Rit (Vísindafélag Íslendinga) - 01.06.1975, Page 77

Of all the sociations of the Cyperacé mýxi this one, together with
the next one, is most closely related to the Eriophormn flói, and
it is often, as a matter of fact, a moot point where to draw the
separating line between them. The topography of the mýri is the
determining factor in this context. It always slopes, although the
slope is at times negligible. The two most common species here are
the same as in the flói of E. angustifolium and C. nigra, but the
relationship between them here is reversed. Thus C. nigra is domi-
nant in physiognomy and often in covering also, although not
always. E. angustifolium is always sterile here, which is the reverse
of the flói, where it is always more or less fertile. Constant species
in this sociation are Calamagrostis neglecta, Cardamine pratensis,
Festuca rubra, Polygonum viviparum, Luzula multiflora, fairly
common are: Vaccinium uliginosum, Comarum palustre, Thalic-
trum alpinum, Festuca vivipara and Galium pumilum. In analyses
from the Flói, 1-3, Agrostis tenuis and Filipendula ulmaria are
constant species, and in parts F. ulmaria is dominant. It may be
regarded as a character species of many mýri tracts in the southern
part of Iceland, particularly where no harvesting took place. In
the northem part of Iceland it also occurs in C. nigra mýri.
The sociation is rich in species, although there is quite a differ-
ence between lowland and highland areas as the Table indicates.
Some disorder is in the biological spectrum, which may in part
be due to the fact that the analyses are made in different parts of
the country. As a whole E percentage is high. H percentage is also
quite high, except for analysis no. 7, where it drops considerably
at the same time as Ch percentage increases significantly, which
may generally be regarded as a characteristic of highland mýri,
i.e. that they show a fairly high percentage of Ch. The analysis
mentioned reveals a transition towards C. nigra — Salix glauca
sociation 48, Tab. XI. 4, but E. angustifolium differentiates be-
cween them. In other respects, both as to species composition and
biological spectrum, there is a relationship with E. angustifolium
•— C. nigra sociation of the flói as described above.
This sociation occurs in a rather wet, usually slightly sloping
mýri, i.e. where the topography bears the slightest deviation from
the flói. Where it is wettest there is a heightened HH percentage.
The mound pattern is often considerable with some vegetation dif-
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