黄土丘陵区小流域土壤水分时空变异

采用定位监测法，对2002—2005年黄土丘陵区小流域土壤水分的时空动态规律及其主要影响因素进行了分析.结果表明，研究区年均土壤水分剖面呈倒“L”型，水分最低点出现在1.0 m深处.表层（0～0.2 m）和下层（2.4 m以下）土壤水分年际间的差异达显著水平，而季节间的显著差异则表现在土壤表层和中层（1.0～2.4 m）；干旱年的降水不足显著提高了中、下层土壤水分的空间变异性，而丰水年的降水补充作用则显著降低了上层土壤水分的空间变异性，对中、下层土壤水分变异的影响不大.坡向对土壤水分变异的影响最大，其次是土地利用类型，坡位的影响最小.在干旱年或每年雨季开始时，坡向对土壤水分的影响随土层的加深而减弱，土地利用类型的影响则随之增强；在丰水年或每年雨季结束时，土地利用类型只对上层土壤水分状况具有显著影响，且其影响程度小于坡向的影响.

Spatiotemporal variation of soil moisture in a small watershed of loess hilly region.

Based on field determinations, the spatiotemporal variation of soil moisture content in a small watershed of loess hilly region from 2002 to 2005 was studied, with the main affecting factors analyzed. The results showed that in the study area, the mean annual soil moisture profile was in an inverse L shape, with the lowest value at the depth of 1 m. The soil moisture contents between the layers of 0-0.2 m and below 2.4 m in different years, and those between the layers of 0-0.2 m and 1.0-2.4 m in different seasons were significantly different. In drought years, the lack of precipitation increased the spatial heterogeneity of soil moisture content in the layers of 1.0-2.4 m and below 2.4 m significantly; while in rainy years, the supplement of precipitation decreased the spatial heterogeneity of soil moisture content in 0-0.2 m layer, but had less effects on that in the layers of 1.0-2.4 m and below 2.4 m. Slope aspect and land use were the two main factors affecting the spatiotemporal variation of soil moisture content, while slope position had less effects. In drought years or by the end of drought season, the effects of slope aspect on soil moisture content decreased, while those of land use type increased with soil depth. In rainy years or by the end of rainy season, slope aspect became the most important affecting factor, while land use type only affected upper soil layer.