中文摘要：

以领春木（Euptelea pleiospermum）、连香树（Cercidiphyllum japonicum）为优势种的珍稀植物群落是神农架山地中海拔地段河岸带中的典型群落类型。在神农架地区4大水系（沿渡河、香溪河、南河和堵河）的河岸带中共调查了48个样地，采用植物群落学方法，分析了该区山地河岸带中珍稀植物群落特征。结果表明：（1）群落中植物种类丰富，科属组成比较分散。共记录到维管束植物749种，隶属144科412属，其中每科仅记录到1个属的有72个科，每属仅记录到1个种的有256个属。（2）在科水平上，热带、亚热带成分与温带成分所占比例几乎相同，在属水平上温带成分占主导。东亚分布成分、中国特有成分所占比例较高，共记录了6个东亚特有科、50个东亚特有属，2个中国特有科、27个中国特有属。（3）中小型草质单叶的落叶阔叶高位芽和地面芽植物是决定该珍稀植物群落外貌的主要成分。（4）群落垂直结构复杂，成层现象明显。第一乔木亚层树冠层分布不连续，第一、第二乔木亚层和灌木层从高到低郁闭度逐渐增大，草本层盖度各样地差别较大，层间植物丰富。该山地河岸带中丰富的珍稀、特有和／或孑遗植物表现出该群落的古老、孑遗性。虽然该区多数珍稀植物为温带性质，但该珍稀植物群落整体上在种类组成、区系分布、生活型谱、叶片性质等方面表现出亚热带亚高山垂直带谱上常绿落叶阔叶混交林的过渡性特征。自上而下逐渐密集的群落垂直结构为幼苗稍耐荫、成年趋于喜光的珍稀植物的不同发育阶段提供了利于其生长的光环境。特殊的地理位置、独特的地形地貌和良好的水热条件使亚热带山地河岸带成为珍稀植物（尤其是孑遗植物）就地保护中一个关键而特殊的区域。

英文摘要：

Riparian communities at middle altitude of the Shennongjia Mountains,with Eupteleapleiospermum and Cercidiphyllum japonicum as principal part, harbor many Tertiary-relic, rare and/or endemic species, some of which are mainly or exclusively confined to riparian habitats. In order to study the characteristics of the rare plant communities, we investigated 48 plots along riparian zones of the four main rivers （Yandu River, Xiangxi River, Nan River and Du River） on the Shennongjia Mountains. Species composition, areal-types, life-form spectrum, leaf characteristic and community vertical structure were analyzed. A total of 749 species were recorded ,belonging to 412 genera and 144 families. Of these ,there were 256 monotypic genera and 72 monotypic families. Analysis of the areal-types of spermatophyte indicated that tropical and subtropical elements were equivalent with temperate elements at family level, but temperate elements were dominant at genus level. As to endemic elements,6 families and 50 genera were endemic to East Asia and 2 families and 27 genera were endemic to China. Physiognomy of these communities was characterized by phanerophytes and hemicryptophytes with mesophyllic and microphyllic herbaceous single leaves. Stratification of tree layer, shrub layer and herb layer was distinct. Tree layer was further subdivided into two sub-layers：upper and lower tree layers. From upper tree layer to shrub layer, the coverage increased gradually. Richness of endemic and/or relic plants indicates the old-growth and relictual characteristics of the riparian rare plant communities. All the features of species composition, areal-types, life-form spectrum and leaf characteristic reveal that the characteristic of the rare communities is characterized as a transition from evergreen broad-leaved forest to deciduous broad-leaved forest. The vertical structure makes it possible to provide favorable light for several riparian rare plants during their whole life history. Specific position, peculiar topography and well wa