The Botany of Iceland - 01.12.1930, Blaðsíða 47

STUDIES ON THE VEGETATION OF ICELAND
37
where the freshwater vegetation is not represented at all, while the
hot springs have another maximum liere.
In a subsequent chapter I shall return to the vegetation spectra
given in table 8. In this connection it will sufíice to point out that
it is probably the same forces, viz. differences of tempe-
rature, which have been active in the formation of the
Icelandic types of vegetation which have determined the
floristic differences of the altitudinal zones.
The factors especially causing differences of temperature in a
given area of Iceland are partly diíferences witli respect to the
amount of snow and partly differences witli respect to the amount
of water. Hence the first task of an analyst of plant formations,
after an examination of the vegetation at various heights above sea
level, will be to investigate the influence on distribution of these
two factors, and by this means attempt a grouping of the Icelandic
types of vegetation.
In the two succeeding chapters I shall therefore give a more
detailed account of the results I arrived at on analysing the forma-
tions on a journey in Iceland in the summer of 1925. In yet
another chapter the influence on the vegetation of ditferences in
snow-covering and the moisture of the soil will be more thoroughly
discussed, and finally the results thus gained will be utilised in
setting up the types of Icelandic vegetation which have, up to the
present, heen more thoroughly investigated.
An analytical study of the formations has hitherto been carried
out in 4 different places in Iceland, viz. on Lýngdalsheiði in Árness-
svsla in the south country, partly at c. 100 m above sea level, and
further at c. 250—300 m and c. 400 m above sea level; on Arnar-
vatnsheiði near Úlfsvatn in the highlands northwest of Langjökull
at c. 500 m above sea level; in the valley bottom at Lækjamót in
Viðidalur in the north country, and in the valley bottom at Norðtunga
in Borgarfjörður in the south-west country.
The investigation was carried out by means of Raunkiær’s
circling method. With a few exceptions, 25 random samples from
eacli locality, each of Vio sq. m., were analysed. I have not thought
it appropriate to take into account other methods of analysis, partly
because those which could here be considered are of a later date
than Raunkiær’s circling metliod and to a cerlain extent resemlile
it, partly because, from a scientific point of view, they must be re-
garded as retrograde. Up to the present, Raunkiær’s circling