Die Strandlinggesellschaften (Littorelletea Br-Bl. et Tx. 43) der Niederlande, in europäischem Rahmen gefaßt
Schaminée, J. H. J.; Westhoff, V.; Arts, G. H. P.
The class Littorelletea includes amphiphyte communities on sites with alternating water level in meso- to oligotrophic, stagnant or slowly running, not or hardly polluted, mostly weakly buffered water. The communities are bound to a mineral soil which is not or hardly covered by organic material. They show a simple structure, in which the isoetid growth form predominates; their species number is rather low. The area of the class includes the humid temperate zone of the northern hemisphere; in Europe the communities concentrate in the atlantic, boreo-atlantic and subatlantic regions. Some character-species show a boreal distribution, e.g. most isoetids; some other ones present an atlantic distribution pattern (e.g. Deschampsia setacea, Eleocharis multicaulis, Hypericum elodes, Luronium natans, Pilularia globulifera, Echinodorus repens, and Ranunculus ololeucos). In The Netherlands, the Littorelletea communities mainly occur in the coastal dunes and the Pleistocene sand districts. Since about half a century, the Littorelletea communities in The Netherlands have strongly decreased, in number of localities and in floristic and ecological quality. The main causes are: (1) an overall draining and consequently drying out of sites; (2) eutrophication of surface waters; (3) air pollution, bringing about acidification of soil and water, mainly by ammonium; (4) decrease of the requested moderate amount of environmental dynamics. The present study is based on 489 relevés, including all available data, published as well as unpublished ones. Eight associations are dealt with, assigned to five alliances. The amplitudes of their character-species are rendered. Fig. 3 presents the distribution of the relevés over the country. A synoptic table represents the floristic assemblage of all associations, including the rate of presence ('frequency') and the fidelity (indication values) of the species. Each association is discussed including: (1) its floristic assemblage, documented with a table of 20 representative relevés; (2) synecology; (3) subdivision, if any; (4) vegetation dynamics; (5) vegetation structure; (6) European and Dutch area, with semiquantitative data about the distribution (number of localities) and the surface covered by the summarized stands; (7) adjacent (contacting) communities.