The Botany of Iceland - 01.12.1945, Blaðsíða 104

446
STEINDÓR STEINDÓRSSON
mainly found on Síðumannaafrjettur and Landmannaafrjettur, where
it is by far the commonest of the shrub heath associations; precisely
these areas, however, have a very abundant precipitation. On Snæ-
fellsöræfi it is also found in the dampest localities of the shrub heath.
On Brúaröræfi, the driest of all these regions, I did not notice it, and
I have my doubts as to whether it is found there.
The biological spectra of the association show a high A percentage,
which here attains its maximum in the shrub heath, whereas the Ch
percentage is relatively low. The G percentage is high and in this as-
sociation likewise reaches the maximum in the shrub heath, especially
in analysis XV, 7. The association is poor in species, and the density
of the species is inconsiderable.
Analysis XV, 7 was taken on the narrow belt of shrub heath found
along the river branches of Jökulsá on Eyjabakkar (see Fig. 7). On
one side this belt is bounded by the river, on the other side by a very
wet flói. The strip of heath is situated at a much higher level than the
flói, perhaps it should most correctly be referred to the jaðar, but on
account of the dominant S. glauca I have referred it to the heath.
Analysis XV, 8 is from Víðidalur, from a damp surface with abundant
moss in the ground vegetation; S. glauca is more vigorous here than is
otherwise the case in the Salix heath. Analysis XV, 9 is from the shrub
heath near Snæfell. Analyses XVI, 1 and 2 are from Kýlingar; they
show the most typical form of the dwarf shrub heath found on Land-
mannaafrjettur. The soil is more sandy than in the other localities in
which this association was observed; I assume, therefore, that it does
not favour sandy soil, which may be one of the reasons why it is not
found on Brúaröræfi. Analyses XVI, 3 and 4 are from Síðumanna-
afrjettur. Although these localities occur at a much lower altitude
above the sea than the other localities, there is no noteworthy difference
in the biological spectra except that the A percentage is slightly lower.
In analysis XVI, 4 S. lanata is so conspicuous that we might speak of
a S. lanata variant. Both analyses are from localities situated near slopes
resulting from wind erosion; I did not come across scrub on Síðuman-
naafrjettur under other conditions, and no other associations than this
one.
7. Salix glauca—S. lanata—Equisetum pratense-Ass.
(Tab. XVI. A-B, 5).
The association is represented here by this one analysis, made in
Kýlingar on Landmannaafrjettur. The association forms small patches