COMPARTMENTALIZED ALLOMETRIC EQUATION FOR ESTIMATING VOLUME AND BIOMASS OF EUCALYPTUS IN AGROFORESTRY SYSTEMS IN KENYA

Abstract

This study used a sample of forty-one Eucalyptus grandis trees ranging from 4 to 44 cm diameter at breast height (dbh). The trees were destructively sampled in Nakuru and Kiambu counties, purposely selected in agro-ecological zone II, III and IV, to collect data on the different compartments to develop compartmentalized volume and biomass models. Stem volumes for the whole tree height or to a specific diameter point from the root point were calculated by integrals of splines formed from taper curves of different diameter points. Densities of different compartments of the stem, branches, stump and roots were determined by dividing their sample disks oven dry weight (wood and bark separately) with the fresh volume of the sample disk, whereas, twigs and foliage densities were determined by dividing their sample dry weight with fresh weight. Compartment’s biomass was calculated by multiplying their volume with respective density. Five equations relating volume/biomass of the different compartments to variables including dbh, tree height and crown length were fitted to the data using R -3.3.3 statistical software. The best model was the one with the lowest Akaike Information Criterion values (AIC) and Residual Standard Error (RSE). The findings show that tree height and dbh were the best predictor for volume and biomass of the different compartments. The developed models are recommended for quantification of compartmentalized products of E. grandis and their carbon stocks. The utilized methodology may also be of interest to researchers, planners and academicians.