Rit (Vísindafélag Íslendinga) - 01.06.1975, Side 131

way confined to mire borders. The ground is fairly mound-pattemed
where the observation was made and there was some vegetation
difference between mounds and hollows. But I have also encoun-
tered it in mire strips with an almost flat surface where it is often
mterspersed with patches of C. nigra mire. In earlier times these
patches were used for haymaking, hut if the grass was not mown for
several years in succession, Betula would extend into the C. nigra
mire. Consequently C. nigra meadow tracts which one would have
encountered 50 years ago, intermingled with the B. nana mire,
have disappeared by now as all haymaking there ceased decades
ago. People knew from experience that if patches of the shrub-mire
were mown, B. nana would disappear and the meadow areas were
enlarged. Grazing did not appear to affect the B. nana mire and
it was in fact regularly used for such purposes especially in winter.
Flæðimýri — Alluvial mire
Caricétum Lyngbyei
The third formation of the Icelandic mýri and flói areas is the
flæðimýri. It differs from the other two, flói and mýri in vegetation,
but more particularly with respect to formation. The flæðimýri ap-
pears exclusively in watery tracts, especially near estuaries where
nvers flow into fiords and fill them up with deposits. They may,
however, appear wherever the river current loses strenght to such
an extent that sand and clay begin to form bottom sediment, but
fhis process prepares for fhe formation of flæðimýri.
The sand deposits accumulate to form mud-flats, so low at first
that they are invariably submerged by the high tide if formed
near the sea, but farther inland they are flooded whenever the
river is swollen. Each flood or tide, however, adds fresh material
the mud-flat or sand-bar. Finally it begins to rise out of the
Water; soon the first plants take root and bit by bit the land col-
Iects a continuous vegetation cover. Usually this vegetated land,
the flæðimýri, is so low that it is flooded whenever the river is ex-
ceptionally swollen. Although the river banks grow higher as they
Usually do and thereby prevent prolonged direct inundation it is
nevertheless true to say that the water level of the flæðimýri rises
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