The Botany of Iceland - 01.12.1945, Blaðsíða 146

488
STEINDOR STEINDÖRSSON
drier than in the remaining part of the oasis. All the rústs are of nearly
the same shape, oblong or oval, but of somewhat different height, rang-
ing from 1 to 2 m. They lie almost in a line along the brook, turning
one end towards it. Water pools occur between the rústs. The intervals
between the rústs are of about the same breadth as the rústs them-
selves. When I visited the place on July 25th, 1937, only a layer c. 30
cm thick had thawed in the rústs, whereas no ice was found in the de-
pressions. The conditions of the vegetation were as follows: Nearest
the pools there was a zone (belt 1) c. 1 m broad in which Eriophorum
polystachyum dominated physiognomically, but mixed with this and
with a high frequency but a low degree of covering occurred Carex
rigida, C. rariflora, and Calamagrostis. The vegetation in this belt was
especially vigorous, in this respect differing greatly from belt 2. In belt 2
the surface exhibits small knolls, and C. rigida dominates physiognom-
ically, but in addition Scdix glauca and Carex rariflora are dominant
species. Belt 3 extends over the edge of the rúst and its lower part. The
vegetation is not continuous, but has open patches. Cetraria is con-
spicuous in the ground vegetation. Dominant species are Salix herbacea
and Cassiope hypnoides, but Pedicularis flammea, Polygonum vivi-
parum, Armeria vulgaris, and Empetrum are likewise of frequent oc-
currence. The vegetation accordingly has the character of a snow-
patch formation. The top of the rúst, belt 4, is a Grimmia heath. Grim-
mia is entirely dominant physiognomically, forming a slosed carpet
with scattered phanerogams, among which Salix herbacea and Empe-
trum nigrum dominate; otherwise the vegetation does not differ from
the Grimmia heath in general. The relation of the Grimmia heath to
the snow-covering is clearly shown here, since it is only found on the
highest tops of the rústs; as soon as a depression with a deeper snow-
covering is found in these, the Grimmia disappears.
If we consider the vegetation of the flá as a whole, its mosaic-like
appearance, which I have tried tö describe above will be remarkable;
however, in order to give a clearer picture, I shall review the most
important associations of the flá.
B e 11 1 does not differ noticeably from the remaining part of
the alpine flói formation. Three associations were found in the flá,
viz. the Eriophorum—Cdlamagrostis-associa.úon, which is the com-
monest, the Eriophorum polystachyum—Carex rigida-association, which
outside the flá is chiefly found in the dampest mýri, and the Calam-
agrostis—Carex Goodenoughii-association, which is also known from
the flói formation in other places, though it is of rare occurrence.