Abstract: Using artificial rainfall,an experiment of soil erosion and its characteristics was conducted in grassland of Bothriochloa ischemum and Artemisia sacrorum,in shrubland of Hippophae rhamnoides and Caragana microphylla,in woodland of Pinus tabulaeformis,and in the bareland,and the farmland as controls.The results shows that the main factors lead to sediment yield are the underlaying surface,the slopes,rainfall intensity,and vegetation coverage,grassland and shurbland are efficient in soil conservation.The sediment yield of the above-mentioned land types are successively woodland<shrubland <grassland <bareland <farmland and their ratio of 1:2:3:50:150,changes with the rainfall intensity and the slope gradient where the land is located.Farmland on steep slopes represent the main source of sediment yield,and returning of cropland to forest or grassland is an effective measure for reducing sediment.The sloping land and rainfall intensity exert great influence upon the sediment yield and the effect of the latter is for more obvious than that of the former.In order to effectively conserve soil,the grassland coverage generally must be at least 50%-60%.The study on sediment producing process shows that large amount of sediment yield usually occurs at the beginning of the rainfall,and gradually decreases with the time the rain vasts.The change in accumulative sediment yield(R) with time(t)conforms to the toppower function:R=a+bt^c.

Key words: Loess hilly region, Grass-shrub vegetation, Sediment yield, Soil conservation benefit, Artificial rainfall

摘要： 利用人工模拟降雨,对白羊草和铁杆蒿草地,柠条和沙棘灌木林地以及对照区(油松林地、裸地和农地)的产沙及其特征进行试验研究。结果表明,影响侵蚀产沙的主要因子有下垫面、坡度、雨强和植被盖度等。草灌植被具有良好的保持土壤功能。不同地类产沙量大小依次为乔木林地<灌木林地<草地<裸地<农地,其宏观产沙比为1:2:3:5 0:150,其产沙比视雨强和坡度而有变化。陡坡农地是侵蚀产沙的主要来源,退耕还林还草是保持水土和减少泥沙的有效措施。坡度和雨强对产沙有显著的影响,其中尤以雨强效应为甚。为有效保持水土,草地植被盖度通常应不低于50%-60%。对草地产沙过程的研究表明,通常降雨初期产沙量较大,以后随着时间的延长而递减,其累积产沙量(R)随着时间(t)的变化符合幂函数方程:R=a+bt^c。

关键词: 黄土丘陵区, 草灌植被, 产沙, 保土效益, 人工降雨