Relative roles of competition, environmental selection and spatial processes in structuring soil bacterial communities in the Qinghai-Tibetan Plateau

The structure and dynamics of microbial communities may be influenced by environmental selection, spatial processes and competition. However, the relative strengths of these processes need to be further elucidated. Here, with a large scale sampling along an elevational gradient of 2000 m in the Qinghai-Tibetan Plateau, we examined the interplay among the three processes, as well as their relative importance to the biogeography of bacterial communities. Variation partitioning showed that environmental selection, competition and spatial variables jointly explained 37% of the total variation among the bacterial communities. The non-spatially structured environmental variables explained more variation than spatial distance or competition. Two environmental factors, elevation and soil pH, were shown to be the main cues determining soil bacterial communities. Environmental variables and spatial distance also exerted indirect effects on community variation via competition. The main conclusion of this study is consistent with the idea that "the environment selects". Competition and spatial processes were less important in shaping bacterial communities of Qinghai-Tibetan Plateau.