Promoting effect of plant diversity on soil microbial functionality is amplified over time

The ongoing biodiversity crisis of plants threatens ecosystem services, emphasizing the need to understand links between plant diversity and soil health. However, how plant diversity influences soil microbial diversity and functions remains unclear, primarily due to insufficient control of covariates and limited long-term investigations. Here, we analyzed a global dataset from plant diversity experiments and found that increased plant richness enhances soil microbial diversity, biomass, and functions. Plant diversity effects on microbial functions shifted from negative in young stands to positive in old stands, indicating that long-term plant diversity benefits microbial functionality. The dual challenges of climate change and biodiversity loss further undermine ecosystem services. Our findings underscore the importance of long-term plant diversity management to sustain soil health and mitigate climate change under the ongoing biodiversity crisis.