Extreme precipitation alters soil nitrogen cycling related microbial community in karst abandoned farmland

Precipitation varies significantly in the southwest China karst regions, with a significant increase in the number of years with abnormally low precipitation during the rainy season and longer dry periods. Soil moisture and nitrogen chemical patterns are the main limiting factors for plant growth in this region. However, there are fewer studies on the impact of extreme precipitation on soil nitrogen cycling in abandoned farmland in karst ecosystems. In this study, we investigated the effects of changes in precipitation frequency and single precipitation amount on the nitrogen-cycle related microbial community in karst abandoned farmland through a two-year precipitation manipulation experiment. Our results showed that more frequent, smaller precipitation events increased soil water content, alleviating water limitation in karst abandoned farmland and resulting in higher abundance of functional genes (nosZ, nrtABCD, gltBD, and gdhB), which accelerated soil nitrogen turnover compared to natural precipitation (Control). The changes in the gene abundance were associated with shifts in the dominant microbial taxa, such as Proteobacteria and Actinobacteria. In addition, nitrogen-cycling microbial communities exhibited resistance and resilience to extreme precipitation conditions. These findings shed light on the influence of precipitation regimes changes on soil nitrogen cycling in karst abandoned farmland, offering valuable insights for predicting the ecosystem's response to future precipitation changes.