Aims Forest biomass carbon(C)stocks are usually estimated by multiplying biomass by a C conversion factor,i.e.C concentration.Thus,tree C concentration is crucial to the assessments of forest C cycles.As stems contrib...Aims Forest biomass carbon(C)stocks are usually estimated by multiplying biomass by a C conversion factor,i.e.C concentration.Thus,tree C concentration is crucial to the assessments of forest C cycles.As stems contribute to the large fraction of tree biomass,the canonical value of 50%or other simplified values of stem C concentration are widely used to represent the values of tree C concentration in the estimations of forest C stocks at different scales.However,C concentration variations between tree organs and within tree size and their impacts on forest C stocks are still unclear.Methods We conducted a global analysis of organ C concentration in age-specific trees based on 576 records of tree age,size(diameter at breast height and biomass)and C concentration data to evaluate the relationships between organ C concentrations and the changes of stem C concentration with tree age and size.Important Findings Tree C concentration varied significantly with organs.Stem C concentration of trees was significantly correlated with that of other tree organs,except for barks and reproductive organs.The stem C concentration increased significantly with tree size and age,which contributed to the increases in C contents of stems and trees.Using the C concentration in stems to represent the C concentrations of other organs and the whole tree could produce considerable errors in the estimations of forest C stocks(−8.6%to 25.6%and−2.5%to 5.9%,respectively).Our findings suggest that tree C accumulation in forests is related to the size-and age-dependent increases in stem C concentration and using specific C concentration values of tree organs can improve the estimations of forest C stocks.展开更多
基金supported by the National Key Research and Development Program of China(grant no.2017YFC0503903)National Natural Science Foundation of China(grant no.31621091).
文摘Aims Forest biomass carbon(C)stocks are usually estimated by multiplying biomass by a C conversion factor,i.e.C concentration.Thus,tree C concentration is crucial to the assessments of forest C cycles.As stems contribute to the large fraction of tree biomass,the canonical value of 50%or other simplified values of stem C concentration are widely used to represent the values of tree C concentration in the estimations of forest C stocks at different scales.However,C concentration variations between tree organs and within tree size and their impacts on forest C stocks are still unclear.Methods We conducted a global analysis of organ C concentration in age-specific trees based on 576 records of tree age,size(diameter at breast height and biomass)and C concentration data to evaluate the relationships between organ C concentrations and the changes of stem C concentration with tree age and size.Important Findings Tree C concentration varied significantly with organs.Stem C concentration of trees was significantly correlated with that of other tree organs,except for barks and reproductive organs.The stem C concentration increased significantly with tree size and age,which contributed to the increases in C contents of stems and trees.Using the C concentration in stems to represent the C concentrations of other organs and the whole tree could produce considerable errors in the estimations of forest C stocks(−8.6%to 25.6%and−2.5%to 5.9%,respectively).Our findings suggest that tree C accumulation in forests is related to the size-and age-dependent increases in stem C concentration and using specific C concentration values of tree organs can improve the estimations of forest C stocks.
