The spatial distribution of forest carbon sinks and sources in China

Forest ecosystems play an important role in the global carbon cycle. The implementation of the United Nations Framework Convention on Climate Change (UNFCCC) and the Kyoto Protocol has made the study of forest ecosystem carbon cycling a hot topic of scientific research globally. This paper utilized Chinese national forest inventory data sets (for the periods 1984-1988 and 1999-2003), the vegetation map of China (1:1000000), and the spatially explicit net primary productivity (NPP) data sets derived with the remote sensing-based light use efficiency model (CASA model). We quantitatively estimated the spatial distribution of carbon sinks and sources of forest vegetation (with a resolution of 1 km) using the spatial downscaling technique. During the period 1984 to 2003 the forest vegetation in China represented a carbon sink. The total storage of carbon increased by 0.77 PgC, with a mean of 51.0 TgC a(-1). The total carbon sink was 0.88 PgC and carbon source was 0.11 PgC during the study period. The carbon sink and carbon source of forest vegetation in China showed a clear spatial distribution pattern. Carbon sinks were mainly located in subtropical and temperate regions, with the highest values in Hainan Province, Hengduan mountain ranges, Changbai mountain ranges in Jilin, and south and northwest of the Da Hinggan Mountains; carbon sources were mainly distributed from the northeast to southwestern areas in China, with the highest values mainly concentrated in southern Yunnan Province, central Sichuan Basin, and northern Da Hinggan Mountains. Increase in NPP was strongly correlated with carbon sink strength. The regression model showed that more than 80% of the variation in the modeled carbon sinks in Northeast, Northern, Northwest and Southern China were explained by the variation in NPP increase. There was a strong relationship between carbon sink strength and forest stand age.