Effects of disturbance and forest fragmentation on woody species conservation in subtropical highlands of northwestern Ethiopia

Rapid fragmentation and human-induced pressures in Ethiopia’s highland forests threaten biodiversity and disrupt key ecological processes, highlighting the need for data-driven conservation strategies. This study evaluates the effects of forest patch size on woody species diversity, population structure, and regeneration dynamics in the dry Afromontane forests of northwestern Ethiopia. Forest patches were identified using the 10 m Global Land Use and Land Cover (GLUC) dataset derived from Sentinel imagery, validated with field data. Vegetation data were collected from 80 nested plots (0.04 ha each) across small, medium, and large forest patch size categories (FPSCs). Woody species diversity and forest structure across forest patch types were assessed using the Shannon–Wiener diversity index, Shannon’s evenness, and the Sorensen similarity index. Statistical differences among patch types were evaluated using one-way ANOVA with Tukey HSD post-hoc tests (p < 0.05). Results revealed significant differences (p < 0.05) in disturbance and woody species diversity across forest patch sizes. Small patches experienced the highest disturbance (40.56 ± 4.31), medium patches were moderately disturbed (21.27 ± 1.7), and large patches were least disturbed (4.48 ± 0.77). Species richness and Shannon diversity increased significantly (p < 0.001) with patch size, with large patches supporting the highest number of species (49.00 ± 1.73) and diversity (3.50 ± 0.09). Structural parameters, including basal area, stem density, and tree height, also increased significantly (p < 0.05) with patch size, whereas seedling and sapling densities declined significantly (p < 0.05) with increasing patch size. These results demonstrate the critical role of large, less-disturbed forest patches in sustaining biodiversity, forest structure, and ecosystem resilience, emphasizing the need for targeted conservation and management to protect these ecologically important forest areas.