Floristic diversity and altitudinal variation of tree species in lower Kanchenjungha Singhalila Ridge, Eastern Nepal

Abstract

The present paper is based on the findings of floristic diversity inventory research work conducted in Lower Kanchenjungha Singhalila Ridge, in Nepal sides of Eastern Himalaya. Knowledge on floristic diversity of particular area can reflect the total resources, their use and conservation status which is very helpful for making necessary conservation strategies and policies. Eastern Himalaya is one of the globally important sites representing the important biodiversity hotspots of the South Asia. Analysis of vegetation helps to develop detailed picture of plant communities of particular geographical location.

Plants specimens were collected by two field visits viz. pre-monsoon and post-monsoon during the period of June-October, 2007. Total 50 square quadrats of 10mx10m sized were laid down following stratified-random sampling method for sampling trees. In each 10m×10m quadrats, the number of individual trees was counted and dbh [diameter at breast height-1.37m, dbh ≥ 10 cm] of each tree was measured. After preservation, identification and management of collected plants, herbarium specimens were prepared and deposited in National Herbarium and Plant Laboratories, Godavari, Lalitpur (KATH) and Tribhuvan University Central Herbarium, Kirtipur (TUCH).

Present study recorded 299 species among them seven species were identified only family level, 22 species only generic level rest of them to species level falling under 184 genera and 86 families. Dicots belong to 69 families, 150 genera and 229 species whereas Monocots include 15 families 32 genera and 39 species. Similarly, Gymnosperms represented two families, two genera and two species. Floristic analysis showed that Rosaceae was the largest family with 23 species followed by Ericaceae 17, and Lauraceae 9 species. The study furnished three new addition to the flora of Nepal viz. Begonia flaviflora H. Hara (Begoniaceae), Carex cruciata Wahlenberg var. argocarpa C. B. Clarke (Cyperaceae), and Strobilanthes helicta Anderson (Acanthaceae). This study also mentioned 11 threatened species of different categories and one endemic species Heracleum lallii (Umbelliferae). 30 tree species were recorded from the altitudinal range of 2100-3000m. Eurya acuminata and Symplocos species were dominant in lower elevation whereas Lithocarpus pachyphylla and Rhododendron species were dominant in upper elevation range. The diversity of tree species showed hump shape relation with elevation gradient.