Soil type and pH mediated arable soil bacterial compositional variation across geographic distance in North China Plain

A challenge in biogeography is to understand what are the factors and how they regulate soil microbial communities. To explore the coexistence pattern of bacterial community and the factors shaping agricultural soil bacterial community at spatial scale, 135 soil samples were collected from a typically agricultural province in the North China Plain and analyzed with high-throughput 16S rRNA gene sequencing. As expected, bacterial community dissimilarity showed significant distance-decay relationships with 42.2% variation explained by geographic distance and physicochemical factors. Bacterial phyla abundance showed different responses to environmental factors among which soil pH was the primary factor shaping soil bacterial community structure. Bacterial communities in acidic soils suggest lower phylotype richness and phylogenetic diversity and its associated network structure showed greater connectivity and stability compared to those in neutral and alkaline soils. Soil bacterial community diversity was also varied with soil type. Unlike the simplest topological features of co-occurrence network in Cinnamon soil, bacterial community structure was more connected and stable in Lime concretion black soil and Kallotenuales but not the predominant taxa were identified as kinless hub. However, Neisseriales, Anaerolineaceae and Nannocystaceae from Proteobacteria and Chloroflexi with higher relative abundance might support higher levels of ecosystem functions in Fluvo-aquic soil. Taken together, our results suggest that geographic distance and pH variation strongly shaped bacterial community structure with correspondingly diverse co-occurrence patterns observed in different soil pH ranges and types.