过草本植物群落的分类和排序，结合对乔木和灌木分布的分析，确定了五台山高山林线的几条植被界线以及五台山森林上限附近植被的性质。结果表明：1）阳坡林线的海拔范围为2 605～2 790 m，阴坡林线的海拔范围为2 810～3 015 m；2）草本植物群落随海拔高度的变化比较明显，阴坡和阳坡从郁闭林到山顶均依次分布林下草本层、林缘草甸、亚高山灌丛草甸、高山草甸，草本植物的分布很好地体现了林线内部景观的差异性；3）海拔高度是高山林线附近草本植物群落空间分异的决定性因素。
As a transitional zone from closed forest to alpine vegetation, timberline is sensitive to climatic change in two aspects, fluctuation of its boundaries and changes to its structure. Therefore, the demarcation of vegetation limits and clarification of vegetation patterns of alpine timberline is critical to studies on the response of alpine timberline to climatic change.Mt. Wutai, with a summit of 3 058 m a.s.l., is the highest mountain in North China. It is also one of several mountains which reach the climatically controlled alpine timberline in the temperate broadleaved forest zone in China. Former studies were focused on the vegetation classification of meadows, vertical changes of plant species diversity and micro to meso-scale patterns of the meadow near the summit. Vegetation analysis on a large scale is still essential to understand the characteristics of vegetation near the timberline.Vegetation investigation was made at 10 m elevation intervals on the shady slope and 20-25 m on the sunny slope from the upper forest limit to the mountain summit. A total of 280 relevès on the shady slope and 75 on the sunny slope were made. TWINSPAN was used to do vegetation classification of herbaceous communities,and to show the relationship between distribution of plant communities and environmental conditions was shown using DCA. After classification and ordination of herbaceous communities and analyses of distribution of trees and shrubs, vegetation boundaries of alpine timberline were delimited and vegetation characteristics of the upper forest boundary were clarified in this paper. On the shady slope, alpine timberline ranges from 2 810 m to 3 015 m a.s.l. The timberline is dominated by Larix principis_rupprechtii with Picea meyeri and Betula albo-sinensis. The quantity of cones demonstrates that the regeneration ability of Larix principis-rupprechtii is much better than that of Picea meyeri. On the sunny slope, alpine timberline ranges from 2 605 m to 2 790 m a.s.l.. It is dominated by Picea meyeri with some Larix principis-rupprechtii. 4 herbaceous communities, understory herbaceous layer, meadow at forest edge, subalpine scrubby meadow and alpine meadow, were distinguished by TWINSPAN on both slopes. The herbaceous communities change markedly with altitude. Understory herbaceous layer, meadow at forest edge, subalpine scrubby meadow and alpine meadow occur in sequence from upper closed forest to mountain summit on both shady and sunny slopes. DCA results showed that elevation is closely related to the changes of herbaceous communities, implying a key role of climate conditions in the spatial differentiation of herbaceous communities.