Tree Species Composition and Above-Ground Biomass Estimation in Secondary Forests of Ekiti State

Secondary forests in the derived savanna and forest transition zones of Ekiti State represent an important but undervalued carbon sink and biodiversity reservoir, particularly given the extensive loss of primary forest cover across southwestern Nigeria. This study quantifies tree species composition, structural parameters, and above-ground biomass in secondary forests of varying age classes (5-10 years, 11-20 years, and over 20 years post-disturbance) in Ekiti State. Systematic sampling using 50 by 20 metre plots was established across eighteen sites in three local government areas. All trees with a diameter at breast height of 10 cm and above were measured and identified. Species richness, basal area, importance value indices, and above-ground biomass were calculated using pantropical allometric equations. Results indicate a progressive increase in species richness and biomass with stand age. Forests in the oldest age class approached primary forest species composition in terms of diversity indices, though structural complexity remained lower. Pioneer species including Musanga cecropioides and Albizia zygia dominated younger stands. Above-ground biomass ranged from 58 tonnes per hectare in young secondary forests to 187 tonnes per hectare in old secondary stands. These findings support the designation of mature secondary forests in Ekiti as formal carbon stock areas under national REDD-plus frameworks. Keywords: secondary forest, above-ground biomass, species composition, Ekiti State, carbon stock