自然降雨下黄土丘陵区草灌植物垂直覆盖结构的减流减沙效应

Abstract

黄土高原是我国水土流失和生态环境问题最为严重的地区之一，植被恢复是防治水土流失的重要措施。植物垂直覆盖结构包括地上冠层、地表枯落物和地下根系，各组分具有不同的水土保持作用，是研究植被与水土流失关系的基本单元。目前，关于植物垂直覆盖结构不同组分对土壤侵蚀影响的研究主要是基于人工模拟降雨，缺少自然降雨条件下不同植物的垂直覆盖结构对产流、产沙和入渗等多过程影响的系统研究。本研究以黄土丘陵区典型的草本（须芒草）、半灌木（铁杆蒿）和灌木（绣线菊）为研究对象，每种植物进行三种处理（自然状态、去除枯落物和仅留根系）以及裸地对照，观测2015-2016年降雨事件的产流产沙量和入渗量，分析植物不同垂直覆盖结构的减流减沙效益及其相对贡献。结果表明：三种植物均具有较好的减流（45.9%-73.2%）、减沙效益（87.5%-94.6%）和增加入渗作用（4.7%-10.8%），灌木的减流效果（73.2%）显著高于草本（45.9%）和半灌木（63.5%），但三种植物间的减沙效益没有显著性差异。冠层的减流作用最大，贡献率接近一半（48%-50%），草本枯落物的减流贡献率与根系基本一致，而半灌木和灌木枯落物的减流贡献率略高于根系。冠层、枯落物和根系的减沙贡献率基本一致（36%、30%和34%），相对而言，草本的根系对控制侵蚀具有更大作用，减沙贡献率达到39%，而半灌木和灌木的冠层减沙贡献率要略高于枯落物和根系。本研究表明，冠层是减流的重要因子，而冠层、枯落物和根系在减沙方面均发挥了重要作用，植物垂直覆盖结构各组分在不同植物间减流减沙能力的差异主要与植物功能性状有关。上述结果将为黄土丘陵区坡面植被恢复和水土流失治理提供科学依据。;The Loess Plateau is one of the areas with the most serious soil erosion and ecological environment problems in China. Vegetation restoration is an important measure to prevent and control soil and water loss. The plant vertical cover structure includes aboveground canopy, surface litter, and underground root system. Each component has a different role in soil and water conservation. It is the basic unit to study the relationship between vegetation and soil erosion. At present, the research on the effects of different components of plant vertical cover structure on soil erosion in loess hilly areas is mainly based on artificial rainfall, and there is a lack of systematic research on the effects of different plants vertical cover structure on runoff, sediment and infiltration under the condition of natural rainfall. The research objects of this study were the typical grass (Andropogon yunnanensis), sub-shrub (Artemisia sacrorum) and shrub (Spiraea pubescens) in loess hilly areas. Each plant was treated with three different vertical cover structure compositions (e.g., intact condition, removing litter and only roots) and bare land control treatment. The runoff, sediment yield and infiltration of rainfall events from 2015 to 2016 were observed. The runoff and soil loss reduction and relative contributions of different vertical cover structures were analyzed. The results showed that the three types of plants had great runoff reduction (45.9%-73.2%), soil loss reduction (87.5%-94.6%), and increased infiltration (4.7%-10.8%). The runoff reduction of shrub (73.2%) was significantly higher than that of grass (45.9%) and sub-shrub (63.5%). However, there was no significant difference in soil loss reduction among the three plants. The canopy had the greatest effect of reducing runoff, with a contribution rate close to half (48%-50%). The contribution of grass litter to runoff reduction was basically the same as that of the roots, while the contribution of sub-shrub and shrub litter was slightly higher than that of the roots. The contribution of canopy, litter and roots to soil loss reduction was basically same (36%, 30% and 34%). In specific, the roots of grass had a greater effect on controlling erosion, and the contribution to soil loss reduction rate reached 39%, while the contribution of sub-shrub and shrub canopy to soil loss reduction rate was slightly higher than that of litter and roots. The study shows that the canopy is an important factor in runoff reduction, while the canopy, litter and roots all play an important role in reducing soil loss. The differences in the ability of the vertical cover structure to reduce runoff and soil loss among different plants mainly related to plant functional traits. The above results will provide a scientific basis for vegetation restoration and soil erosion control on slopes in the loess hilly region.