Groundwater depth regulates assembly processes of abundant and rare bacterial communities across arid inland river basin

Abstract

Although numerous studies on bacterial biogeographic patterns in dryland have been conducted, bacterial community assembly across arid inland river basins is unclear. Here, we assessed the ecological drivers that regulate the assembly processes of abundant (ABS) and rare (RBS) bacterial subcommunities based on 162 soil samples collected in an arid inland river basin of China. The results showed that: (1) ABS exhibited a steeper distance–decay slope, and were more strongly affected by dispersal limitation (75.5% and 84.5%), than RBS in surface and subsurface soil. RBS were predominantly controlled by variable selection (54.6% and 50.2%). (2) Soil electric conductivity played a decisive role in mediating the balance between deterministic and stochastic processes of ABS and RBS in surface soil, increasing soil electric conductivity increased the importance of deterministic process. For subsurface soil, soil available phosphorus (SAP) and soil pH drove the balance in the assembly processes of ABS and RBS, respectively. The RBS shifted from determinism to stochasticity with decreased pH, while the dominance of deterministic processes was higher in low-SAP sites. (3) Groundwater depth seasonality had substantial effects on the assembly processes of ABS and RBS, but groundwater depth seasonality affected them indirectly mainly by regulating soil properties. Collectively, our study provides robust evidence that groundwater-driven variations in soil properties mediates the community assembly process of soil bacteria in arid inland river basins. This finding is of importance for forecasting the dynamics of soil microbial community and soil process in response to current and future depleted groundwater.