Abstract: The effects of disturbance on forest structure and diversity along an altitudinal gradient in the temperate, sub-tropical, and tropical regions of Garhwal Himalaya were assessed. Each region was further categorized into undisturbed (UD), mildly disturbed (MD), and highly disturbed (HD) sites on the basis of magnitude of disturbance in these forests. On UD sites of temperate, sub-tropical and tropical regions, Quercus leucotrichophora, Anogeissus latifolia and Holoptelea integrifolia were the dominant tree species respectively. The highest values of tree density (1028 ind·hm^-2) and total basal cover at breast height (31.70 m² ·hm^-2) were recorded for UD site of temperate region, whereas maximum species diversity (3.128) and equitability (14.09) values were observed for HD site of tropical region. The structure and composition of the forests were greatly affected by the degree of disturbance.

Key words: Oligotrophic bacteria, Ecological characteristics, Environmental science