Bacterial community composition is an important predictor of surface soil fertility across different land use types: a case study in the Three Gorges Reservoir area.

Background: Surface soil is a vital component of terrestrial ecosystems and is of great importance for primary productivity. In Zhangjiachong, a small watershed in Zigui County, central China, human activity and erosion cause extensive surface soil degradation. It is still unclear as to what extent human activity influences soil fertility and soil microorganisms in this area. Methods: Soil samples were collected, during spring and autumn, across a series of land use types with different levels of human activity. We assessed soil fertility and microbial communities using 16S rRNA gene sequencing and Biolog ECO-plates. Results: The results showed that higher levels of human activity were associated with lower soil fertility and microbial metabolic activity, in addition to higher bacterial diversity. Moreover, human activity had negative effects on the relative abundances of Proteobacteria and Acidobacteriota, which were the key drivers of surface soil fertility. Conversely, stronger human activity was associated with lower abundance of Actinobacteriota. This study suggested that human activity had a negative influence on surface soil fertility, and bacterial community composition could be a good predictor of surface soil fertility.