黄土区森林植被对流域径流和输沙的影响

Influence of forest vegetation on runoff and sediment transport of watershed in loess area

为进一步探讨森林植被对流域尺度径流和输沙的影响，给黄土区植被建设提供理论依据，通过对黄土区山西省吉县蔡家川嵌套流域的聚类分析，选取地形地貌特征相似的森林流域和无林流域，对其雨季径流和输沙进行分析。结果表明：森林植被可以大幅度地延缓产流时间、减少小流域的暴雨洪峰流量；随着森林植被覆盖率的增加，流域雨季径流量、径流深和径流系数减少，无林流域比森林流域的雨季径流深和径流系数高5-20倍，少林流域比多林流域的雨季径流深和径流系数高2．7-2．9倍；少林流域暴雨径流输沙量是多林流域的3-6倍，且前者暴雨径流输沙过程线的变化比后者剧烈得多。由于森林植被对流域径流影响的复杂性和尺度依赖性，森林在区域（或大流域）尺度的水文功能评价仍有待进一步深入研究。

In order to deeply study the relationship between vegetation and runoff and sediment transport at the scale of watershed, and to provide theoretical basis for vegetation restoration of Loess area, forested watershed and rangeland watershed with similar terrain and topographical features are selected using method of clustering analysis to inlaid Caijiachan catchment which lies in Jixian county of Shanxi province in loess area, and runoff and sediment transport of which are contrasted and analyzed. The results showed that runoff was delayed dramatically at beginning time, and the peak flow of watershed reduced for forest vegetation played role in holding up and absorbing precipitation depending on canopy layer and litter. Besides, with increase of forest coverage, the amount of runoff, runoff depth and runoff coefficient in rain season decreased. It clarified that runoff depth and runoff coefficient of rangeland watershed in rain season were 5-20-fold as much as those of forest watershed, and those of less forest watershed were 2.7-2.9-fold as much as those of more forest watershed. And sediment yield from less forest watershed by storm was 2-5-fold than those from more forest watershed. Besides, the variation of sediment transport hydrograph of the former was more acute than those of the latter. For the reason of complexity and sealed dependence of runoff influenced by forest vegetation, assess of forest hydrological functions based on regional scale or watershed scale was worth of further research challenges.