水蚀风蚀交错带坡面土壤入渗特性的空间变异及其分形特征

研究在水蚀风蚀交错带的强烈侵蚀中心陕北神木县六道沟流域进行。在一个自然完整坡面上网格布点,采用双环定水头入渗法研究了坡面土壤的入渗特性,在应用传统统计学方法的基础上,将分形理论和地统计学方法结合起来对坡面土壤入渗特性的空间变异进行了研究。获得以下结论:(1)稳定入渗率、平均入渗率和前30 min累积入渗量等三个参数的变异系数分别为0.48、0.36与0.40,在坡面上的变异程度属于中等变异性;(2)三个参数的分维值D分别为1.88、1.92与1.85,样本之间土壤特性值的差异较小,短距离的变异影响占主导地位;(3)研究的土壤在一定的空间范围内具有分形特征。稳定入渗率、平均入渗率与前30 min累积入渗量的自相关范围分别为20~120 m2、0~140 m与40~100 m。

FRACTAL DIMENSION AND SPATIAL VARIABILITY OF SOIL WATER INFILTRATION PROPERTIES ON NATURAL SLOPE IN A WATER-WIND EROSION INTERLACED REGION

The research on soil water infiltration is of great significance to the acquisition of a better knowledge of hydrological circulation of the watershed.A water-wind erosion interlaced region is a place where the most serious soil and water loss happens on the Loess Plateau, and any study on soil infiltration properties and on their spat ial variability of this region will do help to expose process of the soil erosion and improve precision of the watershed hydrological model.Of a natural slope (380 m long) in the Liudaogou catchment, which is typical of the water wind erosion interlaced region, stable infiltration rate, mean infiltration rate and cumulate infiltration capacity within the initial 30 min were measured with a double ring infiltrometer at 57 sampling sites, and the data were analyzed with both the traditional statistical method and the geostatistical method combined with the fractal theory.The results indicate: (1) the coefficient of variation of the above three parameters was respectively 0.48, 0.36 and 0.40 and the spatial variability was medium in degree;(2) the fractal dimension of the three parameters was 1.88, 1.92 and 1.85, respectively, which shows that the difference was rather small between soil samples in values of the soil infiltration properties;and(3) the soil was not a medium with significant theoretical fractal phenomenon, and fractal features existed only in a specific range of space, and the range of spatial autocorrelation for stable infiltration rate, mean infiltration rate and cumulate infiltration capacity within the initial 30 min was 20~120 m, 20~140 m and 40~100 m, respectively.