Role of elevational gradients and climate variables in tree diversity, composition, and regeneration in Chinnar Wildlife Sanctuary of the Western Ghats, India

Elevation influences tree diversity, composition and regeneration in tropical forests. The present study tested whether changes in elevation correlate with variations in species richness and regeneration, which reflect forest structures. The study was carried out in the Chinnar Wildlife Sanctuary of the Western Ghats, India, which is located between the altitudes of 300 to 1800 m relative to sea level. A total of 60 grid plots of 31.6 × 31.6 m size (0.1 hectare) were laid in the forest across five elevational ranges with a 300-m interval. A total of 188 species in 130 Genera and 54 Families were recorded in the present study. A total of 63, 78, 80, 80, and 69 tree species were found in very low (VL), low (L), mid (M), high (H), and very high (VH) elevation zones, respectively. The dominant family across the landscape was Fabaceae, comprising 23 species, followed by Lauraceae and Moraceae, each comprising 11 species. Species-area curves and species-individuals based rarefaction curves across the five elevation zones shows the differences in species richness and the number of tree individuals. The species heterogeneity and abundance were greater in M and H elevation zones compared to others. The non-metric multidimensional scaling (NMDS) plot shows that VL zone is different from L, M, H, and VH zones because it is dissimilar in species composition compared to the others. The Sorensen similarity index was employed to quantify the changes in species composition between mature trees and regenerating individuals among different elevation zones. Changes in species composition between mature and regenerating phases were more frequent in L and H elevation zones than in the others. Our findings show that species diversity and composition are primarily governed by elevation and related climatic factors, which subsequently influence the structural attributes of tree species.