在我国北方少雨地区开展雨水资源、土壤水资源与土壤水分植被承载力研究对于防治林草地土壤旱化和林草植被经营具有重要意义。2002年4月以来,在上黄生态实验站对多年生人工林林外和林内降水、地表径流、植物生长和土壤水分动态进行了定位观测,结果表明:次降雨林冠层截留量为0.2～6.47mm,为降水量的3.1%～53.3%,截留总量占降水量的16.9%;地表径流量为0.24～1.5mm,是降雨量的1.6%～6.8%;柠条林地土壤剖面水分垂直变化可分为活跃层、次活跃层和相对稳定层;年内土壤水分胁迫时,植物通过改变叶的颜色,降低自身的含水率、落叶或产生大量落叶来适应干旱的土壤水环境,但不会死亡。土壤水分植被承载力为土壤水分承载植物的最大负荷,是指在较长时期内,当根层土壤水分消耗量等于或小于降雨补给量时,所能维持特定植物群落健康生长的最大密度。

It is important to conduct research on precipitation,soil water and soil water carrying capacity of vegetation for forest management.In this paper,the authors investigated the canopy interception,surface runoff,plant growth,and soil water dynamics since2002in Shanghuang E-co-experimental Station in semi-arid regions of Loess Plateau.The results show that the water in-tercepted by the Caragana canopies is0.2～6.47mm with an interception rate of3.1%～53.3%.The total canopy interception is16.9%of precipitation.The runoff is0.24～1.5mm,1.5%～6.6%of rainfall.Precipitation is the only source of soil water supply.The vertical change of soil water can be divided into three layers:fast change layer,active layer and hypoactive layer according to precipitation impact on soil water and the character of the dynamic curve of soil water.The seri-ous stress of soil water on plant growth can change the color of leave,reduce plant's mean water content,lead to leaf drop,even to the dropping of most of the leaves,but does not lead to the death of Caragana shrub immediately in a short term less than a year.Soil water carrying capac-ity of vegetation is the ability of soil water to carry vegetation.The limit is the largest density of the vegetation community when soil water consumption is equal to or lower than soil water sup-ply in the root zone of soil layers from which plant roots can take and utilize water on an annual basis under modern management conditions.