Greinar (Vísindafélag Íslendinga) - 01.01.1967, Blaðsíða 50

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however, not necessarily continuous. It is the vegetation
of the slanting slope, but is interrupted wherever the cliffs
are too steep to hold this type of vegetation. Its lower mar-
gin is at high tidemark and the upper border is contiguous
to the puffin colony. This zone varies in width, reach-
ing a higher level on the southern side, which is exposed
to the Atlantic, where the surf is more intense, than on
the side facing the mainland. This vegetation does not
form a continuous mat. It is an open community with plants
growing in small patches in depressions and crevices,
where some soil or anchorage is to be found on the other-
wise bare rock. Estimated ground-coverage is one to five
percent of the total area. The predominating species are
Puccinella maritima and Coclilearia officinalis with Ar-
meria vulgaris, Atriplex patula and Plantago maritima as
associated species.
IV. The Angelica cluster is situated on slopes or rocky
shelves on the northern sides of some of the islands. It
is described by Johnsen (1939). The dominant species is
Archangelica officinalis with Matricaria maritima and
Stellaria media as associated species. On the margins of
the cluster these are sometimes also accompanied by
Festuca rubra.
An account will now be given of the plant communi-
ties of the outer islands, beginning with the largest island
and ending with the smallest, the communities being
grouped in the four associations (Tables IV and V).
Plant distribution of individual islands
Surtsey
The new volcanic island, Surtsey, is the southernmost
of the outer islands. It was built up by volcanic activi-
ties which started on November 14th 1963 and were still
continuing on June 4th 1967. The area of this new island
is approximately 2.5 sq. km, half of which is covered with
lava, the remainder being mostly covered with volcanic
ash and cinder which will presumably later harden into