Community Assembly Mechanisms Facilitate Understanding of Microbial Responses to Habitat Succession along a Spatial Environmental Continuum in Alpine Plateaus

While soil microorganisms mediate important ecosystem functions, their community assembly mechanisms along a spatially connected environmental continuum during alpine habitat succession remain elusive. Here, we profiled the taxonomic and functional characteristics of soil microbiomes across three independent wetland-grassland-bareland continua on the Pamir Plateau. Along this successional gradient, microbial diversity, network complexity, and network stability decreased significantly towards barelands. Null model analyses revealed a pronounced shift in community assembly within barelands, characterized by increased heterogeneous selection and dispersal limitation. This mechanistic shift, driven by severe water scarcity and salt stress, underpins the diminished diversity and network robustness. Notably, soil microbial functional potential peaked in grasslands, likely reflecting enhanced plant-soil feedbacks. By linking community properties to functionality, we demonstrated that microbial diversity, rather than network complexity, serves as the primary biotic driver mediating shifts in soil microbial functional potential. Ultimately, these findings provide a mechanistic understanding of microbial community assembly and functional succession in sensitive alpine ecosystems.