The Botany of Iceland - 01.12.1945, Síða 131

THE VEGETATION OF CENTRAL ICELAND 473
Deschampsia alpina, Poa alpina, and Cerastium trigynum are
likewise members of the first pioneer association, but they only reach
their full development where the moraine is older and drier and the first
pioneers have disappeared. Thus it is these six species which have first
established themselves on the moraine. The other species occurring in
analyses 4-6 will only appear later, and some of them seem to replace
the first-comers when these disappear. Thus the pioneer species, with
the exception of Poa alpina and Deschampsia alpina, have disappeared
in these analyses, but in addition to those two, which here attain their
greatest development on the moraine, Festuca ovina, F. rubra, and
Saxifraga groenlandica have become more conspicuous. We can say
nothing at all as to which formations or which species will be victorious
if the development of the vegetation proceeds so far that an actual
competition between the species will commence. A continued investiga-
tion of the area during a number of years might probably give a reply.
2. The Eyjabakkar Moraine. (Tab. XXIV. A-B).
Eyjabakkajökull is a glacier issuing from the northeastern corner
of Vatnajökull some distance farther eastward than Brúarjökull. From
this glacier springs Jökulsá in Fljótsdal. The gradient of the glacier is
much steeper than of Brúarjökull, but it is often in a similar motion.
Often their advances coincide, thus in 1890, as stated above. Since
then Eyjabakkajökull has receded in about the same way as Brúar-
jökull, but more slowly; thus at present there is only well over one
kilometer frorn the terminal moraine to the front of the glacier; but
the latter has often been in motion since 1890, having alternately
receded or advanced. Where the glacier advanced farthest, a similar
terminal moraine to that in Kringilsárrani has been formed. In front
of the actual morainic ridge the soil, which prior to the advance of
the glacier was very deep, has been compressed so as to form wave-like
folds (see Fig. 10). The whole of this terminal moraine is largely
covered with vegetation in much the same way as the terminal moraine
in Kringilsárrani, though the wind erosion phenomena are more pro-
nounced here than there, especially on the side facing the glacier. The
vegetation of the ridge consists mainly of Gramineae, which, however,
are highly mixed with herbs, e. g. Taraxacum croceum; where the
soil is most sandy; Equisetum arvense is very conspicuous. The ground
moraine slopes rather considerably from the ridge to the glacier’s edge.
The surface is very uneven, and larger or smaller accumulations of
The Botany of Icland. Vol. III. Part IV.
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