Abstract: Based on estimation of soil carbon pools and their variances at the county level with the aid of the DNDC model,farmland soil carbon pool saturation levels,soil carbon sequestration potentials,and differences between upland and paddy field in carbon sequestration capacity in various provinces of the country were analyzed.The results obtained by the authors demonstrate that the farmland soil carbon pool saturation level of China represented the equilibrium value of soil carbon content of farmland cultivated in the same way as it was in 1990 in land use pattern,farming practice,fertilization level and climatic conditions.The finding could serve as basis for selection of land use patterns,farming practices and fertilization methods for farmland.In terms of distribution of soil carbon saturation levels,it was low in North China,and then rising spokewisely with North China as its hub.Assuming the cultivation conditions of the farmland remain the same as they were in 1990,the soil carbon sequestration potential of the farmland of China would be-0.969 Pg.In terms of soil carbon sequestration potential per unit area,Tibet is on the top of the list and Heilongjiang the bottom,showing a declining trend from south to north.Besides,paddy field is much greater than upland in soil carbon sequestration potential.

Key words: saturation level, carbon sequestration potential, DNDC(denitrification-decomposition)model, farmland soil, China, upland, paddy field