The Botany of Iceland - 01.12.1945, Side 69

THE VEGETATION OF CENTRAL ICELAND 411
of a lowland character was found except on the banks of the brook
flowing from the spring. However, these springs are not as hot as those
on Landmannaafrjettur (c. 43°C. as against 72°C.). Moreover, the
Laugar at Snæfell are unsheltered, and the snow-covering does not
exceed the norrnal. These two examples show that a considerable heat
of the soil is required if it is to exert any actual influence on the vegeta-
tion of the surrounding area.
b. TheBrekkur Vegetation (the vegetation of the hillsides).
The formation to be dealt with here is very similar to that of the
grass field. It is found on dry ground, and its surface is without knolls;
the vegetation is closed, and Gramineae or gramineous plants dominate.
Nevertheless I have chosen to record it as a separate formation on ac-
count of the nature of the surface; the surface always slopes, at times
showing a very considerable inclination. It is almost exclusively found
on the lower parts of the mountain sides, particularly where these have
a southward or eastward exposure. Higher up the phanerogamous vege-
tation is more scattered, and the brekkur vegetation passes into the
Grimmia heath. The difference between the phanerogamous vegetation
of these two formations is inconsiderable, but in the Grimmia heath
the phanerogams present are much reduced in number by the Grimmia,
so that the “Feldschicht”, which is entirely closed in the brekkur vegeta-
tion, is very open here. The distinction between these formations is
mostly fairly sharp. The brekkur vegetation has not, as a rule, a partic-
ularly thick or long-lasting snow-covering, so in that respect it differs
greatly from the snow-patch formation, which is often found in grooves
and depressions in the brekkur vegetation. Of all the formations of
the meadow series, the brekkur formation as a rule exhibits the thinnest
snow-covering.
The brekkur formation is rich in species, and the density of the
species is comparatively high considering the height above the sea. How-
ever, there is a considerable difference in these features according to
the situation, altitude, and exposure of the individual localities, which
will be explained in more detail under the description of the individual
associations. The A percentage is generally fairly high, relatively higher
than in the mýri and the heath series, but is still subject to considerable
fluctuations. H is the dominant life-form, though Gh is more prominent
in some few associations. Within the meadow series the brekkur vegeta-
tion shows the highest A and Ch percentages.
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