Soil keystone phylotype diversity and plant diversity co-drive ecosystem stability in the Tibetan alpine grasslands

Soil multitrophic diversity and plant diversity are critical for ecosystem stability, yet their impacts remain poorly understood. Here, we performed an extensive survey across the Tibetan Plateau to examine the impacts of species pool size (γ-diversity), local richness (α-diversity), and species turnover (β-diversity) of soil multitrophic communities and plants on temporal ecosystem stability. Our results showed that the α-diversity of plants and cluster 2, together with the β-diversity of clusters 0 and 1, is positively associated with ecosystem stability. Notably, the stabilizing effect of α-diversity within cluster 2 increased with organism body size and trophic level, being most pronounced in nematodes and protistan consumers. Structural equation models showed that cluster 2 α-diversity and cluster 0 β-diversity enhanced ecosystem stability via direct or plant-mediated pathways. Collectively, this research elucidates the stability effects of above- and below-ground diversity at multiple spatial scales, underscoring the necessity of integrating soil keystone phylotypes and plant diversity into conservation management.