Náttúrufræðingurinn - 2015, Blaðsíða 40

Náttúrufræðingurinn
132
mountains, as well as on the north side
of Snæfellsnes Peninsula7 (Figs. 9, 10).
This same distribution type was used by
Steindór Steindórsson as support for the
theory of overwintering during the ice
age.4
By taking the elevation into account,
the database has also been used to pro-
duce vertical distribution maps, show-
ing a section through the mountains
around Eyjafjörður.7,14 In the snowrich
coastal regions plants dependent on
snow shelter in the winter are found
from the coast up to the mountains, but
are absent from the lowland in the in-
land valleys, where the snow may melt
away at any time during the winter. The
plants will then be exposed to low tem-
perature extremes and winter desicca-
tion of a degree they can not tolerate.
Secure snow protection throughout the
winter will in that region only be found
above 300–350 m. An example for that
distribution type is shown by Vaccinium
myrtillus (Fig. 13), Sibbaldia procumbens
and Omalotheca supina.
The distribution maps based on
10×10 or 5×5 km grid do not differenti-
ate between plants with one occurrence
within the square and those widely dis-
tributed in all suitable habitats. An ex-
ample of this problem is shown by the
map of Campanula rotundifolia (Fig. 14).
That species is ubiquitous in the whole
eastern part of the country, but outside
that region only present in single, wide-
ly separated plots consisting of only few
plants each. The map can easily be mis-
taken and interpreted as having large
centers of distribution in middle North
and Southwest. This is not the case,
since the species is quite rare in both
these areas. This distribution type can
best be explained by early colonization
of C. rotundifolia in some eastern locality,
from where the plants have slowly dis-
persed throughout the eastern part of
the country filling all suitable habitats.
The human settlement in the ninth cen-
tury opened a new method of long dis-
tance dispersal to other districts. At first
it appeared along old travel routes by
horses, and later on in plantations cre-
ated by reforestation experiments using
plant material from the East. Local dis-
tribution out from the resulting isolated
spots has been very slow. Similar situa-
tion is found by Galium boreale, a species
that grows everywhere in the Southwest,
but occurs only sporadically in the
North and East. In many cases the den-
sity of the distribution in certain region
gives an indication on the age of the
species in that area.
Pollen analysis and macrofossils indi-
cate that most of the native, Icelandic
flora arrived already in the first 1–2.000
years after the last glaciation. Only rela-
tively few species have colonized later
until the human settlement offered new
transport possibilities to Iceland for a
group of plants. Rumex longifolius,
Elymus repens, Capsella bursa-pastoris,
Polygonum aviculare, Anthoxanthum odor-
atum subsp. odoratum, Rumex acetosa
subsp. acetosa, Cerastium fontanum subsp.
vulgare, Achillea millefolium subsp. mille-
folium, Tripleurospermum maritimum,
Stellaria media and Poa annua are all spe-
cies or subspecies that probably arrived
with the human settlement in the ninth
century. The two last were probably also
present in the bird cliffs even before the
settlement, and Tripleurospermum might
have been growing here earlier in coast-
al habitats. Their easy transport by birds
and the sea have been demonstrated in
Surtsey.22,35 Agrostis capillaris is here
considered to belong to the native flora
of Iceland opposite to the view ex-
pressed by Steindór Steindórsson.4 The
distribution data indicate also that
Deschampsia cespitosa and Achillea millefo-
lium might have been present in some
regions before the settlement. Later in-
troductions are Senecio vulgaris, Card-
amine hirsuta and Spergula arvensis. They
are widely distributed in the Southwest
and South of Iceland, but apparently
more recent introductions in the North
and East where they are only found in
densely populated areas. Very limited
data are available on plant import to
Iceland in the middle ages until about
1750.
Recently numerical methods have
been used to classify distribution pat-
terns in the flora of Iceland.9 As a result
new distribution pattern appeared, re-
maining rather obscure using the con-
ventional classification methods by eye
(Potamogeton alpinus cluster in Wasowicz
et al. 20149). We should expect further
progress by playing more around with
numerical classification methods of the
distribution patterns in the future.
Þakkir
Ég þakka Helga Hallgrímssyni fyrir yfirlestur handritsins og ábendingar
um ýmislegt sem mátti lagfæra. Einnig þakka ég Margréti Hallsdóttur
fyrir góðar ábendingar varðandi handritið.
Heimildir
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menntafjelag, Kaupmannahöfn. 258 bls.
2. Steindór Steindórsson 1949. Flórunýjungar 1948. Náttúrufræðingurinn
19. 110–121.
3. Steindór Steindórsson 1954. Um aldur og innflutning íslenzku flórunnar.
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4. Steindór Steindórsson 1962. On the age and immigration of the icelandic
flora. Rit Vísindafélags Íslendinga 35. Vísindafélag Íslendinga, Reykjavík.
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Austur-Skaftafellssýslu, Höfn í Hornafirði.
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Kristinsson 2014. Distribution Patterns in the Native Vascular Flora of
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http://vefsja.ni.is/website/plontuvefsja/;
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reitakerfi-islands.
12. Flóra Íslands. Blómplöntur. Skoðað 1. nóvember 2015 á http://www.
floraislands.is/blom.html;
13. Hörður Kristinsson 2010. Íslenska plöntuhandbókin. Blómplöntur og
byrkningar. Mál og menning, Reyjavík. 364 bls.
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plantna á Eyjafjarðarsvæðinu. Flóra 3. 9–74.
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