The Botany of Iceland - 01.12.1945, Side 35

THE VEGETATION OF CENTRAL ICELAND
377
or association fragments. The reason of this is i. a. to be found in the
fact that it is the first time, except for my investigation of Melrakka-
sljetta (Steindórsson 1936), that the Icelandic plant communities have
been investigated from this point of view; I realised this during my
work, for at first I attached no great importance to the investigation
of the individual associations.
For practical reasons, for the sake of clarity and especially in
order to maintain the connection with earlier researches, I group the
associations in formations; in the definition of these both the life condi-
tions and the general physiognomy are taken into consideration. The
formations are defined here in accordance with F r i e s (1913, p. 48) :
“Die Formation ist eine Zusammenfassung von einer Anzahl Assozia-
tionen ohne Riicksicht auf die floristische Zusammensetzung. Die For-
mation wird durch eine physiognomische tlbereinstimmung beziiglich
der verwaltenden Lebensformen charakterisiert”. B r a u n-B 1 a n q u e t
(l.c. p. 261) defines the formation in almost the same way.
In his paper (1930) H. Molholm Hansen makes a first at-
tempt at a complete definition of the most important plant communities
of Iceland, which he groups in a system in which the formations are ar-
ranged according to their snow-covering in the winter and the moisture
of the soil. Molholm Hansen says as follows: “The low tempera-
ture in winter being the factor which has the greatest bearing on the
vegetation, a natural system of the Icelandic types of vegetation, i. e. a
system in which the factors are given in the order of their degree of
importance for the vegetation, must give as the first principle of division
the conditions of snow-covering, as the next the conditions of moisture
and so forth” (l.c. p. 178). In this connection I may point out that
Molholm Hansen deals with the whole country en bloc, though
considering especially the lower regions, while in the present paper I
treat exclusively the central highland, and my investigation is almost
exclusively restricted to regions situated 500 m or more above the sea.
As regards the names of the formations I here use mainly the same as
Molholm Hansen, since several of them have already long ago
been used by the other authors and are in accord with the natural
composition of the formations, and these names are likewise found in
the Icelandic language.
The subjoined table shows the agreement of the formations both
with the names used by Molholm Hansen and with the system
of formations erected by E. R ii b e 1 in his work “Pflanzengesell-
The Botany of Icland. Vol. III. Part IV.
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