COMPARING THE EFFECTS OF GRAZING- PROHIBITION AND MODERATE GRAZING ON MONGOLIA MEDICINAL PLANTS DIVERSITY IN TYPICAL STEPPE | 禁牧和适度放牧对典型草原蒙药材植物多样性的影响比较

chinois. 以植被样方调查方法，于内蒙古锡林郭勒典型草原进行了不同利用状况下植物种和蒙药材植物多样性比较研究．结果如下：在围封22a、围封10a和适度放牧条件下，蒙药材植物在物种组成中所占的比例分别是7．69％、21．95％、31．82％；相对重要值和分别为1．1、7．35、18．9，说明在禁牧状态下，蒙药材植物种类减少，重要值和占该样地全部物种重要值的百分比降低，而且，禁牧时间越长，这个趋势越明显；适度放牧状态下，蒙药材植物种类增多，重要值和占该样地全部物种重要值的比例明显提高。不同利用状况下蒙药材植物3种指数表现各异：围封22a，丰富度、优势度和均匀度都降低：围封10a，丰富度增加，优势度和均匀度受到围封前的状况影响；适度放牧条件下，丰富度高，冷蒿等适牧植物优势度提高，从而均匀度降低。

anglais. This paper studies and compares plant species and Mongolian medicinal plants diversity under different utilization condi- tions of typical steppe in Xilinguole of Inner Mongolia. Vegetation quadrat sampling technique was used for the investigation. The resuits showed that under varing conditions of 22 - year exclosurc, 10 - year exelosure 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.