NLOSS: A mechanistic model of denitrified N2O and N-2 evolution from soil

Soil microbial denitrification is a significant source of atmospheric nitro us oxide (N2O), a trace gas important in global climate change and stratosp heric ozone depletion. In this paper we describe a mechanistic submodel, wh ich is incorporated in the model NLOSS, designed to predict the soil biogen ic source and efflux of N2O and N-2 during denitrification, NLOSS simulates transient soil moisture and temperature, decomposition, soil anaerobicity, denitrifying bacterial biomass, rates of soil nitrogen transformations, so il trace-gas transport, and gas efflux to the atmosphere. Uncertainty in pr edicted N gas effluxes is commuted using a Monte Carlo approach. We test NL OSS's denitrification estimates by comparing predictions with results from a N-15 tracer experiment in a Mexican agricultural system. The model accura tely predicted the measured soil moisture and denitrified N2O and N-2 fluxe s during the experiment. We also apply NLOSS to compute denitrified N trace -gas speciation curves as a function of soil hydrologic properties and mois ture content. These speciation curves will be used in future work to extrap olate the plot-scale modeling results presented here to field and regional estimates of N trace-gas emissions. The results presented here suggest that NLOSS can be used to identify the processes most important for trace-gas l osses and to facilitate efforts to scale plot-level modeling results to reg ional estimates of N trace-gas emissions.