生态建设小流域土壤有机碳迁移过程与侵蚀产沙的耦合关系

Carbon cycle is one of the important processes in maintaining ecosystem development and one of the predominant drivers of global change. Soil carbon stock and its dynamic change are the main contents in the study of carbon cycle, which has been highly concerned by researchers. As one of the profound influence factors on soil carbon, soil erosion is regarded as the most significance indicator to illustrate carbon detachment, transference and sequestration. It is, therefore, the effect of water erosion on soil organic carbon transportation in a small typical loess hilly catchment developed by ecological construction is determined. The main proposes for the study can be summarized such that: (1) At plot scale, to estimate the content value of the organic carbon transference coupling with sediment yielding under different slop regulations. (2) At slop scale, to analyze the changes of erosion intensity and organic carbon redistribution with land use pattern evolution. (3) At check dam scale, to retrieval organic carbon depositing process on the basis of analysis of sedimentation information and further to determine carbon sequestration of check dam. (4) At catchment scale, to detect the effect of sediment yielding on organic carbon dissolving, transferring and depositing process with development of ecological construction. This study can provide scientific references for proper evaluation of ecological construction measures and rational management of erosion control in loess hilly catchment.

碳循环是驱动全球变化的重要过程之一，土壤碳库及其动态变化成为碳循环研究的一个关键环节。土壤侵蚀深刻影响土壤碳库，研究流域土壤侵蚀剥离、输移和沉积过程中有机碳的输出、再分布和固定具有重要的意义。本项目针对侵蚀过程对土壤有机碳迁移的影响，选择黄土丘陵区典型生态建设小流域作为研究区，在小区、坡面、坝地和坝控小流域多个空间尺度上，研究坡面治理水蚀产沙过程有机碳的输移特征，分析坡面土地利用格局演变下侵蚀强度与有机碳再分布规律的响应关系，结合淤地坝淤积信息反演有机碳沉积过程，阐明坝控小流域土壤侵蚀对有机碳输移—沉积过程的作用，明确坝地固碳功能形成机制，为黄土丘陵区小流域综合治理和生态建设评价提供科学依据。

针对侵蚀过程对土壤有机碳迁移的影响，选择黄土丘陵区典型生态建设小流域作为研究区，从小区—坡面—坝地—坝控小流域不同尺度，分析生态建设影响下水蚀产沙与有机碳输移—沉积过程的耦合关系。研究进展如下。.（1）揭示了黄土丘陵沟壑区土地利用变化对土壤有机碳分布的影响。土地利用变化改变了土壤有机碳的分布格局，坡耕地转换成林地、灌木地和草地增加了土壤有机碳，王茂沟流域坡耕地土壤有机碳含量10.11kg m-2，退耕还林、灌和草后，各地类土壤有机碳含量分别为11.89kg m-2、11.77kg m-2、11.41kg m-2。地形因子，包括海拔、坡向、坡度影响到有机碳的含量。.（2）阐明坡面侵蚀与有机碳迁移过程的耦合关系。坡耕地的土壤有机碳浓度空间变化与土壤侵蚀速率空间变化规律相似，有机碳浓度达到最低的位置，土壤侵蚀现象十分明显，而在有机碳浓度达到最大的坡位，土壤沉积现象非常明显。有机碳随着侵蚀-沉积现象的发生，在坡面上形成一个的有机碳“源”和“汇”。.（3）揭示了在黄土高原极端连续降水事件下，首次冲刷的沉积物浓度、沉积物量以及土壤有机碳损失最高，随着冲刷次数的增加，土壤有机碳损失量逐渐的降低。提出了一种经验泥沙流失模型和土壤有机碳流失预测模型。.（4）明确了坝地沉积碳的来源，估算了淤地坝的碳汇效应。王茂沟流域坝地碳主要来自坡耕地，占到所有来源的 65%。该坝地沉积泥沙中共储存有机碳量为 207.86 t。.本研究揭示了黄土丘陵区生态建设与土壤侵蚀协同作用下有机碳的迁移过程。为黄土丘陵区小流域综合治理和碳储量计算提供理论参考。