The Botany of Iceland - 01.12.1945, Blaðsíða 119

THE VEGETATION OF CENTRAL ICELAND
461
species is common to this and thc blown sand associations, viz. Equise-
tum œrvense, which often forms a kind of ground vegetation in the
Elymus association. In this association the high E percentage is espe-
cially noteworthy, and the same applies to the apparent equilibrium
between the H and G percentages. Analyses 3, 5, and 6 were made
in Kýlingar, analysis 4 in Jökuldalir; analysis 7 is from Síðumanna-
afrjettur near Varmafell. It shows a higher number of species and a
higher A percentage than the others. The locality is situated by a small
brook near the margin of a lava flow; sand flats made up of fluvial
sand and volcanic ashes are found along the brook. Some vegetation
was found where the sand was dampest, and there analyses XX, 7 and 8
were carried out. The association is widely distributed in all parts of
the highland where damp, sandy areas are found.
4. Eriophorum Scheuchzeri—Agrostis alba—Equisetum arvense-Ass.
(Tab. XX. A-B, 8).
This association is closely related to the preceding one, but is found
where the sand is wettest and is occasionally flooded by water. The
three character species are quite dominant physiognomically. The
analysis was made very near analysis XX, 7. Otherwise the association
was observed in several places under similar conditions. There is every
indication that it is a pioneer association which, according as the condi-
tions develop, may pass either into a Calamagrostis jaðar and subse-
quently a shrub heath, if fresh sand is constantly added and the land
grows higher and drier, or, if the water for some reason or other is
not draincd off, be transformed into a flói vegetation.
c. The M elur Vegetation (gravel flat vegetation).
By far the greater part of thc interior highland of Iccland is covered
with melur. The surface is covered with big or small stones, which,
however, are of such size and situated so close to each other
that thc wind has no longer any appreciablc influence on it, all thc
finer material having been blown away. The stones vary greatly in
size, from quite small to large blocks. Small quantities of fine material
will often gather in the lee of the stones, and in these places the plants
will take root and barely sustain life. The surface of the melur may be
either level or sloping; in the latter case there is, as a rule, some motion
at the bottom owing to solifluction. Where the inclination of the moun-
tain sides is greatest, talus slopes or screes will form, which are mostly