Quantitative analysis of vegetation structure, composition and species diversity of moist Sal bearing tropical forest of Sumbuk reserve forest in South Sikkim, India

A total of 28 tree species were recorded in 0.024 ha in all along with the sampling plots. The higher individual plant density of trees was recorded for Shorea robusta followed by Schima wallichii and Pinus roxburghii.The high IVI exhibited by Shorea robusta is largely due to its higher relative frequency, relative density and relative dominance compared to other species. The occurrence of many species with low IVI values indicates that most species are rarely distributed in the forest. The result of species diversity showed the highest diversity index for trees (2.78) followed by sapling (2.55) and seedling (2.38). The value of species richness in the present study was found to be falling between ranges 15.81 to 37.81. According to girth classes, the tree species Shorea robusta and Tectona grandis followed almost a normal distribution curve with less trees belonging to smaller and big GBH classes suggesting a fairly stable population in the study area. A reverse J-shaped curve for Lagerstroemia parviflora, Schima wallichii, Pinus roxburghii, Terminalia crenata which depicts more of the characteristics of a stable population is found. Quantitative evaluation and analysis of the community structure are important for accurate assessment of biodiversity.