长江上游亚高山暗针叶林土壤水分入渗特征研究

长江上游以峨嵋冷杉为主的亚高山暗针叶林流域土壤质地较粗，属于壤质砂土。随着森林演替的发展，林地土壤砂粒含量逐渐降低，粉、粘粒含量逐渐增加，以过熟龄峨嵋冷杉纯林的粉粘粒含量为最高。就坡积物而言。随土层深的增加，砂粒含量逐渐增加，粘粒含量逐渐减小。随森林演替的进展和土层深度的减小，土壤容重逐渐减小，土壤孔隙度和土壤贮水力逐渐增大，研究区土壤非饱和导水率随土层深度的增加和土壤含水量的减小而减小，并与土壤含水量呈指数函数关系。随土层深度的增加，土壤饱和导水率呈负指数递减，不同土层到达稳渗的时间有差异，随土层深度的增加，稳渗时间增加，平均在110min左右。该流域暗针叶林带土壤质地上的变化和土壤水分物理性质的分异以及土壤水分的高入渗性是该暗针叶林流域水文循环中森林对水分传输调节的具体体现，也可以为该流域很少见到坡面径流或地表径流，而大部分以壤中流、回归流和地下渗漏等径流形式出现的机制作出有力的解释。

Characteristics of soil water infiltration in sub-alpine dark coniferous ecosystem of upper reaches of Yangtze River

Dark coniferous forest is the predominant type of vegetation in the upper reaches of Yangtze River. Difference among different types of soil exists. The sand content of soil is higher and the soil texture is coarser in the early stage of forest succession. The sand content of soil decreases with the advancement of the forest succession while that of soil in Abies fabri over-mature forest is the lowest. In slope wash soil, the sand content of soil decreases with the increasing soil depth. The soil porosity and soil water-holding capacity increases and soil bulk density decreases with the advancement of forest succession and decrease of soil depth. The deeper soil depth or the smaller soil water content are, the smaller the unsaturated hydraulic conductivity of soil measured by CGA method. Moreover, the correlation of soil water content with unsaturated hydraulic conductivity of soil can be simulated by an exponential function. The saturated hydraulic conductivity of soil decreases exponentially with the increasing soil depth. The time to attain the stable infiltration rate is different among different soil depth, while the deeper the soil depth is, the longer the time needs. The variation in soil texture, soil physical properties and the high infiltration rate of soil there implicated that there are scarce surface runoff, but aboundant in subsurface flow, return flow and seepage, which is the result of regulation by dark coniferous forest on hydrological processes.