The Botany of Iceland - 01.12.1945, Blaðsíða 124

466
STEINDÓR STEINDÓRSSON
5. Salix herbacea—Poa glauca-Ass. (Tab. XXI. A-B, 9).
The association is rather a variant of association 1 poor in Poly-
gonum viviparum. The arctic species attain their maximum in the
associations rich in Salix herbacea, or 95.7 pCt. The analysis was made
in Víðidalur, at c. 720 m. The vegetation was very scattered, and the
soil relatively damp owing to water seeping down the slope from higher-
lying snow-patches. Remarkable is the abundant occurrence of Ranun-
culus glacialis, since this species, as a rule, occurs in snow-patches.
Otherwise the association is a type of the melur vegetation on the
higher slopes of Víðidalur. No closed vegetation is found at this alti-
tude. The greater part of the surface is covered by gravel flats. In
damp depressions Philonotis cushions with a few Carex lagopina, Saxi-
fraga stellaris, S. nivalis, Poa alpina, Deschampsia alpina, and Ceras-
tium trigynum are found, in other words, a mixture of the dý and the
snow-patch vegetation. In some snow-patches there occur Salix her-
bacea, Gnaphalium supinum, and Sibbaldia procumbens. Ranunculus
glacialis is found everywhere, but not more abundantly in the actual
snow-patches than in the melur between them.
6. Silene acaulis-Ass. (Tab. XXI. A-B, 4-5).
The association differs widely in species composition from all the
preceding ones in that the two commonest species Salix herbacea and
Polygonum viviparum are entirely absent. Besides the character species,
Armeria vulgaris, Festuca rubra, Saxifraga oppositifolia, and Carex
incurva are of common occurrence. Both the analyses at hand are from
the vicinity of Hvannalindir. Analysis 4 was made near the oasis,
which is evident from the high frequency figure of Festuca rubra and
Calamagrostis. The locality is a plain which passes without any distinct
limits into a shrub heath. Analysis 5, however, was made farther away
in the typical barren highland melur. The vegetation tufts were very
scattered, and there was some sand-drift. I should think that this ana-
lysis gives the best picture of the highland melur as it is found over
the vast barren tracts. The biological spectrum shows that only arctic
species, even only of group A3, are reprensented in analysis 5. Ch is
the dominant life-form. Thus it may be established that exclusively arc-
tic plants, and mostly chamaephytes, are found on the most typical
highland melur.