Quantifying biological processes producing nitrous oxide in soil using a mechanistic model

Soil nitrous oxide (N2O) is an important greenhouse gas contributing to climate change. Many processes produce N2O in soil and the production rate of each process is affected by climatic-edaphic factors, making the soil-to-atmosphere N2O flux extremely dynamic. Experimental approaches, including natural and enriched isotopic methods, have been developed to separate and quantify the N2O production from different processes. However, these methods are often costly and tedious, hampering their wide application. This study aimed to develop a mechanistic model quantifying the soil N2O production from nitrifier nitrification (NN), nitrifier denitrification (ND), and heterotrophic denitrification (HD), which are considered as the most important biological processes, and to investigate how climatic-edaphic factors affect N2O production from individual process as well as total N2O production. The developed model demonstrated its robustness and capability by reliably reproducing the N2O production from NN, ND, and HD in different types of soils under various moisture contents or oxygen concentrations. The model simulations unraveled how environmental conditions and soil properties control the total N2O production rate by variably regulating individual processes. Therefore, the mechanistic model can potentially elucidate the large spatiotemporal variances of in-situ soil N2O flux and improve the assessment of soil N2O emission at regional and global scales.