The Botany of Iceland - 01.12.1945, Síða 115

THE VEGETATION OF CENTRAL ICELAND
457
flats”, and I have therefore chosen to call it by the same name. I have
only examined the formation in two places, though it is not particularly
rare. It has developed in the same way everywhere, since it owes its
existence to the wind erosion. But it will only develop in places where the
soil is so damp that it is not swept away at once, and in the remains of
soil which are left some few plants will have time to take root. Accord-
ingly the formation is extremely unstable, and it is very doubtful
whether the plants will hold their own and spread over the clayey flat
or whether the erosion is continued and the remnant of soil with its
scattered vegetation will be swept away. However, this is a condition
which, as stated above, characterises all the formations of the fell-field.
The analyses given in Tab. XIX, 1-2 were made in a fairly large
area of flag in Sauðárdalur; probably it was made up of an old “flá”,
the soil of which had dried up and been partially removed. It was still
comparatively damp, but polygon crack systems had formed in the
driest parts of the surface. The vegetation is found in cushions or tufts,
most of them are very vigorous and seem rather to be increasing, though
they have to fight a hard fight against thc effects of the wind. No dead
plant parts are found in the tufts, while this is often the case when the
erosion is increasing. Dominant species are the grasses: Festuca
rubra, Deschampsia alpina, and Poa alpina; in addition to these Ceras-
tium alpinum is the only species of any importance. Analysis 3 was
made in a large area of flag situated in the highest part of the terrain
in Kringilsárrani. Its appearance resembles that of the flag in Saudár-
dalur, and like this it is probably made up of a dried up “flá”, rem-
nants of which are found in the outer parts of the flag. The species
occurring here are mainly the same as are mentioned above, only
Deschampsia alpina is even more conspicuous here than in Sauðár-
dalur; in addition small cushions of Arabis petraea and Cerastium
trigynum are found here. The soil is sandy, and near the margins of
the flag there occur growths of Equisetum arvense; as far as can be
seen, the vegetation is in progression.
The biological spectra show that the arctic species are in great
majority, which is no wonder, since we are here concerned with high-
lying and rather exposed localities. On the basis of these analyses we
cannot say definitely which life-form is dominant, for Ch and H show
alternately the highest percentage. However, if we consider the degree
of covering of the species and the physiognomy of the vegetation, H
will, no doubt, be the dominant life-form.
Molholm Hansen says that the flag vegetation is “peculiar
The Botany of Icland. Vol. III. Part IV.
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