Allometric equations for two South American conifers: Test of a non-destructive method

Abstract

Non-destructive biomass estimation for protected tree species is necessary to understand their population dynamics and the ecological factors affecting species scarcity. We present a method for estimating aboveground biomass of bole, branches and foliage, using data obtained by climbing live trees to collect limited samples and measurements. This method was applied to 26 individuals of Fitzroya cupressoides (Mol.) Johnston, a protected Chilean conifer, and to 12 individuals of a second, morphologically similar, but unprotected species, Pilgerodendron uviferum (D. Don.) Florı́n. Trees were climbed, basal diameter of all branches >1 cm were recorded and four branches per tree were removed for further measurement. The sampled branches were used to develop allometric equations predicting branch, twig and foliar biomass from branch basal diameter. These equations were used to generate whole tree canopy biomass estimates based on climber's measurements of branch basal diameter. Bole biomass was estimated from serial measurements of height, diameter and wood density. Whole tree canopy and bole biomass estimates were then used to develop allometric equations predicting wood and foliar biomass from diameter at breast height. Five of the P. uviferum trees were felled and weighed by conventional methods, and the data used to evaluate error in the non-destructive technique. Although the technique was labor intensive, it was found to yield mean estimates for canopy components that are expected to be within 10% of the true mean for large populations of trees (watershed level studies). Accurate estimation of individual trees may be less reliable, as the amount of dispersion about some of the regressions was quite high (>20%).