Conservation of Tree Species Diversity in Tropical Rainforest Ecosystem of Southwest Nigeria

ADEKUNLE, V. A. J. 2006. Conservation of tree species diversity in tropical rainforest ecosystem of south-west Nigeria. Three reserves, each of size 50 × 50 m, were selected in the ecological zone comprising eight sampling plots. Identification and distribution into families of all woody plants with diameter at breast height (dbh)> 10 cm were carried out. Frequency distribution per ha of each species and relative diversity were determined. A total of 54 different tree species (24 families) were identified in Ala, 41 species (21 families) in Omo and 55 species (20 families) in Shasha Forest Reserves. The most prevalent species in the ecosystem was Strombosia pustulata, while the family Leguminosae had the highest number of species. Eighty-four percent of the species are regarded as rare or threatened with extinction while 16 % were relatively abundant. The highest species diversity indices were obtained in Shasha Forest Reserve (3.656 and 0.914, Shannon and evenness indices respectively), the lowest in Omo Forest Reserve (3.342 and 0.900 respectively). There was no significant difference in the number of individual ha–1 on species basis, the relative density of species and also in the distribution of species into families (p> 0.05). Fifty percent of the species could be regarded as habitat generalists as they occurred in the three reserves. The contribution of the ecosystem to rural livelihood in the supply of some products and in environmental conservation and the need for urgent conservation efforts are highlighted