The Botany of Iceland - 01.12.1945, Blaðsíða 32

374
STEINDÓR STEINDÓRSSON
At the same time the rainfall on Kirkjubæjarklaustur was a little less
than half that amount.
Landmannaafrjettur, also, has no doubt a humid climate, though
it is probably somewhat drier than at Síðumannaafrjettur, as the moun-
tain ranges to the south of it doubtless reduce the amount of rain to
some extent. The vegetation here is also more xerophytic than on Síðu-
mannaafrjettur.
C. S n o w-c o v e r i n g.
In close connection with the precipitation mention should be made
of the snow-covering, but here we have to guess to an even greater
extent than in the case of the other climatic phenomena. Climatic Table
II shows the mean duration of the snow-covering in Möðrudalur, viz.
from October 3rd to June 7th. It should, of course, be borne in mind
that at this season there are often longer or shorter periods when the
ground is free from snow. However, we must assume that farther to-
wards the interior of the highland the snow-covering lingers still longer
than in Möðrudalur. On the other hand the comparatively slight pre-
cipitation on Brúaröræfi will bring about that the snow-covering will
not be particularly thick unless the landscape shows special features.
Nevertheless the relatively permanent snow-covering in the highland
will to some extent smooth out the difference in temperature between
summer and winter for the soil and the vegetation. As a rule the snow
falls before the soil freezes and does not melt away till the spring.
Nevertheless the soil is frozen to a considerable extent often till far into
the summer; thus at the beginning of August I have observed frozen
soil to a depth of 10-20 cm in places which cannot possibly be free of
snow in the winter. On Snæfells- and Lónsöræfi the snow-covering is
no doubt thicker than on Brúaröræfi; the same is probably the case
on Landmannaafrjettur.
D. W i n d s.
Winds must be very frequent in the highland as in other parts of
Iceland. They must be extremely violent on the extensive open plains
of the highland. One can hardly speak of a prevalent direction of the
winds, for they always blow very irregularly. The direction of the wind
appears distinctly from the aforementioned erosion and the destruction
of the vegetation, mostly in connection with the sand drift. Vast tracts