Altitudinal gradient diminishes the impact of vegetation restoration on soil microbial communities in the Eastern Tibetan Plateau

Soil microorganisms are pivotal for plant growth and nutrient cycling in roadside restoration, particularly in sensitive high-altitude ecosystems. However, understanding their response to varied restoration treatments remains unclear. Here, we examined soil microbial community diversity, distribution, and network properties in restored vegetation formations characterized by herbaceous plants only (H), shrubs + herbaceous plants (SH), and trees + shrubs + herbaceous plants (TSH) across elevational gradients (3100 m, 3300 m, 3500 m, and 3800 m). We found that elevation and vegetation type directly influenced bacterial and fungal communities or indirectly via their impact on plant community traits and soil properties. While both factors exerted substantial effects, these diminished with higher elevations. We further found that nitrogen predominantly drove bacterial community changes, while soil water content significantly impacted fungal communities. Bacterial alpha diversity decreased, contrasting with varied fungal alpha diversity with elevation, reflecting the complexity of microbial networks. Identifying restoration-sensitive microbes and keystone taxa highlighted that H-type vegetation contained more of these taxa compared to SH- and TSH-types with woody plants. However, these keystone species, associated with pathotrophs and plant pathogens, negatively correlated with plant properties, suggesting potential benefits of woody vegetation for restoration. Critical environmental variables affecting keystone taxa included elevation, mean annual temperature, mean annual precipitation, pH, ammonium nitrogen, dissolvable organic nitrogen, carbon to nitrogen ratio. Insights derived from managing microbes based on these critical variables offer significant implications for crucial restoration strategies. This study substantially advances our understanding of how elevation and vegetation types shape soil microbiomes on plateau.