Aboveground biomass and corresponding carbon sequestration ability of four major forest types in south China

Abstract

We estimated aboveground biomass carbon (T ABC) and net carbon accumulation rates (T NEP) for trees in four major forest types based on national forest inventory data collected in 1994–1998 and 1999–2003. The four types were Pinus massoniana forest, Cunninghamia lanceolata forest, hard broad-leaved evergreen forest and soft broad-leaved evergreen forest. We analyzed variations in T ABC and T NEP for five stand ages (initiation, young, medium, mature and old). In both time periods, estimated T ABC in all four forest types increased consistently with forest stand age and the oldest stage had the largest T ABC compared with other stages. Broad-leaved forests (hard and soft) had higher T ABC than needle-leaved forests (Pinus massoniana and Cunninghamia lanceolata) for each of the five age stages. The difference of T ABC between broad-leaved and needle-leaved forests increased with forest stand age. Comparison of estimated T NEP by age category indicated T NEP increased from the initiation stage to the young stage, and then decreased from the mature stage to old stage in all four forest types. T NEP for any particular stage depended on the forest type; for instance, broad-leaved forests at both the mature and old stages had greater T NEP than in needle-leaved forests. A logistic curve was applied to fit the relationship between T ABC and forest stand age. In each period, correlations in all four forest types were all statistically significant (P < 0.01) with R 2 > 0.95. T ABC was therefore predicted by these regression functions from 2000 to 2050 and the mean T NEP during the predicted period was estimated to be about 41.14, 31.53, 75.50 and 75.68 g C m−2 a−1 in Pinus massoniana forest, Cunninghamia lanceolata forest, hard broad-leaved forest and soft broad-leaved forest, respectively. Results from both forest inventory and regression prediction suggest broad-leaved forests are greater carbon sinks, and hence have greater carbon sequestration ability especially in the mature and old stages when compared to needle-leaved forests. Broad-leaved forests should have high levels of carbon sequestration when compared with needle-leaved forests in south China.