The Botany of Iceland - 01.12.1945, Side 145

THE VEGETATION OF CENTRAL ICELAND
487
itself is fairly dry, and the rústs are low, but support a scattered vegeta-
tion. The pools are inconsiderable. In the depressions, belt 1, grow
Calamagrostis and Eriophorum polystachyum. The whole rúst harbours
the same vegetation, so that no growths corresponding to belt 3 are
found, and belt 2 is not represented either. The dominant species of
the rúst, belt 4, are Empetrurn nigrum and Salices, notably S. herbacea.
Belt 4 of this rúst exhibits an exceptionally great number and density
of species. All the surroundings would seem to indicate that the flá is
drying up, without, however, any wind erosion setting in at the same
time.
Series 6 (Tab. XXV, 6) and 7 (Tab. XXV, 7 ; Fig. 20) are from
the western side of Kringilsárrani. The flá there differs from the other
areas of flá by occurring on a slightly inclined ground. Its uppermost
and lowermost parts are entirely dried up, but still the flá landscape
is preserved. The difference in the vegetation between the rústs and
the depressions is that the former are covered by a closed Empetrum
association, while Salix glauca dominates in the latter. The flá is
dampest in the centre of the area, where small pools occur, surrounded
by an Eriophorum polystachyum zone. The rústs are large and 2-3 m
high, with steep edges and are ali of very uniform extension. There is
no noteworthy difference between the vegetation on top of the rúst
and that on its sides, that is to say, there is no difference between belts
3 and 4. Series 7 was taken in this part of the flá (Tab. XXV, 7 ; Fig.
20). Belt 1 is here very poor in species, E. polystachyum and Calam-
agrostis dominate; belt 2, which is drier than belt 1, is mainly covered
with Salix glauca, Carex rarijlora, and C. rigida. In the driest part
of the flá the deepest depressions are occupied by this vegetation,
though, as a rule, nearly or entirely without C. rarijlora. This bert
here shows a greater abundance and density of species than is the case
in the other flás. Belt 4 here extends over both the top and the edge
of the rúst. Dominant species are Empetrum, Salix herbacea, and
C. rigida. In series 6, which is from the driest part of the flá, Dryas
octopetala dominates in this belt. The flá areas dealt with here are
situated at an altitude of c. 630 m.
Series 8 (Tab. XXV, 8) is frorn Eyvindarver. The oasis proper is
a fairly large stretch of mýr situated along Þjórsá. Its soil is undoubt-
edly largely made up of fluvial sand. Throughout the oasis there are
numerous lakelets and pools, but only in one place did I observe actual
flá formation, with well developed rústs and the associated vegetation
mosaic. It was situated along a small brook, where the soil was much