Fróðskaparrit - 01.01.2008, Blaðsíða 182

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DISTRIBUTION AND THE IMPACT OF OUTFIELD DRAINAGE ON CARABIDS
CCOLEOPTERA, CARABIDAE) IN NORTH WESTERN EYSTUROY, FAROE ISLANDS
Carabus problematicus might be affected by
draining. The degree of dominance by Ne-
bria salina was seen to change between the
areas, N. salina dominated most on the the
UD area. This can be related to heather-lov-
ing carabids (e.g. Patrobus septentrionis and
Carabus problematicus) occupying relatively
large part of OD compared to the UD area,
see Tables 2 and 3. As a whole the ND area is
more humid than the UD area because of its
aspect; This might explain why species like
Patrobus septentrionis, Patrobus atrorufus
and Trechus obtusus occupy a larger part of
ND area than of UD area (Lindroth, 1985),
see Table 4. No heather was in the ND area,
only grass heath, which was grazed; this can
lead to easier access to collembola (Cole et
al., 2002), and since Notiophilus biguttatus is
a collembola specialist (Cole et al., 2006), the
easier access to collembola is a likely expla-
nation for N. biguttatus having higher abun-
dance in the ND area.
Lindroth (1985) amongotherthingsde-
scribes Nebria rufescens as a cold loving spe-
cies, which might explain why it was more
abundant in the colder north-east facing ND
area than the other two. Even though we
found that Patrobus atrorufus was signifi-
cantly more abundant at the lower altitudes
in both the OD and ND area, many more
were found at the higher altidudes in the OD
area compared to the ND area, see Tables 2
and 4. This can be one reason for the higher
abundance of Patrobus atrorufus in the OD
area as a whole compared to the rest. The
heather in the OD area might create some
shade, which also is important to Patrobus
atrorufus (Lindroth, 1985). By looking at the
OD and the ND area, both appear to be suit-
able to Patrobus septentrionis; a high pro-
portin of the OD area was heather, while a
high proportion of the ND are is meadow-
like. Both kinds of habitat are preferred by P.
septentrionis (Lindroth, 1985), but the OD
area is drier and shows signs of drying up
(Fossa et ai, 2008). This might partly explain
the higher abundance of Patrobus septentri-
onis in the ND area, since P. septentrionis is
described as prefering some humidity (Lin-
droth, 1985).
Conclusion
Fifteen species were found, 14 of which have
been found before. One species Agonum
fuliginosum was recorded for the first time in
the Faroe Islands, and another, Bembidion
bruxellense, was recorded for the first time in
Eysturoy. Most of the species that were dom-
inating were among the dominating species
in all areas. The distribution in time and
space reflects the habitat preferences and
the reproductive cycle of the carabidae. It is
difficult to define any effect from draining
because we do not know how the areas
looked like before, so the differences found
might have been there before. The abun-
dance seen by some carabidae according to
altitude points to effect from draining; these
were Nebria salina, Nebria rufescens, Pa-
trobus septentrionis and Patrobus atrorufus,
and also the higher abundance of Carabus
problematicus in the OD area points to an ef-
fect from draining. Effects can be related to
changes in humidity and vegetation, like an
increase in heather in some areas because of
draining.
Acknowledgements
I want to express thanks to SEV (Faroese
Electricty Supplier), who funded the EIA that