In order to discuss the relationships between grassland degradation and the diet composition,trophic niche of main herbivores (Ovis aries,Spermophilus dauricus,Oedaleus asiaticus) in the Inner Mongolia steppe,the change of both diet composition and trophic niche under different grazing intensities was investigated using n-alkane technique in July-August of 2003.Results showed that the richness of Leymus chinensis and Stipa grandis decreased significantly with the increase of grazing intensity,while the proportion of Salsola collina in the community increased at the same time.Plant species and proportion ingested by sheep,Spermophilus dauricus and Oedaleus asiaticus were different at different grazing intensities.Leymus chinensis was preferred to be ingested among Leymus chinensis,Salsola collina and Stipa grandis.The tropic niche of Spermophilus dauricus and Oedaleus asiaticus was broadened with the increase of grazing intensity.The overlaps of trophic niche were similar among three herbivores.In conclusion,an action of grazing changed the Stipa grandis community that led to the degradation of grassland in Inner Mongolia steppe.Three herbivores here had a fierce competition to grassland resources.Therefore,it was an important practical significance for grazing livestock food safety to control pests and mice population densities and prevent their outbreak.%为探讨典型草原主要食草动物绵羊(Ovis aries)、达乌尔黄鼠(Spermophilus dauricus)和亚洲小车蝗(Oedaleus asiaticus)的食性及其种间生态位变化与草原退化的关系,以内蒙古典型草原为研究对象,于2003年7-8月运用饱和链烷技术研究大针茅(Stipa grandis)群落不同放牧强度下绵羊、达乌尔黄鼠和亚洲小车蝗的食性及其生态位变化.结果表明:随牧压的增大,群落中羊草(Leymus chinensis)和大针茅的数量减少,糙隐子草(Cleisto-genes squarrosa)和猪毛菜(Salsola collina)比例增加；绵羊、达乌尔黄鼠、亚洲小车蝗3种食草动物采食的牧草种类和比例存在一定的差异,但同时采食羊草、猪毛菜和大针茅时优先采食羊草；随牧压的增大,达乌尔黄鼠和亚洲小车蝗的生态位宽度变宽,且在放牧区绵羊的生态位宽度最大,三者生态位重叠程度类似.放牧改变了大针茅群落的植被组成,使其演替为糙隐子草群落,3种食草动物对草地资源存在激烈的竞争,因此,控制鼠、虫的种群密度,防止鼠、虫害的发生对保证放牧家畜的食物安全具有十分重要的现实意义.
展开▼
