The ecological groups (appendix 3 and 4) are defined by biotic and abiotic characteristics, in such a way that the assignment of plant species to ecological groups can be verified by means of direct measurements of the (a)biotic characteristics used. A difference with former subdivisions¹² is the fact that a species can be assigned to more than one ecological group, depending on the ecological amplitudo of the species. The (a)biotic characteristics used are vegetation structure and stage of succession, salinity, substratum, moisture regime, nutrient availability, acidity, dynamics of the ecosystem (sand drift, trampling etc.). Each characteristic has been subdivided in several classes (appendix 1). Combinations of these classes are used to define different habitat types, the so-called ecotope types. Examples of such types are: ‘grassland on dry acid soil of low nutrient availability’, or ‘woodland on wet soil of high nutrient availability’. The assignment of plant species to ecological groups has been based on ecological literature (e.g. 17, 18, 19) and has been tested by using about 20,000 relevées of Dutch vegetations. The plant species have been assigned to as many ecological groups as is necessary to explain two thirds of the occurrence of the plant species in the Netherlands, under the theoretical assumption that all habitat types are equally common. The ecological groups can be used in the analysis of ecological data, in which the occurrence of plant species is interpreted in terms of habitat factors. Computer programs have been written to determine the habitat type using floristic information as an input, assuming that the vegetation and the (a)biotical environment are in equilibrium. The ecological groups can also be used in environmental impact assessment, in studies in which changes in habitat type rather than changes in the occurrence of plant species are used to express the expected changes in the (a)biotic environment.

Gorteria Dutch Botanical Archives

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Naturalis Biodiversity Center

J. Runhaar, C.L.G. Groen, R. van der Meijden, & R.A.M. Stevers. (1987). Een nieuwe indeling in ecologische groepen binnen de Nederlandse flora. Gorteria Dutch Botanical Archives, 13(11/12), 277–359.