The Botany of Iceland - 01.12.1930, Side 167
STUDIES ON THE VEGETATION OF ICELAND
157
Table 31. Agreement in Variation of Biological Spectra aud Species
Group Spectra (cf. Text).
Ch I H PhKTh A A 3 A2, A1, E4 E 3+2+1
% */. | °/o °/o °/o »/o °/o
1. N. Greenland a 35 50 15 » » » »
Iceland b 15 52 33 » » »
Denmark c 3 50 47 » » »
2. Iceland, 8—1200 m. above sea a 00 53 13 80 58 38 5
— 3—800 m b 21 53 20 52 20 49 31
— 0—300 m c 15 52 33 40 15 41 44
3. Vestfirðir, 4—500 m above sea.... a 43 50 7 93 50 50 »
— 2—300 m b 31 51 18 68 27 56 17
— 0—100 m c 17 52 31 41 15 47 38
4. Snow-bare vegetation Vestfirðir.... a 37 52 11 71 32 54 14
Normally snow-covered vegetátion . b 24 55 21 50 13 55 32
Constantly snow-covered vegetation c 20 51 29 28 7 45 48
5. Snovv-covering class I a 47 41 12 72 48 47 5
— - ii b 34 50 16 60 35 51 14
— - iii c 27 58 15 1 34 20 36 44
direction; in all tlie spectra these two groups constitute about lialf
the material.
The effect of a change in temperature is thus the same
in both systems of indicators, but it is niost marked in
the species group system.
Hence, when we have elsewhere in this treatise employed the
species group and life form spectra when considering the external
factors prevalent in the formations, this is quite justiíiable; a spec-
trum, particularly a species group spectrum, will thus be an im-
portant guide in the determination of the external factors which
are of importance for the vegetation.
Variations in the density and number of species in the scale
of external factors bring to light interesting relations. In the 4 classes
of snow-covering I a, I b, II, and III, the mean density of species is
respectively 2.3, 6.8, 13.3, and 10.2, and tlie mean number of species
is 9, 24, 32, and 29; in the 7 classes of moisture the mean density of