华南红壤区河岸植被缓冲带景观格局对土壤侵蚀过程的调控机理研究

Species composition, vegetation succession and distribution of the riparian vegetation buffer zone are suffering serious threats from the intensifying anthropogenic activities in recent years, which will aggravate soil erosion and degenerate ecosystem structure and functions directly or indirectly. Landscape pattern and ecological functions of the riparian vegetation buffer zone have attracted more and more attention. In this project, focusing on the regulation mechanism of riparian vegetation pattern on soil erosion process, taking the red soil area of southern China as the study area and the riparian vegetation buffer zone of Beijiang River as the research object, we will investigate the vegetation type, landscape pattern and their spatial-temporal dynamic,as well as soil physical and chemical properties of the Beijiang riparian and its background area, to study relationship between riparian vegetation pattern, landscape factors and soil properties, and to reveal the regulation mechanism of vegetation pattern on soil erosion via field monitoring, rainfall and scouring simulating experiments, and model simulation. Meanwhile, the coupling model between vegetation pattern and soil erosion process of the riparian vegetation buffer zone will be explored by integrating above achievement and optimizing existing coupling models. Conclusions obtained in this project will not only be benefit for understanding the regulation mechanism of landscape pattern on soil erosion process in-depth, but also be of importance for water and soil conservation of riparian vegetation buffer zone in red soil area of southern China.

近年来，人类活动的增加，使得河岸植被缓冲带的物种构成、植被演替与分布等受到严重影响，造成水土流失加剧，生态系统结构与功能退化。河岸植被缓冲带的结构、功能的研究受到了越来越多的关注。本项目围绕植被缓冲区"格局-土壤侵蚀过程"这一科学问题，选取水土流失状况仅次于黄土高原的华南红壤区为研究区域，以珠江支流北江河岸植被缓冲带为研究对象，调查北江河岸植被缓冲带及其背景区的植被类型、景观格局及其时空动态；分析植被格局、景观要素与土壤理化性质的相互关系；通过野外监测、降雨冲刷模拟与模型分析，阐明植被格局调控土壤侵蚀过程机理;同时，优化现有模型，探索河岸植被缓冲带分布格局与土壤侵蚀过程的耦合机制。本项目的开展，不仅有助于拓展对河岸带植被格局调控土壤侵蚀过程机理的理解，同时为华南红壤区河岸植被缓冲带的构建及其水土流失控制提供理论与应用依据。

本项目选取华南红壤区为研究区域，以珠江支流北江河岸植被缓冲带为研究对象，采用野外调查与模拟试验、室内分析和“3S”技术相结合的方法，围绕“河岸植被缓冲带景观格局对土壤侵蚀过程的调控机理”这一科学问题，通过分析河岸植被缓冲带景观格局时空动态，揭示了研究区在不同时期的景观面积转移、结构变化、梯度特征和驱动因子；通过探讨植被格局与土壤理化性质的相互关系，揭示了河岸植被缓冲带植物物种多样性特征和影响因子、土壤理化性质的空间变异及其与植被类型、植被结构、地形特征等因子的相互关系；通过野外放水冲刷试验，揭示了径流率、径流含沙量、侵蚀产沙量、侵蚀泥沙粒径、水动力参数在裸坡和植被坡（25%）间的差异及其与坡度和放水量之间的关系，厘清了侵蚀产沙与水动力参数之间的相关性；基于优化的渗透性指数（LI），通过尺度推移的方法分析了LI的敏感性，通过USLE验证了LI在研究区的适用性，通过情景模拟探讨了植被分布格局对LI的影响及最优植被格局，基于此，对研究区水土保持功能较低区域提出了调控策略。本项目成果可为华南红壤区河岸植被缓冲带的水土保持功能的恢复与维持提供科学理论依据。