甘肃文县珙桐群落的二维极点排序

采用二维极点排序法定量地将不同地段的6个珙桐群落样地划分为3组，即碧峰沟上源珙桐群落、竹园沟珙桐群落以及石磨河上源珙桐群落。这3个组合与土壤湿度及厚度的梯度变化相一致，表明植物群落与环境密切相关。极点排序图直观地表明了这6个样地的生态分布，且反映出生境的梯度变化，排序图还可反映群落优势种在样地上的定量分布，表明植物种的生态适应性。

The Two-Dimension Point Ordination of the Davidia Involucrata Community in Wen County of Gansu Province

Using point ordination method, the 6 Davidia involucrata communities in different sections can be divided into 3 groups, the communities disributed in Bifeng Gully upper reaches, Zhuyuan Gully and Shim River upper reaches, respectively. The 3 groups coincide with the gradient variation of the soil humidity and thickness. The point ordination chart shows directly the ecological distribution of the 6 communities. It reflects the gradient variation of the habitat. The chart also shows the quantitative distribution of the dominant species and indicates the ecological adaptability of the species.