LINEAR EQUATIONS FOR ESTIMATING THE MERCHANTABLE WOOD VOLUME OF GMELINA ARBOREA IN SOUTHWEST NIGERIA

Abstract

Wood volume equations were developed for gmelina (Gmelina arborea) in Gambari forest of Nigeria using several functional forms, in order to establish the relationships between merchantable wood volume and estimator variables. Result from this study showed that quadratic model was the most efficient for estimating merchantable wood volume in the entire Gmelina plantation as follows: V = 0.0206 + 0.00004D²H (r² = 0.975). Efficiency of equations was markedly depressed when ratios of volume (V), breast height diameter (D) and/or merchantable height (H) were used as dependent variables. Breast height diameter was the best single estimator variable. Although precisions were lost when height measurement was omitted in wood volume equations, estimates based on diameter measurement as single estimator variable were also presented for quick evaluation of standing trees and wood removed by illegal forest takers.