Divergent drivers determine soil bacterial β-diversity of forest and grassland ecosystems in Northwest China

Abstract

The determinants of bacterial β-diversity across the large scale have been well explored, yet little is known that about how the driving factors of bacterial β-diversity differ between the forest and grassland in northwest China. Here, we comprehensively compared the biogeographic patterns and their drivers of bacterial communities in the forest and grassland. We also quantified the relative contribution of two components (replacement and nestedness components) to bacterial β-diversity. We found the significant distance-decay relationships in both two ecosystems, whereas more species turnover correlating with geographic distance was observed in forest ecosystems than grassland ecosystem, and the slope in the forest was significantly steeper than that in grassland. This suggests that bacterial diversity in forest and grassland soil exhibits distinct biogeographic and ecological patterns. More importantly, we found that soil bacterial β-diversity was mainly derived from replacement components in both two ecosystems, implying high proportion of endemic bacterial species distribute in dryland forest and grassland soil. Our results further demonstrated that environmental filtering have dominant effect on soil bacterial β-diversity in both forest and grassland. However, the relative roles of spatial processes varied between forest and grassland, where stochastic processes only have significant influence on soil bacterial β-diversity in forest but not in grassland. Among environmental factors, bacterial β-diversity and turnover components was mainly determined by water availability in grassland soil, but by soil pH in the forest soil. Taken together, our findings collectively suggest that differential ecological drivers underlie distinct biogeographic patterns of bacterial diversity in forest and grassland soil.