Elevational pattern, structure, and regeneration status of woody taxa along a semi-disturbed timberline ecotone in northwestern Himalayas

Abstract

The composition, structure, and patterns of vegetation undergo a noticeable shift along the elevational gradient, and this is regulated by various abiotic variables, primarily the elevation and edaphic characteristics. The present study investigated the change in community characteristics of woody vegetation along a vertical gradient from 2800 m till 4000 m in parts of upper Bani Wildlife Sanctuary in Jammu and Kashmir. In all, 40 woody species were recorded including 11 trees and 29 shrubs with a distinctive hump shaped pattern that becomes steeper with the rising elevation. Quercus semecarpifolia Sm. and Betula utilis D.Don. exhibited a wide elevational range (3000–3500 m asl), eventually forming the climatic climax along southern and northern aspects. The diversity and phytosociological attributes peaked at intermediate elevation with $\overline{H}$=1.74 recorded for trees and $\overline{H}$=2.48 observed for shrubs. The average density and basal cover for trees and shrubs ranged between 75.50 Nha⁻¹ & 20.09 m²ha⁻¹ and 69.31 Nha⁻¹ & 4.50 m²ha⁻¹, respectively. The species turnover rate was recorded high in case of trees (0.11–0.77) and low for shrubs (0.17–0.29). A modest density of 114 seedlings ha⁻¹ and 249 saplings ha⁻¹ was recorded across the forest types. The low seedling (0.22) and sapling (0.48) per tree ratio indicated a low regeneration performance anticipating a very slow upslope movement of the tree line. This may result in population decline of a few select species in future, necessitating effective monitoring and management intervention for which these findings will be helpful.