The Botany of Iceland - 01.12.1914, Síða 54

238
THORODDSEN
In Iceland all which lies ahove 500 metres is a complete de-
sert; this is also true of great parts of all that lies between 300
and 500 metres; at this altitude there are, however, rather ex-
tensive bogs covered with Carices and Eriophorum, especiallv to-
wards the west (N. W. of Langjökull). Larger and smaller desert-
areas are also found lower down; in some places they extend even
to the sea, but in such cases tliey owe their origin to special cir-
cumstances — the destructive influence of glacier-rivers, volcanic
eruptions or blown sand. In many inhabited districts the greater
part of the surface consists of a rocky flat with scanty vegetation;
a dense plant-growtli such as that found in meadows, bogs and
heather-moors covers only a very small part of the entire surface
of the island, perhaps not more than 1500—3000 square km.; but
the amount so covered cannot be stated with any certainty. The
interior plateau owing to its height above sea-Ievel and its climatic
conditions will probably never be of any greater importance, as
regards the livelihood of the inhabitants, than it is at the present
time. Considerable tracts of the lower-lying parts of the plateau
(afrjettir), in spite of the very poor herbage, are used as summer-
pastures for the hardy Icelandic sheep which are driven up into
the mountains about the end of June and fetched home again in
the middle of September. No small percentage, however, of these
sheep perishes yearly by venturing too far into grassless wastes,
falling into rivers and down clefts, being ovei'come by snow-storms,
becoming a prey to foxes, etc.
The snow-line and the glaciei’s form the upper limit of plant-
growth; but from thence down to about 500 metres above sea-level,
individual plants usually occur widely separated; there are, there-
fore, virtually no habitations on the plateau. As the height of the
snow-line in the different parts of the island vai ies greatly, so similar
laws 'govern the occurience of the habitations, which are closeljr
associated with the plant-growth. The highest snow-line occurs in
north-east Iceland, and there the habitations also extend furthest
upwards. Three parishes are found on the plateau itself, viz. Mv-
vatnssveit at 300 metres above sea-level, Fjallasveit at 400—500
metres, and Jökuldalsheiði at 500—530 metres. In the last two
the number of the farmsteads and of the people has been subject
to very gi-eat fluctuations. The inhabitants of these parishes main-
tain themselves almost entirely by sheep-i-earing. In Mývatnssveit
the conditions are however more favourable, as it is situated at a