Abstract: This experiment was carried out for 5 years in Horqin sandy land,Inner Mongolia,which had 4 treatments:Non-grazing (NG),light grazing (LG),moderate grazing (MG) and over grazing (OG).The results showed that different grazing intensities resulted in different development trend of the pasture ecosystem,of which,the injury of OG on pasture ecosystem was very great.The plant diversity,vegetation coverage,plant height and primary productivity under continuous overgrazing for 5 year were 87.9%,82.1%,94.0% and 57.0%,respectively,lower than those in NG.The biomass on the OG pasture was only 2.1% of NG,and the contents of soil clay,C and N as well as the quantities of soil microbes and small animals in OG were respectively 6.0%,31.9%,25.0%,95 0% and 75.9% lower than those in NG,but the soil hardness was raised by 274.0%.Especially,the secondary productivity of the pasture became negative from the third year,and the productive foundation of the pasture ecosystem was completely destroyed.Non-grazing was beneficial to pasture,and enclosure caused an increase in vegetation coverage,plant height and primary productivity.The vegetation coverage,plant height and soil status in LG and MG were not as good as those in NG,but were stable and didn't show worsening trend.Based on the above results,it's considered that on the sandy pasture in the semi-arid area of Inner Mongolia,the rational grass utilization ratio is 45%～50%,and the suitable loading capacity is 3～4 sheep unit·hm^-2.

Key words: Sandy pasture, Ecosystem, Grazing effects