Topographic and Edaphic Factors Shaping Floral Diversity Patterns and Vegetation Structure of Treeline Ecotones in Kumaun Himalaya

Abstract

ABSTRACT Treeline ecotones are ecologically sensitive ecosystems that are increasingly vulnerable to recent global warming and land degradation processes such as soil erosion, nutrient depletion, and organic matter loss. However, little is known about how floral diversity in treeline ecotones responds to changing environmental factors, particularly in the high Himalayan treeline ecotones. The present study examined the potential effects of topographic and edaphic factors on the vegetation structure of treeline ecotones of two mountain summits in Kumaun Himalaya. Using line transects, plots, and quadrats, we recorded 96 plant species from 72 genera and 36 families. Jaccard similarity coefficients revealed varying degrees of similarity in species composition between different aspects and elevations. Beta diversity analysis indicated nestedness as a dominant driver of community composition. Vegetation assessments showed shifts in tree density (ranging from 12.50 to 227.50 individuals per hectare), basal area (ranging from 0.138 to 9.855 square meters per hectare), and dispersion patterns along the elevational gradient. The dominant tree species across all treeline ecotone plots was Rhododendron arboreum . Regeneration was evident, with 69% of trees in smaller girth classes, indicating active recruitment. In addition to vegetation distribution, this study analysed soil characteristics across the treeline ecotones to assess potential land degradation trends. Soil temperature, pH, moisture, and water holding capacity decreased with elevation. South and east aspects had higher temperatures, pH, and phosphorus, while north and west aspects had higher moisture, organic carbon, and nitrogen. Results indicate that decreasing soil moisture, increasing bulk density, and declining total organic carbon at higher elevations and exposed aspects are indicative of degradation processes that may impact long‐term vegetation stability. The significant relationships between soil parameters and species distribution highlight the importance of understanding degradation dynamics in shaping floristic patterns. Non‐metric multidimensional scaling (NMDS) showed distinct clusters of treeline plots based on environmental variables (stress value: 0.17), while canonical correspondence analysis (CCA) demonstrated strong species‐environment correlations, explaining 83.08% of the total inertia. Given the observed soil degradation trends, conservation strategies should prioritize soil stabilization, erosion control, and nutrient depletion to mitigate the risks of ecosystem degradation. This research provides key insights into ecosystem resilience and serves as a foundation for monitoring treeline ecotones under changing environmental conditions.

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