The Botany of Iceland - 01.12.1945, Blaðsíða 96

438
STEINDÓR STEINDÓRSSON
southern species. The mean A percentage of all the analyses is 66.16,
which, however, is a little lower than the A percentage of the whole
flora list from the areas in question. Within the species groups the
species are fairly equally distributed over the four northernmost groups,
viz. the three A-groups and E 4, which agrees fairly well with the flora
spectrum.
The life-form spectrum is fairly equally distributed over the Ch,
H, and G. However, if we com-
pare this formation with the pre-
ceding ones, the Ch percentage
will be distinctly seen to be high-
est here. The same appears from
a comparison with the flora spec-
trum, the Ch percentage of which
is much lower than that of the
shrub heath, the Ch percentage of
the dwarf shrub heath being 36.54
as against the 23.9 of the flora spectrum. Thus the dwarf shrub heath
may be characterised as a chamaephyte formation.
I shall now describe the distribution of this formation within the
area of investigation. Its position in relation to other formations has
already been mentioned and will not be dealt with here. On Brúaröræfi
the formation is widely distributed; the southernmost part of Arnar-
dalur is almost exclusively occupied by shrub heath, and the same is
the case with a large portion of the oasis Þorlákslindir. In Fagridalur
and Sauðárdalur the shrub heath forms belts along the mountain sides
(see Figs. 4 and 7, which show the position of the formations in rela-
tion to each other). In Hvannalindir the shrub heath is widely distrib-
uted, but moss is more conspicuous here in the ground vegetation than
in other places, and at the same time the shrub vegetation is more open.
I should think that we are here near the upper limit of the shrub heath.
The shrub heath likewise occurs along Sauðá and between the rivers
Sauðá and Kringilsá. In Kringilsárrani the shrub heath forms a b'elt
along Jökulsá, but on the whole the terrain is unfavourable here for
the formation of the shrub heath; if anything, it is more favourable for
the development of the brekkur formation. On Snæfellsöræfi the shrub
heath is present, but less widely distributed than on Brúaröræfi. On the
western side of Jökulsá it mostly occurs in two continuous belts, one
along the bank of Jökulsá, the other along the base of the mountain
(see Fig. 8). On the eastern side of Jökulsá the typical shrub heath soon
Fig. 7. Profile from Sauðárdalur.