Warming has differential effects on the diversity, richness and biomass of soil bacteria and fungi

Climate warming has caused widespread global concern. However, how warming affects soil microbial diversity, richness, community structure and biomass is still poorly understood. Therefore, this study conducted a meta-analysis of 1044 observations from 144 publications by collecting relevant data on a global scale. The results showed that warming significantly altered soil temperature, soil water content, community structure of soil bacteria and fungi, and beta diversity of fungi. Warming decreased soil microbial diversity, richness and biomass, but the overall effect was not significant, while warming increased soil physicochemical and plant biomass indicators. Soil bacteria and fungi showed opposite trends in response to warming (e.g., the weighted mean effect values of the bacterial Shannon index, OTU Richness, and PLFA were all negative, whereas those for fungi were all positive), with fungi being more sensitive to warming than bacteria. Model selection analysis indicated that the RR (response ratio) of pH, ecosystem type and warming magnitude are important factors influencing the RR of soil bacterial diversity and richness. In addition, warming significantly decreased the OTU richness of forest soil bacteria and significantly increased the OTU richness of cropland soil fungi. The RR of bacterial richness (Chao1, OTU Richness) was significantly different among ecosystems, whereas that of fungal richness was not. The RR of diversity and richness of soil bacteria showed significant correlations with the RR of pH and warming magnitude. Overall, these findings improve our understanding of soil microbial responses under global warming.