Greinar (Vísindafélag Íslendinga) - 01.01.1967, Blaðsíða 4

2
(Betula pubesoens) was then very widely distributed on
the lowlands, and also to some extent on mountain slopes.
This is indicated by the Old Icelandic Sagas, by old place
names and by pollen analysis. Pollen analysis has shown
that a sudden change occurred at the time of the settle-
ment (Einarsson 1963). Birch and willow (Salix spp.) dis-
appeared from large areas, while various grasses became
correspondingly more widely distributed. Wet soil vege-
tation also increased, but soon erosion started in the drier
places, especially where the soil contained much volcanic
ash, i.e. on the Palegonite Tuff Formation.
The early settlers brought with them domestic animals
from Norway and the British Isles, and undoubtedly plant
seeds were carried with these. For example it seems cer-
tain that Stellaria media, Poa annua and several other
grasses were introduced by the time of the settlement.
Other plants that were probably introduced into Iceland
very early and now grow there in a wild state include
Agropyron repens, Cirsium arvense, Rumex domesticus
and Urtica spp. The two last mentioned may possibly
have been introduced deliberately, perhaps as well as acci-
dentally, as they were used as food and textile plants.
After the time of the settlement. which lasted to about
930, and up to 1900, foreign plants were probably intro-
duced now and then but infrequently due to the small
amount of traffic between Iceland and other countries
and little cultivation in this period. After about 1900
plants were again more frequently introduced. This has
been especially evident in the last few decades, and not-
ably during the World War II, undoubtedly the result of
the great increase in traffic and cultivation and aided by
the recent amelioration of climate (see Eyþórsson 1949).
At the present time in fact the number of species of cul-
tivated and other foreign flowering plants is greater than
the number of native species. Many of the most common
plants around towns and farms are introduced species,
some of which became established at the time of the
settlement, others much later.