Soil pH exerts stronger impacts than vegetation type and plant diversity on soil bacterial community composition in subtropical broad-leaved forests

Soil bacterial communities play vital roles in subtropical broad-leaved forests (SBFs), however, the mechanisms regulating their formation remain poorly understood. The present work aimed to address this question. We used dIVI (Important Value Index of deciduous canopy trees) to quantitively classify three SBFs. Soil bacterial traits such as community composition, diversity and potential interactions (via network analyses) were studied. The relationship between bacterial community composition and environmental factors was analyzed. SBFs were determined as a deciduous forest (DBF, dIVI = 0.99), a mixed forest (MBF, dIVI = 0.52) and an evergreen forest (EBF, dIVI = 0.19). Soil bacterial communities were different considerably among vegetation types, which was largely attributed to soil pH, dIVI and plant diversity, in which soil pH exerted stronger impacts than the others (coefficients of partial Mantel tests: 0.87 for soil pH versus 0.35 for dIVI, 0.26 for plant diversity). Compared to the MBF and the EBF, the DBF exhibited significantly higher bacterial diversity and more intensive potential interactions. This study implies that soil pH, vegetation type and plant diversity are key driving forces of soil bacterial community composition in SBFs, which improves our understanding of mechanisms regulating soil bacterial community composition.