黄土丘陵沟壑区刺槐林冠的水文特征

Hydrological properties of canopy of acacia in loess hilly and gully region

在陕北黄土丘陵沟壑区，通过观测生长季阴阳坡刺槐林地的降雨状况，分析了透流量、干流量、截留量、透流率、干流率、截留率与林外降水量的关系及季节变化。结果表明：透流量、干流量与林外降水量为开口向上的抛物线关系，这一描述比传统的直线关系更能解释其中的物理意义；截留量与林外降水量为单分子式（Mitscherlich）关系，透流率和干流率与林外降水量为指数函数关系；截留率与林外降水量为幂函数关系。透流量、干流量、截留量分别占大气降水量的80．39％～89．19％、2．31％～2．62％、8．51％～16．99％。透流率和干流率随降水量的增加急剧增大，随后增大的趋势很快变缓；截留率随降水量的增加而急剧减小，林冠饱和后截留率保持在某一水平，变化极其缓慢。

The rainfall was redistributed into canopy interception, through-fall and stem-flow when it went through the canopy because of canopy interception. In loess hilly and gully region of northern of Shaanxi province, rainfall in southeastward and northeastward acacia woodlands （Robinia pseudoacacia L. ） was observed in growth stages. The hydrological properties of forest canopy were analyzed. The results showed that the correlativity among through-fall quantity, stem-flow quantity and precipitation were parabola. The correlativity between interception quantity and precipitation was Mitscherlich. The correlativity among through-fall ratio, stem flow ratio and precipitation were exponential function. The correlativity between interception ratio and precipitation was power function. The amount of interception, through-fall and stem-flow respectively accounted for 80.39%-89. 19% , 2.31%-2. 62% , 8.51% - 16. 99% of precipitation. The through-fall ratio and stem flow ratio increased with the increase of precipitation. The interception ratio decreased with the increase of precipitation. The interception ratio varied very slowly and was close to a constant value after forest canopy was saturated. The laws on interception quantity, through-fall quantity and stem-flow quantity with season variation were consistent. It was seen that they were high from Jun. to Sept. and low in May or Oct.. The though-fall ratio was also high from Jun. to Sept. and low in May or Oct.. The stem-flow ratio doesn＇ t vary obviously with season because it was too little. However, the interception ratio was low in rainy season and high in rainless season. The studies on hydrological property of acacia canopy and quantization of redistribution to rainfall by canopy could provide scientific evidences. They were useful for researches to investigate water cycle and transfer in soil-vegetation-atmosphere system and make optimal utilization of water resources in loess hilly and gully region.