Fróðskaparrit - 01.01.1998, Blaðsíða 13

EIN OYGGJALÍVLANDAFRØÐILIG GREINING AV FLORUNI í FØROYUM
19
included in our study. According to Hansen
(1972), the total number of species (minus
subspecies) on the Faroes is 329, 262 of
which are natural, 22 are imported and na-
turalised and 45 are not naturalised and
non-established species.
Results and discussion
The motive for our choice of material is that
it provides a time specific picture of pre-
cisely what species made up the Faroese
flora in 1960-61. The study was very com-
prehensive (Hansen, 1964; 1966; 1972). A
total of 135 stations were examined, evenly
distributed across the Faroe Islands, and
some 20,000 single observations were
made. Every station comprised a few km2.
The Faroese flora has doubtlessly under-
gone changes from 1960 up till the present.
One of the most common species today in
the Tórshavn region seems to be american
willowherb (Epilobium ciliatum), which is
not even mentioned in Hansen (1966). Ne-
vertheless, we find that many alterations in
the distribution maps and even new species
will not dramatically change the conclu-
sions of the present paper because it builds
on as many as 294 species.
fhe number ofplant species
on the individual islands
Based on Hansen’s distribution maps
(1966), we have counted the number of
species localised on each of the 18 major is-
iands. See Table 1.
In the survey period, 112 species of vas-
cular plants were found on the island of
Skúvoy, and the island covers 10 km2.
Mykines is of similar size (10.3 km2), and
Suðuroy Number of species 238 Area, km2 166.0
Stóra Dímun 65 2,7
Skúvoy 112 10.0
Sandoy 222 112.1
Mykines 107 10.3
Vágar 211 177.6
Hestur 118 6.1
Koltur 108 2.5
Nólsoy 145 10.3
Streymoy 221 373.5
Eysturoy 207 286.4
Kalsoy 139 30.9
Kunoy 151 35.5
Borðoy 163 94.9
Viðoy 136 41.0
Svínoy 128 27.4
Fugloy 126 11.2
Lítla Dímun 12 0.8
Table 1. Number of species and areas ofthe 18 largest Faroe Islands. Talva 1. Talið á sløgum og víddin á 18 oyggjum í Føroyum.
even though the two islands are quite unlike
each other, the number of species on
Mykines is almost the same as that of Skúv-
oy, i.e. 107 species. Sandoy is about ten
times bigger (112.1 km2), and slightly more
than twice the amount of species were lo-
calised here, i.e. a total of 222.
This seems to indicate that twice as many
species can be found on areas ten times as
big. The correlation may be formulated
more precisely which is the subject of the
following chapter.
The species-area equation S = cAz
In the early days of plant ecology, attempts
were made to fínd the precise form of cor-
responding materials. Arrhenius (1921)
claimed that the correlation could be de-
scribed by the exponential function S =