The Botany of Iceland - 01.12.1942, Síða 86
84
JOIIS. GRONTVED
higher plants may occur. The number of species and the development
attained by them seems more dependent on the local environmental
factors (exposure, soil conditions, precipitation, snow-cover, etc.) than
on the altitude.
A luxuriant herb-slope vegetation with a lowland character may be
found high up on the mountain sides in south-exposed spots with a fair
amount of moisture, while at a far lower level, on unfavourably exposed
and dry ground we may find only barrens nearly destitute of vegetation.
It is true that a number of lowland plants have an upper limit on
the mountains and on the plateau, but as yet this point has not been
subjected to special investigation.
Only very few highland species, on the other hand, can be said to
have a lower limit, inasmuch as most of the plants which grow near the
snow-line also thrive well near sea-level. As an example may be men-
tioned: Salix herbacea and Sibbaldia procumbens.
These two species are characteristic of the snow-patch vegetation
high up in the mountain, and also widely distributed near sea-level.
Many species, in their upward distribution in the mountains, seem
to have their upper limit determined by the snow-line only. The latter
is at its highest level in the central parts and descends to its lowest level
in the northern part of N.W. Iceland. In districts where the snow-line
is found at a lower level, the mountain species are also met with at a
lower level. Thus for instance Ranunculus glacialis occurs in N.W.
Iceland as far down as about 100 m above sea-level, while in S.W. Ice-
land it only descends to about 300 m.
Our knowledge of the upper, or lower, limit for each species in the
various parts of Iceland is, however, far too insufficient to allow of a
classification. Two papers published by Ingimar Óskarsson (1927,
p. 437 et seq.; 1938, p. 145 et seq.) contain a tabular view of the
altitude up to which the species occurring have been observed. The
first paper deals with the flora in a section of the Vestfirðir peninsula,
the other with the flora of Svarfaðardalur west of Eyjafjörður.
As “mountain-plants” (Hojfjældsplanter) the following have been
listed by Helgi Jónsson (in manuscript). As a rule these mountain-
plants do not, according to H.J., descend lower than about 300 m,
some, however, may occur between 100 and 200 m above sea-level,
and a very few species do not occur below 400 (500) m.