Full-text - Norsk entomologisk forening

202 A. Lillehammer
parts of the area (Figs. 2 and 3), and it is
only in the inner areas that the mean January
temperature falls below 0° C. In the outermost
areas the mean January temperature is
more than +2° C (Fig. 3.1). The whole area
experiences heavy precipitation between 1200
mm and 2000 mm in the outer areas, and
more than 2000 mm in the inner areas·
On the coastal area of the Haugesund
peninsula, west of Skjoldefjorden and Alfjorden,
heights of more than 100 m a.s.l.
are rare. In the central areas, east of Alfjorden
and Skjoldefjorden, the mountains
are higher, between 500 and 700 m a.s.!. in
the outer parts and up to 1000 m a.s.l. in the
inner parts (the area of Sandeid and Vikedal).
In this area there are prominent valleys. In
the inner areas, east of Vikedal, the mountains
are even higher (up to 1600 m a.s.!. in
the north-eastern parts) and the fjords cut
deeply into the mountain massif.
The vegetation of the area of the Haugesund
peninsula consists mainly of bog and
heath vegetation. Wooded areas total about
8 0 /0. In the central area the wooded areas
on average constitute about 24 % of the area.
In the inner area, which is mainly mountainous,
the wooded area totals about 8 %.
River and stream descriptions
In the inner areas, streams and rivers are
abundant and the deep valleys contain some
of the longest and largest rivers in Rogaland.
The streams alternate between fast flowing
and more slow flowing reaches. The stone
size is very variable at all altitudes and
the streams are generally fringed by dwarf
willow up to about 7-800 m a.s.l.
In the lowland areas there is often a
dense fringe of alder, willow and birch along
the rivers and streams, in which the substrate
consists of different gravels and stones. Pollution
is minimal and only occurs for a short
distance near the fjords.
In the central areas, the streams are of the
same type as in the lowland inner areas. The
vegetation is rich along the streams. The
streams are seldom polluted to any noticeable
degree, and if they are, they flow only a
short distance before reaching the sea.
The outer areas have very little wooded
vegetation except in the shallow valleys.
There is often a dense fringe of alder and
other deciduous trees along the streams which
on the whole are smaller and shorter than in
the central and inner areas.
Calcium hardness varied to some extent in
the lowlands. Values up to 1. 7 mg Ca++/1
were found in the coastal and central areas
and up to 0.9 in the inland regions. Usually
the values were much lower and below 1.0
mg Ca++/1. In the highest areas up to
0.4 mg Ca + +/1 was measured. Usually the
values were much lower. The pH is around
6.0 in the lowlands of the whole area, but on
average it is a little higher at the coast than
in the inner areas where the lowest pH value
measured was 5.3.
Stonefly fauna
In this area 19 species were collected
(Table Ill). Diura bicaudata were taken in
lakes and their outlets at higher altitudes,
and Dinocras cephalotes was taken in a stream
at Suldal. The total number of species in the
southern part of West Norway is 20, since
lsoperla difformis was taken at Oltedal,
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