The Botany of Iceland - 01.12.1945, Page 41

THE VEGETATION OF CENTRAL ICELAND
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Molholm Hansen was the first of all botanists to make
statistical analyses of the vegetation of Iceland. Among others he an-
alysed the alpine flói vegetation of Arnarvatnsheiði at c. 500 m above
sea-level (Molholm Hansen 1930, pp. 111-114). The results of
his analyses can be compared with mine. But I think his concept of the
flói too narrow, and this is also H u m 1 u m’s opinion (1936, p. 69 ff).
The “plane Mýri” (level mýri) mentioned by Humlum and the
Carex rariflora-mýú mentioned by Molholm Hansen I refer
without reservation to the flói. My experience as to the occurrence of
C. rariflora differs essentially from that of M 01 h o 1 m Hansen, as
I have often met with this species in the dampest part of the flói as
well as in its drier places.
It is mostly assumed that the flói is only formed in depressions
whence the water cannot be drained. In the highland it is often formed
in inland deltas along rivers in entirely the same way as the Carex
Lyngbyei mýri in the lowland. Thus the largest continuous areas of
flói observed by me in the highland are found on Eyjabakkar and are
formed precisely in this way. Something similar is the case with the
flói in Kýlingar and in Jökuldalir. In these places the ground-water
is not quite stagnant; the surface slopes, though inconsiderably, in the
same direction in which the rivers flow. These areas of flói no doubt
belong to the “Fétmýri” according to MolholmHansen’s defini-
tion of the latter (1. c. p. 180). In another paper (Steindórsson
1936, p. 443) I have pointed out that the otherwise clear division of
the mýri series made by Molholm Hansen is very difficult to
maintain in practice when one examines the species composition of
the different formations. Thus the character species of the Fétmýri,
Carex Lyngbyei, sometimes occurs in the flói; on the other hand there
are areas, at any rate in the highland, which according to their develop-
ment and nature should indisputably belong to the Fétmýri as defined
by Molholm Hansen, which as regards its vegetation is indis-
tinguishable from the most typical flói. For these reasons I follow
Stefánsson and Jónsson in distinguishing only between the
two main types of the mýri series, viz. the flói and the mýri. Still it
would be convenient to mention as a subdivision of the flói what in
Icelandic might be called the “Flæðimýri”, which corresponds to
the German “Verlandungsmoor”, on account of its special mode of
formation along rivers and lakes.
A brief definition of the flói formation based on the descriptions
of earlier authors and on my own observations will then be as follows: