Abstract: Global climate change is causing dramatic changes in precipitation patterns, profoundly affecting aboveground and belowground biodiversity in grasslands. Arbuscular mycorrhizal fungi (AMF), which form symbiotic associations with nearly all grassland plants, play an important role in regulating plant communities and ecosystem functions. However, the patterns of co-variation between AMF and plant communities under different precipitation regimes, especially whether the plant community serves as a key driver of AMF community, remained poorly understood. In this study, we set up a controlled experiment in a typical grassland of Inner Mongolia with three natural precipitation treatments: ambient (control), reduced precipitation (-50%), and increased precipitation (+50%). We aimed to investigate the responses of plant and AMF diversity and spatial compositional variability and to explore the underlying influencing factors. The results showed divergent diversity responses between the plant and AMF communities: plant β-diversity was highest under increased precipitation, whereas AMF β-diversity peaked under reduced precipitation. In contrast, plant and AMF communities exhibited a convergent increase in spatial compositional variability under reduced precipitation, as indicated by higher CV for plants and AVD for AMF. AMF composition was primarily driven by soil water content. Importantly, soil physicochemical properties contributed more strongly than plant community attributes to AMF spatial variability, suggesting a dominant role of abiotic filtering. This study demonstrate that plant and AMF communities can exhibit divergent diversity but convergent spatial organization under different precipitation pattern, highlighting the importance of disentangling diversity patterns from spatial variability when assessing ecosystem responses to global change.

Key words: Precipitation pattern, Arbuscular mycorrhizal fungi, Plant community, β-diversity, spatial variability, Grassland ecosystem