Soil bacterial diversity correlates with precipitation and soil pH in long-term maize cropping systems

Unraveling the key drivers of bacterial community assembly in agricultural soils is pivotal for soil nutrient management and crop productivity. Presently, the drivers of microbial community structure remain unexplored in maize cropping systems under complex and variable environmental scenarios across large spatial scales. In this study, we conducted high-throughput 16S rRNA gene sequencing and network analysis to identify the major environmental factors driving bacterial community diversity and co-occurrence patterns in 21 maize field soils across China. The results show that mean annual precipitation and soil pH are the major environmental factors that shape soil bacterial communities in maize soils. The similarities of bacterial communities significantly decreased with increasing geographic distance between different sites. The differences in spatial turnover rates across bacterial phyla indicate the distinct dispersal capabilities of bacterial groups, and some abundant phyla exhibited high dispersal capabilities. Aeromicrobium, Friedmanniella, Saccharothrix, Lamia, Rhodococcus, Skermanella, and Pedobacter were identified as keystone taxa. Based on the node-level and network-level topological features, members of the core microbiome were more frequently found in the center of the ecosystem network compared with other taxa. This study highlights the major environmental factors driving bacterial community assembly in agro-ecosystems and the central ecological role of the core microbiome in maintaining the web of complex bacterial interactions.