中文摘要：

贺兰山的灰榆群落具有重要的生态学意义和研究价值。在系统的样方调查基础上，对贺兰山灰榆群落类型及特征进行全面分析。结果表明：贺兰山灰榆群落的主要特征与海拔及地形因子相关。种间关联分析显示，群落中存在显著差异的喜阳耐旱种组和阴湿林下种组两组，灰榆与前者呈负相关，而与后者呈正相关。CCA排序将群落分为4个群丛，海拔和坡向是群落类型分异的主要影响因子。针阔混交林群丛分布在高海拔的阳坡，落叶阔叶疏林群丛分布在中高位置的阴坡，灰榆一蒙古扁桃疏林分布在中低海拔的阳坡，灰榆疏灌林分布在最低海拔的阴坡。4个群落的空间分布位置、物种组成和群落特征差异显著。在研究结论的基础上，对贺兰山灰榆群落的重建和保育提出了相对应的措施。

英文摘要：

The Ulmus glaucescens community on Helan Mountain was important in ecological sense, and therefore we conducted field survey on this community relying on systematic sampling plots. The primary results showed that the main features of U. glaucescens communities are influenced by elevation and topographic factors. Two different ecological species groups are appeared after the inter - specific relations analysis, which are speciesgroup incline to dry and non - shady habitats and species group with shade and moisture conditions, and U. glaucescens in negative relation with the first species group and in positive relation with the later group. The ordi- nation of Canonical Correspondence Analysis divided all plots into 4 four plant associations： coniferous and broad - leaves mixed forest on sunny aspect of high elevation, deciduous broad - leaves open forest on shade aspect of middle -high elevation, Ulmus -Amygdalus open forest on sunny aspect of middle elevation, and Ulmus openforest and shrubs on the shade aspect of low elevation. The elevation and aspect are obviously the mare enwron- mental factors in ordination, and therefore the spatial locations, species compositions and community features are all significantly various in 4 plant associations. Based on the above conclusions, several suggestions were promoted for the conservation of Ulmus communities.