TREE TAPER AND VOLUME EQUATIONS FOR GMELINA ARBOREA IN OMO FOREST RESERVE, SOUTHWESTERN NIGERIA.

Abstract

Taper and volume functions 'Were developed for Gmelina arborea , plantations in Omo Forest Reserve, Nigeria. A total often different age series (11, 13, 15, 16, 19,20,21, 24, 25 and 26 years old) of Gmelina arborea plantations in Omo Forest Reserve was investigated. Three temporary 20 x 20 m sample plots were randomly selected from ? each age series, making a total of 30 sample plots. The diameters at the breast height (dbh) of all trees within each sample plot were measured. The trees were subsequently grouped into five dbh classes of 10-20 cm, 20-30 cm, 30-40 em, 40-50 cm and 50 ern and above. The tree which dbh was closest to the mean dbh of each dbh class was selected for further enumeration and felling, resulting in the selection of five trees per age series and 50 trees for the entire study. Before felling, the following measurements were made on each selected tree: diameters at ground level (OG) as well as at 15 em (DI5), 30 ern (030) and 45 em (045) above the ground: crown depth (HC): and total height (HT). After felling, the stump height (Hst) was measured and the log was sectioned into bolts after which the inside-bark and outside-bark diameters of each bolt as well as the length were measured. In addition, the total length of each felled tree from the base to the tip (LL) was measured. Individual tree volume was computed using the conventional formulae, i.e Huber's, Smalian's, and Newton's formulae. In addition, the volume of each bolt was calculated using Huber's formula. The volumes of all the bolts for each felled tree were added to give the tree volume, which served as the basis for comparing the volumes from the three conventional volume formulae, one-way analysis of variance (ANOV A) was used to test for significant differences among the four volume estimates arising from the four different volume formulae. Mean separation was