Nitrous oxide (N2O) can be both produced and reduced to dinitrogen (N2) during microbial denitrification, with the balance between these steps controlling the net flux of this potent climate gas. Here, we first used a meta-analysis of published studies to predict how warming may regulate N2O and N2 production in soils and sediments. However, as most of these former studies used nitrate at far higher than ambient concentrations, the applicability of these predictions to ambient conditions may be limited. In addition, few studies separated denitrification from other microbial pathways contributing to N2O and N2 production. To address these limitations, we used 15N-isotope labelling experiments in freshwater sediments to test how temperature sensitivity varies with limited (10 μM) and replete (100 μM) nitrate. Temperature affected N2O and N2 production only when nitrate was replete, where N2 production increased but net N2O production declined with warming, leading to a lower N2O:N2 production ratio at higher temperatures. These results show that substrate availability can outweigh temperature in controlling the balance between N2O and N2 production, indicating that temperature-based predictions of N2O emissions alone may overestimate the effects of climate warming.
Si et al. (Sun,) studied this question.