Vegetation Structure and Species Composition Inside the Habitat of Critically Endangered White-bellied Heron (Ardea insignis Hume, 1878) Along the Phochu in Punakha district, Bhutan

Floristic compositions and vegetative structures are key determinants for selecting nests and roosting habitats of Critically Endangered White-bellied Heron. However, none of the Bhutanese researchers had ever studied to date. Gradient-directed transect methods were adopted using systematic sampling. Vegetation surveys were carried out inside 10 x 10 m (trees), 5 x 5 m (shrubs), and 2 x 2 m (herbs) in 48 plots across the Pochu landscape. The result shows that the Phochu landscape recorded 10 trees species belonging to six families. Pinus roxburghii is the most dominant species with relative density [RD] (86.77%), relative frequency [RF] (37.50%), relative dominance [RD] (79.93%), and IVI (204.20). While, L. ovalifolia and A. lebbeck were the lowest (RD (0.53%), RF (6.25%), RD (0.07%), (0.83%), IVI (6.85), and 7.61 respectively. While shrub constitutes 19 species and belongs to 14 families. Chromolaena odorata (32.15%, n = 933) and Cymbopogon sp. (21.26%, n = 617) were the most dominant herbs, while, Galium aparine (0.03%, n = 1) were lowest with 38 herbs species belongs to 20 families. For vegetative structures, maximum trees (38.62%, n = 73) DBH ranges from the 11-15 cm, which are found in day roosting site 1 (34.25%, n = 25). While, lowest ((0.53%, n = 1) was DBH ranges of 51-55 cm, 61-65 cm, 66-70 cm and 71-72 cm respectively. Therefore, similar vegetation composition and structure studies are suggested in other core habitats across Bhutan to deduce its habitat ecology for the long-term conservation of Critically Endangered WBH in Bhutan.