The Botany of Iceland - 01.12.1945, Side 73

THE VEGETATION OF CENTRAL ICELAND
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rigida, Equisetum variegatum, Deschampsia flexuosa, and Poa alpina,
but they do not occur constantly or all in company. The association
occurs at considerable altitudes, about 700 m or even higher. The
snow-covering is here much more long-lasting than in association 1,
which is manifested in a greater resemblance to the snow-patch forma-
tion. Thus the two character species are very common in the snow-
patches. The association is comparatively poor in species, and the
number of species varies according to the locality. The A percentage
is relatively high, the same is the case with the Ch percentage, which
here exceeds the G percentage, the reverse of what is the case in as-
sociation 1. The association forms the transition from the brekkur
formation to the Grimmia heath, the same dominating phanerogams
occurring here. It, or at any rate some variants of it, bears great re-
semblance to the snow-patch vegetation. However, we are not here
concerned with snow-patches in the usual sense, but in this connection
it should be borne in mind that at such great altitudes the snow will
settle in the early autumn and will melt later in the spring than in
lower-lying areas. Analyses 4-5 are from Hellisfell near Landmannahel-
lir, c. 700 m above the level of the sea. The conditions show that in
spite of the southward exposure the snow-covering is more prolonged
than is usual in the brekkur vegetation, and the soil remains damp till
later in the summer than is generally the case in the brekkur formation
so that snow-patch plants like Cerastium trigynum may thrive here.
Analysis 6 is from Kýlingur from about the same height as the preced-
ing one, but from a slope with a westem exposure. The analysis was
made on a ridge situated between two snow-patches. The slope was
intersected by more or less deep grooves, which extended down the
slope. A typical snow-patch vegetation is found in the grooves, while
the intermediate ridges are occupied by the brekkur vegetation, re-
presented in the lower parts of the slope by the Elyna Bellardi—Carex
ngiífa-association, while the present association occurs farther up the
slope. At the top Grimmia heaths are found. This zonation is very
distinct in several places. Analysis 7, finally, was made on a slope on
the mountain Sáta, at a height of c. 800 m. Here Carex rigida is dom-
inant, forming an almost entirely closed herb layer vegetation, while
its ground vegetation is formed by Salix herbacea. Grimmia is not
found in this locality, but otherwise the phanerogamous vegetation
agrees entirely with that of the Grirnmia heath,