Impacts of forest expansion on microbial diversity and community assembly in fragmented mountain ecosystems.

Under the influence of global climate change and human activities, forest expansion has become increasingly significant in shaping ecosystems. However, its effects on soil microbial communities remain poorly understood. This study investigates the impacts of forest expansion on soil bacteria, fungi, and protists within mountaintop forest ecosystems. Soil samples were collected from three forest habitats: non-forest expansion mountaintops (NFE-Top), forest expansion mountaintops (FE-Top) and mountain bottoms (FE-Bottom). This study revealed that forest expansion promoted microbial sharing between mountaintop and bottom forests, resulting in greater community similarity between FE-Top and FE-Bottom compared to NFE-Top and FE-Bottom. Notably, forest expansion significantly reduced microbial diversity and altered community composition, particularly within bacterial communities. Microbial network analyses indicated that forest expansion mountaintops were more stable, with higher robustness, and lower vulnerability than non-forest expansion mountaintops. Stochastic assembly processes dominated the microbial communities across all forest habitats, with their relative importance increasing after forest expansion. Furthermore, forest expansion decreased the community-level habitat niche breadth of microbial communities. Distinct environmental factors were the primary indicators of microbial community dissimilarities across different habitats, with TP, pH, and moisture acting as key indicators of these differences in NFE-Top, FE-Top, and FE-Bottom, respectively. These findings highlight the important role of forest expansion in shaping microbial community dynamics and emphasize the potential of microbial communities as indicators of ecosystem changes.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2025 Elsevier Inc. All rights reserved.)