Tree Species Composition, Structure and Importance Value Index (IVI) of Okwangwo Division, Cross River National Park, Nigeria

Assessment of tree species composition and structure was carried out in Okwangwo division of Cross River National Park. Random sampling using quadrats was employed for the study. Each quadrat was 10m x 20m. A total of 25 quadrats were used from the selected plot of one hectare. Tree species and families were identified. Tree height measurement was carried out and used to identify the different layers of tree species in Okwangwo division of the Park. Four distinct layers were identified which include the emergent, the upper canopy, the under storey and the forest floor. A total of 114 different tree species and 37 families were identified. The family Leguminosae had the highest number of species (17). Tree species with 10cm DBH and above were measured and the data were used to calculate relative density (R. D), relative dominance (R. D), and relative frequency (RF). Their results were used to derive the Important Value Index (IVI) which determines the dominant tree species of the entire area under study. Terminalia ivorensis was the most dominant (13.08). The Cross River National Park should design programmes that will create awareness to people around and within the Park to see the need of conserving the flora and fauna species. Selective removal of dominant trees at emergent and upper storey is recommended to introduce sunlight to the forest floor so as to encourage the growth of young and valuable trees species.