黄土高原南部小流域土壤水分时程变化的分层特征及其驱动机制

Layered characteristics and driving mechanisms of temporal soil moisture variation in a small watershed of the southern Loess Plateau

选取位于黄土高原南部的长武王东沟小流域为研究对象,通过对典型样地0-600 cm土壤剖面水分的长期连续测定,系统研究了王东沟小流域土壤水分年内、年际变化的分层特征以及驱动机制。结果表明,土壤水分剖面的时程变化有分层特征,与利用类型关系密切;王东沟小流域0-50 cm土层土壤水分季节变化剧烈,0-150cm土壤含水量在雨季前(6月)降到最低;与雨季前相比,小麦地12月土壤水分恢复深度可达到460 cm,而刺槐林地、苹果园和苜蓿地土壤水分恢复深度最大达到260 cm左右;就同一测点比较,2011年刺槐林地和苹果园300-600cm土壤含水量较2003年减少,而2011年小麦地和荒草地300-600 cm土壤含水量较2003年有所增加。土地利用和地形地貌是驱动王东沟小流域土壤水分变化的主要因素,但是土地利用对深层土壤水分的影响更加显著。

Wangdonggou watershed located in the southern Loess Plateau was selected as the study area in this pa-per .Layered characteristics and driving mechanisms of seasonal and interannual soil moisture variations in the small wa-tershed were comprehensively studied through a long-term observation of soil moisture in 600 cm soil profiles of typical plots .Soil water content in the 0~50 cm layer changed intensively with season .Soil water content in the 0~150 cm soil layer decreased to the lowest before rainy season .In contrast to drought season ,the depth of soil water recharged in De-cember was as much as 460 cm for wheat land ,while the maximum depths recharged were about 260 cm for Robinia pseudoacacia forestland ,apple orchard and alfalfa field .Temporal variations of soil moisture in the profiles were charac-terized by a layered distribution and were closely related with landuse type .As for the same measuring point ,soil water contents in the 300~600 cm layer of Robinia pseudoacacia forestland and apple orchard in 2011 were lower than those in 2003 ,while soil water contents in the same layer of wheat land and natural grassland in 2011 were higher than those in 2003 .Both landuse type and topography are the main driving factors for soil moisture change and however ,landuse type has more significant effect on soil moisture in deep layer .