Environment & Ecosystem Science (EES)

Information on the richness of plant species and the structure of the vegetation in forest reserves are crucial for making well-informed decisions, managing reserve forests sustainably, and promoting successful conservation. The study assessed structural characteristics and plant species diversity in the disturbed and non-disturbed plots in the Ise-Ekiti Forest Reserve, Southwestern, Nigeria. Area sizes of 25 m x 25 m in each of the disturbed and undisturbed were randomly established. In each plot, the woody plants were enumerated and the girth sizes of the woody plants were measured using a diameter tape and Spiegel Relaskop. The results showed that the values of stem density (7520 ha-1 ) and basal area (0.8868 m2 ha-1 ) recorded in undisturbed areas were higher than the values recorded in disturbed areas (5147 ha-1, 0.5236 m2 ha-1) respectively. The Shannon’s Weiner Diversity Index value from the undisturbed areas (H′=3.10) was higher than that of the disturbed areas (H′ =2.83). Simpson diversity index was also found to be higher in undisturbed areas (0.93) compared with the values (0.91) recorded in the disturbed areas. The individual rarefaction curve from the results indicated that undisturbed areas were richer in plant species compared to disturbed areas. The findings also revealed that the relationship between relative dominance-important value index, abundance-stem density, height-diameter at breast height, and relative density-relative frequency of plant species was highly significant in both disturbed and undisturbed plots. The study concludes that essential metrics for comprehending the composition and structure of forests are stem density and basal area, which offer valuable information about the productivity and well-being of ecosystems. It also concluded that low Important Value Index (IVI) values indicate species at risk and highlight the importance of conservation actions, which helps prioritize efforts to conserve species.