作物垂直结构演变对坡面侵蚀过程的影响机制

Sloping farmland is an important source of soil erosion in mountainous areas of China. Crops are the main covering factors for sloping farmland surface, which greatly affects the occurrence and development of sloping farmland erosion. The crop vertical structure reflects hierarchical structure of vegetation community in vertical direction and morphological structure of individual vegetation, which has significant effect on rainfall interception and redistribution, and is an important factor affecting soil erosion. The crop vertical structure would vary rapidly during the crop growth cycle under different conditions of crop variety, planting pattern, planting mode and phenological phase, making the relationship between the crop vertical structure and soil erosion processes more complicated. In our study, the typical crops and fruit trees in the Three Gorges Reservoir area will be selected as research objects. Combined with three-dimensional laser scanning and point cloud reconstruction technology, the variation characteristics of crop vertical structure dynamics will be studied. Next, based on field observation and simulated rainfall experiments, the characteristics of slope erosion under dynamic conditions of crop vertical structure will be analyzed. Then, the effects of crop vertical structure dynamics on slope erosion process will be quantitatively characterized. Finally, the response mechanism of slope erosion process to crop vertical structure dynamics will be revealed. The results of this research will provide scientific basis and technical support for accurate prediction and prevention of soil erosion in sloping farmland.

坡耕地是我国山区土壤侵蚀的主要策源地。作物是坡耕地表面主要的覆盖因素，对坡耕地土壤侵蚀发生发展过程有重要影响。作物垂直结构反映了作物群体垂直方向上的层次构成以及作物形态结构，对降雨截留与再分配过程作用显著，是影响土壤侵蚀的重要因子。随着作物种类、作物布局、种植方式以及物候等条件的改变，作物垂直结构在生长周期内快速变化，使得作物垂直结构与侵蚀过程之间的关系更加复杂化。本研究拟选取三峡库区坡耕地典型作物与果树为研究对象，采用三维激光扫描与点云重建技术相结合的方法，研究作物垂直结构动态演变特征；通过野外监测和模拟降雨试验，分析作物垂直结构动态变化条件下的坡面侵蚀特征；在此基础上，定量表征作物垂直结构动态演变对坡面侵蚀过程的影响，揭示坡面侵蚀过程对作物垂直结构动态演变的响应机制，为我国坡耕地土壤侵蚀精准预测预报和防治提供科学依据和技术支持。

作物垂直结构显著作用于降雨截留与再分配过程，对土壤侵蚀具有重要影响。项目以三峡库区的王家桥小流域为研究区，选择典型作物玉米和大豆为研究对象，基于三维激光扫描与模拟降雨试验，研究了作物垂直结构动态演变特征，系统分析了作物垂直结构动态变化条件下的降雨分配特征，定量表征了作物垂直结构演变对降雨分配过程的影响。研究主要结果如下：（1）基于三维激光扫描与点云重建技术的作物垂直结构参数提取效果良好，总体精度优于85%。随着作物生长，株高、冠径、叶面积指数和植被覆盖度持续增加，质心高度/株高、冠长率和叶倾角保持相对稳定，略有减少；（2）相同雨强条件下，随着生育期推移，雨滴动能削减量、茎秆流率和冠层截留率总体增加，穿透雨率总体减少；雨强大小对穿透雨率和茎秆流率的变化影响较小，雨强大小对冠层截留率影响呈显著负相关关系，对雨滴动能削减量影响呈显著正相关关系；（3）叶面积指数、冠径、株高和植被覆盖度是影响降雨分配过程最关键的作物垂直结构参数；作物垂直结构差异显著作用于降雨分配过程，玉米垂直结构对降雨分配过程的影响较大豆显著，特别是降雨拦截与雨滴动能削减作用，玉米具有更高的抗侵蚀能力。研究结果为定量化描述作物垂直结构演变对土壤侵蚀过程的影响及土壤侵蚀精准预测预报提供理论基础和技术指导，对于我国坡耕地水土流失的科学防治具有重要借鉴意义。