The Botany of Iceland - 01.12.1945, Síða 122

464
STEINDÖR STEINDORSSON
commonest species are: Salix herbacea, Polygonum vivipfirum, Dryas
octopetala, Silene acaulis, Saxijraga oppositifolia, Poa glauca), Ceras-
tium alpinum, Festuca ovina, F. rubra, Luzula spicata, L. arcuata, and
Armeria vulgaris.
(Tables XXI-XXII, A-B).
A striking feature of the biological spectra is the dominance of the
arctic species. The analysis which shows the lowest A percentage has
69.6 and some few analyses show 100 per cent. of arctic species.
Comparing this with M 01 h o 1 m H a n s e n’s results from Arnarvatns-
heiði, we shall find that there the proportion A: E is 4: 1, while here
it is c. 6: 1. Thus my observations show a much higher number of
species and a much greater density than M 01 h o 1 m H a n s e n’s
observations from Arnarvatnsheiði. On the other hand there is good
agreement between the life-form spectra from both places. Ch is the
dominant life-form everywhere, and the H percentage is generally
higher than the G percentage. The Th percentage is inconsiderable,
only one therophyte having been noticed in the highland melur, viz.
Euphrasia latifolia. Thus the melur vegetation can be characterised
as consisting chiefly of arctic species and chamaephytes. I investigated
the following associations in the melur formation:
1. Salix herbacea—Polygonum viviparum-Ass.
(Tab. XXI. A-B, 2, 3, and 8; XXII. A-B, 3-5).
In addition to the character species the following species are the
most frequent in this association: Carex incurva, Calamagrostis neglec-
ta, Festuca ovina, F. rubra. The association, or some few variants of
it, is widely distributed in the neighbourhood of most of the oases in-
vestigated. It may be said to form a kind of transitional link between
the oasis entirely covered by vegetation and the barren highland melur,
though bearing more the character of the latter. Analysis XXI, 2 was
made in Fagridalur at an altitude of c. 600 m on a slope facing to-
wards the west. Analysis XXI, 3 was made on a level melur in Hvan-
nalindir, near a closed Calamagrostis association. The melur was damper
than is generally the case, and mosses were more conspicuous than is
usual in the melur formation. It is readily seen that a pioneer associa-
tion is trying to establish itself on the melur. Analysis XXII, 4 is from
Landmannahellir, altitude c. 620 m, taken in a slope with a southward
exposure. Analysis XXII, 3 was made on Stóri Kýlingur at an altitude