Rit (Vísindafélag Íslendinga) - 01.06.1975, Page 150

finely mound-pattemed, or practically even, but the jaðar invari-
ably has fairly coarse mounds as mentioned before. But the jaðar
vegetation here is probably formed because of similar conditionsj
particularly with regard to the humidity of the soil.
I have divided the J. balticus jaðar into 8 sociations on the basis
of the dominant accompanying species which characterise them
along with J. balticus. A large number of species is a feature they
all have in common. E group constitutes a majority, varying in
size, however, and Ch is usually absent. Th is insignificant, or com-
pletely absent.
86. Juneus balticus — Equisetum palustre — Carex nigra soc.
(Tab. XX A-B 1-10)
This is the most typical sociation of the Juncus jaðar and the
most extensive one as well. It either occurs in the traditional area
between mýri and heath, hardly ever adjacent to flói or flæðimýri
tracts, or it may cover more extensive areas as already mentioned.
J. balticus is always dominant in physiognomy, to such an extent
that the sociation can be distinguished from its surroundings at
some distance. The other character species, however, E. palustre
and C. nigra have the same covering, or even more. Moss is usually
abundant and Rhacomitrium occurs in the driest spots, particularly
in the south of the country. Common accompanying species which
are extensive in covering are: Calamagrostis neglecta, Festuca rubra
and Polygonum viviparum. Other species often attain considerable
frequency in individual analyses.
Analysis 1 Gilsá in Breiðdalur, 2 Berunes, S-Múl., 4 Skáli, Rang.,
and Nefsholt, Rang., are all from similar areas; i.e. a belt, a few
metres in width between mýri and heath or grassfield, similarly
10 from the headland of Vopnafjörður where the jaðar is adjacent
to a strand meadow, which in fact closely resembles a Carex nigra
mire; E. palustre is absent there. Analysis 3 from Lambafell, Rang.,
is from a river bank where E. palustre and C. nigra have a some-
what greater covering than J. balticus. Trifolium repens occurs
there which inter alia indicates affinity to the Equisetum jaðar.
Analysis 5 from Gunnarsholt, Rang. is made in a rather extensive
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