The Botany of Iceland - 01.12.1945, Síða 98

440
STEINDÓR STEINDÓRSSON
conspicuous physiognomically or has a noticeable degree of covering.
On account of its tiny growth it might very well be referred to the
ground vegetation. The association is poor in species, it is present in
Arnardalur and Hvannalindir, where, however, it hardly ever forms
large continuous areas, but occurs interspersed in other formations,
especially in the jaðar formation, with which it is nearly allied. In
places where this association has been observed, the surface is knolly,
the soil is fairly damp and very sandy. Analyses 1-3 were taken in Ar-
nardalur, analysis 4 in Hvannalindir. The biological spectrum shows
low A and Ch perccntages as compared with other associations of the
shrub heath.
2. Salix glauca—Calamagrostis neglecta—Equiseium variegatum-Ass.
(Tab. XIII. A-B, 5-10).
The dominant species in this association, in addition to the three
character species, are Equisetum arvense, Polygonum viviparum, and
Salix lanata. Altogether P. viviparum is very constant in all the as-
sociations of the shrub heath. Analysis XIII, 10 shows a variant in
which E. variegatum is absent, but it bears so close a resemblance to
the other analyses of the association that I include it here; if it does
not belong to this, it forms the transition to the next association. The
association is fairly widely distributed in Fagridalur and Hvannalindir
and on Háumýrar. The surface is level everywhere, but the soil is fairly
damp. The Salix species dominate physiognomically and in regard to
degree of covering. The vegetation is hardly closed. The moss vegeta-
tion is conspicuous, especially in the variant just mentioned. The biolo-
gical spectra show high A and Ch percentages, but nevertheless Gra-
mineae are conspicuous.
3. Salix association rich in moss.
(Tab. XIII. A-B, 11-12; XIV. A-B, 7-8).
In this association mosses are so conspicuous physiognomically that
the land is almost more characterised by them than by the shrubs.
Consequently the phanerogamous vegetation is rather scattered. The
following species are the most conspicuous: Salix glauca, Calamagros-
tis neglecta, Carrex rufina, Juncus balticus, Carex microglochin, Fesiuca
rubrpn; in addition Equisetum arvense and Carex incurva are found.
Otherwise the analyses show a highly differing species composition.