Assessment of Vegetation Structural Diversity and Similarity Index of IITA Forest Reserve in Ibadan, Oyo State, Nigeria

Abstract

The analysis of vegetation structural diversity and similarity index of International Institute of Tropical Agriculture (IITA) forest reserve was carried out by vegetation survey using transects and plot sampling techniques. Forty plots of 10m by 10m each were laid equally along four transect (A, B, C, at 900E and D at 00N). Data were analysed using descriptive statistics, relative density, diversity and similarity indices. The result showed that the forest reserve has one hundred and ninety species of plants belonging to sixty three families. The dominant plant families recorded in the forest are Leguminosae (12.63%), Rubiaceae (8.42%), Euphorbiaceae (7.89%), Apocynaceae (5.26%) and Sterculiaceae (3.68%). The most abundant plant species in the forest are mostly secondary colonizers climbers, shrubs and trees such as Culcasia saxatilis (4.46%), Icacina trichantha (4.10%), Shrub: Alchornea laxiflora (3.86%), Sphenocentrum jollyanum (3.50%), followed by tree: Newbouldia laevis (3.23%), and Funtumia elastica (2.63%) respectively. Transect D had the highest Simpson's diversity index of 0.01184 while the lowest is with C 0.02091. The Simpson similarities indices (Beta diversity) of transects varied from 50.75% to 42.76% for transects B and C, A and C, and C and D respectively. The forest reserve of IITA shows a high diversity (alpha, gamma and beta diversity) of plants and have multiplicity of species, therefore, adequate protection of the reserve should be a priority to maintain and prevent loss of plant biodiversity.

Keywords: Vegetation, structural diversity, IITA forest reserve, plant biodiversity, Simpson's diversity index