Diagnostic analysis of conservation zones using remote sensing and GIS techniques in wet evergreen forests of the Western Ghats – An ecological hotspot, Tamil Nadu, India

This study highlights spatial characterization of evergreen forests of the Western Ghats – an ecological hotspot in Tamil Nadu, India – using remote sensing and GIS-based analysis in conjunction with ground-based phytosociological data. The evergreen forests of Tamil Nadu are distributed in four distinct hill ranges, Nilgiri, Anamalai, Palni and Tirunelveli, having different topographic, bioclimatic and disturbance levels. The evergreen forests in these four hill ranges are characterized for their uniqueness in terms of patch characteristics and phytosociology. A vegetation type map was prepared using IRS LISS III satellite data and was used to study the patch characteristics in terms of patch size, number, shape, porosity and landcover diversity (LD). The phytosociological characteristics, namely species richness, diversity, similarity and community assemblages, were studied using ground data collected from 95 sample points of 0.1 ha size. Patch size and number revealed distinct intactness and disturbance levels in these four hill ranges. Evergreen forests in the Tirunelveli hills comprising 216.09 km2 are distributed in 306 patches, and in the Palni hills, with 285 km2, forests are distributed in 1029 patches, indicating a high level of fragmentation. LD, indicating the spatial heterogeneity of landcover, was very high in the Nilgiri hills and low in the Tirunelveli hills. The spatial analysis helped to delineate homogenous large patches of evergreen forest, which can be adopted for appropriate conservation strategies. A total of 342 tree species belonging to 4490 stems were evaluated for phytosociology. Only 15–28% of similarity in terms of species distribution was found across the hill ranges. Conjunctive analysis of patch characteristics and species distribution showed high species richness in less fragmented evergreen forests and vice versa. The study identified the areas of prioritization in terms of ecorestoration and conservation based on patch and phytosociological characteristics.