A Microbial Model of Nitrous Oxide Production That Differentiates Nitrification and Denitrification Production Across Spatial and Temporal Scales.

Abstract:

N₂O fluxes from soil to the atmosphere are mainly attributable to the activity of two microbial functional guilds: aerobic autotrophic nitrifiers and anaerobic heterotrophic denitrifying bacteria. The controls on N₂O production from these guilds are generally known and include species interactions and a range of environmental factors (e.g., oxygen concentrations, organic matter stoichiometry, substrate availability, mineralization rates). Here we attempt to parse out the conditions controlling N₂O production using a trait-based microbial model that predicts N₂O production by representing the physiology and ecology of nitrifiers and denitrifiers, and the N₂O consumption pathways of heterotrophic bacteria. Following successful application of the standalone microbial model to predict nitrification and denitrification rates and associated N₂O fluxes, we ran the model with output from the Community Land Model (CLM4.5) to examine N₂O production across spatial and temporal scales, during rainfall events and under global change scenarios (e.g., increased temperature and nitrogen deposition). We discuss our output with respect to what is understood about the complexity of belowground ecosystems and how our approach can help constrain the global N₂O budget.