Aims Belowground to aboveground biomass(BGB/AGB)ratio is a highly valued parameter of the terrestrial carbon cycle and productivity.However,it remains far from clear whether plant biomass partition-ing to aboveground and belowground is isometric(equal partition-ing)or allometric(unequal partitioning)at community levels and what factors are necessary in order to regulate the partitioning.This study aimed to comprehensively find out the patterns of biomass partitioning and their regulatory factors across forests in China.Methods The data of AGB and BGB were compiled from 1542 samples for communities across forests in China.Standardized major axis regression was conducted to examine whether AGB and BGB were allocated isometrically or allometrically at a community level.Redundancy analysis was used to analyze the relationships of BGB/AGB ratio with climatic factors and soil properties.Important Findings We found that the slopes of the relationship between logAGB and logBGB were not always comparable to 1.0(isometric allocation)at community levels,including primary forest,secondary forest,and planted forest.Meanwhile,samples in clay,loam,and sand soil types also presented the same phenomenon.Furthermore,the radically different allocations of AGB and BGB were found in northern and southern China.Environmental factors totally explained 3.86%of the variations in the BGB/AGB ratio at the community level,which include the mean annual precipitation,mean annual temperature,potential water deficit index,soil car-bon content,soil nitrogen content,soil clay,soil loam,soil sand,soil pH,and soil bulk density.In addition,the environmental fac-tors also have effects on the BGB/AGB ratio in other categories.The patterns revealed in this study are helpful for better under-standing biomass partitioning and spreading the carbon circle models.
Forests play an important role in acting as a carbon sink of terrestrial ecosystem.Although global forests have huge carbon carrying capacity(CCC)and carbon sequestration potential(CSP),there were few quantification reports on Chinese forests.We collected and compiled a forest biomass dataset of China,a total of 5841 sites,based on forest inventory and literature search results.From the dataset we extracted 338 sites with forests aged over 80 years,a threshold for defining mature forest,to establish the mature forest biomass dataset.After analyzing the spatial pattern of the carbon density of Chinese mature forests and its controlling factors,we used carbon density of mature forests as the reference level,and conservatively estimated the CCC of the forests in China by interpolation methods of Regression Kriging,Inverse Distance Weighted and Partial Thin Plate Smoothing Spline.Combining with the sixth National Forest Resources Inventory,we also estimated the forest CSP.The results revealed positive relationships between carbon density of mature forests and temperature,precipitation and stand age,and the horizontal and elevational patterns of carbon density of mature forests can be well predicted by temperature and precipitation.The total CCC and CSP of the existing forests are 19.87 and 13.86 Pg C,respectively.Subtropical forests would have more CCC and CSP than other biomes.Consequently,relying on forests to uptake carbon by decreasing disturbance on forests would be an alternative approach for mitigating greenhouse gas concentration effects besides afforestation and reforestation.
LIU Ying ChunYU Gui RuiWANG Qiu FengZHANG Yang JianXU Ze Hong
