No significant change noted in annual nitrous oxide flux under precipitation changes in a temperate desert steppe

Abstract As the third most important greenhouse gas, nitrous oxide (N 2 O) poses a significant threat to global warming and the ozone layer. However, the effects of precipitation changes on N 2 O emissions in arid areas remain unclear, particularly in desert steppe environments. Therefore, an in situ control experiment was conducted from July 2018 to July 2020 to examine the N 2 O emissions with changes in precipitation in the Urat Desert Steppe, northwestern China. The results showed that the N 2 O emission rate was relatively low in this desert steppe, at −0.04 to +15.0 μg N m −2 hr −1 with an annual flux of 0.20 ± 0.03 kg N ha −1 . An increasing trend of N 2 O emission was observed in the early growing season (February to June 2019) when the precipitation was increased by 40% and 60% of its natural level. In contrast, no significant change in N 2 O emissions was observed when the precipitation was decreased during the same period. During the middle and late growing season and in the nongrowing season, precipitation changes did not significantly affect N 2 O emissions. In particular, no significant change in the annual N 2 O flux was observed during the entire observation period whether the precipitation was increased or decreased. Furthermore, the results of a structural equation model showed that the most important controlling factor for N 2 O emission is an abundance of key functional ammonia monooxygenase genes of ammonia‐oxidizing archaea, which are restricted by the soil NH 4 + ‐N content, followed by abundances of key functional NO 2 − reductase ( nirK ) and N 2 O reductase ( nosZ ) genes. In contrast, the indirect effect of soil moisture on the abundance of nosZ compensated for the direct effect of soil moisture on N 2 O emissions. These results show that the primary and secondary origins of N 2 O emissions are soil ammonia oxidation and soil denitrification processes, respectively. In these two processes, N 2 O emissions are influenced more by the abundance of key functional microorganisms than by soil moisture, which might be limited mainly by the available soil nitrogen. Overall, the N 2 O emissions in the desert steppe environment were not sensitive to precipitation changes and were regulated mainly by nitrogen‐related key functional microorganisms.