Elevation gradients and environmental variables shaping tree diversity and composition in Srivilliputhur Wildlife Sanctuary, Western Ghats

Srivilliputhur Wildlife Sanctuary holds significant value being a part of Western Ghats, which remains unexplored in terms of vegetation. The current study is the first quantitative assessment of tree distribution along an elevation gradient combined with environmental variables. Sampling was conducted from December 2020 to April 2021 in six elevation zones (Z1 to Z6). A total of 135 plots of 20m × 20m size were established, and the stems were measured (>30 cm GBH). Across a 5.4 ha studied area, 2157 individuals representing 188 tree species and 48 families were documented. Tree density (348-473 ind. ha−1), basal area (21.71-36.59 m2 ha−1), and species richness (84-122) were highest at mid-elevations. One-way ANOVA result highlighted the significant influence of elevation on species richness (p < 0.05). Canonical Correspondence Analysis revealed a good correlation between environmental variables and elevation. Furthermore, beta diversity showed intermediate dissimilarity between zones, ranging from 0.30 to 0.61. Z1 and Z6 exhibited the most dissimilarity (60%). Our study revealed tree diversity was least at higher elevations, suggesting good evidence of elevation and environmental filtering in shaping the overall tree diversity. Besides, the scarcity of a few species showed a point of concern. Hence, the current study suggests the implementation of strategic conservation plans to conserve species diversity in this area.