Species-specific and general allometric equations for estimating tree biomass components of subtropical forests in southern China

Abstract

Chinese subtropical forests contain a diversity of tree species and exhibit a high carbon (C) sequestration capacity, but biomass and C stock assessments in subtropical secondary forests remain uncertain because of a limited availability of allometric equations and an uncertain applicability of existing allometric equations that have not been tested for these forests. We developed allometric equations for important coniferous (Pinus massoniana), deciduous broadleaved (Alniphyllum fortunei, Choerospondias axillaris, Liquidambar formosana) and evergreen broadleaved (Cyclobalanopsis glauca, Litsea rotundifolia, Schima superba) species. A total of 70 trees (10 trees for each species) with diameters at breast height (D) ranging from 2.6 to 50.9 cm were destructively harvested and dissected into tree components (stem, branch, leaf and coarse root). Species-specific equations using D alone as the predictor variable fitted the data well (p 0.72) for each tree component. Including height (H) in the form of D2H only improved the regression fit for A. fortunei and L. rotundifolia. The relationships of branch, leaf and root biomass against D varied among tree species. General equations for functional groups and all species combined showed comparable bias for stem, aboveground and total tree biomass to species-specific equations. We recommend the general equations of multiple species to estimate forest biomass at regional scales and also to estimate stem, aboveground and total tree biomass for each species when species-specific allometric equations are not available at a given site. For branch, leaf and root biomass, species-specific equations are preferred, even though this requires biomass data for additional tree species.