Use of ecological groups in analysis and classification of plant communities in a section of western Quebec

A plant community analysis and classification were done for an integrated ecological study, in the lake Abitibi region, Quebec. Two levels of vegetation analysis were used: the ecological group level and the community level. Species were first grouped according to their sociological affinities. The ecological significance of those groupings was studied by principal component analysis, with the inclusion of abiotic variables, and by the study of ecological profiles. Secondly, the concurrent use of ecological groups permitted the definition and characterization of noda. The relationships between the noda, in the space defined by the ecological groups, were analyzed by principal coordinate analysis on which is superimposed the shortest spanning tree. Those combined analyses permitted the identification of 35 community types which vary mainly according to surficial deposits (organic or mineral), drainage, relative richness of soils in bases, flooding, presence of bedrock outcrops. fire perturbations and microclimate. Those variations are discussed according to the exlusive or non-exclusive character of the ecological groups.