The Botany of Iceland - 01.12.1945, Page 84

426
STEINDÓR STEINDÓRSSON
a marked southward exposure the association is slightly mixed with
scattered individuals of Geranium or Alchemilla minor. Analysis XII, 2
differs somewhat from the others, showing a particularly high Anthox-
anthum odoratum frequency number. This analysis was taken on
Síðumannaafrjettur c. 400 m above the sea in a belt in the upper
part of the snow-patch, at whose bottom association 9 alone prevailed.
g. Salix herbacea-Ass. (Tab. XI. A-B, 7, XII. A-B, 3-6).
On the higher parts of the mountain sides Salix herbacea is the
dominant species of the snow-patches, as a rule, however, it is mixed
with other species. Often the vegetation is not closed, patches which
are either entirely bare or covered only with a grey Anthelia crust
occurring among the phanerogams. Thus two kinds of associations are
met with in the highest-lying snow-patches or in such in which the
snow-covering is especially long-lasting, viz. the Salix herbacea' associa-
tion and the Anthelia nivalis association. The dominant species occur-
ring in these snow-patches in company with Salix herbacea vary some-
what according to the locality, none of them being of constant occur-
rence. The most frequent are Festuca rubra, Poa alpina, and Phleum
alpinum, which, however, always have a very low degree of covering
in spite of high frequency numbers. In addition Polygonum viviparum,
Equisetum arvense, E. variegatum, and Armeria vulgaris occur, but
none of these species are conspicuous physiognomically or in degree of
covering, whereas Gnaphalium supinum, Cassiope hypnoides, and Sib-
baldia procumbens are often character species in company with Salix
herbacea; however, Sibbaldia is, as a rule, less frequent at great alti-
tudes. Furthermore Epilobium anagallidifolium is often met with in
considerable numbers in this association, though it is little conspicuous
in the available analyses.
The biological spectra of the association show a high A percentage,
almost like those of the shrubby heath. The Ch and H percentages
vary somewhat. These two life-forms dominate altemately according
to what species are dominants together with Salix herbacea. It would
be most natural, it is true, to erect here several Salix herbacea associa-
tions, but my analyses were too few and too much alike, so I will refrain
from doing so. I do not doubt, however, that continued investigations
of the snow-patches will render this necessary.
Analyses XII, 3 and 5 are from Geldingsá, taken at an altitude of
c. 650 m. Analysis XII, 5 shows a transition to the Anthelia crust. The