ISSN 1000-3665 CN 11-2202/P

    火烧迹地土壤斥水性和渗透性变化特性

    Research on the change in soil water repellency and permeability in burned areas

    • 摘要: 林火会造成火烧迹地土壤斥水性增强及渗透性降低,导致降雨期间流域内地表产流率激增。在一定条件下,尤其是地形陡峭的高海拔山区,地表产流激增一般是泥石流灾害发生的重要诱因。然而,对于高海拔山区火烧迹地土壤斥水性和渗透性变化特征的研究相对缺乏。以海拔高程3029~4474 m的四川省雅江县恶古乡火烧迹地为研究对象,通过现场水滴入渗试验和圆盘入渗试验,探究斥水性强度分布及其与土壤入渗参数之间的内在联系。结果显示:土壤斥水性强度分布具备较大的空间异质性,林火对斥水性的影响深度在轻度火烧区为2 cm,在中度和严重火烧区为3 cm;研究区土壤渗透能力与斥水性强度呈反比,饱和导水率和吸渗率与水滴入渗时间之间遵循幂函数分布,其变异系数与火烈度呈正比,且严重火烧区部分土壤由于斥水性被高温破坏造成饱和导水率增大;斥水性土壤相较于亲水性土壤出现明显的入渗延迟现象。研究结果丰富了高海拔山区火烧迹地水文特征的研究,为揭示火烧迹地泥石流坡面物源起动机理提供理论依据。

       

      Abstract: Forest fire always results in the newly occurrence (or enhancement) of soil water repellency (SWR), and subsequent reduction in soil infiltration. It dramatically increases the surface runoff rate of a drainage basin. Under certain situation, especially the mountain area with high altitude and steep terrain, augmented surface runoff usually infiltrates the generation of debris flows. But little is known about the distribution of SWR and change in soil permeability in areas with high altitude. Based on the burned area with altitude ranging from 3029 to 4474 m in the Egu village of Yajiang county in Sichuan province, a set of water drop penetration tests and disk infiltration measurements are conducted to study the fire influence on distribution of the severity of SWR and soil permeability. The results indicate that great spatial heterogeneity of Hydrophobic strength of soil exists, and the influence depth of fire impact on SWR is up to 2 cm in the slightly burned area and 3 cm in the moderately and highly burned area. Soil permeability is inversely linked to the severity of water repellency, and the relationship between water drop penetration time and sorptivity and hydraulic conductivity of soil fallow the law of power function. The coefficient of variation in infiltration parameters increases with fire intensity, and part of the severely burned soil loses water repellency due to high temperature in fire and results in increase of saturated hydraulic conductivity. In contrast to hydrophilic soil, an obviously delay in infiltration is found find in the hydrophobic soil. The results of this work enrich the study of hydrological feature in burned areas and can provide the theoretical basis for the motivation of surface material in debris flow generation.

       

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