Impact of soil redistribution in a sloping landscape on carbon sequestration in Northeast China

Soil organic carbon (SOC) in eroded soil can be redistributed from upper slope positions and deposited and sequestered in depressional areas. However, the SOC lost from soil erosion is normally not considered when soil carbon budgets are derived and this could result in an overestimation of SOC loss from the agricultural areas. The impact of soil redistribution on the SOC budget of a sloping landscape in the Black soil region in Northeast China was studied using the presence of the (CS)-C-137 tracer which has been deposited since 1954 and the fly-ash tracer, which was deposited in 1903. Five landscape positions (summit, shoulder-, back-, foot- and toe-slope) were selected and included in this study. The depths of Cs-137 and fly ash and the SOC content of the deposition layers were used to calculate the change in C content of the soil in the various landscape positions over the last century. We found that the most severe soil erosion occurred in soils in the shoulder-slope position followed by the backslope and the summit positions. Soil deposition occurred in the toe-slope position followed by the foot-slope position. A total of 683 kg C was eroded from the summit, shoulder- and back-slopes (in a I m wide strip) over the past 100 years and 418 kg C (about 61.2 percent) was deposited in the low-lying areas (foot- and toe-slopes). Over half (61-5 percent) of the deposition (257 kg SOC) occurred over the past 50 years. Most of the previously reported loss of C from the upper slope positions in the Black soils was in fact sequestered in the deposition areas in the landscape. Copyright (c) 2005 John Wiley & Sons, Ltd.