Quantitative Assessment of Vegetation Layers in Tropical Evergreen Forests of Arunachal Pradesh, Eastern Himalaya, India

The present study deals with first-hand information on quantitative assessments of different vegetation layers (viz. trees, saplings, seedlings, shrubs and herbs) collected from 57 permanent plots (size 400 m2), established for long-term monitoring of biodiversity and study of functional aspects in Namdapha National Park (NPP), Arunachal Pradesh, Eastern Himalaya, India during 2017. We grouped all the plots into six clusters as study sites. A total of 60 taxa of trees, 67 shrubs and 81 herbs were recorded within 57 plots during the study. The average species richness per site for trees was 20.83 ± 1.62, saplings 16.0 ± 1.15, seedlings 15.83 ± 1.35, shrubs 23.83 ± 1.58 and herbs 32.67 ± 0.92. Total stem density varied from 117.5 to and 181 ha^–1 (152.58 ± 10.04 ha^–1) for trees (circumference m31.5 cm), 881 to 3000 ha^–1 (1652.17 ± 317.61 ha^–1) for shrubs and from 76750 to 98545 ha^–1 (92032.17 ± 3246.60 ha^–1) for herbs. Tree regeneration status at all the six study sites was ‘good’ (i.e. density of seedlings > saplings > trees). The distribution of tree stems (circumference m31.5 cm) into different size classes showed highest relative density in the lowest stem size class (10–20 cm diameter) which also indicates good tree regeneration in the study area. Dipterocarpus retusus Blume was the most dominant tree species in the core zone area of NNP with ‘good’ regeneration status.