Interactions between soil bacterial communities, assembly processes and microbial functions along the elevational gradient

The distribution of microbial communities along elevational gradients has been widely reported, but whether there are linkages between soil microbial diversity, community assembly processes and microbial functions in elevational patterns, and whether the patterns are influenced by micro-topography (e.g. slope direction), remain unclear. Here, we collected soils from two slope directions (i.e. north-facing slope and east-facing slope) along the elevational gradient (similar to 2000 m elevational range) of a mountain ecosystem. Unexpectedly, for bacterial alpha diversity or microbial functions (i.e. multifunctionality), we found consistent elevational patterns for both slope directions, with alpha diversity showing a hump-shaped pattern and microbial functions exhibiting a linearly increasing trend. Similarly, for both slope directions, there were significant elevational distance-decay relationships in the bacterial beta diversity pattern. The elevational patterns of soil bacterial diversity were determined by the transitions of community assembly processes, while microbial functions were mainly influenced by bacterial community composition. These results suggest that soil bacterial diversity, community assembly processes and microbial functions are interactive along an elevational gradient, and that these interactions are independent of slope direction. Our study adds new insights into the elevational patterns of soil bacterial communities and their drivers and ecological consequences in mountain ecosystems.