The Botany of Iceland - 01.12.1945, Blaðsíða 93

THE VEGETATION OF CENTRAL ICELAND
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vegetation or into the snow-patch vegetation, if not the fell-field is the
dominant formation on the particular mountain side. The surface is
almost without knolls; the only knolly heath encountered by me was
found near Laugar on Snæfellsöræfi. The snow-covering of the heath
is probably rather thin, it is no doubt thinner and of shorter duration
than those of the mýri series and the brekkur formation, though there
is some difference, which will be pointed out for the individual associa-
tions. Salix glauca and S. herbdcea are the dominant species all over the
dwarf shrub heath, especially the former; S. lanata is sometimes
dominant, otherwise it is rather common except on Snæfellsöræfi; that
it is rare there, is probably because the soil of the shrubby heath is
less sandy in this region than in other of the highland regions in-
vestigated; however, S. lanata has a predilection for dry sandy soil.
Where S. herbacea is very prominent, it is often difficult to distinguish
between the dwarf shrub heath and the snow-patch formation. On
the other hand this species often forms a kind of ground vegetation in
the dwarf shrub heath. In a few places Salix phylicifolia is the dom-
inant species, especially near brooks or springs. In such cases we
might perhaps more correctly speak of scrub than of heath, for under
these circumstances S. phylicifolia may attain a height of 50-75 cm.
Otherwise the shrubs in the dwarf shrub heath are very low and
prostrate, both the Salix species and Empetrum, which is sometimes
the dominant species. Both on Landmannaafrjettur and on Brúaröræfi
the soil of the shrubby heath is very sandy; this affects the ground
vegetation, which, where the soil is sandy, is very poor, consisting only
of some few scattered mosses. Where the soil is less sandy, as on Snæ-
fellsöræfi and Síðumannaafrjettur, there is a fairly luxuriant ground
vegetation of both mosses and lichens, the lichens, in particular, are
very conspicuous in several places on Snæfellsöræfi, so that here the
formation approaches a lichen heath. The layer of sandy soil of the
shrubby heath may be very thick. This could be observed in several
places where the wind had removed parts of the heath. The eroded
slopes might be several metres high.
The lowland formations most closely related to the shrubby heath
are the mó and the Saiix scrub. As already mentioned, the mó vegeta-
tion differs from the shrub heath by its very knolly surface and by the
rare dominance of Salix. In the lowland the Salix scrub is richer in
species than in the heath, and the individual shrubs are much taller
and more vigorous. The dwarf shrub heath is a formation which is
found exclusively in the higher regions.