长历时降雨下红壤坡耕地产流机制及侵蚀响应

Due to the soil forming process and long-term tillage disturbances, the red-soil slope farmland is characterized by loose topsoil and compacted subsoil. The difference of infiltration between topsoil and subsoil layers provides a prerequisite for subsurface runoff generation. Long-duration rainfalls such as continuous rains for days and plum rains are typical in red soil regions of southern China. The near-surface hydrological and sediment transport processes have changed with prolonged infiltration and increased soil moisture under long-duration rainfalls. The long-term natural rainfall in-situ observation and indoor rainfall simulation experiments, combined with the dynamic monitoring of soil moisture in different soil layers, will be conducted on red-soil slope farmland under long-duration rainfalls. Flow hydrodynamics parameters, particle selection in eroded sediments and morphology in erosion surface will be measured to investigate the combined effects of surface-subsurface runoff on hydrodynamic properties. And the dynamic mechanism of surface-subsurface runoff influenced by different factors such as rainfall duration and intensity, slope, etc. will also be explained. The study will reveal the dynamic response mechanism between the selective transport of sediments and rainfall-runoff under long-duration rainfalls. This research is important in understanding the inherent laws of slope erosion of red soil, and the results provide a theoretical basis for the erosion prevention of slope farmland.

红壤坡耕地在成土过程和长期耕作扰动下，形成“表层疏松-底层紧实”的土壤特性，表层和底层入渗性能的差异为壤中流发育提供条件。连阴雨、梅雨等长历时降雨是南方红壤区典型降雨类型，长历时降雨下，坡面入渗过程长、土壤含水量高，改变坡面近地表水文过程和泥沙输移过程。本项目以长历时降雨下的红壤坡耕地为研究对象，以天然降雨长期定位观测试验为主、室内模拟降雨试验为辅，结合不同土层水分实时定位监测、坡面径流水动力学参数测量、侵蚀泥沙颗粒分选和坡面侵蚀形态近景摄影记录等技术和手段，分析地表径流和壤中流耦合对坡面水动力学参数的影响，阐明降雨历时、雨强、坡度等因子对坡面地表径流和壤中流动态变化的影响机制，揭示长历时降雨下坡面泥沙输移分选对降雨径流关系的动力响应机制。研究成果对深化认识红壤坡面侵蚀内在规律有重要意义，为坡耕地侵蚀防控提供理论基础。

项目聚焦南方红壤区典型的长历时降雨事件，系统开展坡耕地降雨产流机制、侵蚀泥沙搬运动力机制、地表径流-壤中流耦合调控技术及调控机制、变更坡耕地土壤质量变化过程及影响机制等方面研究。基于长期定位观测试验和模拟降雨试验，定量了极端降雨对坡耕地产流和产沙的贡献率，阐明了雨型对坡耕地降雨-径流关系与产沙的影响，揭示了地表粗糙度及耕层结构特性等坡耕地典型要素影响下，“地表径流-壤中流”耦合侵蚀过程的动力机制；研究了植被覆盖模式、合理耕层结构构建、地表微地形管理等因素对“地表径流-壤中流”耦合侵蚀过程的调控机制，并明确了相应的技术参数；阐明了坡改梯等变更影响下坡地土壤质量变化过程及微生物驱动机制。研究成果丰富和完善了坡面水蚀过程和机理，为坡地水土流失治理及坡地水土资源高效利用提供了技术支撑。相关成果在本领域主流期刊上发表论文17篇，其中SCI收录论文15篇（中科院1区TOP期刊论文8篇），项目主持人入选湖南省青年骨干教师和湖南师范大学“世承人才”青年学者，项目组成员4人晋升为副高级职称，完成了人才培养目标。