Rit (Vísindafélag Íslendinga) - 01.06.1975, Blaðsíða 64

northwestern parts of Iceland, however, it is rare as well as in the
highland, at least at higher altitudes. In the lower heaths on the
other hand it is common and on lower ranges which protrude he-
tween valleys. But despite this it is seldom so conspicuous as to
characterize the vegetation significantly either in physiognomy or
in covering, and when this happens it is usually in small patches.
The eastem part of Iceland, however, is unique in this respect at
least the Fljótsdalshérað where C. chordorrhiza is one of the most
common flói plants and is dominant there in extensive areas so that
it pushes E. angustifolium aside.
The C. chordorrhiza flói, whether extensive or not, is not unlike
the Eriophorum flói, when E. angustifolium is not in hloom. The
flói tracts are dark hrown when viewed from a distance, the soil
is always very wet, the surface is level and the ground water is
completely stagnant. On the other hand C. chordorrhiza is not very
tolerant of water, when it significantly floods the grassroots, as a
result of which it disappears much like E. angustifolium. The
vegetative cover is continuous, moss in scant supply and the flói
is root rotted. The flói is prohably rather acid, which may he con-
cluded from the fact that wherever C. hmosa occurs it is an ac-
companying species of this association.
As far as I can determine this constitutes a close relation or the
same association as strengstarr svartmyrer in Sikilsdalen (Nord-
hagen 1943, p. 522), mainly, however, a C. chordorrhiza — Dre-
panocladus exannulatus sociation (1. c. 523), both with respect to
vegetative composition and synecological relationships.
In Skrá (Std. 1951) I have presented two sociations of the C.
chordorrhiza flói, but on closer examination I believe it proper to
join them in one C. chordorrhiza — C. limosa sociation, although
C. limosa is absent in some places, in which case it is hardly to be
found in these parts. It can, to be sure, also disappear in the driest
areas of the C. chordorrhiza flói, whereupon other species replace
it, e.g. Equisetum palustre, when we might refer to the C. chor-
dorrhiza — Equisetum palustre sociation, and in wetter areas the
C. chordorrhiza — C. rostrata — E. palustre sociation. This is ac-
tually what I have done in a new edition of Skrá. C. nigra then
often becomes noticeahle and in Fljótsdalshérað you could refer to
the C. chordorrhiza — Scirpus cæspitosus sociation. But all these
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