河北坝上草原东沟植物群落生态梯度的数量分析

运用DCCA排序轴分类，将河北坝上草原东沟的植物群落划分为8类，效果较好．排序图表达了植物群落的环境梯度、结构梯度和人为干扰．第1轴反映了群落在海拔和坡度方面的空间梯度，第2轴反映了群落的坡向分异格局，两轴综合反映了群落沿水分梯度的空间分异．群落的层片构成和各层片物种组成也表现出相应的空间分布格局．白桦局限在阴坡高海拔陡峭处．阴坡灌木与草本层片优势种分别为金露梅与细叶苔草，阳坡则为蒿类和冰草．阳坡群落各层片优势种还存在海拔和坡度分布格局．另外，放牧、耕作和伐树等人为干扰对群落时空分布也有显著影响．一般来说，生境条件较好的群落，人为干扰较严重．

Numerical analysis on ecological gradient of plant communities in Donggou catchment,Hebei Province,China

Based on DCCA-OAC,the plant communities in Donggou catchment,Bashang region,Hebei Province,were classified into 8 types of community.The environmental gradient,structural gradient and human-disturbance could be well expressed in the ordination plot.Axis 1 reflected the spatial pattern of plant communities along the gradient of altitude and slope,while axis 2 showed the plant community distribution on different aspects.The plant communities showed a distribution gradient along moisture gradient as shown by the combination of both axes of DCCA.The communities exhibited different trends in the synusia and species composition.Betula platyphylla was only existed on the high and steep northern aspect.The dominate species of shrub and herbaceous synusia on northern aspect were Potentilla fruticosa and Carex rigescens respectively,while on southern aspect were Artemisia spp.and Agropyron cristatum.The distribution along altitude and slope also existed among dominate species of each synusia on southern aspect.In addition,human disturbance,including grazing,farming and logging,had significant influence on the temporal and spatial distribution of communities.In general,the better the habitat,the more intensive the human disturbance.