This study examined the contribution of protected forest areas as means of biodiversity conservation. This was achieved by assessing the status of the forests in terms of tree species diversity and volume yield for in-situ biodiversity conservation. Data were collected from four plots of one hectare each, randomly located in the strict nature reserve, forest reserve, and sacred grove. In each plot, all tree species (dbh ≥ 10 cm) were identified; their height, diameter at breast height (dbh) diameters at the top, middle and base were measured. Individual stems of 766 ha-1, belonging to 51 tropical hardwood species and 28 families were present in the all the protected areas. Osun Osogbo grove had the highest (38) species abundance, diversity index (3.26), species evenness (0.61) and percentage of endangered tree species (28.9%), strict nature reserve had species abundance (35), diversity index (3.20), species evenness (0.58) and Eda forest reserve had the least species abundance (28), diversity index (2.58%) and species evenness (0.45). Osun Osogbo grove has the highest volume yield 99.74m3, strict nature reserve has 81.10m3, and Eda forest reserve has the least 63.27m3. These are indicative of their importance in in-situ biodiversity conservation. This study provides additional information for the management of protected areas in southwestern, Nigeria and their potentials in in-situ biodiversity conservation.
Keywords: Tree diversity, protected areas, tree structure, biodiversity indices, volume yield