Forest Structure: Assessing Tree Species Diversity and Conservation Status in Afi River Forest Reserve, Nigeria

This study assessed the tree species diversity and conservation status of the Afi River Forest Reserve, Nigeria. A systematic sampling technique was employed to establish 60 plots (50 m × 50 m). All trees with diameter at breast height ≥10 cm were identified to species level, and their diameter at breast height and total height were measured. Data were analyzed using descriptive statistics, while species diversity indices were computed using Shannon–Wiener (H′), Simpson’s dominance (λ), Margalef’s richness (M), Pielou’s evenness (E), and Importance Value Index. The study identified 114 tree species across 85 genera and 38 families, with a mean density of 206 trees ha−1 and a basal area of 23.69 m2 ha−1. The diameter and height distributions followed an inverted J-shape, with the 10–25 cm diameter at breast height class containing the most individuals (383 ha−1, 46.4%) and the 11–14 m height class the highest (159 ha−1, 19.2%). The forest exhibited high diversity (H′ = 4.25, λ = 0.98, M = 14.18, and E = 0.53), indicating a diverse and structurally balanced forest community. Staudtia stipitata had the highest Importance Value Index (29.92), whereas Chrysophyllum perpulchrum had the lowest (0.57). Locally, 55.3% of species were classified as rare, 29.8% as occasional, 11.4% as frequent, 2.6% as abundant, and 0.9% as dominant. Globally, 62.3% were of least concern, 14.9% vulnerable, 14.9% not evaluated, 7.0% near threatened, and 0.9% endangered. Overall, Afi River Forest Reserve supports high tree species richness and structural complexity. Targeted enrichment planting of endangered and vulnerable species is recommended.

Cite this article as: Chukwu, O., Osho, J. S. A., Alo, D. A. A., Ige, P. O., & Odeleye, S. (2026). Forest structure: assessing tree species diversity and conservation status in Afi River Forest Reserve, Nigeria. Forestist, 76, 0145, doi: 10.5152/ forestist.2026.25145.