降雨作用下植被根系对边坡土体水文效应的影响

Influence of vegetation roots on the hydrological effects of slope soils under rainfall

摘要

我国东南丘陵山地地质环境脆弱，台风、暴雨等极端降雨频发，在高植被覆盖区引发了大量的群发性浅表层土质滑坡。本文以福建省武平县高植被覆盖区为研究对象，通过现场滑坡调查、采集土坡原状土柱，开展降雨模拟试验，探讨极端降雨条件下植被根系对边坡水文效应的影响及其与浅层滑坡的关联机制。结果表明，体积含水率与基质吸力的响应时间随土层深度增加呈线性延长趋势。植物群落通过根系作用显著改变土壤渗透性能，其渗透速率由大到小排序为灌木群落，草本群落，裸土。灌木群落在50~70cm深度的根土界面出现显著水力边界效应，形成生态水文功能的分层滞水结构。植被土壤表现出明显的空气进入值(air entry value，AEV)降低，提升土壤的饱和导水性能，削弱了持水能力。因此，在极端降雨条件下植物群落显著提升水分入渗速率导致根区土体快速饱和，基质吸力丧失，并在根系分布区形成分层滞水结构，进而诱发滑坡灾害。研究成果对揭示降雨作用下植物群落根区土坡水文效应，探究高植被覆盖区群发性浅表层土质滑坡成灾机制具有重要的理论及实际意义。

Abstract

The geological environment of the hilly and mountainous areas in southeastern China is fragile, with frequent extreme rainfall events such as typhoons and torrential rains, triggering numerous clusters of shallow soil landslides in high vegetation covered areas. This paper takes a high vegetation covered area in Wuping County, Fujian Province as the research object, and conducts rainfall simulation experiments through field landslide investigations and the collection of undisturbed soil columns from the slopes to explore the influence of vegetation roots on slope hydrological effects under extreme rainfall conditions and its correlation mechanism with shallow landslides. The results show that the response time of volumetric water content and matrix suction increases linearly with increasing soil depth. Plant communities significantly alter soil permeability through root action, with the permeability rate ranked from highest to lowest as follows: shrub communities, herb communities, and bare soil. Shrub communities exhibit a significant hydraulic boundary effect at the root-soil interface at a depth of 50~70cm, forming a stratified water holding structure with eco-hydrological functions. Vegetated soils show a significant decrease in air entry value (AEV), increasing the soil’s saturated hydraulic conductivity and weakening its water-holding capacity. Therefore, under extreme rainfall conditions, plant communities significantly increase the water infiltration rate, leading to rapid saturation of the root zone soil, loss of matrix suction, and the formation of stratified water trapping structures in the root distribution area, thereby inducing landslide disasters. The research findings have important theoretical and practical significance for revealing the hydrological effects of plant community root zone soil slopes under rainfall and for exploring the mechanism of clustered shallow soil landslides in high vegetation coverage areas.

关键词

植物群落 / 滑坡 / 土柱入渗 / 水文响应 / 根－土复合体

Key words

plant communities / landslides / soil column infiltration / hydrologic response / root-soil composite

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基金资助

国家自然科学基金项目(U2005205)