Biomass yield and biomass functions for plantation grown Nauclea diderrichii in the humid tropical rainforest zone of South-Western Nigeria

Abstract

Adequate management of forest plantations requires estimation of biomass yield as well as functions for estimating biomass. This paper presents biomass yield and functions for estimating total above ground biomass (TAGB), stem, branch and foliage biomass for even-aged plantations of Nauclea diderrichii (Opepe) in Nigeria. Data were obtained from 81 trees, harvested from stands of different ages. TAGB of Opepe ranged from 32.5 t ha^-1 (5 years) to 287.5 t ha^-1 (30 years). While 84.5% of TAGB was allocated to stem, 13.5 and 3% were allocated to branch and foliage respectively. All functions had good fits, with very high adjusted R2 (over 0.97) and very low standard error of estimate. Diameter at breast height (dbh) alone as predictive variable accounted for over 97% of the variation in biomass. Little improvement in the ability of the functions to explain variations in biomass was achieved by including total height variable in the functions. In addition, the plot of residuals showed that the functions with only dbh performed generally better than those that included height variable in their predictions. Consequently, the functions with only dbh as independent variable were recommended for use in estimating biomass of Opepe in Nigeria.

Keywords: above-ground-biomass, Nauclea, indigenous species, plantation, predictive functions

Ghana Journal of Forestry Vol. 15&16 2004: 30-39