Numerical classification and ordination in alpine vegetation ecology as a contribution to the association of modern computer methods with plant sociological tradition
Tuexenia 5: 181-190
ISSN/ISBN: 0722-494X Accession: 006006841
As part of an attempt to combine numerical classification methods as well as objective sampling procedures with the phytosociological tradition of Central Europe, a comparative study was carried out on identification and classification of high-altitude grassland communities in the Alps. The central question was whether a group of concrete phytocoenoses, which had been identified with a particular Braun-Blanquet syntaxon in the field, would appear as a homogeneous group in a numerical classification. For numerical classification the computer program TWINSPAN was used, and for evaluating the identification and classification results, the TWINSPAN output was also displayed in ordination diagrams. The ordination was carried out by the computer program DECORANA. Within broad limits the groups of the numerical analysis coincide with the syntaxa of the Braun-Blanquet-system, identified in the field. This can be explained by the character of phytosociological data as being a redundant information system. By a given species composition in a plant community, the cover values of the species are predetermined. Emphasizing mainly character species or dominant species with their cover values, as was done in traditional classification, means nothing more than that little information was lost when ignoring the whole species list. Thus the main feature of the numerical methods, namely to treat the whole species composition, is in fact no essential improvement for classification. The numerical methods should be considered as more sophisticated, and their main advantage will be the easier and accelerated data handling as well as a more objective basis for hypothesis generation.