Problems and use of structure in the classification of vegetation. The diagnostic evaluation of structure in the Braun-Blanquet system

It is a well-known fact that vegetation can be classified on the basis of quite different criteria; e.g. by physiognomy, structure, dynamic processes, floristical composition, and even – a scientifically less satisfying way – by habitat. It is not the aim of this study to give a critical review of these starting-points. The author’s purpose is to consider the Braun-Blanquet system of vegetation classification, which is a system claiming to be based on floristical composition, and to analyse how far, in reality, structural criteria are involved in it. This article does not consider whether Braun-Blanquet syntaxonomy is the only valuable or even the best one. In fact it is, however, the most widely used and uniform system of vegetation classification, enabling us to compare plant communities over an area as large as (e.g.) Europe, and, therefore, also presenting a basis for such items as geographical comparison of habitats, vegetation mapping of large areas, or the analysis of geographical differences in the autecological behaviour of taxa. It may thus be useful to see whether the higher units of this inductive system correspond to the units of the more or less deductive formation systems of the world, based on physiognomy and structure.