黄土高原退耕坡地土壤水分空间变异性研究

Study on spatial variability of soil moisture on the recultivated slope-land on the Loess Plateau

以神木生态观测站为例，利用经典统计学方法对黄土高原退耕坡地土壤水分在空间三维不同方向和不同位置的空间变异性进行了研究，并对空间变异的尺度和时间依赖性等问题进行了探讨，以便为坡地水分管理和植被恢复提供参考。研究结果表明土壤水分在垂直方向和水平方向（垂直于坡长方向）的平均变异程度为弱变异；而在东西方向（坡长方向）、二维平面和三维空间上为中等变异性；土壤水分沿坡长方向从坡顶到坡脚表现出先减小后增大的趋势，且在各坡位变异程度不一．呈现出变异程度为坡上〉坡中〉坡下的趋势；土壤水分沿南北方向表现为阴坡〉山脊〉阳坡的明显趋势，其变异程度为阳坡〉阴坡；在40～200cm土层深度内，土壤水分在垂直方向表现出先减小后增大的趋势，且在各土层的变异程度与各层平均土壤水分成明显的正相关。

In order to provide some recommendation for the water management and the vegetation restoration on slope-lands, the study on the spatial variability of the soil moisture in different directions and positions on the recultivated slope-land on the Loess Plateau is carried out at the Shenmu ecological station both by the field measurements and the statistical analysis. In this paper, some key issues related to the spatial variability such as scale and time-dependence are discussed. The results show that the mean variation of the soil moisture is weak along the vertical and the N-S direction （perpendicular to slope）, while it is moderate when the E-W direction, 2-D and 3-D space are considered. Along the slope, the soil moisture decreases and then increases from its top to the bottom, and the sequence of the magnitude of the heterogeneity is the top-slope 〉 the mid-slope 〉 the bottom-slope; in the N-S direction, the soil moisture increases from the sunshine slope to the shadow slope, and the magnitude of the heterogeneity of the sunshine slope is larger than that of the shadow slope; in the vertical direction, the soil moisture decreases and then increases below the depth of 200era from the soil surface, and the magnitude of the heterogeneity is significantly positive correlated to the mean moisture of the same soil layer.