Rit (Vísindafélag Íslendinga) - 01.06.1975, Side 38

5. E. angustifolium — Carex rariflora — C. nigra sociation
(Tab. II A-B 1-2)
This sociation distinguishes itself from sociation no. 2 because
here C. rariflora is a dominant species. It could, however, he re-
garded as a variant of sociation no. 4, since C. nigra quite frequent-
ly occurs. Yet, it should be noted that this sociation occurs in drier
places than sociation no. 4. The surface is not quite level, and the
terrain resembles an intermediate stage between flói and mýri.
The only observations available are from Búlandsnes in Suður-
Múlasýsla. I am not prepared to make any assertion about how
common the sociation generally is, but there was quite a large
tract of land at the observation site. I think it likely that sociation
6, E. angustifolium — C. rariflora can frequently phase into this
sociation.
6. E. angustifolium — Carex rariflora sociation
(Tab. H A-B 3-21)
The above mentioned flói sociations have all been taken either
from lowland areas or the border between high- and lowland, and
therefore they are rarely found at an altitude of more than 300
metres above sea level. In this connection we might keep in mind
that Carex nigra, which is found in all of them and is often domi-
nant or a character species, hardly ever occurs above that altitude,
unless special conditions prevail.
This sociation is the most common one in the highland flói, but
it is also found in the lowland, although it is much rarer there and
never extends over substantial areas. Only two analyses, i.e. no. 3
and 4, are introduced here and they were taken in the lowland.
The sociation always occurs in the wettest parts of the flói, regard-
less of whether it covers large areas or small. In the lowland it
occurs in patches among the related flói sociations, or it phases
into Carex rostrata sociations. In the highland it often covers fairly
large areas e.g. at Kýlingar and at Eyjabakkar. The surface is
always level, but it sometimes has low undular formations or level
mounds. There is, however, no vegetation difference apart from
the possibility that C. rariflora might be slightly more sparse on
38