Rit (Vísindafélag Íslendinga) - 01.06.1975, Page 140

also occur in moist blown sand where pools form in depressions.
The vegetation is formed in the same way in both cases. The Eri-
ophorum Scheuchzeri association is most common in the highland,
but it occurs in lowland regions as well, although it rarely forms
such a continuous vegetative cover there. Continuous seepage of
fresh water through the sand is an essential condition for the growth
of this vegetation type. When the sand rises and dries out, or if
humus begins to collect in it, E. Scheuchzeri gradually disappears
and other plant communities take over. This association is always
pioneer vegetation in such areas. Let me interject at this stage that
I cannot agree with the theory which classifies Eriophorum Scheu-
chzeri and Carex Lachenalii as snow-patch sociations in the same
association as Nordhagen does (1943 p. 498). This is not justifiable
because those sociations are too diverse in their composition of spe-
cies and occur in totally different environments.
There is no peat formation in the E. Scheuchzeri flæðimýri. The
bottom layer is practically pure sand, and moss vegetation is in-
significant. The E. Scheuchzeri association is a pioneer association
as already mentioned. It cannot be expected, therefore, to remain
stable, but belongs to, or rather constitutes a special evolutionary
stage in the flæðimýri vegetation. Extraneous influences, such as
grazing or harvesting, probably do not significantly affect it, though
they may possibly retard the evolution of the plant communities.
Practically all the species found in this association are eutroph-
mesotrophic or indifferent with respect to acidity.
Although the E. Scheuchzeri association has a small number of
species I feel it is justifiable to divide it into three sociations. Close-
ly related to it are: Catabrosa aquatica, Equisetum arvense and
Agrostis stolonifera sociations all at similar stages of evolution, and
at a further stage of development the Calamagrostis neglecta so-
ciation appears.
The E. Scheuchzeri sociation has been described by many Scandi-
navian authors who all concur that it occtirs in an environment
resembling that which has been described above. The sociations in
the Scandinavian countries, however, do not entirely correspond
to those in Iceland, but this is obviously the same plant community.
In this connection one may refer to Eriophorum Scheuchzeri soc.
Nordhagen 1943 p. 405, Tengwall 1920 p. 405, E. Scheuchzeri Wiese
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