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中文摘要：
通过分析我国1980年来耕作土壤有机质的实测数据，对比研究了90年代末和80年代初两个时段土壤有机碳密度的变化特征，并对变化的原因和未来发展趋势进行了探讨。结果表明，总体上我国实测点位（或区域）耕作土壤平均有机碳密度在此期间略有增加。其中，华北黄淮海潮土和褐土区、下辽河平原棕壤农业区和长江以南的水稻土区增幅分别达19％（0．24kg／m^2）、14％（0．29kg／m^2）和16％（0．29kg／m^2）；相反，云南砖红壤区、东北和内蒙的黑土和黑钙土区有机碳损失，下降幅度分别达27％（1．01kg／m^2）和3％（0．11kg／m^2）。黄土高原的黑垆土和黄绵土区，山西北部的褐土区、新疆西北部的灌耕土区没有明显变化。两时段有机碳密度的空间分布与气候带总体一致，但20年间有机碳含量变化与80年代初的初始含量呈显著负相关。有机碳含量在低值区增加与近年来农田轮作、施肥和灌溉面积增加等农作措施的改善有关，而高值区的下降则与耕作时间短、强度大和初始含量高有关。根据现有耕作土壤与未耕作状态的碳损失状况估算，如果能在未来30～50年通过合理的农业措施使土壤有机碳损失量恢复50％，则华北、西北、华中南、西南和东北地区分别可能具有约51％、26％、7％、17％和30％的增长空间，指示我国耕作土壤具有较大的碳汇潜力。
英文摘要：
Based on measured data of soil organic carbon from 75 plots and 205 regions in China,changes in organic carbon density from 1980 to 2000 in cultivated soils in China, causes of the changes and future trends were addressed. The results show that the average organic carbon density in cultivated soils has experienced a carbon gain during the period. The significant carbon gains are in fluvo-aquic soils in North China,brown earths in lower reaches of the Liaohe River and paddy soils in South China, and the increases are 19 % （0.24 kg/m^2 ）, 14%（0. 29 kg/m^2 ） and 16 % （0. 29 kg/m^2 ） respectively. On the contrary, SOC have decreased by 27 % （1.01 kg/m^2） in the Latosols in Southwest China and by 3 % （0. 11 kg/m^2） in Phaeozems and Chernozems in Northeast China. There are no changes in dark loessial soils and loessial soils in the Loess Plateau, Cinnamon soils in Shanxi Province and irrigated silting soils in northeastern Xinjiang. The distribution of soil organic carbon density is consistent with the climatic zone from 1980 to 2000, but a significant negative relationship between the carbon change and its original content in early 1980s was revealed, and 4-5 kg/m^2 is the critical value for increasing and decreasing. The SOC increase in lower soil carbon content regions is mainly driven by improved human management practice such as the expansion of irrigation and fertilization in recent years, while the decrease in higher content regions could be due to the shorttime intensified tillage and its high original content. In the coming 30-50 years the cultivated soil would increase by 510%, 260%, 70%, 17%, and 30 % respectively in North, Northwest, Southeast, Southwest and Northeast China by improving land management, based on comparing with their noncultivated counterpart and assuming a restoration of -50% of the lost SOC. It would provide a considerable potential to sequestrate carbon from the atmosphere in China.
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