Population Structure and Regeneration Status of Tree Species: An Assessment in the Ranikhet Forest of Almora District, Kumaon Himalaya, Uttarakhand, India

The phytosociological data were collected and analyzed to understand tree species composition, diversity, and regeneration patterns across three distinct forest habitats (Oak, Pine, and Oak-Pine mixed) in the Ranikhet forest of Almora District, Kumaon Himalaya, Uttarakhand, India. The study was conducted from 2021 to 2022. A total of 120 plots with a radius of 10 m were established using a stratified random technique to sample tree data. Regeneration (seedlings and saplings) was quantified in 3 m radius concentric circular plots within the existing 10 m tree plots. Results reveal considerable differences in species composition and regeneration patterns across habitats. The Oak-Pine mixed habitat exhibited the highest species richness (15 species) and diversity (Shannon index: 1.625). In contrast, the Pine habitat showed the lowest diversity (Shannon index: 0.1526) with high dominance of Pinus roxburghii (IVI: 280.89). Tree density varied noticeably across habitats, with the highest in Oak-Pine forest (467.09 individuals/ha), followed by Pine (357.99 individuals/ha) and Oak (291.17 individuals/ha) habitats. Regeneration analysis indicated that invasive species like Acacia dealbata are successfully established across all habitats, while native species showed variable regeneration patterns. The Oak habitat demonstrated good overall regeneration (seedling density: 3740.77 individuals/ha), whereas Pine and Oak-Pine habitats showed fair regeneration. The high seedling-to-tree ratios for invasive species and the absence of regeneration for several native species raise significant conservation concerns. Quercus leucotrichophora showed fair regeneration in Oak and Oak-Pine habitats but good regeneration in Pine habitat, suggesting potential for oak expansion under favourable conditions. Similarity analysis revealed moderate habitat overlap (Simpson’s similarity index: 45.45-61.53%), suggesting distinct ecological niches with the highest similarity between Oak and Pine habitats (61.53%). The findings highlight concerns about the expansion of invasive species and regeneration challenges for some native species, providing valuable insights for sustainable forest management and conservation strategies in the Western Himalayan region. The habitat-specific differences in diversity indices and regeneration patterns underscore the importance of maintaining habitat heterogeneity at the landscape scale for preserving the region’s forest biodiversity.