COMPARING THE EFFECTS OF GRAZING-PROHIBITION AND MODERATE GRAZING ON MONGOLIA MEDICINAL PLANTS DIVERSITY IN TYPICAL STEPPE

This paper studies and compares plant species and Mongolian medicinal plants diversity under different utilization conditions of typical steppe in Xilinguole of Inner Mongolia. Vegetation quadrat sampling technique was used for the investigation. The results showed that under varing conditions of 22-year exclosure,10-year exclosure and moderate grazing,the ratios of Mongolian medicinal plant species were 7. 69 %,21. 95 % and 31. 82 % respectively in proportion to the total plant species; the sum of the relative importance values were 1. 1,7. 35 and 18. 9. Under grazing-prohibition condition,the number of Mongolian medicinal plant species decreased and the importance value as well as the importance value percentage of the entire plant species in the quadrat decreased. The longer grazing-prohibition period was,the more obvious this trend was. These figures increased markedly under moderate grazing condition. The species richness,dominance and evenness indexes for Mongolian medicinal plants display various behaviors under different utilization conditions: they were decreased after 22 years of exclosure. The species richness increased under 10-year exclosure condition,but other two indexes were influenced by pre-exclosure conditions. Under moderately grazed condition,both biological richness and dominance of grazing-suitable plants such as Artemisia frigida were improved while evenness decreased.