基于多影响因素交互作用的黄土坡耕地细沟侵蚀过程研究

Rill erosion is a complex process that is affected by many factors. At present, researches on the impact of various factors on rill erosion have achieved a lot of results, however, the research on the interaction of different factors during the process of rill erosion is weak, and the mechanism of multi-factor interaction is still unclear. In this study, from the perspective of the interaction of five factors including rainfall, upslope inflow, slope gradient, slope length and surface roughness that affect rill erosion on loess hillslopes, on the basis of completing the orthogonal experiment considering interaction, complete tests are performed after the experiments considering interactions have been achieved. Comprehensive analysis methods of experimental data including analysis of variance, fixed effect models and structural equation models are used to identify the main influencing factors, as well as the sensitive factors with significant interaction effects and their form of interaction terms during rill erosion processes. The contribution rate of the main effect and interaction effect of various factors to the rill erosion parameters such as runoff rate, sediment yield rate, rill morphology and rill flow hydrodynamics. Furthermore, the quantitative relationship between rill erosion parameters, the main effect and interaction effect of multiple factors. In addition, the influence of multi-factor interaction on the formation of rills is explored, and a comprehensive critical index for the occurrence of rill erosion under the combined action of multiple factors is constructed. The research results are expected to provide a basis for deepening the mechanism of rill erosion, improving the soil erosion model and controlling soil erosion on sloping farmland of the Loess Plateau.

细沟侵蚀是一个在多因素综合影响下的复杂过程，不同因素之间存在交互作用；当前关于各个因素对细沟侵蚀影响研究已取得大量成果，但多因素的交互作用对细沟发生及侵蚀过程的定量影响研究相对薄弱、作用机制尚不明晰。本项目从影响黄土坡耕地细沟侵蚀的降雨、上方汇流、坡度、坡长和地表糙度等5种因素交互作用的角度出发，在完成考虑交互作用的正交试验基础上开展完全试验进行相互验证，综合运用方差分析、固定效应模型及结构方程模型分析方法，识别细沟侵蚀过程中的主要影响因素、存在显著交互作用效应的因素及其交互效应项，量化各因素及其交互作用效应对细沟侵蚀参数（产流产沙、细沟形态及水动力特性）的贡献、建立细沟侵蚀参数与各因素的主效应项、交互效应项之间的定量关系式；探讨多因素交互作用下细沟发生的临界条件、构建细沟发生的综合性临界表征指标，以期为深化细沟侵蚀机理、完善坡面侵蚀预报模型及合理防治黄土坡耕地土壤侵蚀提供基础支撑。

目前关于上方来水、坡度、降雨、成土母质等因素交互作用条件下的坡面侵蚀和细沟发育过程与机理研究亟需加强；山丘区不同类型水土保持措施对RUSLE模型P因子值的定量影响仍不明晰。本项目以黄土陡坡、湖北省山地丘陵区及其不同母质红壤为研究对象，基于人工模拟降雨和放水冲刷试验、不同坡度和植被类型野外径流小区土壤侵蚀观测数据、改进的RUSLE模型模拟等技术方法，研究了黄土坡面细沟网发育、细沟侵蚀与水动力学特征之间的定量关系；明确了坡度和流量对细沟侵蚀过程和细沟形态特征的影响、分析了细沟流水力学特征并阐明了细沟侵蚀的水动力学机制；构建了泥质页岩和第四纪红黏土红壤产流产沙率、细沟侵蚀量与流量的定量关系；通过考虑不同类型水土保持措施对P因子值的定量影响来改进RUSLE模型，并利用湖北省山丘区96个径流小区长期(2000-2015年)土壤侵蚀监测数据验证了改进RUSLE模型的模拟精度。获得主要结论如下：细沟发育初期，沟底下切和沟头溯源侵蚀明显，而在细沟发育活跃期，细沟展宽明显；描述细沟侵蚀速率和细沟形态的最佳水动力学参数分别为水流功率和流速；与坡度相比，雨强对坡面平均流速影响更大；侵蚀泥沙中砂粒含量与原始红壤质地和细沟水流能量密切相关，成土母质对红壤坡面径流冲刷侵蚀和细沟发育过程存在显著影响；改进RUSLE模型在湖北省典型山丘区的应用表现出较高的效率(R2=0.89)；改进RUSLE的模拟精度相较原模型提高了28.0%，水土保持措施显著降低了不同土地利用类型的P因子值；不同因素交互作用的土壤侵蚀效应不容忽视，雨强与流量的交互作用、侵蚀性降水量与坡度的交互作用均明显促进坡面侵蚀的发生。研究成果可为深化多因素交互作用下的细沟侵蚀机理、改善RUSLE模型在山丘区的适用性以及合理布设水土保持措施提供借鉴。