Full-text - Norsk entomologisk forening

Norwegian stoneflies II 215
of Finnmark, northern Norway and can in
this sense be compared with the inner areas
of Rogaland (area 1). The main differences
are in latitude, vegetation belts and in the
fact that the oceanity factor is much lower.
Area description
Ten streams and 2 lakes were investigated
in the area. The central parts consist largely
of sandstone and greenstone, while the peripheral
parts consist of little altered Eocambrian
sediments. Drift material is present,
especially in the stream valleys.
The climate has a pronounced continental
character. Precipitation generally lies between
400 and 600 mm a year, although the
southern parts can have below 400 mm. The
June isotherm is similar to the inner fjords
of area 1 (western Norway). The July temperature
is lower and can be compared to
the western coastal areas or the mountain
areas of southern Norway.
In the Alta area there are deep valleys
which converge on the fjord at Alta. In the
southern and eastern parts of the area, mountains
between 800 and 700 m a.s.l. are common,
while in the western parts the landscape
is generally higher, with mountains of 1100
m a.s.l. and above. Around the village of
Alta and the lower parts of the valleys there
are pine woods, mixed with willow, alder
and other deciduous trees. Above this, in the
Sub-Alpine belt, there is largely birch and
willow.
Stream descriptions
The main river in this area is the River
Alta. In addition, there are numerous small
and large streams. In places there is a dense
fringe of deciduous trees along the streams
which consists mainly of willow, alder and
birch. In the Sub-Alpine belt willow dominates
alongside the streams and may be very
dense and high in the lower sections. Higher
up the bushes are lower, but growth may still
be dense. In the Alpine belts the willow
gradually disappears (Figs. 9, 10).
Calcium hardness was measured both
during 1968 and 1972 in several places, and
values varied between 0.9 and 2.7 mg
Ca++/l. Values of pH lay generally between
Fig. 9. Stream by Leirbotnvann in the Sub-Alpine
belt.
Fig. 10. Stream in Stokkedalen in the Low-Alpine
belt.
6.0 and 6.8, although somewhat lower in the
higher areas.
Stonefly fauna
In this area 18 species of stoneflies were
taken (Table VIII). Of the five species which
are restricted to northern Norway, only two
were represented, N emoura arctica and Nemoura
sahlbergi.
The dominant carnivore was Arcynopteryx
compacta, which occurred in lakes, lake outlets,
and in streams. Diura bicaudata was
also common and was taken in streams, lakes
and lake outlets. Diura nanseni was taken in
streams and lake outlets and all three species
were taken together in the outlet of a lake
(Fig. 10). The most common herbivores were
Capnia atra, Leuctra hippopus, and Nemoura
cinerea. In this area 16 species were taken in
streams, 7 in lake outlets, and 5 in lakes.