Estimating Biomass partitioning in Mytilaria laosensis Using Additive Models

If the additivity of the biomass allometric equation is not taken into account, it can result in erroneous estimation of forest biomass. The aim of this study was to evaluate biomass allocation patterns within separate tree parts, and to develop additive allometric equations for Mytilaria laosensis in southeast China. For this study, 42 destructive sampled trees were used to develop allometric equations for total biomass. We estimated biomass allocation by calculating the biomass fraction of each component (stem, branches, roots and leaves). We examined the relationships between each biomass fraction and diameter at breast height, tree height and crown diameter as independent variables. The seemingly unrelated regressions method was used to fit the biomass into additive allometric equations. The stem had the largest proportion of biomass (70.44%), followed by roots (20.35%), and branches (7.17%), with the smallest proportion of biomass being in the leaves (2.04%). Stem, leaf, and branch biomass ratios increased with diameter at breast height, while a reverse trend was found for belowground biomass ratios. The additive biomass models showed a good model fit explaining 94-98% of variance. This study contributes to species-specific allometric equations and the knowledge of crown, aboveground, and total biomass, which is lacking for most subtropical forests. The allometric biomass model constructed in our study can be used to estimate the biomass and carbon pool of Mytilaria laosensis plantations in Southeast China.