Orchid diversity of Tropical Wet Evergreen forests in Digboi Forest Division, Assam, India

The present study was conducted to investigate the orchid flora in 15 reserve/proposed reserve forests under Digboi Forest Division of Assam to assess their habitat ecology for occurrence reorganization. Presently 111 numbers of orchid species were recorded, of which 92 species were epiphytic while merely 19 species were found with terrestrial habit. Terrestrial orchids have shown much localized occurrence, maximum number occurring in Upper Dihing RF, which is part of rain forest Dihing Patkai National Park. Host range of epiphytic orchids revealed 27 species, Lagerstroemia speciosa sheltered highest number of orchids followed by Dipterocarpus retusus, Tectona grandis and Bischofia javanica. In view of the documented species 24.45% of the total species were Rare, 3.64% vulnerable, 3.64% near threatened, 6.36% endangered and 2.73% critically endangered making the area a significant orchid habitat. Forest destruction, drastic depletion of forest areas and illegal mining activity have detrimental effects on the population of orchids.