Estimating crown biomass of three coniferous tree species using cross-sectional area at the base of live crown

Aim of study: The error in estimating branch biomass, foliage biomass, and crown biomass (i.e. sum of branch and foliage biomass) based on the diameter at the live crown base was evaluated. Area of study: The foci were hinoki cypress [Chamaecyparis obtusa (Siebold et Zucc.) Endl.], Japanese larch (Larix kaempferi (Lamb.) Carrière), and Sakhalin fir [Abies sachalinensis (Fr.Schmidt) Mast.] in plantation forests located in Japan. Material and methods: Nineteen cypress trees were destructively sampled in the four stands. Measurements from 64 cypress trees, 44 larch trees, and 27 fir trees were included in the analysis. A power function was applied as an allometric equation to establish the relationship between the diameter at the live crown base and the foliage, branch, and crown biomass. Cross-validation was performed to evaluate the precision and accuracy of biomass estimation for each component using the power function. Crown biomass was estimated from stem volume by using the basic wood density and the biomass expansion factor as a traditional method to compare the error. Main results: Little bias was detected in the estimation of foliage, branch, or crown biomass. The percent root mean squared error was the lowest for branch biomass (36%, 26%), followed by crown biomass (52%, 26%) and foliage biomass (84%, 34%) for cypress and larch, respectively. These percent root mean squared errors were smaller than those using an allometric equation based on diameter at breast height and total height. Research highlights: This study indicates the potential of using a single common allometric equation for each species to accurately estimate crown biomass.