The Botany of Iceland - 01.12.1930, Page 112

102
H.M0LHOLM HANSEN
series: mo, jaðar, mýri, and ílói depends on the increasing content
of moisture in the soil. In the following I shall describe the phy-
siognomic, biological, and floristic relations of the individual types
of vegetations.
The Melar Vegetation. Cf. figs. 15—17 and table 22 A, 1 —6.
As mentioned above, the inelar vegetation occurs at the top and
on the ridges of the moraine walls. In the winter, when the land-
scape is covered with snow, these are either bare or have a very
slight snow-covering. Consequently the frost penetrates deeper into
the earth which again causes a slower process of thawing in the
spring. This in connection with the position causes solifluction
from the ridge of the hill towards the depression. On a steep slope
the material will pour down in large tongues, as seen in fig. 23; if
the slope is less steep, it will arrange itself in small ledges with a
naked, gravelly horizontal surface, outwardly bounded by an edge
covered with plants which connects the two corners of the ledge
like a sweeping garland. Looking towards the depression, such an
area of solifluction looks very poor in plants (cf. fig. 16), looking
towards the ridge of the hill, the same surface seems somewhat
more clothed with plants (cf. flg. 17).
The characteristics of inelar are thus a slight or no snow-
covering, solifluction, and a bare gravelly or stony soil.
The composition of the melar vegetation has been given in
table 22 A, 1—6. Despite the open vegetation a relative abundance
and density of species occur. The average number of species is 27,
the density c. 8, varying from 5.6 to 9.4. In the biological spectrum
the chamaephytes dominate with an average percentage of 52.4, H
and especially G are relatively less important. The Th percentage
is c. 2. Even if this figure is low, it is comparativelj7 high compared
with the Th percentage of the south countrj7, a fact which it seems
natural to connect with tlre relatively continental climate of the
highlands. On melar in the north country the Th percentage is
still higher; here the climate not only tends to be more continental
than in the soutli country, but is also milder than in the highlands.
The A and E species are as 4 to 1; within the A sub-groups
A 3 is especially conspicuous, the average percentage being 55.4. Of
the E sub-groups only E 4 occurs and with a somewhat lower per-
centage than in the other types of vegetation.