Rit (Vísindafélag Íslendinga) - 01.06.1975, Page 91

48. C. nigra — E. palustre — Salix glauca sociation
(Talj. XI A-B 1-4)
This sociation was only investigated in the highlands where it
is, however, comparatively rare and only occurs in a very special
kind of environment, almost exclusively in the lower highland
regions. It may be regarded as a highland sociation corresponding
to sociation 46 in the lowlands. The sociation occurs where the
ground is somewhat sloping, moderately moist, often with small
knolls or practically even. Apart from the character species, C.
Bigelowii, C. rariflora and sometimes Vaccinium uliginosum are
rather conspicuous.
The biological spectrum shows a higher E percentage than usual
in the highlands which indicates some connection with the lowland
mire. G is the dominant lifeform, but the Ch percentage is every-
where considerable higher than in lowland mire sociations.
Analyses 1 and 4 are from Fagridalur in Brúaröræfi at an alti-
tude of about 600 m above sea level which is unusually high, but
it should be noted that the area is particularly sheltered and the
valley or its vegetation is in many respects similar to the lowland
flora. The land slopes considerably and the surface is mostly even.
Analysis 4 differs with respect to E. palustre which disappears,
this being a clear transitional form to Salix heath.
Analyses 2—3 are from Síðumannaafréttur (at an altitude of
about 400 m) where the sociation is relatively extensive, but the
environment resembles Fagridalur, although this area is less shel-
tered. I have not elsewhere investigated this sociation where it is
widely distributed.
49. C. nigra — Scirpus cæspitosus — C. chordorrhiza sociation
(Tab. XIx 8-11)
Observations of this sociation originate from Borgarfjörður and
Snæfellsnes where the sociation is extensive, but this generally
applies in areas where Scirpus cæspitosus occurs to any great ex-
tent. The sociation is an intermediate stage between the C. nigra
mire and the Scirpus mire to be described later. The surface is
usually characterised by low, flat knolls. The moisture of the soil
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