STUDY OF TREELINE ECOTONE TO ASSESS LONG-TERM IMPACT OF ENVIRONMENTAL CHANGE IN MT. EVEREST REGION, NEPAL HIMALAYA

Abstract

Treeline is an excellent bioindicator of climate change impacts on high altitude biota. However, very few studies on the biological impacts of climate change have been reported from Nepal due to the lack of baseline information. This study of treeline ecotones in Mt. Everest region, Nepal Himalaya aims to prepare baseline information on structure and position of treeline to monitor the response of the ecotone to environmental change. This study was carried out at three treeline sites of Sagarmatha (Mt. Everest) National Park, in eastern Nepal Himalaya. Two to four belt transect plots (size: 20m wide, 100-190m long) were laid in each sites which included treeline as well as tree species limit. The present position of treeline with associated tree species composition was recorded and the position of each tree was mapped. Tree species in the site were represented by Abies spectabilis, Betula, utilis, Juniperus recurva, Rhododendron campanulatum, Salix sp. and Sorbus microphylla. Irrespective of the sites, R. camapanulatum was found growing at the highest elevation followed by S. microphylla, A. spectabilis and B. utilis. The population density ranged from 83 to 400 plants/ha with average density of 27 and 127 plants/ha for Abies and Betula, respectively. Size class distribution revealed an inverse-J shaped to multimodal bell shaped (DBH and Height) distribution indicating a situation of continuous to sporadic regeneration depending on the species and sites. As the size-class distribution graphs presented different shapes for different species and different sites, it is concluded that there exists a dynamic nature of the treeline ecotones and the species have site-specific and species-specific regeneration conditions. This study is expected to make a reference baseline for long term monitoring of treeline ecotones.