Náttúrufræðingurinn - 1978, Qupperneq 22

Clapham, A. R., T. G. Tutin og E. F.
Warburg. 1962: Flora of the British
Isles. Cambridge. 2. útg.
Fernald, M. L. 1950: Gray’s Manual of
Botany. New York. 8. útg.
Gröntved, J. 1942: The I’teridophyta and
Spermatophyta of Iceland. Bot. Icel.
4 (1). Copenhagen 8c London.
Hylander, N. 1953: Nordisk Kiirlváxt-
flora. I. Stockholm.
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SUMMARY
Juncus gerardii Loisel. recorded
in Iceland
by Arnthor Gardarsson,
Institute of Biology,
University of Iceland, Reykjavik.
The rush Juncus gerardii Loisel. is re-
corded as new to Iceland. About 5 stands
totalling some 300 m2 were found in an
estuarine saltmarsh at Leiruvogur, Mos-
fellssveit, sw. Iceland on 21 September
1976. The stands were composed almost
wholly of Juncus gerardii. Their zonal
distribution (Fig. 2) was similar to Eleo-
charis uniglumis, i.e. somewliat below
mean spring tide level. Salinity at the
locality was about 2%0 and was presum-
ably low but variable. Althougli the
stands showed vigorous growth: mean
height about 40 cm, standing crop abouL
615 g m~2 (one measurement), the plants
flowered during September and no seeds
could be found later in the autumn.
Juncus gerardii has been recorded ear-
lier in Iceland, but as no specimens were
available tliese records were considered
unsatisfactory (Gröntved 1942). The large
dense stands of J. gerardii in Leiruvogur
show up clearly on the earliest aerial
photographs available, in 1954, and did
not then differ appreciably in extent
from present observations. Estuarine
habitats in Iceland are little known bio-
logically and are moreover heavily grazed
by lifestock. The above observations are
taken to indicate that /. gerardii may be
an old-established native species in Ice-
land rather than an introduced alien (as
suggested by late blooming and location
near tlie comparatively densely settled
Reykjavik area).
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