Class (plant sociology)

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The class is a rank in plant sociology in which vegetation is divided into plant communities (or phytozoenoses ) according to floristic similarity, that is, according to the similarity of the composition of plant species. The class is the highest of the four main grades of the plant-sociological system, it follows on the fourth level after the association (the basic unit of the system), the association and the order . Many vegetation experts finally combine the classes into plant formations . Formations are not dealt with in syntaxonomy, however, as they are not defined according to the floral composition.

The class (also Latin: classis) can be broken down into subclasses if necessary, but this breakdown is optional. Class names are formed with the standardized suffix " -etea " and can be recognized by this. If a distinction is made between subclasses, the name ending " -enea " is mandatory. For example, the European meadows and pastures (economic grassland) are included in the class Molinio-Arrhenatheretea . As in the other ranks of syntaxonomy, the ending is added to the name (or the root of the name) of a plant genus , in the example of the genus Arrhenatheretum , the genus of the species common oat ( Arrhenatherum elatius ). In this case, the name of a second genus, Molinia ( pipe grass ), is added, as the class is named after two species; Names can be formed with one or two, but never with more species names.

In the full name, the genus name can be followed by the species name ( epithet ) placed in the genitive . This is often left out, but is necessary if the name would otherwise be ambiguous or ambiguous. For example, the holm oak forests of the Mediterranean are included in the class Quercetea ilicis, named after the holm oak , Quercus ilex . Quercetea alone would be misleading, as numerous other forest communities are named after other species of the genus Quercus . As a rule, the name of the class is derived from the name of one of its orders, associations or associations; it is not infrequently formed from a combination of two of them.

The result is the hierarchy:

  • Association, ending -etum.
    • Association, ending -ion.
      • Order, ending -etalia
        • Class, ending -etea .

As usual, a class must have been published “validly” in a scientific publication (in compliance with certain formal regulations). In scientific papers dealing with syntaxonomic questions, the name of the first descriptor, often abbreviated, is appended to the name of the class, often combined with the year of the first description (this is also occasionally abbreviated), for example Molinio-Arrhenatheretea Tüxen 1937. The Syntaxonomic names are very unstable due to the relatively young age of the research direction and standards that have only developed over time, so that numerous synonyms can be found in the literature, although the name changes are not infrequently made for purely nomenclatory reasons.

As is customary in plant sociology , all units are characterized by types of character , also called characteristic types. For plant societies with the rank of a class, these are the class character types. For newly described classes, the specification of class character types is mandatory. Differential types are also used to characterize them , which also occur in other syntaxa, but whose occurrence or absence in a certain class helps to differentiate them from related classes. The character types of subordinate syntaxa, i.e. from the orders or associations of the class, are normally not class character types, since they only occur in a part of the units. However, classes are allowed that contain only one order, in which case class and order characteristics coincide. As in the standard plant-sociological method, the character types are determined by arranging vegetation images in vegetation tables, but these are often aggregated into so-called continuity tables in the higher-ranking units.

Classes as higher-ranking syntaxa in many cases cover a wide spectrum of plant communities in different locations and do not always have a uniform floristic composition. In contrast to the associations and orders, it was not always possible to reproduce the belonging together of the classes of European vegetation using numerical methods. Most vegetation experts no longer strictly apply the principle of floristic similarity on which the method is based on the class level, by dividing vegetation stands of similar species composition but different structure and physiognomy, for example forest, bush, perennial and lawn communities into different classes. When examining the delimitation of the Czech and Slovak classes using statistical methods, the more extreme the site conditions were, the more precisely these were defined, while the vegetation of middle sites was more difficult to characterize due to the many overlapping species. But the species-rich classes of natural and semi-natural vegetation units could also be well characterized.

The number of differentiated classes is interpreted differently by different vegetation experts. In a European overview, the EuroVeg Checklist project, 109 classes were distinguished for European vegetation. The Red List of Plant Societies in Germany distinguishes between 50 classes. Although outdated, the Oberdorfer system is still widely used in Germany.

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  • HE Weber, J. Moravec, J.-P. Theurillat (2000): International Code of Phytosociological Nomenclature. 3rd edition. Journal of Vegetation Sciencel 1: 739-768.
  • Josias Braun-Blanquet: Plant Sociology: Basics of Vegetation Science. 3rd edition, Springer Verlag, 1964 (new edition 2013). ISBN 978-3-7091-8110-2 , definition on pages 130-131.
  • Otti Wilmanns: Ecological Plant Sociology. Quelle & Meyer Verlag, Heidelberg, 3rd edition 1984. (UTB for science 269). ISBN 3-494-02027-2 .

Web links

Individual evidence

  1. ↑ Ladislav Mucina & Eddy van der Maarel (1989): Twenty years of numerical syntaxonomy. Vegetatio 81: 1-15.
  2. ↑ M. Chytrý M. & L. Tichý L. (2003): Diagnostic, constant and dominant species of vegetation classes and alliances of the Czech Republic: A statistical revision. Folia Facultatis Scientarium Naturalium Universitatis Masarykinae Brunensis, Biologia 108: 1-231.
  3. ↑ I. Jarolímek, J. Šibík, L. Tichý, J, Kliment (2010): Sharpness and Uniqueness of the phytosociological classes of Slovakia. Annali the Botanica PDF
  4. ↑ EuroVeg Checklist. University of Göttingen, Department of Vegetation Analysis & Phytodiversity, 2018.
  5. ↑ Ladislav Mucina et al. (2016): Vegetation of Europe: hierarchical floristic classification system of vascular plant, bryophyte, lichen, and algal communities. Applied Vegetation Science 19 (Supplement 1): 3-264. doi: 10.1111 / avsc.12257
  6. ↑ Erwin Rennwald: Directory and Red List of Plants companies in Germany. Series of publications for vegetation science 35. ISBN 978-3-7843-3505-6 .