Number of global change factors alters the relative roles of abundant and rare microbes in driving soil multifunctionality resistance.

There is increasing evidence that ecosystems are affected by multiple global change factors, impeding the sustainability of multiple soil functions. Biodiversity can buffer ecosystem functions against environmental changes, a concept largely supported by insurance and portfolio theories. However, the role of soil biodiversity, especially the diversity of abundant and rare microbial taxa, in regulating soil multifunctionality resistance under an increasing number of global change factors remains poorly explored. Here, we assessed the effects of the diversity of abundant and rare microbial taxa on soil multifunctionality resistance under different numbers of global change factors using 650 microcosms. The increasing number of global change factors reduced the effects of the diversity of abundant and rare microbial taxa on soil multifunctionality resistance and shifted their relative importance. The diversity of abundant taxa showed stronger positive effects on soil multifunctionality resistance under one or two global change factors. However, the diversity of rare taxa had stronger effects under multiple co-acting global change factors. The resistance of abundant and rare microbial taxa was significantly associated with their respective diversity effects on soil multifunctionality resistance. These effects were represented by standardized slopes that evaluated the relationships between microbial diversity and multifunctionality resistance under varying numbers of global change factors. Our findings indicate a shift in the relative importance of the diversity of abundant and rare microbial taxa in regulating soil multifunctionality resistance with an increasing number of global change factors, providing new insights into the relationship between soil biodiversity and ecosystem stability under environmental disturbances.