摘 要 ：采用时空互代法，以不同年限坡改梯田为研究对象，分析了陇东黄土丘陵区梯田土壤有机碳（SOC）的时空分布特征。结果表明，1）陇东黄土丘陵区黄绵土在坡改梯后近50 a内，农田0—60 cm土层土壤有机碳处于持续累积状态，20—40 cm与40—60 cm土层SOC较坡耕地的增幅分别为54.6%和52.4%，大于表层增幅 （33.7%）（P<0.05）；各土层SOC随梯田年限的变化趋势基本一致，在修建初期（0~8 a）累积较快并超过坡耕地SOC水平（P<0.01），24 a 后有了显著提高（P<0.05），后期SOC累积变化不显著。2）不同土壤类型及地形下SOC含量及累积速率有所差异，0—20 cm 土层的SOC在黄绵土中累积最为明显，20—40 cm与40—60 cm 两个土层SOC在红粘土中的累积量最为显著（P<0.05）；阴坡表层SOC大于阳坡，梯田修建25 a 后阴坡平均SOC较阳坡高22.1%。3）梯田土壤有机碳的时空变异受土壤类型的影响最大，其贡献率达62.0%，海拔和坡向影响次之，两者可解释20.4%的有机碳的变异；梯田年限和施用有机肥可分别解释11.7%和5.8%的变异。陇东黄土丘陵区坡改梯田土壤在当前经营状况下表现出较弱的碳汇效应。
Abstract:In order to reveal spatial-temporal distribution characteristics of soil organic carbon (SOC) under different influencing factors (terrace age, soil type, altitude, slope aspect, etc) after slope cropland changed into terraces in the hilly loess plateau of eastern Gansu Province, the terraces with different ages were chosen based on the way of interaction of time and space. The results demonstrate that the SOC content in 0-60 cm soil layer of the loessial soil in terraces is continuously accumulated in nearly 50 years after the terraces building. Compared with the SOC content of slope cropland, the contents of SOC in 20-40 cm and 40-60 cm soil layers in 50 years later are increased by 54.6% and 52.4% respectively, while the increasing range of 0-20 cm soil is only 33.7% (P<0.05). The content of SOC is increased significantly and exceeds the SOC content of slope cropland with the increase of terrace ages during the initial 8 years（P<0.01）. Significant increase of SOC is found after 24 years but there is no significant change later (P<0.05). The contents and accumulation rates of SOC are different in different soil types and terrains with the terrace age. The SOC accumulation in 0-20 cm layer of the loessial soil is the most obvious compared with the deeper layers, whereas, there are significant increases of SOC in 20-40 cm and 40-60 cm layers in the red clay soil (P<0.05). The SOC content in 0-20 cm layer in the northward slopes is higher than that in the southward slopes. Compared with the southward slopes, the average of SOC in the northward slopes is increased by 22.1% after 25 years. The spatial-temporal variance of SOC is mainly influenced by soil types which could explain 62.0% of the organic carbon variance. The slope aspect and altitude could explain 20.4% of the variance in all, and the terracing age and organic fertilizer could explain 11.7% and 5.8% of the variance respectively. These results indicate that the terrace soil has a weaker SOC accumulation effect under the current land management conditions.