Biogeographical patterns and drivers of bacterial community in the Qinghai-Tibetan Plateau

Qinghai-Tibetan Plateau (QTP) has been ranked as one of the main hotspots of biodiversity. The biogeographic research on soil bacteria lags behind that of animals and plants, especially on the QTP. In this paper, we explored soil bacterial communities across two alpine grassland ecosystems (alpine steppe and alpine meadow) on QTP in China. Bacterial alpha-diversity differ significantly, which could be attributed to changes in plant cover and total phosphorus (TP) content. The dominant bacterial phyla were Actinobacteriota (28.54 %), Proteobacteria (22.74 %) and Acidobacteriota (12.96 %). Obvious distance-decay of bacterial community was observed across environ-mental factors and geographic distance (P < 0.001). Partial Mantel tests indicated that differences of bacterial community in whole data and alpine steppe were driven by the joint impacts of environmental factors and geographic distance, while differences of bacterial community in alpine meadow were driven by a sole impact of geographic distance. The MRM model explained 57.2 % and 49.4 % of the variability in the whole data and alpine meadow, respectively (P < 0.001), with pH being the most important variables explaining the similarity of bacterial community, followed by geographic distance, available phosphorus (AP) content and C/N. In addition, 25.6 % of the variability in alpine steppe was explained by the MRM model (P < 0.001), with geographic distance being the most important variables explaining the similarity of bacterial community. In summary, our findings suggested that alpha-diversity patterns, and the driving factors of the bacterial community structure were different across two ecosystem types, and environmental factors and geographic distance played different roles on the bacterial community structure in alpine steppe and alpine meadow. This study provides new understanding of soil microbial geography, and ecosystem functions driven by soil bacteria.