壤中流驱动下红壤坡耕地可溶性有机碳的迁移机制

The migration of soil dissolved organic carbon (DOC) at the soil-water interface is an important loss way for soil carbon pool and could affect the water environment. Up to now, available knowledge is enough about the transfer and transport of soil organic carbon driven by the surface runoff, but the dynamics of soil organic carbon, especially DOC controlled by the interflow is not clear. In this study, the field site was located at Jiangxi Eco-science Park of Soil and Water Conservation, China. Taking typical red soil slope farmland as the research object, monitoring and studying the soil organic carbon concentrations and its yields in surface runoff and sediment, as well as in interflow of different soil layers by large-sized drainage Lysimeter and simulated rainfall experiment. The focus of the study lies in the transfer flux and process of DOC driven by soil interflow, and its responses to external conditions (including rainfall intensity, slope and tillage measures). Besides, the differences between the hydrophilic and hydrophobic components of DOC were analyzed by UV and fluorescence spectra. Research results will help us determining the contributions of interflow in C loss in red soil slope farmland, deepening the scientific understanding of the relationship between soil erosion and carbon cycle, and enriching the study of soil and water loss in red soil region. It also has important practical significance to control the loss of organic carbon from the source and maintain soil quality.

可溶性有机碳（DOC）在土壤-水界面的径流迁移是土壤碳库损失的重要途径，并影响到水体环境，但目前壤中流及壤中流与地表径流共同影响下耕地有机碳的运移规律研究相对薄弱。项目以南方第四纪红黏土红壤坡耕地为对象，采取室内模拟降雨和野外径流小区原位监测相结合的方法，开展不同雨强、坡度和耕作方式下的降雨-产流-产沙过程观测，监测径流在地表和壤中流的分配，研究径流中DOC浓度及其在不同坡位、不同土壤深度的空间分布；重点分析壤中流驱动下DOC的迁移过程及通量负荷对雨强、坡度和耕作方式等外界条件变化的响应；并通过紫外和荧光光谱分析，区分DOC的亲水性和疏水性组分对条件变化响应的差异，明确壤中流对有机碳损失的贡献，探讨壤中流驱动下DOC迁移模式与机制。结果有助于认识有机碳的垂直损耗问题，加深土壤侵蚀与碳循环关系的科学认知，丰富红壤区水土流失规律研究，在从源头控制有机碳流失、维持土壤质量上也具有重要的实际意义。

目前壤中流及壤中流与地表径流共同影响下耕地可溶性有机碳的运移规律研究相对薄弱。项目以南方第四纪红黏土红壤坡耕地为对象，采取室内模拟降雨和野外径流小区原位监测相结合的方法，研究了壤中流驱动下DOC的迁移过程及通量负荷对雨强、坡度和耕作方式等外界条件变化的响应，明确了红壤坡地壤中流对有机碳损失的贡献，揭示了壤中流驱动下DOC迁移模式与机制。结果表明：.（1）降雨强度是红壤坡耕地地表产流产沙、DOC浓度和流失通量的主要影响因素。地表径流驱动下，DOC浓度随降雨强度的增大而减小，其流失通量随降雨强度的增大而增大。壤中流驱动下DOC浓度和流失通量均随着降雨强度的增大而减小。.（2）红壤坡耕地壤中流中DOC的流失比地表径流更易受坡度的影响，且坡度对DOC流失的影响会随着花生生长期的延长减弱。地表径流驱动下DOC浓度和流失通量均随着坡度增大而增大，壤中流驱动下DOC浓度和流失通量均随着坡度的增大而减小。.（3）红壤坡耕地壤中流DOC的流失比地表径流更易受耕作方式的影响。翻耕条件下，壤中流更易产流，且产流量较大，DOC浓度和流失通量均大于免耕。.（4）红壤坡耕地地表径流DOC的流失比壤中流更易受花生生长期的影响。地表径流携带的产沙量、DOC浓度和流失通量均是花生生长前期（幼苗期和开花下针期）大于生长后期（结荚期和成熟期）。壤中流中DOC流失通量在花生生长前期大于生长后期。 .（5）红壤坡耕地地表径流与壤中流中.DOC的流失受外界因素的影响较大。地表径流携带的DOC受降雨强度的影响最大，耕作方式的影响最小。壤中流携带的DOC受耕作方式影响最大，生长期影响最小。坡面地表产流产沙量受降雨强度的影响最大，坡度的影响最小。壤中流产流受坡度的影响最大，生长期的影响最小。各影响因素组合间的交互作用较小。.（6）红壤坡耕地地表径流携带的DOC通量（95%±12.2%）显著大于壤中流（5%±12.2%）。地表径流（占总径流的比例97%±9.9%）显著大于壤中流（3%±9.9%），并且随地表径流流失的可溶性有机碳浓度（163.5 mg/L）也显著大于壤中流（40.8 mg/L）。