Biodiversity in mosaic communities: Soil microbial diversity associates with plant functional groups relating to soil available phosphorus in Tibetan alpine meadow

Natural landscape of alpine grassland is characterized by nested occupations of distinct communities, i.e., mosaic communities that differ not only in dominant plants but also in soil microbiome. Yet, we know little about the decoupled or coupled relationship between plant and soil microbial diversity, involving plant-soil feedback and confounding effects of environmental factors, synergistically maintaining biodiversity and function in mosaic communities. Here, we measured plant and soil microbial diversity in mosaic plots dominated by different plant functional groups (i.e., typical, sedges-, grasses-, legumes- or forbs-dominated communities) in the same Tibetan alpine meadow. We examined the difference in plant and soil microbial diversity between distinct communities using generalized linear models and assessed the relationships between plants, soil microbes, and edaphic factors using canonical discriminant analysis and generalized partial regression. Compared to the typical community: i) plant diversity increased and decreased in forbs- and sedges-dominated plots, respectively; ii) soil bacterial diversity increased in plots dominated by sedges and grasses; and iii) soil fungal diversity increased in plots dominated by sedges and legumes. The increase in soil bacterial diversity is associated with increasing standing biomass, plant diversity and soil available phosphorus but decreasing soil pH and soil available nitrogen, accounting for 52-66% of the variation. Despite being less pronounced, soil fungal diversity was positively associated with plant diversity and soil available phosphorus but tended to be negatively associated with standing biomass. In short, the results revealed that under complex interaction of soil-plant-microbes, the biodiversity of soil microbes is strongly coupled with plant functional groups relating to the availability of soil phosphorus, maintaining ecosystem function and service in soil phosphorus-limited mosaic meadows.