Effects of Moso Bamboo (Phyllostachys edulis) Forest Expansion on Soil Bacterial and Fungal Community Structure and Diversity in Subtropical China

The disorderly expansion of Moso bamboo (Phyllostachys edulis) into adjacent forests has become a serious ecological issue in southern China; however, the response of soil microbial communities remain unclear. This study investigated the succession patterns of bacterial and fungal communities through high-throughput sequencing and soil physicochemical analysis across three expansion stages in subtropical China: mixed coniferous–broadleaf forests, bamboo–forest transition zones, and pure Moso bamboo stands. The results indicate that Moso bamboo expansion altered soil bacterial and fungal beta-diversity without changing alpha-diversity. Random forest and redundancy analyses revealed distinct microbial group drivers. Bacterial communities were driven by available phosphorus (37.1% explained variance), with expansion intensifying soil phosphorus limitation and selecting for groups adapted to low-phosphorus environments (e.g., Acidobacteria). Fungal communities were primarily influenced by bulk density (21.3% explained variance), as the bamboo rhizosphere system altered soil physical structure, resulting in a significant loss of ectomycorrhizal fungi (e.g., Russula) and a corresponding decline in Basidiomycota abundance. This study confirms that Moso bamboo expansion reorganizes the soil microbial ecosystem through two pathways: chemical nutrient limitation and physical space remodeling. By revealing the subterranean ecological consequences of Moso bamboo expansion, this study provides a theoretical foundation for sustainable management of subtropical forests.