Stand structure, community composition and tree species diversity of sub-tropical forest of Nagaland, Northeast India

Tree species composition and diversity were assessed in six forest communities at an altitudinal gradient (i.e. from 247 to 1478 m) by laying four plots of 0.1 ha in each site within sub-tropical forest belt in Mokokchung, Nagaland. A total of 777 individuals belonging to 118 species, 84 genera and 43 families were recorded. The most dominant families from these sites were: Fagaceae, Moraceae, Anacardiaceae and Malvaceae. The tree density (individuals ha(-1)) in the present study ranged from 313 in Dillenia-Duabanga-Macaranga community to 330 in Morus-Vernonia-Hovenia community. The total basal area (m(2 )ha(-1)) ranged between 22.95 and 38.03 in Morus-Vernonia-Hovenia and Bombax-Melia-Gmelina community, respectively. The dominance-diversity curve showed high equitability and low dominance in forest communities (i.e. Trema-Kydia-Callicarpa, Morus-Vernonia-Hovenia and Alnus-Duabanga-Morus) occupied higher altitudes (1145-1478 m) and followed a log-normal distribution pattern. Whereas, the dominance-diversity curve showed low equitability and high dominance in communities (i.e. Bombax-Melia-Gmelina, Dillenia-Duabang-Macaranga and Albizia-Sapium-Gmelina) occupied lower altitudes (247-674 m) and followed a short hooked curve pattern. The Shannon diversity index ranged from 2.95 to 3.88 indicating high tree species diversity in forest communities studied. The Simpson dominance index ranged from 0.03 to 0.09. Over all this study provides useful information on tree species composition and diversity of subtropical forest of Nagaland which can be used as baseline data by the forest department to develop plans for the conservation of forest in subtropical forest, Northeast India.