紫色土坡耕地侵蚀演化特征及其对作物防蚀的响应机制

Slope farmland of purple soil was studied in order to sustainable development in this study for the ecological environment construction and water resources in the upper reaches of the Yangtze River.By the methods of field artificial rainfall simulation experiments and laboratory analysis, the changing characteristics of cross-slope with different growth stages was analyzed during splash erosion, sheet erosion and rill erosion based on soil surface roughness. It was obtained to the coupling relationship between the evolution of splash erosion - sheet erosion - rill erosion and runoff, erosion, sediment yield.The critical condition and the contribution rate were clarified during the splash erosion, on-chip erosion and rill erosion occurred in the crop growth period and slope erosion processes. To seek a different stage of preventing and controlling erosion and reveal the response of the corrosion mechanism of erosion of the evolution of crop, the corresponding study was done. The study provide theory basis for revealing the erosion characteristics and erosion process model, and at the same time, it can provide new ideas and theoretical basis for the guidance of sloping farmland management.

本研究针对长江上游生态环境建设和水土资源可持续发展的关键，以紫色土坡耕地为研究对象，采用野外人工模拟降雨试验与室内分析相结合的方法，从地表糙度角度，探索横坡垄作在溅蚀、片蚀和细沟侵蚀过程中随作物生长的变化特征，阐明其在溅蚀-片蚀-细沟侵蚀侵蚀演化中与径流、侵蚀产沙的耦合关系，弄清溅蚀、片蚀与细沟侵蚀在作物不同生育期及坡面侵蚀过程中发生的临界条件及贡献率，寻求不同侵蚀阶段的最佳防蚀期，揭示侵蚀演化过程中作物防蚀的响应机制。这一研究，为进一步理解紫色土坡耕地水蚀机理及侵蚀过程模型的建立奠定基础，为指导坡耕地管理提供新的思路及理论依据。

本项目以紫色坡耕地为研究对象，通过野外人工模拟降雨及室内分析相结合的方法，系统研究了不同降雨、坡度条件下，横垄坡面溅蚀-片蚀-细沟侵蚀侵蚀演化中玉米生育期与径流、侵蚀产沙的耦合关系，揭示其对作物防蚀的响应机制。项目主要研究结果如下：.（1）玉米各生育期，坡面溅蚀总量的80%来自上坡。玉米苗期，坡面溅蚀总量与向下溅蚀量随雨强的增大而增加。玉米拔节期后，1.0 mm/min雨强下溅蚀作用最强，且20°坡面溅蚀总量和向下溅蚀量高于15°坡面。玉米冠下溅蚀速率随雨强的增加逐渐增大，抽雄期溅蚀作用最强；冠下雨强和溅蚀速率呈不均匀空间分布，二者不具有同步性。（2）不同条件下片蚀产流率总体表现为苗期＞成熟期＞抽雄期＞拔节期，产沙率表现为苗期＞成熟期＞拔节期＞抽雄期。片蚀水动力学参数在拔节期或抽雄期最小，苗期或成熟期最大。（3）苗期、拔节期细沟侵蚀发育过程为跌坎、断续细沟、细沟发育、细沟调整；抽雄期、成熟期细沟侵蚀发育过程为溅蚀坑、溅蚀坑贯穿、细沟发育、细沟调整。15°与20°坡面间的细沟产沙量在各生育期均无显著差异，细沟产流量均呈增加的趋势。细沟流流态主要分布于“缓过渡流”区，抽雄期细沟流流态向“缓层流”区延伸，苗期和成熟期局部达到“缓紊流”区。（4）玉米苗期和成熟期，雨强、雨前糙度与溅蚀总量以及坡度、雨前糙度与向上溅蚀量均呈显著或极显著线性关系。玉米抽雄和成熟期，坡度、雨前糙度与向下溅蚀量和溅蚀总量呈显著或极显著线性关系。（5）片蚀产流率、产沙率与水动力学参数间分别呈极显著正相关的线性和幂函数关系；片蚀产沙强度与水动力学参数间呈极显著正相关的幂函数关系，水流功率和单位能量可较好描述片蚀过程侵蚀产沙。（6）苗期，产流率与单位水流功率呈二次函数关系；拔节期，产流率与单位水流功率呈幂函数关系；抽雄期、成熟期，产流率与单位水流功均呈对数函数正相关。苗期，产沙率与单位水流功率，以及抽雄期、成熟期产沙率与单位能量均呈二次函数。