Rit (Vísindafélag Íslendinga) - 01.06.1975, Blaðsíða 23

flat, which means that sizeahle stretches of flói do not occur on
slopes except on terraces of varying width. The flói is therefore
usuaHy associated with valley bottoms and the open lowland plain
districts where flói areas often cover extensive stretches of land,
■which, however, is often rent hy ridges and hills. The most exten-
sive areas of flói in Iceland occur therefore in the lowland of
Southern Iceland, e.g. in Landeyjar, Holt, Flói and at Skeið, and
they extend through Borgarfjörður and Mýrasýsla all the way
westward to Snæfellsnes. In Húnavatnssýsla, Skagaheiði and Mel-
rakkaslétta there are great continuous flói areas, not to mention all
the lower part of Fljótsdalshérað. There are also extensive flói areas
covering the lower moors of the highland, which are nowhere as ex-
tensive as in the district hetween Borgarfjörður and Húnavatnssýsla.
At higher altitudes the flói areas merge into tundra moors, which
are a certain type of mire intertwined with dry mound vegetation.
Apart from these biggest flói districts, such flói areas occur almost
throughout Iceland, although their coverage is often small in area,
since the landscape does not allow flat mires.
Surface, mounds: As already mentioned, the surface of the flói
is mostly level. If mounds occim there, they are few and sparse,
but they can often be quite large. Their vegetation often differs
from that of the surrounding flói, shrub growth in particular is
common thereon e.g. Betula nana, Yaccinium uliginosum, Em-
petrum and Salix varieties. Here we do not distinguish between
Empetrum species, hut usually it is the Empetrum hermafroditum.
Few examples show more clearly how the ground-water level de-
termines vegetation in the mire, since there is hardly any other
difference in biological conditions than the greater depth to the
ground-water level under the surface of the mounds. The flói
mounds are often formed because they are located in the shallowest
Icacts of the flói or they develop where some extraneous materials
have been deposited in the flói enabling small shrubs to take root.
These have then heaped up extraneous material thus enlarging the
mound. Where there is a slight gradient in the flói area, ■—■ it can
be so slight that it is not detectable unless it is surveyed —, mound
ridges often develop which can be at right angles to the slope direc-
úon. Such ridges are well known in the mires of Scandinavia, and
they vary in size and even shape. These mound ridges however,
23