Abstract: To investigate the effects of grazing and topography on alpine shrub populations， in this study the effects of topography and grazing on population growth， inter-species relationships in alpine scrub in the Qilian Mountains were analyzed by using the populations of Potentilla anserina and Poa subfastigiata as the research objects， through setting up three kinds of terrain， namely， valley， shady slopes， and sunny slopes and five different distances from livestock pens for each terrain type as grazing plots. The results showed that grazing and topography jointly regulated the growth of two plant populations. The increase in grazing pressure gradient （reduced distance from the livestock pens） inhibited the vertical （plant height） and horizontal （crown width） growth of the two species， and increased the population density and vegetation cover. The valley was characterized by a balance of water and heat resources， and the two species coexisted in the highest density， with shady slope has better humidity conditions and stable water supply， which was conducive to the growth and reproduction of moisture-loving Potentilla anserina. The sunny slope had ample sunlight and suitable thermal conditions， favoring the dominance of Poa subfastigiata in their ecological niche. The topography indirectly influenced the competition of the populations by altering the heterogeneity of microhabitats， while grazing directly influenced the competition through trampling. Topography indirectly affected population competition by altering microhabitat heterogeneity， grazing directly affects population dynamics through trampling and foraging. Topography and grazing influenced the competitive landscape of moisture-loving and drought-tolerant species， thereby affecting their status in the community. This study quantified the pathways of topography and grazing on the growth and interspecific relationships of alpine shrub populations， which can provide a scientific basis for the sustainable utilization of the alpine ecological barriers.

Key words: Alpine scrub, Grazing, Topography, Potentilla anserina, Poa subfastigiata, Population dynamics

摘要： 为探究放牧和地形对高寒灌丛种群的影响，以祁连山高寒灌丛的鹅绒委陵菜（Potentilla anserina）和散穗早熟禾（Poa subfastigiata）种群为研究对象，通过设置谷地、阴坡、阳坡3种地形及每种地形5个不同距畜圈距离的牧压梯度样地，分析放牧和地形对种群生长、种间关系的影响。结果表明：放牧与地形共同调控2种植物种群的生长，牧压梯度上升（距畜圈距离减少）抑制两种植物纵向（株高）和横向（冠幅）生长，降低种群密度与植被盖度；谷地水热资源均衡，两种植物共存且密度最高，阴坡因湿度条件更优，水分供应稳定，利于喜湿的鹅绒委陵菜种群生长和繁殖，阳坡光照充足，热量条件适宜，更适于散穗早熟禾种群占据优势生态位。地形通过改变微生境异质性间接影响种群关系，放牧则直接通过践踏与采食影响种群动态；地形与放牧通过改变喜湿-耐旱物种的竞争格局进而影响其在群落中的地位。本研究量化了地形-放牧共同作用对高寒灌丛植物种群生长、种间关系的调控路径，可为高寒生态屏障的可持续利用提供科学依据。

关键词: 高寒灌丛, 放牧, 地形, 鹅绒委陵菜, 散穗早熟禾, 种群动态