Abstract: This study evaluated the impact of geographic distance and environmental factors on β-diversity and its components across 184 tree community plots distributed among nine nature reserves in northwestern Hubei, combining topographic and climatic variables. Results demonstrated that: (1) β-diversity and species turnover significantly increased with geographic distance, with species turnover comprising the dominant component of β-diversity decomposition; (2) Partial Mantel tests indicated significant correlations between β-diversity and both environmental and geographic distances; (3) Multiple regression on distance matrices (MRM) revealed that environmental factors accounted for a greater proportion of the variation in β-diversity than geographic distance. Specifically, geographic distance explained only 7.15%, 3.76%, and 7.58% of total β-diversity in the tree, shrub, and herbaceous layers, respectively—values markedly lower than those attributable to environmental factors; (4) Variance partitioning using principal coordinates of neighbor matrices (PCNM) indicated that, in the tree, shrub, and herbaceous layers, total β-diversity and turnover components explained 14.66% and 19.17%, 10.93% and 13.29%, and 13.75% and 18.98% of the variance, respectively. These findings suggest that both environmental filtering and dispersal limitation jointly shape the β-diversity of these plant communities, with environmental filtering exerting a more pronounced effect.