Method to estimate coarse root biomass and lost mass during excavation in subtropical secondary forests

Coarse root biomass (CRB) is an important pool of biomass and carbon in forest ecosystems. Accurate estimation of CRB is fundamental to understanding carbon cycling in forest ecosystems. However, very few allometric equations... [ view full abstract ]

Coarse root biomass (CRB) is an important pool of biomass and carbon in forest ecosystems. Accurate estimation of CRB is fundamental to understanding carbon cycling in forest ecosystems. However, very few allometric equations developed for the CRB and CRB lost during excavation seldom examined in subtropical forest. In this study, we used excavation method to determine coarse root of seven subtropical dominant tree species, including coniferous (Pinus massoniana), deciduous (Alniphyllum fortunei, Choerospondias axillaris, Liquidambar formosana), and evergreen broadleaved (Cyclobalanopsis glauca, Litsea rotundifolia, Schima superba). The lost mass during excavation were estimated by developing a regression equation to relate the mean proportion of the lateral root loss beyond 1.5 m from the ground stump and diameter at breast (DBH) interval at 5 cm. The results showed that the average increase for CRB after correction is 11.65 kg, indicating that significant amounts of lateral of roots (15.49%) was lost during the excavation. The linear-transformed regression (LR) and nonlinear regression (NLR) were used to estimate CRB as a function of diameter at breast height (DBH) or crown width (CW). All allometric equations for seven tree species and three functional groups were significant (P<0.001), and LR performed better than NLR approach. The results indicated the method for correcting lost mass and the DBH-based allometric equations can be useful for evaluating coarse root carbon storage in subtropical secondary forest.