Rit (Vísindafélag Íslendinga) - 01.06.1975, Page 120

meadows and this may be a contributing factor in their different
vegetation forms.
68. Equisetum palustre — C. nigra — Agrostis tenuis sociation
(Tab. XV A-B 8-11)
As stated earlier all the observations of this sociation emanate
from meadow tracts. This may provide the explanation for the
increased occurrence of gramineous vegetation; in fact 68 and 69
would be one and the same sociation if it was not for the effect
of haymaking. This sociation is in fact widely distributed in mea-
dow mires all over the country, but the only available observations
are from Flói, Landeyjar and Vopnafjörður. Together with 69 this
sociation has close affinity with the C. nigra — Equisetum palustre
sociation (46) but it grows on drier ground and the mounds are
generally coarser. The species are fairly nmnerous, but generally
fewer than in the C. nigra mire. The reason for this is not clear,
but it may be caused by the fact that in this case the difference
in vegetation between mounds and hollows is less pronounced than
it was there, so that some of the hygrophilous species of the C. nigra
mire are absent here. The soil is not dry enough, however, to con-
stitute a favourable environment for the dry-ground species proper.
Apart from the character species the following are most prominent:
Agrostis canina, Festuca rubra, F. vivipara, Calamagrostis neglecta,
and in places Poa pratensis and Deschampsia cæspitosa and in 8
Anthoxanthum odoratum. Cardamine pratensis and Luzula multi-
flora are also high in frequency.
The biological spectrum shows a very high E percentage, Ch has
practically disappeared and H is the dominant lifeform. Nothing is
to be stated about topography and the general conditions beyond
what emerges in the general description of the association.
Analyses 8 is unique in some respects. It was made near a
river bank at Hof in Vopnafjörður. There the mounds are smaller
than elsewhere in this sociation and the ground is exceptionally
dry. This vegetation type is very common all over the country
where the topography is similar and it may be regarded as a kind
of transitional form to Equisetum grass field which often occurs on
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