黄土高原样带典型地貌类型坡面土壤水分分布特征及其差异

Distribution Characteristics of Soil Water on Slopes in Typical Landform Types on Loess Plateau

为掌握黄土高原典型地貌类型丘陵沟壑区和高塬沟壑区的坡面土壤水分分布特征,选取3个典型坡面(长武高塬沟壑区,安塞丘陵沟壑区,神木丘陵沟壑区(风蚀水蚀交错区)),分析3个坡面土壤水分的时空分布和对应环境因素的分布特征,并采用地统计分析比较不同地貌类型坡面土壤水分的差异。根据不同地貌类型区坡面土壤含水量变异系数(CV)平均值的剖面变化,0~500 cm土壤剖面可以划分为速变层(0~40 cm)、活跃层(40~100 cm)、次活跃层(100~200 cm)和相对稳定层(200~500 cm);除丘陵沟壑区坡面0~40 cm和100~200 cm土层外,其他土层土壤含水量均具有较好的空间结构特征,理论半方差函数模型可对其进行较好的模拟,拟合模型结果一般表层土壤含水量为球状模型,深层土壤含水量为高斯模型;由于地形、土壤和植被等因子空间分布的差异性,高塬沟壑区坡面土壤含水量的空间变化与容重、海拔高度和最大叶面积指数有显著相关关系(P<0.01),而丘陵沟壑区和风蚀水蚀交错区坡面土壤含水量的空间变化分别只与最大叶面积指数和土壤质地有显著相关关系(P<0.05)。黄土高原典型地貌类型区不同土层间土壤含水量差异较大,地统计分析可以很好地表达坡面水分的空间异质性。

To assess the distribution characteristics of soil water on the slopes on the Loess Plateau of China,three typical slopes(tableland gully region in Changwu,hilly and gully region in Ansai,and hilly and gully region(water-wind erosion crisscross region)in Shenmu)were selected to analyze the spatial and temporal distribution of soil water and corresponding environmental factors,and the differences in soil water on slopes were compared by geostatistical analysis.According to the mean variation coefficient(CV)along soil profiles at three locations,vertical changes in soil profile at 0-500 cm were divided into four layers:a fast-changing layer(0-40 cm),an active layer(40-100 cm),a sub-active layer(100-200 cm)and a relatively stable layer(200-500 cm).The soil water content had good spatial structure characteristics except for 0-40 cm and 100-200 cm soil layers in the hilly and gully region slope,which can be well simulated by the theoretical semi-variance function model.The surface soil water content of the fitting model was spherical model in general,while the deep soil water content was gaussian model.There were significant differences for the correlations between soil water content in the three slopes and the influencing factors of topography,soil texture and vegetation.There was a significant correlation between soil water content in tableland gully region and the bulk density,altitude and leaf area index(P<0.01).Soil water contents in hilly and gully and water-wind erosion crisscross regions were only significantly correlated with the maximum leaf area and soil texture(P<0.05),respectively.There is a significant difference in soil moisture content between different soil layers in the typical landform types of the Loess Plateau,and geostatistical analysis can be well used to express the spatial heterogeneity of soil water content on a hillslope.