ largely between the models, especially for the water content reduction function. From a sensitivity analysis it follows that the model is most sensitive to the parameters of the water content reduction function, indicating that these parameters and the water content must be determined with great accuracy. (c) 2005 Elsevier B.V All rights reserved.}, keywords = {nitrous-oxide evolution, management model, winter-wheat, forest soils, potential denitrification, generalized-model, rainfall events, empirical-model, water-quality, n2o emissions, actual denitrification, elasticity, potential denitrification, reduction functions, sensitivity analysis}, doi = {10.1016/j.geoderma.2005.06.010}, ISSN = {0016-7061}, } @ARTICLE{Heinen2006b, title = {Application of a widely used denitrification model to {Dutch} data sets}, author = {Heinen, M.}, journal = {Geoderma}, year = {2006}, volume = {133}, number = {3--4}, pages = {464--473}, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {In many modelling studies on N cycling, denitrification is considered by a simplified process model. A widely used model describes denittification as potential denitrification reduced by the soil conditions nitrate N content (N), degree of water saturation (S) and temperature (7). H\'enault and Germon, 2000 [H\'enault, C. and Germon, J.C., 2000. NEMIS, a predictive model of denittification on the field scale. Eur. J. Soil Sci., 51: 257-270.] showed that this model worked satisfactorily for two data sets where parameters had been specifically derived for these data sets. This paper demonstrates that it may not always work well for other data, i.e., Dutch data sets. The model was parameterized for each of eight Dutch data sets, consisting of three sand, two heavy loam and three peat sites. After parameter optimisation the model is not able to predict individually measured actual denitrification rates. However, for sand and loam soils, but not for peat soils, the correspondence between measured and predicted average actual denitrification is good. This means that the calibrated model can predict, for those specific locations, cumulative denitrification rather well, provided that detailed information on soil conditions is available, either from measurements or from simulation models. The parameters and thus the reduction functions differed between the data sets. Parameter values within a class of soils, say sand, loam, and peat, were different. So care should be taken when using parameter values obtained from other studies. Albeit simple in its mathematical formulation, a widely used simplified denitrification process model needs to be parameterized for each location.}, keywords = {nitrous-oxide emissions, spatial heterogeneity, soil denitrification, field-scale, plow layer, peat soil, grassland, variability, losses, rates, actual denitrification, parameter identification, potential denitrification, reduction functions}, doi = {10.1016/j.geoderma.2005.08.011}, ISSN = {0016-7061}, } @ARTICLE{Smith2008, title = {Evaluation of two process-based models to estimate soil {N$_2$O} emissions in Eastern Canada}, author = {Smith, W. N. and Grant, B. B. and Desjardins, R. L. and Rochette, P. and Drury, C. F. and Li, C.}, journal = {Canadian Journal of Soil Science}, year = {2008}, volume = {88}, number = {2}, pages = {251--260}, publisher = {Agricultural Inst Canada, 280 Albert St, Suite 900, Ottawa, Ontario K1p 5g8, Canada}, abstract = {Process-based models play an important role in the estimation of soil N2O emissions from regions with contrasting soil and climatic conditions. A study was performed to evaluate the ability of two process-based models, DAYCENT and DNDC, to estimate N2O emissions, soil nitrate- and ammonium-N levels, as well as soil temperature and water content. The measurement sites included a maize crop fertilized with pig slurry (Quebec) and a wheat- maize-soybean rotation as part of a tillage-fertilizer experiment (Ontario). At the Quebec site, both models accurately simulated soil temperature with an average relative error (ARE) ranging from 0 to 2\%. The models underpredicted soil temperature at the Ontario site with ARE from -5 to -7\% for DNDC and from -5 to -13\% for DAYCENT. Both models underestimated soil water content particularly during the growing season. The DNDC model accurately predicted average seasonal N2O emissions across treatments at both sites whereas the DAYCENT model underpredicted N2O emissions by 32 to 58\% for all treatments excluding the fertilizer treatment at the Quebec site. Both models had difficulty in simulating the timing of individual emission events. The hydrology and nitrogen transformation routines need to be improved in both models before further enhancements are made to the trace gas routines.}, keywords = {dynamics following application, nitrous-oxide evolution, carbon- dioxide fluxes, 19th consecutive year, rainfall events, ecosystem model, pig slurry, daycent, forest, driven, nitrous oxide, process-based model, dndc, greenhouse gas emissions, soil}, ISSN = {0008-4271}, } @ARTICLE{Gabrielle2006b, title = {Process-based modeling of nitrous oxide emissions from wheat-cropped soils at the subregional scale}, author = {Gabrielle, B. and Laville, P. and Duval, O. and Nicoullaud, B. and Germon, J. C. and H\'enault, C.}, journal = {Global Biogeochemical Cycles}, year = {2006}, volume = {20}, number = {4}, publisher = {Amer Geophysical Union, 2000 Florida Ave Nw, Washington, Dc 20009 USA}, abstract = {[ 1] Arable soils are a large source of nitrous oxide (N2O) emissions, making up half of the biogenic emissions worldwide. Estimating their source strength requires methods capable of capturing the spatial and temporal variability of N2O emissions, along with the effects of crop management. Here we applied a process-based model, Crop Environmental REsources Synthesis (CERES), with geo-referenced input data on soils, weather, and land use to map N2O emissions from wheat-cropped soils in three agriculturally intensive regions in France. Emissions were mostly controlled by soil type and local climate conditions, and only to a minor extent by the doses of fertilizer nitrogen applied. As a result, the direct emission factors calculated at the regional level were much smaller ( ranging from 0.0007 to 0.0033 kg N2O-N kg(-1) N) than the value of 0.0125 kg N2O-N kg(-1) N currently recommended in the IPCC Tier 1 methodology. Regional emissions were far more sensitive to the soil microbial characteristics governing denitrification and its fraction evolved as N2O, soil bulk density, and soil initial inorganic N content. Mitigation measures should therefore target a reduction in the amount of soil inorganic N upon sowing of winter crops, and a decrease of the soil N2O production potential itself. From a general perspective, taking into account the spatial variability of soils and climate thereby appears necessary to improve the accuracy of national inventories, and to tailor mitigation strategies to regional characteristics.}, keywords = {greenhouse-gas emissions, n2o emissions, agricultural fields, inventory, denitrification, methodology, variability, ceres}, doi = {10.1029/2006GB002686}, ISSN = {0886-6236}, } @ARTICLE{Gabrielle2006a, title = {Simulation of nitrous oxide emissions from wheat-cropped soils using {CERES}}, author = {Gabrielle, B. and Laville, P. and H\'enault, C. and Nicoullaud, B. and Germon, J. C.}, journal = {Nutrient Cycling in Agroecosystems}, year = {2006}, volume = {74}, number = {2}, pages = {133--146}, publisher = {Springer, Van Godewijckstraat 30, 3311 Gz Dordrecht, Netherlands}, abstract = {Estimation of nitrous oxide (N2O) emissions from arable soils, in relation to crop fertilization, is essential to devise strategies to mitigate the impact of agriculture on global warming. This paper presents the development and test of a N2O model resulting from the linkage of a dynamic soil-crop simulation model (CERES) with two sub-models of N2O production and reduction in soils. These sub-models (NOE and NGAS) account for both the nitrification and denitrification pathways. The resulting models (CERES NOE and CERES-NGAS) were tested against experimental data collected on three contrasting wheat-cropped soils representative of the Beauce agricultural region in France. Although the input variables for the N2O modules were correctly simulated, CERES-NGAS was over-responsive to soil water content in a Haplic Calcisol, and strongly over-estimated the N2O fluxes as a result. On the other hand, CERES-NOE predicted correct mean N2O emission levels for all sites, but failed to simulate the peak fluxes observed in the weeks following fertilizer application in the most N2O-productive soil. Both models achieved root mean squared errors in the 23- 26 g N-N2O ha(-1) day(-1) range, significantly higher than the average experimental error on the measurements. On the other hand, their mean deviations were acceptable, being lower than 2.2 g N-N2O ha(-1) day(-1), compared with a mean observed flux of 7.9 g N-N2O ha(-1) day(-1). Overall, the response of CERES- NOE to soil type was more accurate, but this came at the cost of costly, site-specific characterization on the soils' biological properties. The development of pedo-transfer functions to infer these parameters from basic soil characteristics appears as a pre-requisite for the use of CERES-NOE on a wider scale.}, keywords = {n2o emissions, denitrification, model, nitrification, evolution, carbon, ncsoil, sites, ceres, fertilization, greenhouse gases, modelling, nitrous oxide}, doi = {10.1007/s10705-005-5771-5}, ISSN = {1385-1314}, } @ARTICLE{Henault2005, title = {Predicting in situ soil {N$_2$O} emission using {NOE} algorithm and soil database}, author = {H\'enault, C. and Bizouard, F. and Laville, P. and Gabrielle, B. and Nicoullaud, B. and Germon, J. C. and Cellier, P.}, journal = {Global Change Biology}, year = {2005}, volume = {11}, number = {1}, pages = {115--127}, publisher = {Blackwell Publishing Ltd, 9600 Garsington Rd, Oxford Ox4 2dg, Oxon, England}, abstract = {This paper presents a new algorithm, Nitrous Oxide Emission (NOE) for simulating the emission of the greenhouse gas N2O from agricultural soils. N2O fluxes are calculated as the result of production through denitrification and nitrification and reduction through the last step of denitrification. Actual denitrification and nitrification rates are calculated from biological parameters and soil water-filled pore space, temperature and mineral nitrogen contents. New suggestions in NOE consisted in introducing (1) biological site-specific parameters of soil N2O reduction and (2) reduction of the N2O produced through nitrification to N-2 through denitrification. This paper includes a database of 64 N2O fluxes measured on the field scale with corresponding environmental parameters collected from five agricultural situations in France. This database was used to test the validity of this algorithm. Site per site comparison of simulated N2O fluxes against observed data leads to mixed results. For 80\% of the tested points, measured and simulated fluxes are in accordance whereas the others resulted in an important discrepancy. The origin of this discrepancy is discussed. On the other hand, mean annual fluxes measured on each site were strongly correlated to mean simulated annual fluxes. The biological site-specific parameter of soil N2O reduction introduced into NOE appeared particularly useful to discriminate the general level of N2O emissions from site to site. Furthermore, the relevance of NOE was confirmed by comparing measured and simulated N2O fluxes using some data from the US TRAGNET database. We suggest the use of NOE on a regional scale in order to predict mean annual N2O emissions.}, keywords = {nitrous-oxide emissions, agricultural soils, aggregated soils, field- scale, gas fluxes, denitrification, model, nitrification, water, anaerobiosis, database, denitrification, modelling, nitrification, nitrous oxide, soil}, doi = {10.1111/j.1365-2486.2004.00879.x}, ISSN = {1354-1013}, } @ARTICLE{Miehle2006, title = {Quantifying uncertainty from large-scale model predictions of forest carbon dynamics}, author = {Miehle, P. and Livesley, S. J. and Li, C. S. and Feikema, P. M. and Adams, M. A. and Arndt, S. K.}, journal = {Global Change Biology}, year = {2006}, volume = {12}, number = {8}, pages = {1421--1434}, publisher = {Blackwell Publishing, 9600 Garsington Rd, Oxford Ox4 2dq, Oxon, England}, abstract = {Linking environmental computer simulation models and geographic information systems (GIS) is now a common practice to scale up simulations of complex ecosystem processes for decision support. Unfortunately, several important issues of upscaling using GIS are rarely considered; in particular scale dependency of models, availability of input data, support of input and validation data, and uncertainty in prediction including error propagation from the GIS. We linked the biogeochemical Forest- DNDC model to a GIS database to predict growth of Eucalyptus globulus plantations at two different scales (similar to 0.045 ha plot(-1) scale and similar to 100 ha grid(-1) scale) across Victoria, in south-eastern Australia. Results showed that Forest-DNDC was not scale dependent across the range of scales investigated. Reduced availability of input data at the larger scale may introduce severe prediction errors, but did not require adjustment of the model in this study. Differences in the support of input and validation data led to an underestimation of predictive precision but an overestimation of prediction accuracy. Increasing data support, produced a high level of prediction accuracy ((-)e\%), but a medium level of predictive precision (r(2)=0.474, ME=0.318) after statistical validation. GIS error contribution could be detected but was not readily or reliably quantified. In a regional case study for 2653 ha of E. globulus plantations, the linked model GIS system estimated a total standing biomass of 95 260 t C for mid-2003 and a net CO2 balance of -45 671 t CO2-C yr(-1) for the entire year of 2002. This study showed that regional predictions of forest growth and carbon sequestration can be produced with greater confidence after a comprehensive assessment of upscaling issues.}, keywords = {process-oriented model, sensitivity-analysis, no emissions, productivity, gis, sequestration, validation, tasmania, biomass, soils, carbon sequestration, dndc, environmental modelling, eucalyptus, forestry, gis, prediction error, uncertainty analysis, upscaling, validation}, doi = {10.1111/j.1365-2486.2006.01176.x}, ISSN = {1354-1013}, } @ARTICLE{Barton2008, title = {Nitrous oxide emissions from a cropped soil in a semi-arid climate}, author = {Barton, L. and Kiese, R. and Gatter, D. and Butterbach-Bahl, K. and Buck, R. and Hinz, C. and Murphy, D. V.}, journal = {Global Change Biology}, year = {2008}, volume = {14}, number = {1}, pages = {177--192}, publisher = {Blackwell Publishing, 9600 Garsington Rd, Oxford Ox4 2zg, Oxon, England}, abstract = {Understanding nitrous oxide (N2O) emissions from agricultural soils in semi-arid regions is required to better understand global terrestrial N2O losses. Nitrous oxide emissions were measured from a rain-fed, cropped soil in a semi-arid region of south- western Australia for one year on a sub-daily basis. The site included N-fertilized (100 kg N ha(-1) yr(-1)) and nonfertilized plots. Emissions were measured using soil chambers connected to a fully automated system that measured N2O using gas chromatography. Daily N2O emissions were low (-1.8 to 7.3 g N2O-N ha(-1) day(-1)) and culminated in an annual loss of 0.11 kg N2O-N ha(-1) from N-fertilized soil and 0.09 kg N2O-N ha(-1) from nonfertilized soil. Over half (55\%) the annual N2O emission occurred from both N treatments when the soil was fallow, following a series of summer rainfall events. At this time of the year, conditions were conducive for soil microbial N2O production: elevated soil water content, available N, soil temperatures generally > 25 degrees C and no active plant growth. The proportion of N fertilizer emitted as N2O in 1 year, after correction for the 'background' emission (no N fertilizer applied), was 0.02\%. The emission factor reported in this study was 60 times lower than the IPCC default value for the application of synthetic fertilizers to land (1.25\%), suggesting that the default may not be suitable for cropped soils in semi-arid regions. Applying N fertilizer did not significantly increase the annual N2O emission, demonstrating that a proportion of N2O emitted from agricultural soils may not be directly derived from the application of N fertilizer. 'Background' emissions, resulting from other agricultural practices, need to be accounted for if we are to fully assess the impact of agriculture in semi-arid regions on global terrestrial N2O emissions.}, keywords = {simulated summer rainfall, filled pore-space, agricultural soils, microbial biomass, tropical forest, fertilizer n, n2o, australia, wheat, denitrification, australia, co2, emission factor, fallow, nitrogen fertilizer, rain-fed, wheat}, doi = {10.1111/j.1365-2486.2007.01474.x}, ISSN = {1354-1013}, } @ARTICLE{Werner2007, title = {A global inventory of {N$_2$O} emissions from tropical rainforest soils using a detailed biogeochemical model}, author = {Werner, C. and Butterbach-Bahl, K. and Haas, E. and Hickler, T. and Kiese, R.}, journal = {Global Biogeochemical Cycles}, year = {2007}, volume = {21}, number = {3}, publisher = {Amer Geophysical Union, 2000 Florida Ave Nw, Washington, Dc 20009 USA}, abstract = {Beside agricultural soils, tropical rainforest soils are the main source of atmospheric N2O. Current estimates of the global N2O source strength of tropical rainforest soils are still based on rather simplistic upscaling approaches and do have a large range of uncertainty. In this study, the biogeochemical ForestDNDC-tropica model was recalibrated and intensively tested on the site scale prior to inventory calculations. For this, the model was coupled to a newly developed global GIS database holding relevant information on model initialization and driving parameters in 0.25 degrees x 0.25 degrees resolution. On average, the mean annual N2O emission source strength of rainforests ecosystems worldwide for the 10-year- period 1991-2000 was calculated to be 1.2 kg N2O-N ha(-1) yr(-1). Using a total rainforest area of 10.9 x 10(6) km(2), this amounts to a total source strength of 1.34 Tg N yr(-1). The result of an initialization parameter uncertainty assessment using Latin Hypercube sampling revealed that the global source strength of N2O emissions from tropical rainforests may range from 0.88 to 2.37 Tg N yr(-1). Our calculations also show that N2O emissions do vary substantially on spatial and temporal scales. Regional differences were mainly caused by differences in soil properties, whereas the pronounced seasonal and interannual variability was driven by climate variability. Our work shows that detailed biogeochemical models are a valuable tool for assessing biosphere-atmosphere exchange even on a global scale. However, further progress and a narrowing of the uncertainty range do crucially depend on the availability of more detailed field measurements for model testing and an improvement of the quality of spatial data sets on soil and vegetation properties.}, keywords = {nitrous-oxide emissions, process-oriented model, trace-gas emissions, pnet-n-dndc, nitric-oxide, brazilian amazon, vegetation model, co2 emissions, wet tropics, costa-rica}, doi = {10.1029/2006GB002909}, ISSN = {0886-6236}, } @ARTICLE{Pilegaard2006, title = {Factors controlling regional differences in forest soil emission of nitrogen oxides ({NO} and {N$_2$O})}, author = {Pilegaard, K. and Skiba, U. and Ambus, P. and Beier, C. and Bruggemann, N. and Butterbach-Bahl, K. and Dick, J. and Dorsey, J. and Duyzer, J. and Gallagher, M. and Gasche, R. and Horvath, L. and Kitzler, B. and Leip, A. and Pihlatie, M. K. and Rosenkranz, P. and Seufert, G. and Vesala, T. and Westrate, H. and Zechmeister-Boltenstern, S.}, journal = {Biogeosciences}, year = {2006}, volume = {3}, number = {4}, pages = {651--661}, publisher = {European Geosciences Union, Max-planck-str 13, 37191 Katlenburg-lindau, Germany}, abstract = {Soil emissions of NO and N2O were measured continuously at high frequency for more than one year at 15 European forest sites as part of the EU-funded project NOFRETETE. The locations represent different forest types (coniferous/deciduous) and different nitrogen loads. Geoaphically they range from Finland in the north to Italy in the south and from Hungary in the east to Scotland in the west.}, keywords = {3-year continuous record, trace gas fluxes, nitric-oxide, norway spruce, beech forest, field-measurements, saturated spruce, european forests, limed soil, deposition}, ISSN = {1726-4170}, } @ARTICLE{Li2005, title = {Carbon sequestration in arable soils is likely to increase nitrous oxide emissions, offsetting reductions in climate radiative forcing}, author = {Li, C. S. and Frolking, S. and Butterbach-Bahl, K.}, journal = {Climatic Change}, year = {2005}, volume = {72}, number = {3}, pages = {321--338}, publisher = {Springer, Van Godewijckstraat 30, 3311 Gz Dordrecht, Netherlands}, abstract = {Strategies for mitigating the increasing concentration of carbon dioxide (CO2) in the atmosphere include sequestering carbon (C) in soils and vegetation of terrestrial ecosystems. Carbon and nitrogen (N) move through terrestrial ecosystems in coupled biogeochemical cycles, and increasing C stocks in soils and vegetation will have an impact on the N cycle. We conducted simulations with a biogeochemical model to evaluate the impact of different cropland management strategies on the coupled cycles of C and N, with special emphasis on C-sequestration and emission of the greenhouse gases methane (CH4) and nitrous oxide (N2O). Reduced tillage, enhanced crop residue incorporation, and farmyard manure application each increased soil C-sequestration, increased N2O emissions, and had little effect on CH4 uptake. Over 20 years, increases in N2O emissions, which were converted into CO2-equivalent emissions with 100-year global warming potential multipliers, offset 75- 310\% of the carbon sequestered, depending on the scenario. Quantification of these types of biogeochemical interactions must be incorporated into assessment frameworks and trading mechanisms to accurately evaluate the value of agricultural systems in strategies for climate protection.}, keywords = {trace gas fluxes, long-term experiments, n2o emissions, organic- carbon, denitrification activity, fertilized grassland, agricultural soils, methane fluxes, united-states, forest soil}, doi = {10.1007/s10584-005-6791-5}, ISSN = {0165-0009}, } @ARTICLE{ButterbachBahl2004, title = {Quantifying the regional source strength of {N}-trace gases across agricultural and forest ecosystems with process based models}, author = {Butterbach-Bahl, K. and Kesik, M. and Miehle, P. and Papen, H. and Li, C.}, journal = {Plant and Soil}, year = {2004}, volume = {260}, number = {1--2}, pages = {311--329}, publisher = {Kluwer Academic Publ, Van Godewijckstraat 30, 3311 Gz Dordrecht, Netherlands}, abstract = {The process-based models DNDC and PnET-N-DNDC were evaluated with regard to their potential to calculate regional inventories of N-trace gas emissions from agricultural and forest soils. To extend the model predictions to regional scale, we linked the models to a detailed GIS-database for Saxony, Germany, which was holding all the spatially and temporally differentiated input information and other model drivers. Total annual N2O- emissions from agricultural soils in Saxony ranged from 0.5-26.0 kg N2O-N ha(-1) yr(-1) and were calculated to amount to approx. 5475 t N2O-N yr(-1) in the year 1995, which compares quite well with previous estimates based on the IPCC approach (4892 t N2O-N yr(-1)). Compared to the agricultural soils, N2O- emissions from forest soils in Saxony (range: 0.04-19.7 kg N2O-N ha(-1) yr(-1)) were much lower and amounted to 1011 t N2O-N yr(-1). In comparison with other sources of N2O in Saxony our estimates show, that - even in such a highly industrialised region like Saxony - soils contribute more than 50\% to the total regional N2O source strength. Simulated emissions of NO from the agricultural and forest soils were approx. in the same magnitude than for N2O. The modelled NO-emission rates ranged from 0.4-26.3 kg NO-N ha(-1) yr(-1) for the agricultural soils and 0.04-28.3 kg NO-N ha(-1) yr(-1) for the forest soils with total emissions of 8868 t NO-N yr(-1) (agricultural soils) and 4155 t NO-N yr(-1) (forest soils). Our results indicated that the agricultural and forest soils were a significant source, which contributed 17.9\% of the total NOx emissions from various sources in Saxony. Furthermore, a series of sensitivity tests were carried out, which demonstrated that variations in soil organic carbon content (SOC) and soil texture significantly effect the modelled N-trace gas emissions from agricultural soils at the regional scale, whereas, in addition, for forest soils also the soil pH is within the sensitive factors. Finally, multi-year simulations were conducted for the region with observed meteorological data from 1994-1996. The results demonstrated that the modelled interannual variations, which were obviously induced by only the climate conditions, in the N-gas emissions were as high as 36\%. The high interannual variations imply that multi-year (e.g., 5-10 years), instead of single baseline year, simulations would produce more reliable estimates of mean soil N2O-emissions at regional scale. With respect to the Kyoto protocol this means that the mean N2O- emissions from soils in the period 1988-1992 should be evaluated instead of focusing on a single year, 1990.}, keywords = {nitrous-oxide emissions, 3-year continuous record, process-oriented model, nitric-oxide, n2o emissions, sensitivity-analysis, mitigation options, saturated spruce, ipcc methodology, methane fluxes, process based models, pnet-n-dndc, dndc, soil no/n2o- inventory}, ISSN = {0032-079X}, } @ARTICLE{Henault2000, title = {{NEMIS}, a predictive model of denitrification on the field scale}, author = {H\'enault, C. and Germon, J. C.}, journal = {European Journal of Soil Science}, year = {2000}, volume = {51}, number = {2}, pages = {257--270}, publisher = {Blackwell Science Ltd, P O Box 88, Osney Mead, Oxford Ox2 0ne, Oxon, England}, abstract = {We have developed a predictive model of denitrification in soils, NEMIS, based on data from a cultivated field composed of denitrification rates measured on undisturbed soil cores and the corresponding soil water-filled pore space, nitrate content and respiration. This model is a multiplicative combination of a potential denitrification rate measured under standard conditions defined in this paper, and dimensionless functions of nitrate content, water-filled pore space and temperature. The model was applied to two further databases obtained independently of its definition. Significant correlation was observed between the simulated and measured denitrification rates. The sensitivity of NEMIS to systematic variations of the input variables and of the coefficients included in the dimensionless functions was tested using these databases. NEMIS seems to be a very useful tool particularly adapted for interpolating a small number of denitrification measurements from a simple database composed of soil potential denitrification rate and the evolution of soil water-filled pore space, nitrate content and temperature. Its main limitation is its high sensitivity to the water-filled pore space from which denitrification starts to occur and which is included in the water function.}, keywords = {nitrous-oxide production, aggregated soils, n-fertilizer, temperature, grassland, nitrate, losses, rates, anaerobiosis, simulation}, ISSN = {1351-0754}, } @ARTICLE{Garrido2000, title = {Inhibitory capacities of acetylene on nitrification in two agricultural soils}, author = {Garrido, F. and H\'enault, C. and Gaillard, H. and Germon, J. C.}, journal = {Soil Biology \& Biochemistry}, year = {2000}, volume = {32}, number = {11--12}, pages = {1799--1802}, publisher = {Pergamon-elsevier Science Ltd, the Boulevard, Langford Lane, Kidlington, Oxford Ox5 1gb, England}, abstract = {Acetylene is currently used to distinguish between the relative contribution of nitrification and denitrification to soil emissions of the greenhouse gas, N2O. The basis of this method is that acetylene at low partial pressures inhibits nitrification without affecting N2O reduction. This paper reports experiments where low acetylene partial pressures were insufficient to totally inhibit nitrification in an hypercalcareous rendosol at water potentials higher than -3.5 MPa while they were always sufficient in a redoxic luvisol. (C) 2000 Elsevier Science Ltd. All rights reserved.}, keywords = {nitrous-oxide, denitrification, nitrification, soil, acetylene, water potentials}, ISSN = {0038-0717}, } @ARTICLE{Garrido2002, title = {{N$_2$O} and {NO} emissions by agricultural soils with low hydraulic potentials}, author = {Garrido, F. and H\'enault, C. and Gaillard, H. and Perez, S. and Germon, J. C.}, journal = {Soil Biology \& Biochemistry}, year = {2002}, volume = {34}, number = {5}, pages = {559--575}, publisher = {Pergamon-elsevier Science Ltd, the Boulevard, Langford Lane, Kidlington, Oxford Ox5 1gb, England}, abstract = {N2O and NO production were studied on five agricultural soils with low hydraulic potentials. All experiments were performed in a laboratory under standard incubation conditions to limit any intrinsic soil heterogeneity. The mechanisms involved in NO and N2O production was investigated using the inhibitory properties of acetylene on nitrification and N2O reduction. This work confirmed that N2O and NO could be produced by soils under aerobic conditions. Nitrification seemed to be the only process involved in NO production and the main process involved in N2O production by the five studied soils when the water content was low. Nevertheless, aerobic denitrification with N2O release was observed in one soil. The proportion of N emitted as NO and N2O through nitrification varied considerably from soil to soil and, in some soils, also varied with soil hydraulic potential, ranging from 0 to 2.5\%, and from 0.03 to 1\%, respectively. This study clearly shows that both NO emission and the gaseous N emitted in aerated conditions should be taken into account in determining the N-budget on cultivated soils. (C) 2002 Published by Elsevier Science.}, keywords = {nitrous-oxide production, nitric-oxide, aerobic denitrification, heterotrophic nitrifiers, nitrosomonas-eutropha, nitrification, nitrate, ammonia, rates, fertilizers, nitrification, denitrification, soil, nitric oxide, nitrous oxide, hydraulic potentials, acetylene}, ISSN = {0038-0717}, } @ARTICLE{Gosse1999, title = {{Water, carbon and nitrogen cycling in a rendzina soil cropped with winter oilseed rape: the Chalons Oilseed Rape Database}}, author = {Gosse, G. and Cellier, P. and Denoroy, P. and Gabrielle, B. and Laville, P. and Leviel, B. and Justes, E. and Nicolardot, B. and Mary, B. and Recous, S. and Germon, J. C. and H\'enault, C. and Leech, P. K.}, journal = {Agronomie}, year = {1999}, volume = {19}, number = {2}, pages = {119--124}, publisher = {Editions Scientifiques Medicales Elsevier, 23 Rue Linois, 75724 Paris Cedex 15, France}, abstract = {The Chalons Oilseed Rape Database holds the results of a comprehensive experiment on the dynamic fluxes of water, carbon and nitrogen within a soil-crop system at the field-scale, conducted in the Champagne region in France. The Chalons experiment started with the sowing of a rapeseed crop (Brassica napus L.) in September 1994, and stopped at its harvest in July 1995. It involved three fertilizer N treatments and a bare control. The soil was a rendzina overlying a subsoil of mixed compact and cryoturbed chalk. The variables monitored were: crop biomass, C and N content, soil matric potential, water and mineral N contents, actual evapotranspiration, nitrous oxide emissions, and ammonia volatilization, along with the usual meteorological data. Mass- balance estimates of water drainage and NO, leaching below the root-zone, along with N-15 balances accounting for the short- term dynamics of fertilizer N are also available. The data are accessible on the Internet through a World Wide Web server by means of a specific frontend, and may be used to test or calibrate soil-crop models. ((C) Inra/Elsevier, Paris.).}, keywords = {models, internet database, nitrogen cycle, rendzina, oilseed rape}, ISSN = {0249-5627}, } @article{Johnsson1991, title = {Simulation of field scale denitrification losses from soils under grass ley and barley}, author = {Johnsson, H. and Klemedtsson, L. and Nilsson, A. and Bo, H. and Svensson, B.}, journal = {Plant and Soil}, year = {2004}, volume = {138}, number = {2}, pages = {287--302}, abstract = {Denitrification losses from soils under barley and grass ley crops were simulated. The model, which includes the major processes determining inputs, transformations and outputs of nitrogen in arable soils, represents a scale compatible with information generally available in agricultural field research. The denitrification part of the model includes a field potential denitrification rate and functions for the effect of soil aeration status, soil temperature and soil nitrate content. Easily metabolizable organic matter is assumed not to limit denitrification. Simulated values were compared with denitrification measurements made during two growing seasons in the barley and grass ley treatments of a field experiment in central Sweden. Calibration revealed that the optimal parameter values describing the effect of soil aeration on denitrification rates were similar for both treatments. The response function derived agreed well with two data sets found in the literature. The potential denitrification rate constant, derived in the simulations, was higher for grass ley than for barley, which was consistent with the differences in overall rates of carbon and nitrogen turnover found between treatments. The simulated mean denitrification rates for the two seasons were within 20% of the mean of the measured values. However, simulated denitrification showed less temporal variability and a less skewed frequency distribution than measured denitrification. Some of the measured denitrification events not explained by the model could have been due to the stimulating effects of soil drying/wetting and freezing/thawing on microbial activity.}, keywords = {barley - grass ley - nitrogen losses - nitrogen model - soil denitrification}, ISSN = {0032-079X}, } @ARTICLE{Ding2007, title = {{Nitrous oxide emissions from an intensively cultivated maize-wheat rotation soil in the North China Plain}}, author = {Ding, W. X. and Cai, Y. and Cai, Z. C. and Yagi, K. and Zheng, X. H.}, journal = {Science of the Total Environment}, year = {2007}, volume = {373}, number = {2--3}, pages = {501--511}, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {N2O emissions from a maize-wheat rotation field were monitored in the Fengqiu State Key Agro-Ecological Experimental Station (Fenaqiu County, Henan Province, China) from June 2004 to June 2005. The experiment included four treatments: a bare (crop-absent) soil treated with 150 kg N ha(-1) (WN150) and soils fertilized with 0 (N0), 150 (N 150), and 250 (N250) kg N ha(-1) and cropped with maize or wheat. The bulk of the N2O emissions occurred in pulses following the application of fertilizer N at soil temperatures of 15 degrees C or more. The application of fertilizer N significantly increased the N2O emission, from 636 g N2O-N ha(-1) year(-1) in the N0 treatment to 4480 g N2O-N ha(-1) year(-1) in the N250 treatment. However, this increase primarily occurred during the maize growing season. The emission factor of applied fertilizer N as N2O was 1.05-1.34\% and 0.24-0.26\% during the 105-day maize and 241-day wheat growing seasons, respectively, and was on average 0.61-0.77\%. Increasing the rate of fertilizer application increased the emission factor during the maize growing season. The presence of maize appears to increase N2O emission by 45\% versus bare soil during the maize growing season. And, N2O emission during the maize season were significantly related to CO, production (R=0.43-0.81, n=30, P < 0.05). N2O emission was greatly affected by soil moisture during the maize growing season and by soil temperature during the wheat growing season. The maximum rates of nitrification occurred when soil moisture was in the range of 45-60\% WFPS, with the optimum value being approximately 50\%. However, soil moisture influenced N2O emission only when the soil temperature was at the optimum level. It is suggested that reducing the application rate of basal fertilizer N during the maize growing season could decrease N2O emission. (c) 2006 Elsevier B.V. All rights reserved.}, keywords = {global n2o budget, denitrification, nitrate, losses, field, fertilizer, fluxes, nitrification, water, respiration, crop, emission factor, mineral fertilizer n, nitrification, temperature, wfps}, doi = {10.1016/j.scitotenv.2006.12.026}, ISSN = {0048-9697}, } @ARTICLE{Renault1994, title = {Oxygen-transport and Anaerobiosis in Aggregated Soils - Contribution to the Study of Denitrification}, author = {Renault, P. and Sierra, J. and Stengel, P.}, journal = {Agronomie}, year = {1994}, volume = {14}, number = {6}, pages = {395--409}, publisher = {Editions Scientifiques Elsevier, 141 Rue Javel, 75747 Paris Cedex 15, France}, abstract = {Anaerobiosis was studied in aggregated soils in order to improve the knowledge of physical factors affecting denitrification. A numerical model was used to simulate oxygen transport and anaerobiosis in homogeneous aggregates of various shapes and dimensions, with possible occlusions of some parts of their external surface. These occlusions are due to contacts with neighbouring aggregates and to water menisci around them. It is possible to obtain similar results using an empirical model. By using this model and a model describing oxygen diffusion in the inter-crumb pore space we obtained relationships between anaerobiosis and water content similar to previously proposed empirical relationships between denitrification and water content. The model showed interactions between the effects of water content, temperature and soil structure. Experiments were carried out using gas chromatography and oxygen microelectrodes. Microbial respiration depends on oxygen and carbon dioxide concentrations. Carbon dioxide generally inhibits respiration but may increase it at low level. There is a large variability in global respiration of natural aggregates and oxygen concentration distribution is irregular inside them, as a consequence of the distribution of the pore space and probably the distribution of the organic matter. For aggregates of remoulded soil, it is possible to simulate their global respiration and the oxygen concentration distribution inside, when accounting for carbon dioxide transport and oxygen effect on microbial respiration.}, keywords = {soil anaerobiosis, gaseous diffusion, microbial respiration, numerical modeling, oxygen microelectrode}, ISSN = {0249-5627}, } @article{Stanford1975, author = {Stanford, George and Dzienia, Stanislaw and Vander Pol, Roger A.}, title = {{Effect of Temperature on Denitrification Rate in Soils}}, journal = {Soil Sci Soc Am J}, volume = {39}, number = {5}, pages = {867-870}, year = {1975}, abstract = {The effect of temperature on denitrification rate was studied with nine soils differing widely in organic matter content and chemical and physical characteristics. In the range of 15 to 35C, the temperature coefficient of denitrification, Q10, was approximately 2. Denitrification rates at 35 and 45C were similar. Between 10 and 5C, denitrification rate declined abruptly. The lower limit of the temperature range conforming to a Q10 of 2 was estimated to be 11C. In this study of water-logged soils sealed from the atmosphere, denitrification appeared to obey first-order kinetics. }, URL = {http://soil.scijournals.org/cgi/content/abstract/soilsci;39/5/867}, eprint = {http://soil.scijournals.org/cgi/reprint/soilsci;39/5/867.pdf} } @ARTICLE{Maag1996, title = {Nitrous oxide emission by nitrification and denitrification in different soil types and at different soil moisture contents and temperatures}, author = {Maag, M. and Vinther, F. P.}, journal = {Applied Soil Ecology}, year = {1996}, volume = {4}, number = {1}, pages = {5--14}, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {Nitrous oxide is produced from denitrification and nitrification processes in soils, and contributes to global warming and stratospheric ozone depletion. Laboratory experiments with six soils ranging in clay content between 4-12\% were designed to investigate the effect of water and temperature on the partitioning of N2O from denitrification and nitrification. The nitrification rates at 70\% field capacity (FC) were significantly higher in the loamy soils (980-1440 mu g N kg(-1) soil day(-1)) than in the sandy soils (60-460 mu g N kg(-1) soil day(-1) ). The nitrous oxide produced by nitrification differed similarly between the soil types resulting in ratios of N2O-N relative to NO3--N, which were only ranging from 0.28 to 0.48\% with an average of 0.39\%, indicating a rather constant relationship between nitrifrcation and nitrous oxide emission. Maximum nitrification rates occured at 20 degrees C and 100\% fired capacity (FC) and was 1/3 at 40\% FC. At lower temperatures only small responses to changes in soil moisture were observed. The percentage of N2O-N produced by nitrification increased with increasing soil moisture (0.49\% at 40\% FC and 0.93\% at 100\% FC) and decreased with increasing temperature (0.49\% at 5 degrees C and 0.17\% at 20 degrees C). The denitrification activity (N-2 + N2O) in the sandy loam soil responded significantly to both increased soil moisture and increased temperature, whereas the coarse sandy soil only reacted to increased temperature. In the coarse sandy soil the Q(10)-values were in the range from 1.9 to 3.4, and the values were ranging from 4.9 to 8.9 in the sandy loam soil. As for the denitrification activity also the N-2 to N2O ratio increased exponentially with increasing temperature, which implies a linear relationship between the Iog(N-2 to N2O ratio) and the temperature. The N-2 to N2O ratios were lower in the coarse sandy soil than in the sandy loam soil, and were in the range from 0 to 16.}, keywords = {nitrosomonas-europaea, n2o production, water-content, nitric-oxide, mineralization, inhibition, acetylene, ammonium, carbon, manure, denitrification, laboratory experiment, moisture, n-2 to n2o ratio, nitrification, temperature}, ISSN = {0929-1393}, } @article{Skopp1990, author = {Skopp, J. and Jawson, M. D. and Doran, J. W.}, title = {{Steady-State Aerobic Microbial Activity as a Function of Soil Water Content}}, journal = {Soil Sci Soc Am J}, volume = {54}, number = {6}, pages = {1619-1625}, year = {1990}, abstract = {Soil physical properties often regulate aeration-dependent microbial activities important to nutrient cycling, soil fertility and environmental quality. Microbial activity depends on soil water content and is maximum at a water content where the limiting effects of substrate diffusion and O2 supply are equal. The mechanism whereby this occurs and predictions of the soil water content where aerobic microbial activity is a maximum were the objectives of this study. In particular, this study predicted the shape of the microbial activity vs. water content function from soil physical concepts. Soil physical processes are assumed to influence microbial activity by limiting the steady flux of a required substrate or O2 to sites of microbial activity. Steady-state flux relations are used to define the activity function. The dependence of diffusion coefficient on water content or air-filled porosity is assumed. With these assumptions, it is possible to show that a maximum in the activity function exists. The predicted shape of the activity curve is consistent with experimental observations. The relationship between aeration-dependent microbial activity and soil water content facilitates evaluating the indirect effects of soil management practices, such as tillage, on microbial activity. }, URL = {http://soil.scijournals.org/cgi/content/abstract/soilsci;54/6/1619}, eprint = {http://soil.scijournals.org/cgi/reprint/soilsci;54/6/1619.pdf} } @article{Linn1984, author = {Linn, D. M. and Doran, J. W.}, title = {{Effect of Water-Filled Pore Space on Carbon Dioxide and Nitrous Oxide Production in Tilled and Nontilled Soils}}, journal = {Soil Sci Soc Am J}, volume = {48}, number = {6}, pages = {1267-1272}, year = {1984}, abstract = {The percentage of soil pore space filled with water (percent water-filled pores, % WFP), as determined by water content and total porosity, appears to be closely related to soil microbial activity under different tillage regimes. Soil incubated in the laboratory at 60% WFP supported maximum aerobic microbial activity as determined by CO2 production and O2 uptake. In the field, % WFP of surface no-tillage soils (0-75 mm) at four U.S. locations averaged 62% at time of sampling, whereas that for plowed soils was 44%. This difference in % WFP was reflected in 3.4 and 9.4 times greater CO2 and N2O production, respectively, from surface no-tillage soils over a 24-h period as compared to plowed soils. At a depth of 75 to 150 mm, % WFP values increased in both no-tillage and plowed soils, averaging approximately 70% for no tillage compared with 50 to 60% for plowed soils. Production of CO2 in the plowed soils was enhanced by the increased % WFP, resulting in little or no difference in CO2 production between tillage treatments. Nitrous oxide production, however, remained greater under no-tillage conditions. Substantially greater amounts of N2O were produced from the N-fertilized soils, regardless of tillage practice. Production of CO2 and N2O was primarily related to the % WFP of tillage treatments although, in several instances, soil-water-soluble C and NO-3 levels were important as well. Calculations of relative aerobic microbial activity between no-tillage and plowed soils, based on differences in % WFP relative to maximum activity at 60%, indicated linear relationships for CO2 and N2O production between WFP values of 30 to 70%. Below 60% WFP, water limits microbial activity, but above 60%, aerobic microbial activity decreases--apparently the result of reduced aeration. }, URL = {http://soil.scijournals.org/cgi/content/abstract/soilsci;48/6/1267}, eprint = {http://soil.scijournals.org/cgi/reprint/soilsci;48/6/1267.pdf} } @ARTICLE{Sutton2007, title = {Challenges in quantifying biosphere-atmosphere exchange of nitrogen species}, author = {Sutton, M. A. and Nemitz, E. and Erisman, J. W. and Beier, C. and Bahl, K. B. and Cellier, P. and de Vries, W. and Cotrufo, F. and Skiba, U. and Di Marco, C. and Jones, S. and Laville, P. and Soussana, J. F. and Loubet, B. and Twigg, M. and Famulari, D. and Whitehead, J. and Gallagher, M. W. and Neftel, A. and Flechard, C. R. and Herrmann, B. and Calanca, P. L. and Schjoerring, J. K. and Daemmgen, U. and Horvath, L. and Tang, Y. S. and Emmett, B. A. and Tietema, A. and Penuelas, J. and Kesik, M. and Brueggemann, N. and Pilegaard, K. and Vesala, T. and Campbell, C. L. and Olesen, J. E. and Dragosits, U. and Theobald, M. R. and Levy, P. and Mobbs, D. C. and Milne, R. and Viovy, N. and Vuichard, N. and Smith, J. U. and Smith, P. and Bergamaschi, P. and Fowler, D. and Reis, S.}, journal = {Environmental Pollution}, year = {2007}, volume = {150}, number = {1}, pages = {125--139}, publisher = {Elsevier Sci Ltd, the Boulevard, Langford Lane, Kidlington, Oxford Ox5 1gb, Oxon, England}, abstract = {Recent research in nitrogen exchange with the atmosphere has separated research communities according to N form. The integrated perspective needed to quantify the net effect of N on greenhouse-gas balance is being addressed by the NitroEurope Integrated Project (NEU). Recent advances have depended on improved methodologies, while ongoing challenges include gas- aerosol interactions, organic nitrogen and N-2 fluxes. The NEU strategy applies a 3-tier Flux Network together with a Manipulation Network of global-change experiments, linked by common protocols to facilitate model application. Substantial progress has been made in modelling N fluxes, especially for N2O, NO and bi-directional NH3 exchange. Landscape analysis represents an emerging challenge to address the spatial interactions between farms, fields, ecosystems, catchments and air dispersion/deposition. European up-scaling of N fluxes is highly uncertain and a key priority is for better data on agricultural practices. Finally, attention is needed to develop N flux verification procedures to assess compliance with international protocols. (C) 2007 Elsevier Ltd. All rights reserved.}, keywords = {gas-particle interactions, surface-exchange, simulation-model, ammonia exchange, dutch heathland, climate-change, oxide fluxes, trace gases, deposition, soil, nitrogen, fluxes, micrometeorology, modelling, landscape, regional up-scaling}, doi = {10.1016/j.envpol.2007.04.014}, ISSN = {0269-7491}, } @ARTICLE{Galloway2008, title = {{Transformation of the nitrogen cycle: Recent trends, questions, and potential solutions}}, author = {Galloway, J. N. and Townsend, A. R. and Erisman, J. W. and Bekunda, M. and Cai, Z. C. and Freney, J. R. and Martinelli, L. A. and Seitzinger, S. P. and Sutton, M. A.}, journal = {Science}, year = {2008}, volume = {320}, number = {5878}, pages = {889--892}, publisher = {Amer Assoc Advancement Science, 1200 New York Ave, Nw, Washington, Dc 20005 USA}, abstract = {Humans continue to transform the global nitrogen cycle at a record pace, reflecting an increased combustion of fossil fuels, growing demand for nitrogen in agriculture and industry, and pervasive inefficiencies in its use. Much anthropogenic nitrogen is lost to air, water, and land to cause a cascade of environmental and human health problems. Simultaneously, food production in some parts of the world is nitrogen-deficient, highlighting inequities in the distribution of nitrogen- containing fertilizers. Optimizing the need for a key human resource while minimizing its negative consequences requires an integrated interdisciplinary approach and the development of strategies to decrease nitrogen-containing waste.}, keywords = {future, consequences, perspective, deposition, climate, cascade, system}, doi = {10.1126/science.1136674}, ISSN = {0036-8075}, } @ARTICLE{Erisman2007, title = {Reduced nitrogen in ecology and the environment}, author = {Erisman, J. W. and Bleeker, A. and Galloway, J. and Sutton, M. S.}, journal = {Environmental Pollution}, year = {2007}, volume = {150}, number = {1}, pages = {140--149}, publisher = {Elsevier Sci Ltd, the Boulevard, Langford Lane, Kidlington, Oxford Ox5 1gb, Oxon, England}, abstract = {Since the beginning of the 19th century humans have increasingly fixed atmospheric nitrogen as ammonia to be used as fertilizer. The fertilizers are necessary to create amino acids and carbohydrates in plants to feed animals and humans. The efficiency with which the fertilizers eventually reach humans is very small: 5-15\%, with much of the remainder lost to the environment. The global industrial production of ammonia amounts to 117 Mton NH3-N year(-1) (for 2004). By comparison, we calculate that anthropogenic emissions of NH3 to the atmosphere over the lifecycle of industrial NH3 in agriculture are 45.3 Mton NH3-N year(-1), about half the industrial production. Once emitted ammonia has a central role in many environmental issues. We expect an increase in fertilizer use through increasing demands for food and biofuels as population increases. Therefore, management of ammonia or abatement is necessary. (C) 2007 Elsevier Ltd. All rights reserved.}, keywords = {ammonia emissions, species richness, deposition, grasslands, management, abatement, cycle, nh3, consequences, biodiversity, reduced nitrogen, emission, nitrogen cycle, ammoma effects, abatement}, doi = {10.1016/j.envpol.2007.06.033}, ISSN = {0269-7491}, } @ARTICLE{Laville2005, title = {Measurement and modelling of {NO} fluxes on maize and wheat crops during their growing seasons: effect of crop management}, author = {Laville, P. and H\'enault, C. and Gabrielle, B. and Serca, D.}, journal = {Nutrient Cycling in Agroecosystems}, year = {2005}, volume = {72}, number = {2}, pages = {159--171}, month = jun, publisher = {Springer, Van Godewijckstraat 30, 3311 Gz Dordrecht, Netherlands}, abstract = {Fertilized agricultural soils are a significant source of NO, a gas involved in tropospheric ozone formation. The aims of the research reported here were to measure NO fluxes over the length of the growing season of wheat and maize crops, and to build a model of soil NO emissions from arable land. Field experiments were carried out on a 1-ha field divided into two parts. The first one was cropped with wheat and harvested in late July, 2002, whereas the second part was sown with maize and harvested in October. The wheat and maize received 130 kg N ha(-1) and 140 kg N ha(-1), respectively. For each crop, NO fluxes were measured during 10 months every 2 weeks using manual closed chambers, and continuously with a wind tunnel immediately after nitrogen fertilization. Fertilizer application significantly affected NO emissions: the largest NO emissions were recorded a few days after nitrogen application. This delay depended on the kinetics of nitrogen incorporation in the soil, as influenced by rainfall. The emissions measured on the maize field (2.6\% of the fertilizer amount applied) were more important than those on the wheat field (1.0\% of the fertilizer amount applied), owing to differences in timing of nitrogen application, with respect to climate and crop growth. Relationships between soil nitrification rate and NO emission obtained from laboratory incubations, and experimental data appeared useful and relevant to predict NO emissions at the field-scale.}, keywords = {nitric-oxide emissions, estimating ammonia volatilization, wind-tunnel technique, agricultural soils, nitrous-oxide, n2o emissions, nitrification, temperate, inventory, turnover, arable soils, biogenic, influencing factors, modelling, no emission}, ISSN = {1385-1314}, } @ARTICLE{Rolland2008, title = {Modeling of nitric oxide emissions from temperate agricultural soils}, author = {Rolland, M. N. and Gabrielle, B. and Laville, P. and Serca, D. and Cortinovis, J. and Larmanou, E. and Lehuger, S. and Cellier, P.}, journal = {Nutrient Cycling in Agroecosystems}, year = {2008}, volume = {80}, number = {1}, pages = {75--93}, publisher = {Springer, Van Godewijckstraat 30, 3311 Gz Dordrecht, Netherlands}, abstract = {Arable soils are a significant source of nitric oxide (NO), most of which is derived from nitrogen fertilizers. Accurate estimates of NO emissions from these soils are essential to devise strategies to mitigate the impact of agriculture on tropospheric ozone production and destruction. This paper presents the implementation of a soil NO emissions submodel within the environmentally-orientated soil-crop model, CERES- EGC. The submodel simulates NO production via the nitrification pathway, as modulated by soil environmental drivers. The resulting model was tested with data from 4 field experiments on wheat- and maize-cropped soils representative of two agricultural regions of France, over three years, and encompassing various climatic conditions. Overall, the model provided accurate predictions of NO emissions, but shortcomings arose from an inadequate vertical distribution of N fertilizer in the soil surface. Inclusion of a 2-cm thick topsoil layer in a 'micro-layer' version of CERES-EGC gave more realistic simulations of NO emissions and under-lying microbiological process. From a statistical point of view, both versions of the model achieved a similar fit to the experimental data, with respectively a MD and a RMSE ranging from 1.8 to 6.2 g N-NO ha(-1)d(-1), and from 22.8 to 25.2 g N-NO ha(-1)d(-1) across the 4 experiments. The cumulative NO losses represented 1-2\% of NH4+ fertilizer applied in the case of maize crops, and about 1\% in the case of wheat crops. The 'micro-layer' version may be used for spatialized inventories of NO emissions to improve air quality prediction.}, keywords = {available measurement data, pnet-n-dndc, nitrous-oxide, global inventory, n2o emissions, gas emissions, forest soils, nitrification, fertilizer, fields, no emissions, temperate crops, ceres-egc, process modeling, goodness of fit}, doi = {10.1007/s10705-007-9122-6}, ISSN = {1385-1314}, } @ARTICLE{Duxbury1982, title = {Emission of nitrous oxide from soils}, author={Duxbury, J. M. and Bouldin, D. R. }, journal={Nature}, volume={298}, pages={462--464}, year={1982} } @article{Li2001, title={Comparing a process-based agro-ecosystem model to the {IPCC} methodology for developing a national inventory of {N$_2$O} emissions from arable lands in {China}}, author={Li, C. and Zhuang, Y. and Cao, M. and Crill, P. and Dai, Z. and Frolking, S. and Moore III, B. and Salas, W. and Song, W. and Wang, X.}, year={2001}, journal={Nutrient Cycling in Agroecosystems}, volume={60}, number={1-3}, pages={159--175} } @ARTICLE{Grant2004, title = {Estimated {N$_2$O} and {CO}$_2$ emissions as influenced by agricultural practices in {Canada}}, author = {Grant, B. and Smith, W. N. and Desjardins, R. and Lemke, R. and Li, C.}, journal = {Climatic Change}, year = {2004}, volume = {65}, number = {3}, pages = {315--332}, publisher = {Kluwer Academic Publ, Van Godewijckstraat 30, 3311 Gz Dordrecht, Netherlands}, abstract = {The Denitrification-Decompostion (DNDC) model was used to estimate the impact of change in management practices on N2O emissions in seven major soil regions in Canada, for the period 1970 to 2029. Conversion of cultivated land to permanent grassland would result in the greatest reduction in N2O emissions, particularly in eastern Canada where the model estimated about 60\% less N2O emissions for this conversion. About 33\% less N2O emissions were predicted for a change from conventional tillage to no-tillage in western Canada, however, a slight increase in N2O emissions was predicted for eastern Canada. Greater N2O emissions in eastern Canada associated with the adoption of no- tillage were attributed to higher soil moisture causing denitrification, whereas the lower emissions in western Canada were attributed to less decomposition of soil organic matter in no-till versus conventional tilled soil. Elimination of summer fallow in a crop rotation resulted in a 9\% decrease in N2O emissions, with substantial emissions occurring during the wetter fallow years when N had accumulated. Increasing N-fertilizer application rates by 50\% increased average emissions by 32\%, while a 50\% decrease of N-fertilizer application decreased emissions by 16\%. In general, a small increase in N2O emissions was predicted when N-fertilizer was applied in the fall rather than in the spring. Previous research on CO2 emissions with the CENTURY model (Smith et al., 2001) allowed the quantification of the combined change in N2O and CO2 emissions in CO2 equivalents for a wide range of management practices in the seven major soil regions in Canada. The management practices that have the greatest potential to reduce the combined N2O and CO2 emissions are conversion from conventional tillage to permanent grassland, reduced tillage, and reduction of summer fallow. The estimated net greenhouse gas (GHG) emission reduction when changing from cultivated land to permanent grassland ranged from 0.97 (Brown Chernozem) to 4.24 Mg CO2 equiv. ha(-1) y(-1) (Black Chernozem) for the seven soil regions examined. When changing from conventional tillage to no-tillage the net GHG emission reduction ranged from 0.33 (Brown Chernozem) to 0.80 Mg CO2 equiv. ha(-1) y(-1) (Dark Gray Luvisol). Elimination of fallow in the crop rotation lead to an estimated net GHG emission reduction of 0.43 (Brown Chernozem) to 0.80 Mg CO2 equiv. ha(-1) y(-1) (Dark Brown Chernozem). The addition of 50\% more or 50\% less N-fertilizer both resulted in slight increases in combined CO2 and N2O emissions. There was a tradeoff in GHG flux with greater N2O emissions and a comparable increase in carbon storage when 50\% more N-fertilizer was added. The results from this work indicate that conversion of cultivated land to grassland, the conversion from conventional tillage to no-tillage, and the reduction of summerallow in crop rotations could substantially increase C sequestration and decrease net GHG emissions. Based on these results a simple scaling-up scenario to derive the possible impacts on Canada's Kyoto commitment has been calculated.}, keywords = {nitrous-oxide emissions, permanent pasture, soil carbon, dndc model, management, tillage, fluxes}, ISSN = {0165-0009}, } @ARTICLE{DelGrosso2006, title = {{DAYCENT} national-scale simulations of nitrous oxide emissions from cropped soils in the United States}, author = {Del Grosso, S. J. and Parton, W. J. and Mosier, A. R. and Walsh, M. K. and Ojima, D. S. and Thornton, P. E.}, journal = {Journal of Environmental Quality}, year = {2006}, volume = {35}, number = {4}, pages = {1451--1460}, publisher = {Amer Soc Agronomy, 677 S Segoe Rd, Madison, Wi 53711 USA}, abstract = {Until recently, Intergovernmental Panel on Climate Change (IPCC) emission factor methodology, based on simple empirical relationships, has been used to estimate carbon (C) and nitrogen (N) fluxes for regional and national inventories. However, the 2005 USEPA greenhouse gas inventory includes estimates of N2O emissions from cultivated soils derived from simulations using DAYCENT, a process-based biogeochemical model. DAYCENT simulated major U.S. crops at county-level resolution and IPCC emission factor methodology was used to estimate emissions for the approximately 14\% of cropped land not simulated by DAYCENT. The methodology used to combine DAYCENT simulations and IPCC methodology to estimate direct and indirect N2O emissions is described in detail. Nitrous oxide emissions from simulations of presettlement native vegetation were subtracted from cropped soil N2O to isolate anthropogenic emissions. Meteorological data required to drive DAY CENT were acquired from DAYMET, an algorithm that uses weather station data and accounts for topography to predict daily temperature and precipitation at I-km 2 resolution. Soils data were acquired from the State Soil Geographic Database (STATSGO). Weather data and dominant soil texture class that lie closest to the geographical center of the largest cluster of cropped land in each county were used to drive DAYCENT. Land management information was implemented at the agricultural-economic region level, as defined by the Agricultural Sector Model. Maps of model-simulated county-level crop yields were compared with yields estimated by the USDA for quality control. Combining results from DAYCENT simulations of major crops and IPCC methodology for remaining cropland yielded estimates of approximately 109 and approximately 70 Tg CO2 equivalents for direct and indirect, respectively, mean annual anthropogenic N2O emissions for 1990-2003.}, keywords = {daily solar-radiation, agricultural lands, complex terrain, n2o emissions, model, precipitation, temperature, humidity, systems}, doi = {10.2134/jeq2005.0160}, ISSN = {0047-2425}, } @ARTICLE{Lokupitiya2006, title = {Agricultural soil greenhouse gas emissions: {A} review of {N}ational {I}nventory {M}ethods}, author = {Lokupitiya, E. and Paustian, K.}, journal = {Journal of {E}nvironmental {Q}uality}, year = {2006}, volume = {35}, number = {4}, pages = {1413--1427}, publisher = {Amer Soc Agronomy, 677 S Segoe Rd, Madison, Wi 53711 USA}, abstract = {Parties to the United Nations Framework Convention on Climate Change (UNFCCC) are required to submit national greenhouse gas (GHG) inventories, together with information on methods used in estimating their emissions. Currently agricultural activities contribute a significant portion (approximately 20\%) of global anthropogenic GHG emissions, and agricultural soils have been identified as one of the main GHG source categories within the agricultural sector. However, compared to many other GHG sources, inventory methods for soils are relatively more complex and have been implemented only to varying degrees among member countries. This review summarizes and evaluates the methods used by Annex 1 countries in estimating CO, and N2O emissions in agricultural soils. While most countries utilize the Intergovernmental Panel on Climate Change (IPCC) default methodology, several Annex 1 countries are developing more advanced methods that are tailored for specific country circumstances. Based on the latest national inventory reporting, about 56\% of the Annex 1 countries use IPCC Tier I methods, about 26\% use Tier 2 methods, and about 18\% do not estirnate or report N2O emissions from agricultural soils. More than 65\% of the countries do not report CO2 emissions from the cultivation of mineral soils, organic soils, or liming, and only a handful of countries have used country-specific, Tier 3 methods. Tier 3 methods usually involve process-based models and detailed, geographically specific activity data. Such methods can provide more robust, accurate estimates of emissions and removals but require greater diligence in documentation, transparency, and uncertainty assessment to ensure comparability between countries. Availability of detailed, spatially explicit activity data is a major constraint to implementing higher tiered methods in many countries.}, keywords = {organic-carbon storage, new-zealand, land-use, management impacts, terrestrial carbon, nitrous-oxide, forest soils, model, ecosystems, budget}, doi = {10.2134/jeq2005.0157}, ISSN = {0047-2425}, } @ARTICLE{Desjardins2005, title = {Management strategies to sequester carbon in agricultural soils and to mitigate greenhouse gas emissions}, author = {Desjardins, R. L. and Smith, W. and Grant, B. and Campbell, C. and Riznek, R.}, journal = {Climatic Change}, year = {2005}, volume = {70}, number = {1--2}, pages = {283--297}, publisher = {Springer, Van Godewijckstraat 30, 3311 Gz Dordrecht, Netherlands}, abstract = {Carbon sequestration in agricultural soils is frequently promoted as a practical solution for slowing down the rate of increase of CO2 in the atmosphere. Consequently, there is a need to improve our understanding of how land management practices may affect the net removal of greenhouse gases (GHG) from the atmosphere. In this paper we examine the role of agriculture in influencing the GHG budget and briefly discuss the potential for carbon mitigation by agriculture. We also examine the opportunities that exist for increasing soil C sequestration using management practices such as reduced tillage, reduced frequency of summer fallowing, introduction of forage crops into crop rotations, conversion of cropland to grassland and nutrient addition via fertilization. In order to provide information on the impact of such management practices on the net GHG budget we ran simulations using CENTURY (a C model) and DNDC (a N model) for five locations across Canada, for a 30-yr time period. These simulations provide information on the potential trade-off between C sequestration and increased N2O emissions. Our model output suggests that conversion of cropland to grassland will result in the largest reduction in net GHG emissions, while nutrient additions via fertilizers will result in a small increase in GHG emissions. Simulations with the CENTURY model also indicated that favorable growing conditions during the last 15 yr could account for an increase of 6\% in the soil C at a site in Lethbridge, Alberta.}, keywords = {nitrous-oxide evolution, rainfall events, crop rotations, sequestration, canada, model, grassland, chernozem, dynamics, tillage}, ISSN = {0165-0009}, } @ARTICLE{Neufeldt2008, title = {Mitigation strategies for greenhouse gas emissions from agriculture using a regional economic-ecosystem model}, author = {Neufeldt, H. and Schafer, M.}, journal = {Agriculture {E}cosystems \& {E}nvironment}, year = {2008}, volume = {123}, number = {4}, pages = {305--316}, publisher = {Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands}, abstract = {Environmentally effective and economically efficient strategies and measures to reduce GHG emissions from agricultural systems could significantly contribute to GHG emission abatement. As a case study we therefore estimate the possible environmental and economic impacts of different mitigation policies (emission tax, emission cap, nitrogen tax, and livestock extensification) for typical farming systems in the German federal state of Baden-Wurttemberg by coupling an economic farm model with a biophysical model. This allows for an integrated analysis of the complex interactions between socioeconomic and biological systems and provides policyrnakers with information necessary to take responsible action.}, keywords = {nitrous-oxide emissions, abatement costs, germany, systems, agricultural greenhouse gas emissions, economic-ecosystem modeling, greenhouse gas mitigation policies, farming systems, emission cap, nitrogen tax, livestock extensification, marginal abatement costs}, doi = {10.1016/j.agee.2007.07.008}, ISSN = {0167-8809}, } @ARTICLE{Grant2003, author={Grant, R. F. and Pattey, E.}, title={Modelling variability in {N$_2$O} emissions from fertilized agricultural fields}, journal={{Soil Biology and Biochemistry}}, volume= {35}, number={2}, year={2003}, pages= {225--243}, abstract={Estimates of long-term landscape-scale N2O emissions for greenhouse gas inventories are complicated by large temporal and spatial variability. Much of this variability is likely caused by topographic effects on surface and subsurface water flows. We hypothesized that this variability could be explained as degassing events during anaerobic soil conditions and during transitions from anaerobic to aerobic soil conditions as controlled by precipitation and subsequent water redistribution in complex landscapes. We simulated degassing events in the ecosystem model ecosys run in three-dimensional mode to simulate a fertilized agricultural field with topographic variation derived from a digital terrain map. N2O emissions modelled from two areas within the field that had received 15.5 and 9.9 g N m-2 as urea in May 1998 were compared with those measured by micrometeorological flux towers during June and July 1998. Modelled N2O emissions during 1998 accounted for 2.3 and 2.0% of urea N applied at 15.5 and 9.9 g N m-2, respectively. Degassing events in the model coincided with a key N2O emission event measured in the field during several days after a rainfall in mid-June. During this event, modelled and measured surface fluxes rose rapidly to exceed 1 mg N m-2 h-1 for 2-3 d before declining. Emissions modelled concurrently at different topographic positions within the landscape during the emission event had coefficients of variation that varied over time between 30 and 180%. Much of the spatial variability in modelled emissions was attributed to temporal differences in the progression of emission events at different landscape positions caused by lateral water movement. The magnitude of temporal and spatial variability in N2O emissions suggests that aggregation of flux measurements to regional scales should be based upon sub-daily measurements at representative landscape positions, rather than upon less frequent measurements at individual sites as currently done. The use of three-dimensional ecosystem models with input from digital terrain maps may provide a means for such aggregation to be conducted.}, keywords = {Ecosys; N2O flux; N fertilizer; N2O modelling; Landscape; Spatial variability} } @ARTICLE{Fisher2003, author = {B. E. A. Fisher and M. P. Ireland and D. T. Boyland and S. P. Critten}, title = {{Why use one model? An approach for encompassing model uncertainty and improving best practice}}, journal = {Environmental Modelling and Assessment}, year = {2002}, volume = {7}, pages = {291--299} }