Ecology of treeline vegetation in Western Himalaya: Anthropogenic and climatic influences

Abstract

A landscape level survey of vegetation structure and composition was conducted along the treeline ecotone in Western Himalaya in the states of Uttarakhand and Himachal Pradesh. We used a combination of field surveys and remote sensing data (Landsat MSS and TM images) to quantify the extent and distribution of various classes of forests, forest cover, patterns of vegetation structure and composition and recent changes in forest cover along the treeline ecotone. Total area under the treeline ecotone (3000-4000 m) in these states comes to ca. 11587 km2, of which Himachal Pradesh has higher representation (6818.4 km2). In terms of extent, conifers (Abies and Pinus) occupy the largest cover followed by brown or Kharsu oak (Quercus semecarpifolia) and birch (Betula utilis). Mean tree density was 553 individuals ha-1 which ranged between 440 and 690 individuals ha-1. Average elevation of the treeline was approximately 3615 m above mean sea level, and the maximum altitude of tree growth was 4200 m. Time series analysis of remote sensing data reveals that there has been no altitudinal shift in the upper treeline during the last 40 years, although forest canopy cover has increased or decreased significantly within a protected area and outside, respectively.