Forest conversion-induced soil biota homogenization destabilizes ecosystem functions

Abstract The conversion of natural forests to agricultural land threatens soil biodiversity and ecosystem stability, but its integrated impacts on soil multitrophic communities remain poorly understood. Here, we examined the relationships between forest-to-agriculture conversion, soil multitrophic community diversity, and temporal stability along a 3000 km transect in the Yangtze River Basin. Forest conversion increased the α-diversity of copiotrophic bacteria, but decreased the α-diversity of mycorrhizal fungi, parasitic protists, and most nematode functional groups. Crucially, it consistently decreased β-diversity across all functional groups, homogenizing soil communities. This homogenization destabilized ecosystem productivity by impairing soil nitrogen cycling and weakening plant–soil feedbacks. While the loss of α-diversity was observed in certain groups, it was the decline in β-diversity, or spatial variation, that emerged as the primary driver of reduced ecosystem stability. Our findings challenge conventional conservation paradigms by demonstrating that preserving ecosystem stability requires prioritizing β-diversity through sustainable agriculture and habitat protection.