Effects of sheep grazing and precipitation patterns on sandy grassland vegetation in Inner Mongolia, China

To understand the effects of grazing by domestic sheep and of precipitation on sandy grassland vegetation in northern China, a field grazing and enclosures experiment was conducted from 1992 to 2006 in Horqin Sand Land, Inner Mongolia. Results indicated that (1) overgrazing resulted in severe damage to grassland vegetation, but moderate grazing had no significant effects on species richness and diversity, though it can result in a slight decrease in plant cover and height, while light grazing or no grazing (enclosures by fence) benefited the restoration of degraded vegetation; (2) although average species richness, plant diversity, vegetation cover and canopy height were higher in rainy years or warm, moist periods than in drought years or sustained drought periods, the differences in height and species richness were not significant; (3) continuous overgrazing can result in unpalatable herbage becoming dominant in the grassland community; (4) a sustained wet climate was favorable to perennial herbage and annual mesophytes, while annual xerophytes became dominant under sustained drought; (5) the proper grazing intensity for the Horqin sandy grassland is 3-4 sheep per hectare in rainy years, which should be reduced to 2- 3 sheep per hectare in drought years.