Global change factors caused the decoupling of soil nutrient dynamics and asynchrony of microbial community and ecological function in temperate grassland soil

Soil microbial communities and grassland ecosystem processes are increasingly confronted with multiple global change factors (GCFs). Yet, there is a lack of research on the interactions among multiple GCFs on soil microbial community and function. Here, we conducted a simulation experiment to investigate the individual and interactive effects of the four most pressing and common GCFs, including elevated carbon dioxide (eCO2), warming (eT), decreased precipitation (dP) and increased nitrogen (eN), on soil physicochemical properties, bacterial and fungal communities, and EEAs (extracellular enzyme activities) related to carbon (C), nitrogen (N), and phosphorus (P) cycles in temperate grassland soil. In general, eCO2, eN, and dP tended to increase EEAs, and had neutral effects on microbial diversity and community composition. As a result of eT, soil pH, total carbon, total nitrogen, EEAs and microbial diversity declined, whereas plant biomass, total phosphorus, microbial richness and network complexity and stability increased. Therefore, warming shifted the nutrient restriction from phosphorus to nitrogen, resulting in the decoupling of nutrients. Bacterial networks and dominant species may be more sensitive to eT and dP, and less sensitive to eN than fungi. Neutral or slightly negative relationships were found between enzymes and microbial richness, diversity and dominant species, and the responses of microbial community and ecosystem function were asynchronous under global change. In addition, our results revealed significant higher-order interactions among GCFs affecting soil physicochemical properties, microbial community and functionality, which may provide insights and suggestions for future ecological adaptations to global change.