以青海湖地区围栏封育二十年的高寒草原群落个体植株作为对照，比较研究了紫花针茅、冰草、早熟禾、猪毛蒿四种优良牧草个体和异叶青兰、披针叶黄华、狼毒三种杂毒草个体在放牧压力下植株形态特征的变化，发现优良牧草个体对长期放牧的形态响应与杂毒草类不一致，优良牧草在长期放牧的条件下表现出“个体小型化现象”，但是杂毒草却是不明显，在地上生物量上表现的尤为突出。个体形态变异差异造成了植株个体对环境资源的利用能力的相对改变，各植物种群占有的生态位（资源空间）发生“形变”，优良牧草类多数种群生态位“收缩”，杂毒草类多数种群生态位“扩张”，草原群落中的各种群重新组织，优势种出现更替，是高寒草原群落退化演替在个体水平的解释。

Compared with the grass individuals of alpine steppes community fenced for twenty years, the variation of morphological characteristic of four good herding grass species( Stipa purpurea, Agropyron cristatum, Poa pratensis, Artemisia scoparia) and three miscellaneous poison grass species (Dracocephalum heterophalum, Thermopsis lanceolata, Stellera chamaejasme) under grazing stress is studied, we find that the responses of good herding grass individuals to long-term grazing are not consistent with the responses of miscellaneous poison grass individuals. Good herding grass individuals show “Individual Miniaturization Phenomenon”, but miscellaneous poison grass individuals do not become miniaturized, especially for aboveground biomass. Different individual morphological variation results in the change of utilization ability to environmental resources, so the environmental spaces and resources (hypervolume niche) each population occupies in the community becomes “reshaped”, that of most good herding grass populations becomes "contracting " and it is "extending "for most miscellaneous poison grass populations, therefore the status of plant populations in the degraded grassland community changes, the dominant species alternates. This is the individual morphological principles of the degradation of alpine steppes community.