Tree growth variables were collected at Elephant and Biosphere reserves of Omo Forest Reserve, Ogun State for volume model and form factor development. Ten(10) plots of equal sizes (50 x 50m) were randomly located in each of the forests using the systematic line transect sampling method. Trees with DBH ≥ 20 cm were enumerated. Growth variables measured include diameter at breast height, diameter at the base, diameter at the top, and the diameter at the middle of all living trees using the girth tape and Spiegel relaskop for trees with large buttresses or diameter while the total height was measured with the Spiegel Relaskop. Most of the tress in the Biosphere reserve fall in the diameter class of 20-30cm class. All data were screened with volume calculated using the Newton’s formula .Correlation analysis was carried out to examine the linear relationship between volume and other growth variables. Three regression models were developed, assessed and validated. Assessment was based on the correlation coefficient (R), coefficient of determination (R2), standard error (SE) and F- ratio while validation was done using the residual analysis to examine the plausibility of the models for volume estimation. The tree form factor which is the ratio of the volume of the tree to that of a geometric solid was also estimated with the form factor for the whole forest estimated at 0.74 and the form factor for the Biosphere reserve and Elephant reserve estimated at 0.50 and 0.52 respectively.
