Rit (Vísindafélag Íslendinga) - 01.06.1975, Síða 36

-—- C. nigra sociation, which grew there on low mound ridges, but
in between in leyel tracts the E. angustifolium — C. chordorrhiza
sociation became predominant. The most common accompanying
species were C. nigra, C. panicea, Equisetum fluviatile and Scirpus
cæspitosus. Moss was almost non-existent, whereas it was abundant
in the Equisetum sociation on the ridges. Then there is another
observation from Orrastaðir in Húnavatnssýsla. There the topo-
graphy was such that a fairly large pond had dried up leaving a
flói where the bottom of the pond had been. Apart from the two
character species there also grew C. nigra, C. rariflora, C. saxatilis,
Calamagrostis neglecta, Equisetum fluviatile and Juncus alpinus.
The paucity of species was noteworthy. The soil was open in many
parts, so that it is possible that the flói area has not fully developed
from the open bottom of the pond.
The biological spectrum differs particularly from sociation no. 2
in its higher percentage of HH, as was to be expected since the
terrain here is wetter and the vegetative cover is widely disrupted
by small pools and ponds.
4. E. angustifolium — Carex saxatilis sociation
(Tab. I A-B 5-11)
This sociation is in every significant respect closely related to
the sociations above, especially 1-2. The main difference is that
Carex nigra has now ahnost vanished, but C. saxatilis is undisput-
ably dominant and it characterizes the sociation along with E.
angustifolium. Among other conspicuous species of this sociation
C. rariflora may be mentioned, although it is not constant, but fhe
sociation often lies close to the E. angustifolium — Carex rariflora
sociation. It always occws in wet areas and the surface is comple-
tely level.
Occasionally it merges into small patches with a pure C. saxa-
tilis sociation, particularly in the wettest areas, as will later be
described. The sociation is widely distributed throughout the coun-
try, but it seldom covers large tracts of land. Apart from Mel-
rakkaslétta I have hardly observed it to any extent except at a
considerable altitude, i.e. at about 200 metres above sea level. It
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