Soil moisture is a major limiting factor for vegetation restoration in northern Shaanxi Province of the Loess Plateau. Soil moisture variation research at steep slope is the premise of forest and grass construction. But steep slope soil moisture variation in different seasons, different slope aspects and different slope gradients are rarely systematically researched. Take a natural recovery basin in northern Shaanxi Province of the Loess Plateau for example; we investigated the changes of soil moisture at steep slope with seasonal variation and depth discrepancy. The results showed: (1) in this area, consuming period, restoring period, decreasing period and stable period of soil moisture are: March to June, July to September, October to November, December to February of the next year, respectively. (2) The most active layer of soil moisture variation occurs at the depth of 0-60 cm. Soil moisture content not only increases with depths increasing, but also presents significant differences among layer. (3) Followed by the rule of vertical variation, the weak absorbing soil moisture layer, utilizing layer and weak regulating layer are the depths of 0-40, 40-60, and 60-100 cm, respectively. (4) In the perpendicular direction of steep slope, soil moisture condition is rich at deeper than 40-50 cm, where a favorable growing environment for vegetation could be provided.%土壤水分是制约陕北黄土区陡坡林草植被建设主要限制因素,深入系统的研究陡坡土壤水分变异规律是科学开展林草植被建设的重要前提.目前,陡坡不同季节、不同坡向、不同坡度的土壤水分变异规律尚未见系统的研究.为此,本研究通过观测陕北黄土区坡面尺度的自然恢复流域陡坡土壤含水量,研究分析了陡坡土壤水分季节变化规律、陡坡土壤水分垂直变化规律,结果表明:(1)陕北黄土区陡坡的土壤水分消耗期、土壤水分积累期、土壤水分消退期和土壤水分稳定期分别对应3-6、7-9、10-11和12月-次年2月；(2)0～120 cm土层中0～60 cm土层土壤含水量变化活跃.土壤水分随着土层深度的增加而增加,且各层间的差异也越来越显著；(3)基于土壤水分的垂直变化规律,陡坡的土壤水分弱利用层、土壤水分利用层、土壤水分调节层分别为0～40、40～60和60～100 cm.(4)在垂直于陡坡坡面方向上,深度大于40～50 cm的土壤层能为植被生长提供良好的土壤水分环境,有利于人工植被建设在陡坡开展.
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