Abstract:

Estimating carbon storage in terrestrial ecosystems has been a central focus of research over the past two decades because of its importance to terrestrial carbon cycles and ecosystem processes. As one of the most widespread ecosystem types, China’s grasslands play an important role in global change research. The grasslands in China, which are distributed primarily throughout the temperate regions and on the Tibetan Plateau, were classified into 17 community types. In the present study, a statistical model was established to estimate grassland biomass and its geographical distribution in China based on a grassland inventory data set and remote sensing data (Normalized Difference Vegetation Index) using GIS and RS techniques. We found that there was a significant correlation between aboveground biomass density and the maximum annual NDVI when expressed as a power function (R2=0.71, p<0.001). The aboveground biomass was estimated to be 146.16 TgC (1Tg=1012 g) and belowground biomass was estimated as 898.60 TgC (6.15 times of the above biomass) for a total biomass of 1 044.76 TgC. This value accounts for about 2.1%-3.7% of the world’s grassland biomass. The grassland biomass is distributed primarily in the arid and semiarid regions of Northern China and the Qinghai-Xizang Plateau. The average biomass density of China’s grasslands was 315.24 gC·m-2, smaller than the world average. The aboveground biomass density decreases from southeastern China toward the northwest corresponding with changes in precipitation and temperature. Furthermore, aboveground biomass density reached the lowest levels at 1 350 m elevation and peak levels at 3 750 m above sea level which most likely is related to China’s three-step topographical background. The ratio of total biomass of grassland to forest biomass in China is 1/4, much higher than that of the world, suggesting a greater contribution of grasslands to China’s carbon pool.