模拟降雨下黄土坡面水沙过程对3种灌草植被垂直结构变化的响应

Abstract

植被对坡面产流产沙过程的影响随植被类型及其垂直结构组分的变化而变化，然而这些因素如何影响坡面水沙过程却缺乏定量分析。利用野外径流小区和人工模拟降雨试验，研究了黄土丘陵区3种典型灌草（沙棘、柠条、苜蓿）及其不同垂直结构组分（叶、茎、枯落物、根系）对坡面产流和产沙过程的影响。结果表明：3种灌草均具有较好的减流减沙效益，且减沙作用强于减流作用，与裸地相比，灌草植被减少径流量32.49%-44.86%，减少侵蚀量72.99%-80.63%，降低坡面流速29.17%-45.83%。苜蓿的减流效益最佳，为44.86%，柠条的减沙效益最佳，为80.63%。3种植被的减流效益在不同产流时期差异明显，从产流初期到中期和后期逐渐减少，减沙效益在不同产流时期则没有明显变化。植被垂直结构不同组分对于减流减沙效益的相对贡献与其形态特征以及其空间分布方式有着密切的关系。地上部分对于减流效益和减速效益有较大的相对贡献率，平均为75.42%和68.38%，而不同植被茎、叶和枯落物的相对贡献具有一定的差异。根系则发挥较大的减沙作用，平均相对贡献为78.44%。植被垂直结构组分越完整，减流减沙效益越显著。研究对黄土丘陵区水土保持、植被恢复和建设提供重要的科学依据和理论指导。;The effect of vegetation on the processes of runoff and sediment production on slopes varies with vegetation types and their vertical structural components. However, there are few quantitative analysis on how these factors affect runoff and sediment yield processes on the slope. In this study, based on field runoff plots and artificial simulated rainfall experiments, the effects of three different typical shrubs (Hippophae rhamnoides, Caragana korshinskii, and Medicago sativa) and their different vertical structural components (leaf, stem, litter, and root) on runoff and sediment yield processes in the loess hilly region were studied. The experiment was carried out in Anjiagou catchment of Dingxi, Gansu Province and the runoff and sediment reduction of these three shrubs were apparent. Compared with the bare slope, runoff and sediment reduction ratios of three shrub and grass vegetations were from 32.49%-44.86% and from 72.99%-80.63%, and the flow rate reduction was about 29.17%-45.83%, respectively, indicating the better sediment reduction effects. Amongst three shrub and grass vegetations, M. sativa has the best flow reduction benefit, which was about 44.86%, and C. korshinskii has the best sediment reduction benefit, which was 80.63%. The runoff reduction benefits of the three types of vegetation differed are significantly at different runoff generation periods, and gradually decreased in the early, middle and late runoff periods; while the sediment reduction benefits had no obvious changes in different runoff periods. The relative contribution of different components of the vegetation vertical structure to the benefits of flow reduction, and sediment reduction was closely related to its morphological characteristics and its spatial distribution. The contribution rate of the above-ground part to the flow reduction benefit and deceleration benefit was 75.42% and 68.38% on average, respectively, while the relative contributions of different vegetation stems, leaves and litter have some differences. Compared with the Aboveground part of vegetation, the root system played a greater role in reducing sediment, with a relative contribution of 78.44%. The more complete the vertical structure of vegetation, the more significant the benefits of vegetation reduction and sediment reduction. This paper provides an important scientific basis and theoretical guidance for soil and water conservation, plant restoration and construction in the loess hilly areas.