Rit (Vísindafélag Íslendinga) - 01.06.1975, Síða 50

Polygonum viviparum is much rarer here than in the Eriophorum
flói. This association is in the main confined to the lowland areas,
although analyses are presented here from the highland where it
is much rarer. Nowhere does it cover large areas, but it occurs in
patches in the Eriophorum flói, usually in the wettest parts. The
association is even poorer in species than the Eriophormn flói, and
the composition of species is similar to that of the flæðimýri. Still
I do not hesitate to include it in the flói, because the terrain in
which it occurs can not in any way be distinguished from the flói
areas with respect to origin and formation. Peat formation occurs
there as well as in the flói, which is absent in the flæðimýri. But
what can then cause the patches in the flói to change so much in
vegetation and appearance that the prime character species of the
Eriophorum flói disappears almost completely, but another species,
which otherwise is extremely rare in the Eriophorum flói, replaces
it. The moisture content of the flói has no effect on it, and it is in no
way different from many sociations of the Eriophorum flói. Here
I want to mention what I have discovered in this context. It is
known that one of the main conditions for the growth of Carex
Lyngbyei is that it have adequate access to water rich in minerals,
at least during part of the year. On the other hand it can tolerate
the desiccation of land for a part of the summer. But where C.
Lyngbyei becomes a dominant species in flói vegetation, I believe
that this comes about by one of two processes. Either the C. Lyng-
byei sociation is created through the outlets of springs or ditches,
which have then filled up the flói to some extent with their deposits,
and thereby conditions for flæðimýri have been formed. Or, that
C. Lyngbyei in mires and flói areas seems to favour very much
those parts where iron-blended clay collects on the surface. This
clay consists mostly of bog iron (Fe2H3 , H20), and it collects in
shallow depressions, being deposited there probably to some extent
by surface water. In these depressions containing bog iron there
is always a C. Lyngbyei sociation, and it is almost an inflexible
rule both in flói and mire areas that, if red clay is detected on the
surface, then C. Lyngbyei grows there, although it is most often
so sparse that there is no question of it forming a sociation. Noth-
ing will be said about the acidity of the C. Lyngbyei flói, but it
may be assumed to be less acid than the Eriophoriun flói.
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