A Model to Simulate Microbial Denitrification with Epic: Description, Evaluation, and Applications.

We will describe a mechanistic model to simulate microbial denitrification implemented in the terrestrial ecosystem model EPIC. Based on principles of chemistry, physics, and biology the model predicts nitrous oxide (N2O) and dinitrogen (N2) production under anaerobic conditions. Carbon oxidation releases electrons that drive a demand for electron acceptors such as O2 and oxides of N (NO3-, NO2-, and N2O). When denitrification occurs, there is an adjustment of C decomposition based on the ratio of actual vs. potential electrons accepted by O2 and oxides of N. Movement of O2, CO2, N2O, and N2 through the soil profile is modeled using the gas transport equation solved at hourly time steps. Bubbling equations also move N2O and N2 through the liquid phase to the soil surface under highly anaerobic conditions. We will present model evaluation results using data describing non-linear responses of N2O production to N application and other examples of N2O emissions under diverse experimental conditions.