Abstract. Nitrous oxide (N2O) is an important greenhouse gas that also contributes to the depletion of stratospheric ozone. With high temporal and spatial heterogeneity, a quantitative understanding of terrestrial N2O emission, its variabilities and reponses to climate change is challenging. We added a soil N2O emission module to the dynamic global land model LM3V-N, and tested its sensitivity to soil moisture regime and responses to elevated CO2 and temperature. The model was capable of reproducing the average of cross-site observed annual mean emissions, although differences remained across individual sites if stand-level measurements were representative of gridcell emissions. Modelled N2O fluxes were highly sensitive to water filled pore space (WFPS), with a global sensitivity of approximately 0.25 Tg N year−1 per 0.01 change in WFPS. We found that the global response of N2O emission to CO2 fertilization was largely determined by the response of tropical emissions, whereas the extratropical response was weaker and different, highlighting the need to expand field studies in tropical ecosystems. Warming generally enhanced N2O efflux, and the enhancement was greatly dampened when combined with elevated CO2, although CO2 alone had a small effect. Our analysis suggests caution when extrapolation from current field CO2 enrichment and warming studies to the global scale.
Global soil nitrous oxide emissions in a dynamic carbon–nitrogen model