The spatial patterns of total vegetation biomass, shoot and root biomass, as well as root to shoot (R/S) ratio were estimated by the atmospheric-vegetation interaction model (AVIM2) at the resolution of 0.1°×0.1° grids across China. The relationships between soil moisture, precipitation, temperature, and the spatial distributions of vegetation biomass as well as the R/S ratio were also studied.
The results indicate that the spatial distributions of total biomass, root and shoot biomass as well as R/S ratio were limited by both water and energy. During the study period of 19611990, total carbon stocks in vegetation in China is estimated to be 14.04 Gt C (1Gt=1015g), with a mean value of 1.54kg Ｃ/m2. The total vegetation biomass and shoot biomass have the same overall pattern in spatial distributions: the highest values occurred at the northeast and northwest areas of China and the lowest value located at the west areas of China. In terms of regional distribution, valley bottom area of southwestern China are dominated by evergreen broadleaf forest and needle leaf forest where water and heat conditions are excellent and total biomass is the highest, above 10kg Ｃ/m2. Part of hilly and mountainous areas in southeastern coastal zone of China where dominated by evergreen needle leaf forest, with total vegetation biomass of 510 kg Ｃ/m2. In southern part of Qinghai-Tibet Plateau, hilly and mountainous areas of southwestern province Yunnan and Guizhou, part of the areas south of the Huaihe River as well as Great Xing’an and Changbai mountains in Northeast China, vegetation is dominated by deciduous broadleaf forest, deciduous needle leaf forest and mixed forest, with vegetation total biomass above 5kg Ｃ/m2. Total crop biomass in northern China is about 0.7kg Ｃ/m2; the total biomass of alpine steppe and desert steppe in Inner Mongolia Plateau and southern part of Qinghai-Tibet Plateau ranges mostly from 0.2 to 0.5 kg Ｃ/m²; and that in desert and semi-desert areas of western China is less then 0.2 kg Ｃ/m².
For the same vegetation type, the total biomass is positively correlated with precipitation, soil moisture, and temperature. Vegetations growing in warm and humid areas, their total biomass is greater than those growing in the cold and dry area. Excepting for shrub lands, the correlation coefficients of total vegetation biomass to precipitation and soil moisture are greater than that to temperature. This means that the influence of water availability on the spatial distribution of total biomass is greater than energy.
The spatial patterns of R/S ratio in China have significant spatial variation. A boundary was found along Great Xing’an, Taihang Mountain, Qin Mountain and the southeast of Tibetan Plateau. The R/S ratios on the southeast areas of the boundary are much smaller than those on the west areas. The simulated mean R/S ratios of croplands, shrub lands, deserts and grasslands are 0.19, 0.91, 5.5 and 5.2, respectively. The R/S ratios of forest in China range form 0.19 to 0.36. The spatial distribution of R/S ratio is negatively related to that of annual mean temperature, soil moisture and annual precipitation. The correlation coefficients of R/S ratio to precipitation and soil moisture are greater than that to temperature, suggesting that the R/S ratios of vegetations growing in warm and humid areas are smaller than those growing in cold and dry areas, and the influence of the water on the spatial distribution of R/S is greater than energy.