Species‐Specific Shrub Encroachment Drives Divergent Soil Fungal Assembly Processes and Network Structures in Alpine Meadows

ABSTRACT Shrub encroachment is rapidly transforming alpine meadow ecosystems worldwide, yet its consequences for belowground microbial organization remain insufficiently understood, particularly when different shrub species exert contrasting ecological effects. Here, we investigated how three dominant shrub species— Rhododendron capitatum , Salix oritrepha , and Dasiphora fruticosa —influence soil fungal communities across encroachment gradients in an alpine meadow on the northeastern Qinghai–Tibet Plateau. Using a space‐for‐time substitution approach combined with high‐throughput sequencing and network analysis, we analyzed soil fungal community composition, inferred functional guild structure, community assembly processes, and correlation‐based co‐occurrence network topology. Shrub encroachment was associated with changes in soil fungal community composition. Across species, the inferred relative abundance of putative saprotrophic fungi declined with encroachment, and taxa putatively identified as ectomycorrhizal fungi were consistently enriched in interspaces. Fungal community assembly showed species‐specific patterns. Under R. capitatum , stochastic processes dominated (ecological drift: 66.7%–80% of assembly), with reduced co‐occurrence network complexity. In contrast, encroachment by S. oritrepha and D. fruticosa suggested increased habitat homogenization and a shift toward stronger deterministic assembly: ecological drift declined by 46.67% and 60.03%, respectively, while homogeneous selection and network complexity increased. Notably, only severe D. fruticosa encroachment showed higher robustness in node‐removal simulations, whereas network robustness did not differ significantly among encroachment stages for R. capitatum or S. oritrepha plots. Collectively, these results suggest that shrub encroachment does not exert uniform effects on soil fungal communities; instead, shrub identity is associated with divergent community organization patterns and inferred assembly pathways.