Elevational Patterns and Environmental Drivers of Dominant Bacterial Communities in Alpine Forest Soils of Mt. Taibai, China

Alpine ecosystems, as one of the most representative terrestrial ecosystems, have garnered significant attention due to their susceptibility to human activities and climate change. However, the distribution patterns and driving factors of alpine soil bacterial communities remain to be further explored, especially for different dominant phyla. This study investigated the soil bacterial community composition, elevational patterns, and relationships between bacterial diversity and environmental factors at four elevation gradients (2406–3204 m) on Mt. Taibai, Qinling Mountains, China, using 16S rRNA sequencing. The results showed that the dominant bacterial phyla were Acidobacteria, Actinobacteria, Proteobacteria, and Chloroflexi, accounting for over 69% of the bacterial sequences in soil samples. Dominant bacterial communities exhibit distinct elevation gradient patterns in diversity and community structure. The α-diversity of Actinobacteria and Chloroflexi decreases with increasing elevation, whereas that of Proteobacteria and Acidobacteria increases. Moreover, the community structure of Actinobacteria shows greater variation across elevations than the other three dominant bacterial groups, with significant differences observed among elevations. Redundancy analysis and distance decay analysis revealed that elevation was significantly correlated with the soil bacterial community structure (p < 0.01). Different dominant bacterial communities were regulated by distinct environmental factors, providing strong evidence for understanding microbial community assembly. Therefore, the α- and β-diversity of soil bacteria on Mt. Taibai exhibit distinct elevational variations, and elevation-driven plant diversity and pH may be key factors shaping the spatial distribution of soil bacteria.