Structural Organization and Biodiversity Gradient in Forest, Agroforestry and Wetland Ecosystems of Gonda, Uttar Pradesh, India

Abstract

A comparative phytosociological assessment was conducted across three land-use systems—forest land, agroforestry, and wetland ecosystems—in Gonda district, Uttar Pradesh, to evaluate vegetation structure and diversity patterns during 2022–23. Quadrate-based sampling (10 m × 10 m for trees; 5 m × 5 m for shrubs) was employed to quantify density, frequency, basal area, and Importance Value Index (IVI). Tree diversity indices were computed using Shannon–Wiener (H′), Simpson’s dominance (1–D), and Pielou’s evenness (J′). Forest land exhibited moderate diversity (H′ = 1.67) with strong dominance of Shorea robusta (IVI = 98.54), reflecting a semi-monodominant stand structure. Agroforestry systems showed plantation-driven dominance of Tectona grandis (IVI = 95.24) with comparatively lower diversity (H′ = 1.56) and evenness (J′ = 0.68), indicating structural simplification due to management practices. Wetland ecosystems recorded the highest species richness (S = 12), Shannon diversity (H′ = 2.20), Simpson index (0.87), and evenness (J′ = 0.89), demonstrating greater heterogeneity and balanced species distribution. Seasonal analysis of herbaceous vegetation revealed maximum diversity during the rainy season (H′ up to 2.45 in wetlands), highlighting the regulatory role of soil moisture and hydrological conditions. The observed diversity gradient highest in Wetland followed by Forest and Agroforestry underscores the influence of land-use intensity and moisture regime on vegetation organization in the Gangetic plains. The findings provide quantitative evidence for ecosystem-level differentiation and emphasize the conservation importance of wetland habitats within managed rural landscapes.