Background and Aims

We aimed to elucidate how anthropogenic disturbances influence plant community assembly by integrating taxonomic, phylogenetic and functional diversity, and to quantify the relative effects of environmental drivers amid large-scale water conservancy projects.

Methods

We surveyed 123 forest community plots across the Three Gorges Reservoir Area (TGRA) in China and assessed the relative contributions of various environmental factors to plant taxonomic, phylogenetic and functional diversity by using random forest analyses and structural equation models.

Key Results

We found phylogenetic overdispersion and functional clustering within plant communities in the TGRA. Anthropogenic disturbances, particularly proximity to the nearest railway line, emerged as the primary driver of the three plant diversity indicators. Notably, none of the functional traits displayed significant phylogenetic signal, indicating a decoupling of functional and phylogenetic diversity occurred in areas of high human disturbances. As the intensity of disturbances increased, phylogenetic diversity increased, with plant communities shifting from clusters of closely related species towards more random assemblages. In contrast, functional diversity decreased, with communities becoming more functionally similar. This suggests that functional traits may evolve independently of phylogenetic history, challenging traditional perspectives on community assembly.

Conclusions

Our study demonstrates a critical divergence in biodiversity responses to anthropogenic pressure: while disturbances enhance phylogenetic diversity through environmental filtering, they simultaneously induce functional homogenization via trait-mediated selection processes. This divergence highlights the inadequacy of single-metric assessments and underscores the importance of integrative frameworks for understanding community assembly in human-modified ecosystems.