Biodiversity in mosaic communities: Predicting soil microbial diversity using plant functional traits in alpine meadow

It is well known that the mosaic patches of alpine meadows are primarily shaped by plant-soil interactions. However, we know little about whether and how plant functional traits mediate the influence of edaphic factors on soil microbial diversity through the mass and diversity effects. In this study, we investigated plant functional traits in five distinctive of mosaic patches (communities) dominated by different plant functional groups in a Tibetan alpine meadow. We measured key functional traits for every plant species within each plot to calculate the functional composition (i.e., community-weighted mean, CWM) and structure (i.e., functional diversity, FD) of the plant community to examine the mass and diversity effects of plants on soil microbial diversity. In general, the difference in soil microbial diversity across the mosaic communities can be predicted by changes in CWM and FD of plant communities incorporating edaphic factors. The change in FD of five plant traits alone can predict 46% variation for soil bacterial richness, and up to 91% variation for soil fungal richness when the direct effect of edaphic factors was included. In response to variations in soil available phosphorus and pH, an increase in plant CWM and FD of leaf phosphorus and nitrogen content significantly promoted the richness of soil bacteria but lowered soil fungal richness. Hence, plant functional traits play a critical role in mediating the effects of edaphic factors on soil microbial diversity through mass and diversity effects. Our study not only illustrates the functional significance of plant traits in shaping plant-soil interactions in mosaic communities of the Tibetan alpine meadow but also promotes research linking biodiversity in mosaic patches to the functionality of the fragile alpine ecosystem.