Tree species composition and diversity in montane forests of Garhwal Himalaya in relation to environmental and soil properties

The montane forests of Garhwal Himalaya were investigated for tree species composition and diversity in relation to environmental and edaphic variables. A stratified random sampling approach was adopted to collect the field data from each forest. A total of 39 tree species belonging to 31 genera and 23 families were recorded from the sampling area (6 forest stands × 10 plots in each). Lauraceae with 5 species was the largest family while Quercus (4 species) emerged as the largest genus. Species-area curve (asymptote) predicted more species than the observed number of species. Cluster analysis has shown that the two Abies pindrow dominant forest stands had the highest similarity in tree species composition. The tree stem density ranged from 540–1170 ha−1, basal area 23.01–55.94 m2 ha−1, Shannon-Wiener diversity index 1.69–2.49, evenness index 0.42–0.74, beta diversity 0.40–0.82 and similarity index 0.17–0.54 in the six studied forests. Two-way indicator species analysis (TWINSPAN) identified four distinct tree communities in the study area with Daphniphyllum himalayense, Abies pindrow, Quercus oblongata, and Pinus roxburghii as indicator species of corresponding communities. Canonical correspondence analysis (CCA) ascertained the TWINSPAN results and revealed the relation of tree species with environmental and edaphic variables. The phytosociological attributes of tree species varied from one forest stand to another; however, the tree species richness, density, and diversity peaked at intermediate elevation on the north aspect. Findings reveal that tree composition and diversity in the montane forests of Garhwal Himalaya are influenced by both environmental (elevation and slope aspect) and soil variables (texture, water holding capacity, moisture content, available N, exchangeable P, and pH). This study will help in understanding the forest distribution across the western Himalaya, guiding the conservationists and policymakers in carrying out conservation-related management activities, designing the long-term monitoring studies and assessing the effects of ongoing and future climate change and disturbances.