Abstract: On the grazing gradient consisting of six different stocking rates,niche breadths and niche overlaps for 11 main plant populations in Inner Mongolia typicaI steppe were measured,and the following results were concluded:1)Leymus chinensis and Stipa grandis had relatively narrow niche breadths(0.298,0.565)and could endure only light grazing.While Agropyron michnoi,Potentilla tauacetifolia,and Melissitus rulhenica had intermediate niche breadths(0.857,0.891,0.849),which could endure moderate grazing intensity.2)Cleistogenes squarrosa,Potentilla acaulis.Carex duriuscula,Artemisia frigida,Kochia prostrata,Artemisia commutata had extremely wide niche breadths(being0.978,0.931,0.970,0.969,0.939,0.924respectively).These species could endure heavy grazing intensity,showing considerable ability in utilizing resources.3)It could be seen that the species with greater niche breadths generally had greater niche overlaps with other species,and the niche overlaps among species that had similar morphological characters were much greater.

Key words: Niche breadth, Niche overlap, Stocking rate, Inner Mongolia typical steppe

摘要： 对内蒙古典型草原主要植物种群在不同放牧强度下生态位分化规律进行研究。结果表明,羊草、克氏针茅的生态位.宽度相对较窄,分别为0.298和0.565.表明对放牧较敏感.属宜轻牧植物。扁蓿豆、冰草和菊叶委陵菜的生态位宽度(0.849,0.857,0.891)适中.属宜中牧植物。而糙隐子草、冷蒿、星毛委陵菜、寸草苔、木地肤和变蒿等耐牧性较强.具有很宽的生态位宽度分别为0.978.0.969,0.931.0.970.0.938.0.924,具有很强利用环境资源的能力。生态位重叠的研究结果表明.具有较大生态位宽度的种群与其他种群间的生态位重叠较大；具有相似形态特性的种群间的生态位重叠较大。

关键词: 生态位宽度, 生态位重叠, 放牧率, 内蒙古典型草原