The Botany of Iceland - 01.12.1930, Side 139

STUDIES ON THE VEGETATION OF ICELAND
129
In the 4 moisture series examined so far, the life-forms show,
in the main, the same sequence.
If the biological spectra are based on species lists alone, we
get the same sequence.
This distribution must be regarded as more speciíic to the life-
forms than to conditions in Iceland.
In Denmark the vegetation of Norholm Heath has been ex-
amined with the same minute graduation of the external factors as
in Iceland. The sequence of the maxima of the life-forms in the
scale of moisture was the same on Norholm Heath (which, however.
had more than 7 grades) as in Iceland, viz. HH. G, H, and Ch
from below upwards. The rise in the Ch percentage in the lower
section of the scale is not found here, however; on the other hand,
there is a rise of the H percentage.
Raunkiær (1909,1912), C. Olsen (1914, 1921), and Grontved
(1927) examined the vegetation on solid soil exposed to the sun.
From their researches it will likewise appear that, if biological
spectra for tlie various (more diffusely limited) zones of moisture
are worked out on the basis of the circling results, the sequence will
he HH, G, H, Ch, and Th.
If biological spectra for the various zones of moisture from sunny
°pen solid soil were worked out on the basis of the species lists
alone, the sequence of life-forms was still seen to be the same.
The correlalion between moisture of soil and life-form pointed
°ut above must be said, therefore, to be generally valid. In con-
sidering the physical causes active in tlie formation of life-forms,
a knowdedge of this correlation is indispensable.
The Species-Groups. Their Distribution in the Scale of Moisture.
On the basis of particulars of the presence and quantitative
distribution of the individual species in northern Europe and the
adjacent arctic regions we liave, in a previous chapter, divided the
Icelandic llora into groups according to the temperature requirements
°f the species.
The ílora was first divided into twm large groups: the A group
v>’hich has its main distribution in arctic regions to the north ot or,
iu mountain regions, above, the tree limit, the 20 per cent Ch bio-
chore; and the E group which has its rnain distribution in the
The Botany of Iceland. Vol. III.
9