Abstract: In order to understand the differences of carbon density of shrub and grass in the middle reaches of the Yellow River in different climate types,three different climate(sub) areas in Shanxi province were chosen as the research objects on the basis of detailed investigation.In the typical area of each of three different climate(sub) areas the carbon density of shrubs,grass,their fine roots and surrounding soils was determined.The results showed that the trend of variation of carbon density of shrub and grass vegetation was evident from north to south in the middle reaches of the Yellow River with an increase in temperature and precipitation.The vegetation carbon density increased significantly and the carbon density of grass was higher than that of shrub;the carbon density difference in shrub between the ground and underground parts was bigger,whereas the carbon density difference in grass between the ground and underground parts was smaller.Moreover,the distribution pattern of shrub and grass between the ground and underground parts were similar.The soil organic carbon was mainly distributed in the 0~20 cm range of depth.In the northern,central and southern parts soil carbon density decreased with the increase of soil depth and soil carbon density in southern part was significantly higher than that in the northern part.

Key words: The Yellow River, shrub and grass, climate, carbon density