Characteristics of Soil Microbial Communities and Their Driving Factors in Different Forest Types and Vegetation Types in the Wuzhishan Tropical Rainforest

Tropical rainforests are among the most biodiverse ecosystems on Earth and play a critical role in global carbon cycling and ecosystem functioning, yet research on soil microbial communities in these regions remains limited. This study investigated the characteristics of soil microbial communities and their driving factors across different forest and vegetation types in the Wuzhishan tropical rainforest. A total of 48 soil samples were collected from 20 m × 20 m plots representing three forest types (primary, secondary, and artificial) and four vegetation types (lowland rainforest, mountain rainforest, cloud forest, and mountaintop shrub). Soil bacterial communities were analyzed using Illumina MiSeq sequencing of the 16S rRNA gene (V3–V4 regions), with sequence data processed in Mothur for diversity analysis and in the R package Vegan for community structure analysis. Microbial diversity did not differ significantly among the three forest types, whereas lowland rainforest exhibited significantly higher diversity than vegetation types at higher elevations. The most prevalent bacterial phyla were Proteobacteria, Acidobacteria, and Actinobacteria. Community structure differed markedly, particularly between plantation and natural forests, as well as between lowland rainforests and other vegetation types. Soil organic carbon (SOC) and total phosphorus (TP) were the main factors associated with community differences during forest succession, whereas pH, SOC, and total nitrogen (TN) were more strongly associated with variation along the elevational gradient. These findings indicate that forest succession and elevation independently influenced tropical soil microbial communities. Lowland rainforests supported the highest microbial diversity, whereas plantations harbored distinct communities compared to natural forests, with soil nutrients and pH closely associated with microbial community assembly. Therefore, conservation strategies should protect lowland rainforests to maintain high microbial diversity and encourage the recovery of plantations toward more natural forest conditions, while incorporating soil nutrient management—especially SOC, TP, and pH—into tropical forest rehabilitation may help support long-term ecosystem stability and soil health.