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
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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
