Identifying soil N$_2$O sources by combining laboratory experiments with process-based models

Nitrification and denitrification are two important biological processes producing N$_2$O in soils, but their contributions to N$_2$O emissions are not well understood, hindering precise mitigation measures. Here, we developed process-based models (PBM) with and without transport (T) to partition N$_2$O sources by tracking nitrogen flows (NF) through different reaction pathways. The model with transport (PBM-T-NF) well predicted N$_2$O production from nitrification and denitrification in two different repacked soils with a shallow depth of 8 mm under moisture conditions ranging from 40 to 100% waterfilled pore space (WFPS), demonstrating its robustness and reliability. In comparison, the model without transport (PBM-NF) failed to capture the N$_2$O dynamics and the relative contribution of denitrification to N$_2$O production (CD), highlighting the need of including mass transport in predicting N$_2$O dynamics. The PBM-T-NF model was further employed to