Greinar (Vísindafélag Íslendinga) - 01.01.1967, Blaðsíða 49

47
layer the soil is rich in minerals, which derive from the
basic tuff below. The meadow land is to some extent ferti-
lized by various seabirds constantly swarming over the
islands during the nesting period. This accounts for a
rather high fertility level of the soil and vigorous growth.
The dry meadow land has a predominance of grasses, with
Festuca rubra, Poa pratensis and Agrostis tenuis as the
dominant species. The associated species are Ranunculus
acris, Poa trivialis, Rumex acetosa, Cerastium caespitosum
and Taraxacum acromauris. All these species are of com-
mon occurence in cultivated hayfields in Iceland (Stein-
dórsson 1964). As a rule the meadow land vegetation on
the outer islands resembles some cultivated grasslands as
regards species and growing conditions. The bryophyta
are completely absent from this plant community, as is
the case with well cultivated hayfields.
The growth of the grass species is vigorous. The height
of mature culms reaches 20 inches, and the yield is five
to six tons of dry hay pelr hectare (50 to 60 lbs/acre) judg-
ed from samples collected in Sudurey and Álsey. The pro-
ductivity is thus quite high, almost comparable with that
of an average cultivated hayfield in Iceland. When this
observation was made no sheep had been grazing on the
southern islands since the volcanic activity started in the
Surtsey area. Previous to that a number of sheep had
been grazed on the islands all the year round as far back
as records go. The gi’azing of the sheep may be selec-
tive to some extent; in dry seasons the sheep have a ten-
dency to feed on the more succulent broad-leaved herbs,
as drinking water is limited. It is the farmers’ opinion
that the vegetation on the islands became more produc-
tive after the volcanic activity commenced and that Matri-
caria and Ranunculus are now more abundant. The vol-
canic activity may have affected the growth directly by
the fertilizing effect of the ash or indirectly by terminat-
ing the grazing of sheep.
III. The coastal cliff vegetation is situated in the splash-
ing zone, forming a fringe round the islands, which is,