The Botany of Iceland - 01.12.1945, Blaðsíða 53

THE VEGETATION OF CENTRAL ICELAND
395
3. Carex rigida-Ass., rich in Salix.
(Tab. V. A-B, 1-3; Tab. IV. A-B, 6; Tab. VI. A-B, 3).
This type of mýri is distributed over Snæfellsöræfi and the eastern
part of Brúaröræfi. It was not found on Landmannaafrjettur, but on
Síðumannaafrjettur. As shown by the tables, the composition of the
species varies somewhat. Thus Eriophorum polystachyum is prominent
in V, 1-2, where we might speak about a variant rich in Eriophorum.
Salix herbacea is lacking in IV, 6, but is otherwise conspicuous. The
total of points of the Equisetum species varies here. In spite of this
difference there is no doubt that we are here concerned with the same
association. C. rigida is the dominant species in every respect, both
physiognomically and in regard to degree of covering; the Salix species,
also, occur in considerable numbers, though the proportion between
S. glauca and S. herbacea varies somewhat. Polygonum viviparum is
likewise an important species and occurs fairly regularly. The moss
vegetation is abundant; this applies both to the commonest mýri mosses
and to Sphagnum, and even some Grimmia may be found in the
largest cushions. The association is found on the same kind of soil every-
where. The surface is very knolly, somewhat inclined, and comparative-
ly dry. Some difference in the vegetation is traceable on the knolls and
in the depressions, but it is not so great that two associations can be
distinguished. The mosses, in particular, are most abundantly re-
presented on the knolls, while the phanerogams grow more scattered
than in the depressions. As far as I can make out, this mýri type in
the highland is a substitute for the Carex Goodenoughii mýri in the
lowland. The A percentage here exceeds the E percentage. G dominates
among the life-forms, and the Ch percentage is very high. Analyses V,
1-3 were carried out in different places on Snæfellsöræfi, where the
association is extensively distributed both along the eastern side of the
Snæfell mountain range and on the vast Jökuldalsheiði. AnalysisIV, 6 is
from Kringilsárrani, where the association is met with here and there.
Analysis VI, 3 is from Síðumannaafrjettur, where the association oc-
curs occasionally, but without spreading over large areas. It would seem
that a fairly considerable inclination of the surface is an indispensable
condition for the occurrence of the association. Molholm Hansen
describes the same type of vegetation from Amarvatnsheiði (1. c.
p. iii ff.). Closely related communities in the neighbouring countries
seem to be Salicetum herbaceae muscosum in Greenland (Böcher 1933,
p. 101) ; furthermore, the C. rigida myr in Jotunheimen with a fre-
27*