The ordination axes clustering based on detrended canonical correspondence analysis ordination and its application to the analysis of the ecological gradients of plant communities

Based on Detrended Canonical Correspondence Analysis(DCCA),a new classification method,DCCA Ordination Axes Clustering(OAC)was introduced and was applied to the classification of the plant communities in Bashuigou catchment,Guandi Mountain,Shanxi Province.Five types of communities can be identified with the method.It is concluded that there are obvious differences of community structure and environmental factors among the community types by using the Analysis of Variance and Multiple Comparison.So,the OAC based on DCCA expresses the ecological gradients of communities and environment clearly. For the OAC based on DCCA combining the vegetation and environmental factors,it expresses the gradients and the variation characteristics of the community structure and environment well.The axis 1 illustrates the gradients towards warm and dry,representing the horizontal variation of micro topography and the types of wooden plant community.Along the axis 1,the shrub community replaces the forest community,and the Populus spp.+ Betula spp. Picea spp.forest and the Larix principis rupprechtii Picea meyeri forest are replaced by the Populus davidiana Quercus liaotougensis forest.However the scale of variation is small.The axis 2 means the gradients towards cold and wet,caused by the vertical variation of altitude and the types of plant community.Along the axis 2.the herbaceous community replaces the forest and shrub community,and the Populus spp.+ Betula spp. Picea spp.forest and the Populus davidiana Quercus liaotungensis forest are replaced by the Larix principis rupprechitii Picea meyeri forest.However,the scale of variation is large.At all,the two dimensional plot of the axis 1 and axis 2 can clearly reflects the spatial gradients of communities in this area. The OAC based on DCCA is good as DCCA,and it can remove Arch effect and relate more environmental factors.Also,it is good as OAC,and its can finish clustering by itself,and it means definite ecological relations.This new method has some advantages in the study on the relationships between the community and environment.