Population structure and regeneration pattern of Himalayan birch (Betula utilis D.Don) in the timberline zone of Nanda Devi Biosphere Reserve, Western Himalaya, India

The present study aimed to analyse the population structure, forest composition and regeneration dynamics of Betula utilis D.Don in two core zone of Nanda Devi Biosphere Reserve. A total of 346 plants species belonging to 198 genera and 82 families were recorded dominated by Asteraceae (24) followed by Rosaceae (21 species) and Ranunculaceae (19 species), respectively. The total tree stand density was ranged between 1133 ind.ha−1 and 2137 ind.ha−1 in the south and north aspect of the each sites. Among tree species B. utilis was showed the dominant tree species with highest density ranged between 663 ind.ha−1 and 1525 ind.ha−1 at north and south aspects of both sites. Highest seedling density (1033 saplings ha−1 and 1783 seedlings ha−1) and sapling density (1033 saplings ha−1 and 1470 saplings ha−1) was recorded for B. utilis in north and south aspects. The density-diameter curve of B. utilis forest resembled a reverse J-shape which exhibits good regeneration with higher number of individuals in seedling and sapling stages, followed by a sharp decline in tree classes. This study suggests urgent need of long term ecological monitoring of timberline zone to assess the significant change in timberline vegetation and development of sustainable management plans.