The Botany of Iceland - 01.12.1945, Blaðsíða 49

THE VEGETATION OF CENTRAL ICELAND
391
carpet. Cyperaceae dominate in most cases, but in company with them
there occur various Gramineae in large numbers, furthermore Equise-
tum palustre and several dwarf shrubs, of which Salix glauca is the
commonest in the highland mýri. The geophytes constitute the do-
minating life-form, but sometimes they may be surpassed by either
hemicryptophytes or chamaephytes. The southern species (the E-
groups) are not so conspicuous here as in the flói, and in many cases
the arctic species are in the majority. The mýri is described by earlier
authors in almost the same way as here. However, neither S t e f á n s-
s o n nor J ó n s s o n mention the abundant occurrence of shrubs.
Molholm Hansen (1. c. p. 180) defines the mýri vegetation in
almost entirely the same way as done here, but he does not seem to
have noticed that the H-percentage may at times be very high. I cannot
see the necessity of making the detailed division made by M 01 h o 1 m
H a n s e n, as I have explained above. The formation called mýri
here for the greater part corresponds to M 0 1 h o 1 m H a n s e n’s “Hal-
lamýri”.
It applies to this vegetation, as was already stated about the flói,
that the early descriptions were mainly based on the lowland types or
the mýri formation found on the mountain sides nearest the inhabited
regions. In the lowland there is, as a rule, a sharp boundary between
the mýri and the flói, but this is not the case in the highland. Moreover
it may often be very doubtful which associations should be referred to
the flói and which to the mýri, and this appears distinctly from the
descriptions of the individual associations. The alpine mýri is much
poorer in species than the lowland mýri and sometimes not by far so
knolly. The boundaries between this and the related formations, on
the one hand the flói, and on the other hand the jaðar and the shrub
heath, are very ill-defined. The main difference from the flói soil is that
the mýri soil is drier, and its surface, as a rule, lies slightly higher than
that of the flói and is mostly sloping.
Of the species which are nearly always found in abundance in the
lowland mýri but are absent from the alpine mýri, Carex Gooden-
oughii is the most important. This species, which is predominant over
vast areas of mýri in the lowland, is hardly found in the highland.
Here it has been replaced by other species as for instance Carex rigida,
Calamagrostis neglecta, and Salix glauca, while these species are very
rare in the lowland mýri.
Comparing the vegetation of the alpine flói with that of the mýri,
we can hardly draw other conclusions than that the two formations oc-