Comparison of Constant and Variable Allometric Ratios for Estimating Populus tremuloides Biomass

Abstract

An allometric model that incorporates a variable allometric ratio (VAR) was fitted to Populus tremuloides biomass data for bolewood, bolebark, live branch, leaf, and current twig stem components. This model was compared to a log-liner transformation of the power function, which imposes a constant allometric ratio (CAR). Although the VAR model did not improve the estimation of bolewood biomass, it significantly improved the estimation of live branch and leaf biomass, and provided less biased estimates of bolebark and current twig weights relative to the CAR model. The VAR model was superior to the power function as a model of allometric relationships that do not remain constant as the organism grows. It allowed for initially large allometric ratios that declined linearly with increasing stem diameter. For. Sci. 33(2):294-300.