Appropriate Volume Functions for Leguminosae Family in Two Tropical Rainforests in Cross River State, Nigeria
Journal of Environment and Ecology
Volume equations were developed for tree species of leguminosae family in two tropical rainforest, Nigeria. The data used consist of merchantable volume, stump diameter, diameter at breast height and merchantable height for 22 tree species. The number of observations per species ranged from 1 to 30 while the diameter at breast height ranged from 10.00 cm to 132.20 cm. The result in this study shows that generalised logarithmic volume function (also termed Schumacher's volume function) performed
... function) performed better than other forms of volume functions. For example, the best adjudged volume for all species combined were and . The merchantable volume developed from double-variable function indicates negative intercept while the single-variable volume function represents the logarithmic nonlinear function and performed best within the limit of data used for each species group. The method of species grouping in this study was morphological and was based on sub-families of tree species. The ISSN 2157-6092 2014 www.macrothink.org/jee 207 results indicate that D 2 H as weighting factor was found to be appropriate in reducing heteroscedasticity. The model being significant indicates a good fits and confirmed the effectiveness of weighted predictor in stabilising error variance. The resulting volume functions possessed desirable statistical properties and model behaviours, and can be used to estimate timber volume in the tropical rain forest areas of Nigeria. The volume equations based on stump diameter alone are adequate to provide estimates of tree volume illegally removed. 209 species are classified according to ecomorphological attributes of the sub-family. Journal of Environment and Ecology The objectives of this study were to aggregate leguminosae species in two tropical rainforests into sub-family groups and develop appropriate tree volume equations for each group of species. It is hoped that the equations will serve as efficient tools for obtaining reliable estimates of growing stock in the tropical rain forest ecosystem. Methodology Study Area This study was conducted in the Afi River and Oban Forest Reserves which are located in Cross River State (Fig. 1) . The forests are considered as biodiversity hotspot of global significance (Myers et al. 2000 , Oates et al. 2004 ). Afi River Forest Reserve Afi River Forest Reserve lies approximately between latitudes 6 o 08΄ and 6 o 26΄N and longitudes 8 o 50΄ and 9 o 05΄E and covers a total land area of 383.32 km 2 including the area known as Afi Mountain. The topography is extremely complex with many connected ridge systems, isolated peaks and outcrops, and ranging between 200m -1200m above sea level.