Relative contributions of vegetation and soil properties to microbial community structure and function in alpine and subalpine meadows of the southeastern Tibetan Plateau.

Introduction: Ongoing climate warming is expected to promote the upward expansion of subalpine meadows and the gradual replacement of alpine meadows on the southeastern margin of the Tibetan Plateau. However, the mechanisms by which these vegetation transitions reshape belowground microbial taxonomic composition and metabolic functional potential remain poorly understood. Methods: We investigated soil microbial community structure and functional potential in alpine meadow (AM) and subalpine meadow (SM) ecosystems in the Napahai Basin by integrating vegetation surveys, soil chemical analyses, enzyme activity assays, and metagenomic sequencing. Results and discussion: Altitudinal differences in hydrothermal conditions were associated with pronounced divergence in plant community composition and soil nutrient status between the two meadow types. Although microbial α-diversity did not differ significantly, β-diversity analyses revealed distinct taxonomic and functional differentiation. Functional annotations based on CAZymes and KEGG indicated that variation in microbial functional potential was closely associated with coordinated changes in carbon, nitrogen, and phosphorus availability, suggesting that microbial metabolic strategies shifted along the environmental gradient. Random forest and partial least squares path modelling further showed that plant community composition exerted a stronger direct influence on microbial functional configuration than soil-mediated indirect effects. These findings highlight the prominent role of vegetation in shaping microbial functional potential and underscore the sensitivity of belowground ecological processes to vegetation transitions along environmental gradients in high-elevation meadow ecosystems.