Biomass relationships for tree species in regenerating semi-deciduous tropical moist forest in Cameroon

Abstract

To enable carbon accumulation in regenerating tropical forest to be assessed, regression equations which permit the estimation of above and below ground biomass from measurements of stem diameter ( D) and height ( H) were derived from destructive harvests and dimensions of 14 trees distributed among five species in the moist tropical forest zone of Cameroon. Coarse root biomass (over 10 mm diameter) was assessed by complete excavation and fine root biomass (10 mm or less in diameter) by coring. Tree biomass (above and below ground) was linearly related to D 2H and to cross-sectional area of the stem. Above ground biomass estimates predicted by the equations developed in this study were smaller than those predicted by published multi-species equations. However, adjusting the estimates to take account of differences in timber density, brought the predictions closer to those from existing equations. Root biomass found in this study was larger than in previous work. The root: shoot ratio was significantly ( P < 0.05, r 2 = 60%) and positively correlated with tree size ( D 2H ). The fitted regression equation was Root shoot =0.223+0.0199× 2h where D is stem diameter at breast height (m) and H is tree height (m). The mean root/shoot ratio based on this study and recalculation of other published studies from moist tropical forests was about 0.25. Fine root amounts increased as forests aged from less than 1 year to 30 years, but there were no significant differences in fine root biomass between forests aged 30 (about 9 t ha −1) and mature forest. Branch surface area was positively correlated ( r 2 = 0.95) with leaf area.