CONSERVATION OF TREE SPECIES DIVERSITY IN TROPICAL RAINFOREST ECOSYSTEM OF SOUTH-WEST NIGERIA

Abstract

ADEKUNLE, V. A. J. 2006. Conservation of tree species diversity in tropical rainforest ecosystem of southwest
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. Eightyfour
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.