Study on grassland's responses to global climate change and its carbon sequestration potentials.

The comprehensive and sequential classification system of rangeland(CSCS) was applied in analysis of the succession of grassland types and the dynamics of carbon sequestration tendency between the periods of the 1950-2000 and 2001-2050 year,which indicates that the main contributors to the carbon sequestration capacity of the Chinese grassland area,in sequence,the tundra and alpine grassland,temperate humid grassland,steppe and semi-desert.They in total occupy 85.52% of the all total potential grassland areas of China and 93.29% of the country's entire carbon sequestration capacity of potential grassland per year.In a global view,the main parts of the grassland are the savanna,tundra and alpine types and these two types occupy 48.50% of the total global potential grassland and 72.22% of the global potential grassland carbon sequestration capacity per year.In current situation of strong(A2a) and weak(B2a) in global climate warming and drying,China will reduce its grassland while increase its forest area in comparing to its status during 1950-2000.In contrast to the trend in China,from the global perspective,grassland will increase while forest area will decrease.Under the model of strong(A2a) and weak(B2a) in global climate warming and drying process,China will increase 14.6% and 18.5%,while the world will increase 17.3% and 16.8% in terms of carbon sequestration capacity per year.However,the two are different in their mode of increase.The global increase is characterized by huge increase of potential carbon sequestration capacity in the temperate humid grassland,while the China's increase is characterized by its decrease in the same area.Comparing with the global trend the warming and drying tendency in China is more intense in terms of carbon sequestration capacity of potential grassland per year.Although the factors caused the global climate warming and drying cannot be controlled by human beings but the system problems can only be dealt with by the means of system synthesis,which is the mission for all pastoral practitioners.