关键词: 黄土丘陵区, 草灌植被, 产沙, 保土效益, 人工降雨

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