Allometric equations and height-diameter models for estimating above-and below-ground biomass of Colophospermum mopane J.Léonard. in Mozambique

Abstract

This study aimed to develop species-specific biomass allometric equations (BAE) for the estimation of above-ground biomass (AGB) and below-ground biomass (BGB) of Colophospermum mopane, J.Léonard species in Mozambique and to evaluate the feasibility of including total height estimated by the height-diameter (H-D) model in the equations to improve the accuracy of biomass estimation. We applied a destructive method and felled 120 trees of C. mopane in Mabalane and Tambara districts. We measured breast height diameter, total height (H), and dry weight of each component (roots, stem, branches, and leaves). We fitted three BAE and fifteen H-D models using OLS and non-linear least squares regression. A validation procedure checked all models for applicability. We conducted a forest inventory using 78 temporary clusters, each consisting of four plots measuring 100 m x 20 m, to estimate the average AGB and BGB of C. mopane using the best-fitting BAE and H-D model. We also compared the best BAE of C. mopane with existing, locally developed species-specific BAEs. The study found that the model, including the interaction of D2 and H, performed better than the model with separate D and H variables. However, models including D and H performed similarly to models with D alone. The Power model and HossfeldIV performed best among the models with 2 and 3 parameters, respectively. Integrating the H-D model into the BAE for AGB and estimation can improve the efficiency and reliability of biomass estimation and stand volume by forest inventory data. Overall, this research is timely as there is an urgent need to improve the assessment of biomass and carbon emissions in mopane woodland (MW) in southern Africa, given their spatial extent, and to support climate goals and the sustainable management of these ecosystems.