Effects of Urban-Rural Environmental Gradient on Soil Microbial Community in Rapidly Urbanizing Area

Rapid urbanization considerably changes the urban-rural landscape, soil environment, and soil ecosystem functions. Within terrestrial ecosystems, microorganisms play key roles in soil ecosystem functions and are highly vulnerable to the effects of rapid urbanization. However, research on the effects of changing environment along urban-rural gradient on the composition, diversity, and network structure of soil microbial community remains limited. In this study, we analyzed the effects of land use pattern, human activities, and soil properties on soil bacterial community in urban, peri-urban, and rural areas. Results revealed substantial differences in soil bacterial composition, diversity, and network structure among urban, peri-urban, and rural soils. Peri-urban areas emerged as hotspots of soil microbial diversity compared with urban and rural areas. The results of a co-occurrence network analysis demonstrated that bacterial community in rural soils exhibited a complicated and stable network, whereas soil bacterial network in urban and peri-urban soils were unstable, especially in urban soils. The intensity of human activity on the land surface and proportion of forestland were the key factors affecting soil bacterial community. Human activity and land use may not only directly affect soil bacterial community but also indirectly affect soil bacterial composition and diversity by changing soil properties. This study can enhance our understanding of the influence of urbanization pattern on soil microbial community and their potential consequences on soil ecosystem and human health.