Altered precipitation affects soil enzyme activity related to nitrogen and phosphorous but not carbon cycling: A...

Altered precipitation significantly influences soil function in terrestrial ecosystems. As a bioindicator of soil function, soil extracellular enzyme activity (EEA) plays a crucial role in mediating ecosystem responses to altered precipitation. However, the global patterns and regulatory mechanisms of altered precipitation impacts on soil EEAs remain unclear. We conducted hierarchical mixed-effects meta-analyses to explore the responses and regulators of carbon, nitrogen, phosphorus hydrolytic EEAs, and carbon oxidative EEA to changes in precipitation, using the largest dataset to date, comprising 1185 observations of 14 soil EEAs from 73 publications. The results indicated that soil nitrogen hydrolytic EEA increased by 14.3% under increased precipitation, while phosphorus hydrolytic EEA decreased by 8.8% under decreased precipitation, showing higher sensitivity to altered precipitation compared to carbon-degrading EEAs. These responses varied across ecosystem types and depended on the magnitude of precipitation manipulation (MPM). Specially, decreased precipitation significantly reduced phosphorus hydrolytic EEA in forests, while increased precipitation enhanced nitrogen hydrolytic EEA in grasslands. Furthermore, these effects were linearly correlated with MPM, deviating from the expected nonlinear double asymmetric model. The response of soil hydrolytic EEAs was predominately regulated by soil water content, organic carbon, and microbial biomass. These findings underscore the higher sensitivity of nitrogen and phosphorus cycling EEAs to altered precipitation compared to carbon cycling EEAs and extend the application of the double asymmetric model for understanding soil EEAs' responses to precipitation changes. This synthesis provides essential insights for predicting biogeochemical cycling and improving ecosystem models to evaluate ecosystem functions under altered precipitation.