Community structure and species diversity of forest vegetation in a protected area of Western Himalayan region of India

The monitoring of species diversity is a key pre-requisite for understanding and managing forest ecosystems. The vegetation assessment of the forests at the habitat and community levels in the forest ecosystems can help in its proper monitoring and formulation of conservation strategies. With this aspect, the present study was conducted in the Shimla water catchment Sanctuary (SWCS) of Western Himalayan region from 2011 to 2014. A total of 476 species of vascular plants were recorded with angiosperms (101 families, 307 genera, and 431 species), gymnosperms (3 families, 7 genera, and 9 species), and pteridophytes (11 families, 17 genera, and 36 species). Among these 39 species were the trees, 81 shrubs, 320 herbs, and the remaining 36 species were pteridophytes. The quantitative analysis showed the presence of 312 species at varying altitudes, aspects, slopes in the different identified communities. Further, tree communities were delineated based on IVI while shrub communities on the basis of relative density. A total of twenty-one forest communities (trees 15 and shrubs 6) were identified in the altitudinal range between 1850 to 2750 m above msl. In general, Shannon diversity index (H’) for trees ranged from 1.40 to 2.10, seedlings (0.67–1.51); saplings (0.62–1.72); shrubs 2.02–3.16 and herbs 2.47–4.38 while the values of concentration of dominance for trees ranged from 0.17 to 0.45, whereas in seedlings these values varied from 0.28 to 0.77. Saplings showed a range of 0.18–0.57, shrubs from 0.03 to 0.17, and herbs 0.03–0.16 for the values of Cd. The similarity values were evaluated by the Jaccard index among different communities in the tree, seedling, sapling, shrub, and herb layers which showed the presence and absence of various species. More than 50 per cent similarity was found in the shrub layer (77 community pairs) followed by seedling layer (61 community pairs), sapling layer (47 community pairs), and tree layer (44 community pairs). Least similarity (less than 50 per cent) was found for herb layer (7 community pairs) with maximum dissimilarity. The high level of dissimilarity can be attributed to the high level of disturbance in the forest layer. The application of vegetation indices can be a useful tool in predicting the structure of the forest vegetation and also vital in developing adequate management strategies for conservation of plant diversity. In the SWCS, the plant communities with high species diversity and more heterogeneity require specific conservation strategies as these can be considered as rich zones or pockets of floral diversity in this ecosystem. Invasions by non-native species can be a threat to the forest flora that needs proper management.