Rit (Vísindafélag Íslendinga) - 01.06.1975, Blaðsíða 96

I have studied the C. Bigelowii mýri at an altitude of 180-200 m
above sea level, where the boundaries between highland and low-
land tend to occur at exceptionally low altitudes. It is my opinion
that when C. Bigelowii becomes dominant in mýri areas and con-
spicuous in grasslands one has reached the real boundaries between
highland and lowland vegetation.
The C. Bigelowii mýri is not uniform in appearance, but it is
usually characterised by the bluish-grey shades of C. Bigelowii so-
ciations which are dominant everywhere in its physiognomy. Usu-
ally C. Bigelowii is sterile in these mýri areas. It is generally rather
low and stocky, but taller and spindlier than where it grows in
drier areas. In the dampest mire it often resembles C. nigra. It is
probable that a cross-breed between those two species occurs, parti-
cularly in the lower-lying mýri tracts. The phanerogamous cover
is seldom continuous. Between the C. Bigelowii plants there occurs
low shrub growth: Salix herbacea, S. glauca, Vaccinium uliginosum
and even other species. There is often considerable moss. In the
driest parts Bhacomitrium is often conspicuous, so that it charac-
terises the vegetation cover to a certain extent. The surface is most
often pattemed, sometimes coarse-knolled, in which case the mýn
phases into a C. Bigelowii heath. If the knolls are large there is
always some difference in vegetation between the knolls and the
hollows. In this case Rhacomitrium, for example, always grows
on the knolls if it occurs at all. The moisture content is very similar
to the C. nigra mýri. The C. rigida mýri, however, never becomes
as wet as the wettest parts of the C. nigra mýri.
Peat formation is always insignificant, almost nonexistent in
parts, as is normally found in highland mýri tracts. There is often
sand in the soil and below it, both blown sand from adjacent ero-
sion and sand areas and fluvial sand. Water never becomes stag-
nant in the C. Bigelowii mýri which often slopes considerably.
Strips of C. Bigelowii along flói tracts can, however, he very gently
inclined, in which case they may be said to constitute a transi-
tional form to the Eriophorum flói, without a clear borderline.
Salix is always extensive in the driest parts of the C. Bigelowii
mýri, turning it into a Salix heath without a clear boundary. The
relationship hetween the vegetation covers is roughly indicated
on the accompanying sketch.
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