中国农田生态系统土壤碳库的饱和水平及其固碳潜力

在利用反硝化-分解（DNDC）模型估算中国分县农田土壤碳库及其变化量的基础上，分析中国分省农田土壤碳库的饱和水平，估算各省市自治区农田土壤的固碳潜力，比较旱田与水田固碳能力的差异。结果表明：笔者所得到的中国农田土壤碳库的饱和水平可代表在1990年的土地利用方式、耕作措施、施肥水平和气候条件不变的情况下农田土壤经过耕种后所能达到的碳含量的平衡值，为农田选择土地利用方式、耕作栽培措施和施肥方式以固定更多的碳素提供依据。在分布上，中国农田土壤碳库的饱和水平以华北地区较低，以华北地区为中心向外呈辐射状递增。在1990年的土地利用方式、耕作措施、施肥水平和气候条件不变的情况下，中国农田土壤的固碳潜力为-0．969Pg。从单位面积的固碳潜力看，以西藏自治区最高，黑龙江省最低；从分布看，从南向北有逐渐递减的趋势。中国水田比旱田有更大的固碳能力。

Saturation levels and carbon sequestration potentials of soil carbon pools in farmland ecosystems of China

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.