Rit (Vísindafélag Íslendinga) - 01.06.1975, Page 154

ber of species occurred there than at Skógar and herbaceous plants
were more frequent, e.g. Ran. acris and Trifolium repens. Here the
roots were not penetrated by sand.
93. J. balticus — Festuca rubra — F. vivipara sociation
This sociation is closely related to sociation 87, since it was ob-
served on the same location. In fact, it might possibly be more
properly regarded as a váriant thereof. Moss is less abundant than
in sociation 82, the vegetation cover is denser and the soil moister.
The principal difference between those two sociations is the in-
creased occurrence of the Festuca species, particularly F. vivipara,
and the disappearance of Kobresia. This sociation might be regarded
as closely approximating grassfield, whereas 87 is unmistakably
most closely related to heath.
b. Juncus filiformis jaðar (Juncétum filiformis)
On certain locations J. filiformis becomes dominant in the jaðar.
This happens almost exclusively in areas where the mire tract is
adjacent to slopes with grassfield vegetation. J. filiformis sometimes
occurs, however, in small moist depressions within heath tracts
where the snow tends to linger, as may be gathered from the oc-
currence of Nardus stricta in such parts. The surface is flat. The
biological spectrum shows that here the number of species is below
average for a jaðar. A and H percentages are higher than usual
in jaðar areas.
94. Juncus filiformis — Carex nigra sociation
(Tab. XXI A-B 4-5)
Both the observations are made at Vatnsnes, Húnavatnssýsla,
but this sociation is generally the most common sociation of the
J. filiformis jaðar, and may be regarded as its typical vegetation.
The soil is usually fairly moist, above the average for jaðar, which
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