Pattern of forest structure and species regeneration along with elevation gradients and aspects in evergreen oak forest belt of the Western himalaya

Mountain ecosystem represents significant biodiversity hotspots, where diverse geographical landscape, elevation and slope-aspect shape vegetation composition, ecosystem processes and forest sustainability. The present study assessed the influence of elevation (2100–3300 m) and slope aspects (SW, NE, NW) on community structure, population dynamics, and regeneration status of tree species in the sub-alpine forests of the Chopta–Tungnath region, Kedarnath Wildlife Sanctuary, Western Himalaya. A systematic random sampling approach was conducted, and a total of 105 plots were studied across the elevational belts. The present study was recorded 39 tree species belonging to 21 families and 32 genera. Multivariate statistical analysis (PCA, cluster analysis) revealed high similarity in community composition across aspects, Quercus leucotrichophora, Q. semecarpifolia, Rhododendron arboreum, Abies pindrow, and A. spectabilis emerging as ecologically dominant taxa. Tree density was highest at mid elevations, while seedling and sapling densities showed strong spatial variation, with regeneration bottlenecks more evident at higher elevations. Along the studied elevation gradient the total basal area (TBA) peaked averagely at mid elevation across the aspects (2400–2900 m), in some elevation belts TBA exceeded 60 m2/ha, which was quite high, indicating perhaps the retention of old growth forest. Population structures deviated from the ideal inverse J-shaped curve, reflecting poor recruitment. Regeneration analysis revealed that none of the species had ‘good’ regeneration; rather, most species were classified as ‘fair’ or ‘poor’ with some ecologically important taxa (Q. semecarpifolia, A. spectabilis, and Taxus baccata subsp. wallichiana) not regenerating in several aspects. Aspect-specific differences imply that environmental limitations and anthropogenic pressures, such as grazing and tourism, significantly affect regeneration dynamics. The present study identifies regeneration failure as a primary conservation issue for high-elevation forests of the western Himalaya and underscores the necessity for adaptive, aspect-sensitive forest management practices to maintain ecosystem resilience with the changing climatic conditions and disturbance regimes.