DNDC (DeNitrification DeComposition)

Criterion	Explanation
General Description	Carbon and nitrogen biogeochemical model for agricultural ecosystems. Important ecological drivers of the model include climate, soil, vegetation and human activities. Model can be used to predict crop growth, soil temperature and moisture regimes, soil carbon dynamics, nitrogen leaching, and gas emissions. Model bridges carbon and nitrogen biogeochemical cycles with primary ecological drivers.
Model Domain	General
Developer	University of New Hampshire: Professor Changsheng Li.
Hardware computing requirements	PC operating Windows with 64M memory are minimum requirements, additional recommended requirements include 350MHz processor or higher and graphics adapter of SVGA or higher.
Code language	Visual C++ 6.0
Original application	Original model developed to simulate rain-event driven N₂O, N₂ and CO₂ evolution from agricultural soils using three sub-models (thermal-hydraulic, decomposition, denitrification) (Li et al., 1992; Gilhespy et al., 2014).
Public/proprietary and cost	Model publicly available. No associated cost for use.
Physically or empirically based	Physically based model on carbon and nitrogen biogeochemical processes. Empirically based on equations produced from laboratory studies.
Mathematical methods used	Model incorporates classical laws of physics, chemistry and biology and empirical equations generated from laboratory studies, to parameterize geochemical or biochemical reaction for decomposition, urea hydrolysis, ammonia volatilization, nitrification, denitrification and methane dynamics processes. Model specific equations and procedures are provided in UNH, 2017. Model consists of various sub-models: Soil-climate, crop growth, decomposition, nitrification, denitrification and fermentation.
Input data requirements	Model can be operated using site or regional mode. Input consist of ecological drivers: climate parameters (temperature, precipitation, humidity, wind speed, solar radiation, humidity), soil parameters (temperature, pH, texture, clay content, bulk density, porosity, field capacity, soil organic carbon, salinity, soil slope, microbial activity index, land use) and cropping management (crop type, tillage, fertilization, amendments, irrigation, flooding, physical structures, grazing, cutting, number of cropping systems applied, duration of cropping). Meteorological, soil, cropping management and microbial data can be obtained through public databases. Detailed land and cropping management information can often be obtained from land managers.
Outputs	Soil properties (temperature, moisture, pH, oxidation-reduction potential, substrate concentration profiles (nitrate, dissolved organic carbon, ammonium, etc.), daily and annual crop biomass, carbon and nitrogen pools/fluxes/budgets, water budget). Plant-soil system gas emissions (carbon dioxide–CO₂, methane–CH₄, ammonia–NH₃, nitric oxide–NO, nitrous oxide–N₂O and dinitrogen–N₂). Output is on timescale of days, years to centuries. Output files are in plain text format, quick viewing of results also provided in model program.
Pre-processing and post-processing tools	Model application file, database files.
Representation of uncertainty	Uncertainty in data input can be specified by user. Uncertainty in model simulations can be calculated in program using Monte Carlo approach (site mode) or Most Sensitive Factor method (regional mode).
Prevalence	Very commonly applied model, used by academic and government entities. Applications vary widely (forested wetlands, livestock farms, pasture lands, etc.) and have led to the development of many specialized versions of DNDC for various locales. Limited in used for modeling in the Bay-Delta regions, DNDC model validations performed for the Bay-Delta (Deng and Salas, 2017; Li et al., 2014; Merrill et al., 2010).
Ease of use for public entities	Easy to moderate, no special training required, user guide available. No specialized hardware or software necessary.
Ease of obtaining information and availability of technical support	No commercial help desk available. User support available upon request from contact at http://www.dndc.sr.unh.edu/ or from individual modelers.
Source code availability	Model available at http://www.dndc.sr.unh.edu/. Source code available upon request.
Status of model development	Development and expansion of model is on-going with contributions from various researchers, modelers and agencies.
Challenges for integration	Integration challenges not clear. Model able to simulate output from various timesteps and spatial resolutions.

References

Gilhespy, S.L., Anthony, S., Cardenas, L., Chadwick, D., del Prado, A., Li, C., Misselbrook, T., Rees, R.M., Salas, W., Sanz-Cobena, A. and Smith, P., 2014. First 20 years of DNDC (DeNitrification DeComposition): model evolution. Ecological Modelling, 292, pp.51-62.

Deng, J., Salas, W., 2017. Improving DNDC Modeling Capability to Quantify Mitigation Potential of Nitrous Oxide from California Agricultural Soils. California Environmental Protection Agency, Air Resources Board, Research Division.

Li, C., Six, J., Horwath, W.R. and Salas, W., 2014. Calibrating, Validating, and Implementing Process Models for California Agriculture Greenhouse Gas Emissions. California Environmental Protection Agency, Air Resources Board, Research Division.

Li, C., 2012. User's Guide for the DNDC Model (version 9.5). Institute for the Study of Earth, Oceans, and Space. University of New Hampshire, Durham, NH.

Li, C., Frolking, S. and Frolking, T.A., 1992. A model of nitrous oxide evolution from soil driven by rainfall events: 1. Model structure and sensitivity. Journal of Geophysical Research: Atmospheres, 97(D9), pp.9759-9776.

Merrill, A., Siegel, S., Morris, B., Ferguson, A., Young, G., Ingram, C., Bachand, P., Shepley, H., Singer, M. and Hume, N., 2010. Greenhouse gas reduction and environmental benefits in the Sacramento-San Joaquin Delta: advancing carbon capture wetland farms and exploring potential for low carbon agriculture. The Nature Conservancy. [Available at http://www.stillwatersci.com/resources/2010merrilletal_deltacarbon.pdf].

UNH (University of New Hampshire), 2017. DNDC version 9.5 Scientific Basis and Processes. http://www.dndc.sr.unh.edu/papers/DNDC_Scientific_Basis_and_Processes.pdf (accessed 21 October 2018).

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