Moderate precipitation reduction enhances nitrogen cycling and soil nitrous oxide emissions in a semi‐arid grassland

Abstract The ongoing climate change is predicted to induce more weather extremes such as frequent drought and high‐intensity precipitation events, causing more severe drying‐rewetting cycles in soil. However, it remains largely unknown how these changes will affect soil nitrogen (N)‐cycling microbes and the emissions of potent greenhouse gas nitrous oxide (N 2 O). Utilizing a field precipitation manipulation in a semi‐arid grassland on the Loess Plateau, we examined how precipitation reduction (ca. −30%) influenced soil N 2 O and carbon dioxide (CO 2 ) emissions in field, and in a complementary lab‐incubation with simulated drying‐rewetting cycles. Results obtained showed that precipitation reduction stimulated plant root turnover and N‐cycling processes, enhancing soil N 2 O and CO 2 emissions in field, particularly after each rainfall event. Also, high‐resolution isotopic analyses revealed that field soil N 2 O emissions primarily originated from nitrification process. The incubation experiment further showed that in field soils under precipitation reduction, drying‐rewetting stimulated N mineralization and ammonia‐oxidizing bacteria in favor of genera Nitrosospira and Nitrosovibrio , increasing nitrification and N 2 O emissions. These findings suggest that moderate precipitation reduction, accompanied with changes in drying‐rewetting cycles under future precipitation scenarios, may enhance N cycling processes and soil N 2 O emissions in semi‐arid ecosystems, feeding positively back to the ongoing climate change.