Rit (Vísindafélag Íslendinga) - 01.06.1975, Side 93

surface is rather patterned and there is some difference in vegeta-
tion between knolls and hollows; the most important single factor
being the Rhacomitrium which grows exclusively on the knoll-tops
and sometimes characterises them. Rhacomitrium is reported to
grow in mires in Rritain (Oswald 1949, p. 18). He states that in
Calluna-Scirpus sociations Rhacomitrium grows only in the driest
areas where it is most exposed to the wind. Tansley (1953, p. 718)
also refers to Rhacomitrium on knolls in the Rlanket bogs. Although
these are in other respects not related vegetation areas, it is never-
theless evident that mire-sociations with Rhacomitrium can ap-
pear in this country under circmnstances similar to those which
apply in mires in Britain, since the climate in the south of Iceland
is not unlike that of the British moors respite lower temperatures.
51. C. nigra — Nardus stricta sociation
(Tab. XIx A-B 12)
The only analysis of this sociation is from Tunga in Bolungavík,
where it is closely related to the Nardus-Antoxanthum sociation
which is to he described at a later stage, and it might possibly be
looked upon as a variant of that sociation. The main difference be-
tween these sociations is that C. nigra is here dominant along with
Nardus stricta, both in physiognomy and covering. The analysis
is taken from a level, sloping, relatively dry mire -— with a higher
moisture content, however, than where the Nardus sociation grows,
and consequently C. nigra is mostly absent here. Otherwise the
sociations have many species in common, and it is hard to draw
a distinct line between those two sociations. Nothing can be said
about distribution, apart from the fact that it occurs in many
places in the West fiords, but usually only in small areas.
a. 2. Carex rariflora mýri — Caricétum rariflorae
Nothing specific is to be stated about this association. It has been
found exclusively in the highland, where it is, however, infrequent.
Possibly it should be regarded as part of the flói or even flæðimýri
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