Greinar (Vísindafélag Íslendinga) - 01.01.1967, Blaðsíða 44

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the Westman Islands, later to be joined by Sturla Frid-
riksson and other groups of investigators. During that
summer five excursions were made to the various islands,
the last trip being on Sept. 9th 1965. During the summer
of 1966 the students B. Johnsen and Thorbjörn Broddason
continued the investigation on the islands and skerries
in the period from July 16th to August 9th.
Method of research
In the summor of 1965 botanical investigations were car-
ried out on the vegetation of the outer islands as well as
on three mountain isolates in Southern Iceland. Herbar-
ium material was collected as well as live specimens for
laboratory study (Fridriksson and Johnsen 1966). Dur-
ing the second summer an examination of the vegetation
of individual islands was continued, with a detailed study
of the number of species, their distribution and associa-
tions. In this connection emphasis was laid on the eco-
logical studies. Plant distribution was measured by two
methods. Most frequently the point-measurement method
was used for the estimation of coverage of species as
given in percentage terms; secondly frequency measure-
ments were carried out as described by Raunkiaer (1907).
According to the latter measurement, species of plants
within a circle of 0.1 square metre in area are recorded.
Plant distribution in 25—40 circles was investigated, the
centre of each circle being determined by throwing a
marker at random. The percentage of each species is
then estimated by taking those occurring in all circles
as 100%, and others according to the number of circles
in which they are found. These measurements were under-
taken with a special view to comparison with the observa-
tions made previously by B. Johnsen in 1933 on Bjarnar-
ey and Heimaey (Johnsen and Fridriksson 1967).