植被多元覆盖结构对坡面产流产沙过程的调控机制

Vegetation characterization is a key factor to evaluate the soil and water conservation of vegetation, The idiomatic vegetation index-vegetation coverage hided the features of vegetations’ hierarchical structure, So，it is difficult to description the structural function of vegetation accurately，and there are limitations in assessing the role of vegetation in soil and water conservation，Therefore it is a key scientific issues to build a quantitative indicator which can express the functional characteristics of vegetations’ coverage structure, and by using it to reveal the effect of vegetation on runoff and sediment yield. Based on the principles and methods of commonly vegetation index and the different function of coverage hierarchy to soil and water conservation, by simulated rainfall in different vegetation types in field plot, to study the present the characterization index and calculation method of multiple coverage structure, and describ the responsed relationship between multiple coverage structure and runoff and sediment yield, validate and quantitatively express the effectiveness of vegetations’ multiple coverage structure index, And then to establish the coupling relationship between rainfall - multiple coverage structure index - runoff and sediment yield, thus to reveal the mechanism of vegetations’ multiple coverage structure on rainfall runoff and sediment yield, The research results provide a theoretical basis for quantitative evaluation of vegetation erosion and interpretation of the causes of water and sediment changes. The research results will provide an important theoretical basis for quantitative evaluating the erosion reduction effect of vegetation and interpreting the causes of water and sediment changes.

植被表征指标是评价植被水土保持功能的关键因子，常规植被覆盖度指标掩盖了下垫面植被覆盖的层次结构性特征，很难准确表征植被因子的结构性功能，在评价植被水土保持作用方面有一定的局限性，构建一个准确表达植被覆盖结构功能性特征的量化指标，是揭示植被对产流产沙作用机制的关键科学问题。因此，本项目基于现有植被覆盖指标/因子的表达原理和不同层次覆盖的水土保持功能，通过野外不同植被类型坡面小区模拟降雨试验观测，研究提出具有物理意义的植被多元覆盖结构指标表征和计算方法，阐明坡面产流产沙过程对植被多元覆盖结构的响应关系，验证并定量表达植被多元覆盖结构指标的有效性，建立降雨―植被多元覆盖结构指标―产流产沙的耦合关系，揭示植被多元覆盖结构对降雨产流产沙的调控机制。研究成果对定量评价植被减蚀作用和诠释水沙变化成因提供理论基础。

植被表征指标是评价植被水土保持功能的关键因子，常规植被覆盖度指标掩盖了下垫面植被覆盖的层次结构性特征，很难准确表征植被因子的结构性功能，在评价植被水土保持作用方面有一定的局限性，构建一个准确表达植被覆盖结构功能性特征的量化指标，是揭示植被对产流产沙作用机制的关键科学问题。. 本项目结合自然界植被覆盖结构多样，不同覆盖结构植被减水减沙效益差异显著的现象，基于现有植被覆盖指标/因子的表达原理和不同层次覆盖的水土保持功能研究成果，通过采取不同覆盖结构植被坡面模拟降雨试验和植被结构、生物量持水特性典型调查等方法，将完整覆盖植被分解为高层覆盖、地表覆盖和根系层，开展了不同植被覆盖层坡面降雨产流产沙过程观测。. 项目剥离分析了不同覆盖结构组合情景下植被对降雨产流及产沙过程的调控作用，辨析了植被调控产流和调控产沙的主导覆盖结构，并从生物量截留降雨、地表覆盖阻滞径流、增加入渗等角度定量揭示了植被覆盖调控产流产沙的作用机制；同时分别基于不同结构层调控产流和产沙能力的大小构建了植被覆盖结构表征参数——植被产流盖度指数和产沙盖度指数，经初步验证，产流产沙参数和植被覆盖结构指标之间的相关关系优于传统植被覆盖度指标。该研究对于分类揭示植被的水土保持作用和科学运用植被的调控理论服务于生态保护和水土保持高质量的实践具有重要意义。