Environmental drivers of soil microbial activity and diversity along an elevational gradient

Microbial functional and structural patterns and drivers along elevational gradients have recently received increasing attention. In this study, we examined soil bacterial and fungal community diversity, compositions, and microbial activities (i.e., soil basal respiration and extracellular enzyme activities) across an elevational gradient from 1148 m to 2080 m (consists of six elevations) in the Yuanmou dry-hot valley located in Southwest China. Environmental factors, including soil temperature, moisture content, pH, soil organic carbon (SOC), total nitrogen (TN), the C/N ratio, total phosphorus (TP), and aboveground plant biomass were also determined. The results showed that soil bacterial alpha diversity (Shannon index) was unaffected by elevation, whereas fungal alpha diversity firstly increased significantly from 1148 m to 1539 m but did not increase further at higher elevations. Bacterial Shannon index was significantly correlated with SOC, whereas fungal Shannon index was remarkably associated with soil temperature. Microbial activity, beta diversities and community composition varied with elevation, but none of them showed a consistent trend. Monte Carlo test revealed that soil moisture followed by temperature, and pH, were the primary drivers of bacterial community composition. Soil fungal community composition significantly depended on soil moisture. Overall, our study suggested bacterial diversity and composition were determined by climatic (moisture and temperature) and edaphic properties (SOC and pH), while fungal diversity and composition were structured mainly by climatic factors. These findings may contribute to a better understanding of microbial responses along elevational gradients in this semi-arid region.