Forest structure and regeneration responses to altitudinal and disturbance gradients in the temperate Garhwal Himalaya

Understanding anthropogenic disturbances is crucial for preventing forest degradation, vegetation loss, and disruption of natural regeneration, all of which remain major global concerns. The present study aimed to assess the regeneration potential and structure of some ecologically important tempereate forests along an altitudinal and disturbance gradients in Bhagirathi Catchment Area of Garhwal Himalaya. Following a reconnaissance survey, twenty four forest stands were identified between 1500 and 3000 m asl, representing varying degrees of disturbance. The results have revealed that disturbance significantly hampered tree regeneration and adversely affected community parameters. Consequently, species richness and density values declined with increasing disturbance intensity. The species richness of trees, saplings, and seedlings ranged from 2 to 20, 2 to 15, and 2 to 10, respectively. Correspondingly, the tree density varied from 411 to 840 trees ha − 1 , saplings from 587 to 3655 saplings ha − 1 , and seedlings from 944 to 6572 seedlings ha − 1 . The logarithmic population curves exhibited patterns ranging from near-linear to reverse-J and sigmoid-shaped distributions, indicating variability in regeneration dynamics among species. Our results showed a significant positive correlation between sapling and tree densities ( r = 0.452) and seedling and sapling densities ( r = 0.584). The regression plots have shown canopy cover as a regulating variable explaining variation in the seedling density (R 2 = 0.2316, F = 6.6295, P = 0.0173), sapling density (R 2 = 0.2628, F = 7.8442, P = 0.0104), and total regeneration (R 2 = 0.2962, F = 9.2608, P = 0.0060) across all the forest stands. The findings indicate that species with no or poor regeneration at certain altitudes require immediate conservation and management interventions to identify the underlying causes and implement their assisted regeneration, therby ensuring their long-term population persistence.