Rit (Vísindafélag Íslendinga) - 01.06.1975, Page 105

ciation is very widely distributed in these parts on hillsides and
mountain slopes. Analysis XIIIx. 5 is from Húsafell in Borgar-
fjörður at an altitude of approximately 300 m above sea level
where the ground is dry with such an abundance of moss that it
covers almost 50% of the surface and the sociation is widely dis-
tributed in this area.
58. C. Bigelowii — Salix glauca sociation
(Tah. XÍII A-B 1-5 and Tab. XIIIx A-B 6)
The observations originate in Gnúpverjaafréttur, Kringilsárrani,
Bárðdælaafréttur and at Ketilsstaðir in Jökulsárhlíð, or the south-
ern, northern and eastem part of the country at varying altitude.
It is often difficult to distinguish this sociation from the previous
one. Furthermore, it is often barely distinguishable from heath.
Apart from the character species the following are most important:
Equisetum arvense, E. variegatum, Polygonum viviparum, Salix
herbacea, Empetrum hermafroditum, Thalictrum alpinum, and
Vaccinium uliginosum. Salix glauca is not always noticeable in fre-
quency, but it is most conspicuous in physiognomy of all species
with the exception of C. Bigelowii. C. rariflora only occurs in few
places, the land being drier than its proper surroundings. The bio-
logical spectrum is similar to that of 57, but the H percentage is
sometimes higher. The geography resembles that of sociation 57.
Yet the ground is generally somewhat damper here, sometimes
almost as moist as in the C. Bigelowii — C. rariflora sociations.
The surface slopes, but less so than in 57 and the mounds are gen-
erally finer. Analysis 5 is in some respects unique. It is from
Gnúpverjaafréttur on a narrow strip of land, between the bed of
a brook and Eriophorum flói. The sociation invariably occurs in
these parts where the geography is similar to that described above.
The land is coarse patterned and so dry as to approximate heath.
Rhacomitrium, however, is insignificant. Festuca rubra and Poa
alpina are so conspicuous in the vegetation that they approach the
frequency of C. Bigelowii. Patches of this kind are much sought
after by sheep and can often be spotted from afar by the flocks
grazing there. These patches, therefore, tend to become overgrazed
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