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VI. Case Studies
Investigations on the ecology ofarctic animals have by no means covered the entire
geopraphical area. In fact, the literature on the Arctic repeatedly refers to the same
small number of place names. All of the data presented here originate from these
regions, i.e., Spitsbergen (Svalbard), northern Scandinavia (Abisko, Kevo,
Messaure), Point Barrow and Prudhoe in Alaska, Ellesmere Island and Devon
Island in the Canadian Archipelago. Additional investigations have been carried
out in Scoresby Sound in eastern Greenland, and a number of studies originate
from regions south of the Arctic Circle, such as Hudson Bay, south and west
Greenland, Iceland (Myvatn, Thjorsaver) as well as from Hardangervidda and
Dovre-Fjell iri southern Norway. Other regions are poorly represented: examples
are provided by the Sarek region ofSweden, where faunistic studies got offto such a
good start 50 years ago, and the important region of northern Greenland. The
significance of the better investigated of these areas can best be illustrated in the
form of a series of case studies
1.
"Warm" Arctic: A Section Through Northern Scandinavia from
Troms~
(Norway) to Kevo (Finland).
(Fig. 120)
Scandinavia is the only arctic region without permafrost. Its coast is ice-free
throughout the entire year, the growth period is relatively long and summer
temperatures are high. On the Norwegian coast the climate is maritime, which in
combination with the strong coastal winds is responsible for the absence of trees
right down to sea level. At the inland ends of the long fjords the timberline ascends
to 300 m above sea level and the forest consists chiefly of birch with a slight
scattering of pine. There are still orchards and vegetable gardens (currants and
rhubarb) as well as cattle farming with hay harvesting. Compared with the coast of
southern Norway rainfall is low, with barely 500 m annually. Consequently there is
considerable incoming radiation even at 300 km north of the Arctic Circle. The
proximity of the sea ensures a long period of growth.
To the east ofthe steep mountains which provide shelter from wind and weather
the climate is more continental, the growth period shorter, precipitation even less,
as a consequence of which there is stronger sunshine. Due to the altitude and the
short summer season neither cattle farming nor horticulture are possible. The
valleys are covered with birch forest, the proportion of pine increasing towards the
east until in Kevo it is the predominant species. We have now reached the very
continental region with its brief growth period, where temperatures are high in
H. Remmert,
Arctic Animal Ecology
© Springer-Verlag Berlin Heidelberg 1980
Case Studies
162
Fig.120a-d.
Types of landscape in northern Scandinavia. a Near Tromsii (Norway) b Abisko (Sweden)
c Finland d for comparison: East Greenland tundra near the polar circle
"Warm" Arctic: A Section Through Northern Scandinavia from Tromso
163
164
Case Studies
summer and low in winter. Only a few metres in altitude separate the pine forests
from the treeless Fjell plateau.
Within a relatively short distance we have thus left the temperate and fairly
warm regions with their long growing season, and have entered the dry continental
regions where growth is confined to a very short period, but with very high summer
temperatures.
This is a situation that is thoroughly atypical for the Arctic and, not
surprisingly, the fauna is composed of animals of a very wide range of ecological
origin. The first group includes the usual European forms, and even some warmth-
loving forms such as the mountain lizard (Lacerta vivipera), viper (Vipera berus)
and frog (Rana temporaria). The marine birds on the west coast of Norway are
similar with respect to species composition and racial differentiation to those of
southern Norway or the British Isles: razorbill, cormorant, shag, white-tailed eagle,
black-backed gull and herring gull are even found far north of the Arctic Circle
(nothing is known about the zone at the threshold of the true Arctic, where black-
backed gull and herring gull meet yellow-footed gulls from the polar seas, and
guillemot and Briinnich's guillemot meet). Other central European elements
encountered are the starling, magpie, oyster catcher and the marine nematoceran,
Clunio. These elements are mixed with forms that are usually designated "arctic",
although they are also met much farther south in the mountains, and even in the
Alps. Examples are provided by rock and willow ptarmigan, redpoll and ring ouzel.
Snowy owls, long-tailed ducks, common scoter, whimbrel, black-throated diver,
horned grebe, red-necked phalarope and arctic skua are found as far south as
southern Norway (Hardangervidda, Dovre-Fjell). In addition, however, there are
typical arctic forms that either do not occur south ofthe Arctic Circle or, if so, only
in small numbers and far to the east, which is a type of distribution known to
botanists as "northern unicentric".
It
is chiefly exhibit by a number of butterflies,
although the northern redbacked vole, Clethrionimus rutilus, provides us with an
example among the mammals, and it is also seen in birds such as the lesser white-
fronted goose, the bar-tailed godwit (Limosa lapponica), the little stint and, to a
lesser extent, the bean goose (Fig. 121). Only some of these forms turn up in the
Norwegian part of our section, and most of them are first seen much farther east.
Still farther to the east they are joined by animals typical ofthe Siberian tundra, like
the red-throated pipit and the spotted redshank. The typical plant representatives
of the northern unicentric type ofdistribution are Pedicularis hirsuta and Cassiope
tetragona.
Towards the east, typical taiga organisms like the flying squirrel (Glaucomys),
hawk owl, great grey owl, three-toed woodpecker, crossbill, nutcracker and
Siberian jay appear in gradually increasing numbers whilst central European forms
like the magpie, sparrow and starling gradually disappear.
The high summer temperatures favour the existence of a diverse collection of
herbivorous insects, which show a tendency to explosive multiplication with
devastating consequences for the birch forests. Operophtera brumata and Oporinia
autumnata have been responsible for destroying large expanses of such forest, with
the result that either the timberline has receded considerably (Fig. 97b, in the
vicinity of Kevo) or the forest has taken many years to recover (near Abisko). Both
species are also fairly numerous in localities far to the south, but they do not
"Warm" Arctic: A Section Through Northern Scandinavia from Troms0
165
c
o
B
A
E
F
I<'ig. l2lA-F. Distribution of arctic types of terrestrial plants and animals. A Agriades aquilo B
Euphydryas iduna Dalm C Colias hecla lef D Artemisia norvegica Fr. E Stercorarius pomarinus F
Pagophila eburnea. The range ofdistribution ofthese species nowhere extends south ofthe Arctic Circle
(so-called northern unicentric species). Only ( D) is a southern unicentric type of species
multiply in the same catastrophic manner.
It
seems that outbreaks of such
dimensions are only possible under the special set of conditions prevailing on the
northern limits of the birch forest. The summer temperatures are still high enough
for the mass increases but the fauna is no longer of sufficient diversity to exert a
buffering action against the vast numbers of moths. No mass outbreaks of
inchworm have been reported from Tromso, so that a reinvestigation at this point
would probably bring interesting results. Anthills (Formica) in sufficient density
suppress outbreaks of Oporinia (Laine and Niemela, 1980).
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VI. Case Studies
Investigations on the ecology ofarctic animals have by no means covered the entire
geopraphical area. In fact, the literature on the Arctic repeatedly refers to the same
small number of place names. All of the data presented here originate from these
regions, i.e., Spitsbergen (Svalbard), northern Scandinavia (Abisko, Kevo,
Messaure), Point Barrow and Prudhoe in Alaska, Ellesmere Island and Devon
Island in the Canadian Archipelago. Additional investigations have been carried
out in Scoresby Sound in eastern Greenland, and a number of studies originate
from regions south of the Arctic Circle, such as Hudson Bay, south and west
Greenland, Iceland (Myvatn, Thjorsaver) as well as from Hardangervidda and
Dovre-Fjell iri southern Norway. Other regions are poorly represented: examples
are provided by the Sarek region ofSweden, where faunistic studies got offto such a
good start 50 years ago, and the important region of northern Greenland. The
significance of the better investigated of these areas can best be illustrated in the
form of a series of case studies
1.
"Warm" Arctic: A Section Through Northern Scandinavia from
Troms~
(Norway) to Kevo (Finland).
(Fig. 120)
Scandinavia is the only arctic region without permafrost. Its coast is ice-free
throughout the entire year, the growth period is relatively long and summer
temperatures are high. On the Norwegian coast the climate is maritime, which in
combination with the strong coastal winds is responsible for the absence of trees
right down to sea level. At the inland ends of the long fjords the timberline ascends
to 300 m above sea level and the forest consists chiefly of birch with a slight
scattering of pine. There are still orchards and vegetable gardens (currants and
rhubarb) as well as cattle farming with hay harvesting. Compared with the coast of
southern Norway rainfall is low, with barely 500 m annually. Consequently there is
considerable incoming radiation even at 300 km north of the Arctic Circle. The
proximity of the sea ensures a long period of growth.
To the east ofthe steep mountains which provide shelter from wind and weather
the climate is more continental, the growth period shorter, precipitation even less,
as a consequence of which there is stronger sunshine. Due to the altitude and the
short summer season neither cattle farming nor horticulture are possible. The
valleys are covered with birch forest, the proportion of pine increasing towards the
east until in Kevo it is the predominant species. We have now reached the very
continental region with its brief growth period, where temperatures are high in
H. Remmert,
Arctic Animal Ecology
© Springer-Verlag Berlin Heidelberg 1980
Case Studies
162
Fig.120a-d.
Types of landscape in northern Scandinavia. a Near Tromsii (Norway) b Abisko (Sweden)
c Finland d for comparison: East Greenland tundra near the polar circle
"Warm" Arctic: A Section Through Northern Scandinavia from Tromso
163
164
Case Studies
summer and low in winter. Only a few metres in altitude separate the pine forests
from the treeless Fjell plateau.
Within a relatively short distance we have thus left the temperate and fairly
warm regions with their long growing season, and have entered the dry continental
regions where growth is confined to a very short period, but with very high summer
temperatures.
This is a situation that is thoroughly atypical for the Arctic and, not
surprisingly, the fauna is composed of animals of a very wide range of ecological
origin. The first group includes the usual European forms, and even some warmth-
loving forms such as the mountain lizard (Lacerta vivipera), viper (Vipera berus)
and frog (Rana temporaria). The marine birds on the west coast of Norway are
similar with respect to species composition and racial differentiation to those of
southern Norway or the British Isles: razorbill, cormorant, shag, white-tailed eagle,
black-backed gull and herring gull are even found far north of the Arctic Circle
(nothing is known about the zone at the threshold of the true Arctic, where black-
backed gull and herring gull meet yellow-footed gulls from the polar seas, and
guillemot and Briinnich's guillemot meet). Other central European elements
encountered are the starling, magpie, oyster catcher and the marine nematoceran,
Clunio. These elements are mixed with forms that are usually designated "arctic",
although they are also met much farther south in the mountains, and even in the
Alps. Examples are provided by rock and willow ptarmigan, redpoll and ring ouzel.
Snowy owls, long-tailed ducks, common scoter, whimbrel, black-throated diver,
horned grebe, red-necked phalarope and arctic skua are found as far south as
southern Norway (Hardangervidda, Dovre-Fjell). In addition, however, there are
typical arctic forms that either do not occur south ofthe Arctic Circle or, if so, only
in small numbers and far to the east, which is a type of distribution known to
botanists as "northern unicentric".
It
is chiefly exhibit by a number of butterflies,
although the northern redbacked vole, Clethrionimus rutilus, provides us with an
example among the mammals, and it is also seen in birds such as the lesser white-
fronted goose, the bar-tailed godwit (Limosa lapponica), the little stint and, to a
lesser extent, the bean goose (Fig. 121). Only some of these forms turn up in the
Norwegian part of our section, and most of them are first seen much farther east.
Still farther to the east they are joined by animals typical ofthe Siberian tundra, like
the red-throated pipit and the spotted redshank. The typical plant representatives
of the northern unicentric type ofdistribution are Pedicularis hirsuta and Cassiope
tetragona.
Towards the east, typical taiga organisms like the flying squirrel (Glaucomys),
hawk owl, great grey owl, three-toed woodpecker, crossbill, nutcracker and
Siberian jay appear in gradually increasing numbers whilst central European forms
like the magpie, sparrow and starling gradually disappear.
The high summer temperatures favour the existence of a diverse collection of
herbivorous insects, which show a tendency to explosive multiplication with
devastating consequences for the birch forests. Operophtera brumata and Oporinia
autumnata have been responsible for destroying large expanses of such forest, with
the result that either the timberline has receded considerably (Fig. 97b, in the
vicinity of Kevo) or the forest has taken many years to recover (near Abisko). Both
species are also fairly numerous in localities far to the south, but they do not
"Warm" Arctic: A Section Through Northern Scandinavia from Troms0
165
c
o
B
A
E
F
I<'ig. l2lA-F. Distribution of arctic types of terrestrial plants and animals. A Agriades aquilo B
Euphydryas iduna Dalm C Colias hecla lef D Artemisia norvegica Fr. E Stercorarius pomarinus F
Pagophila eburnea. The range ofdistribution ofthese species nowhere extends south ofthe Arctic Circle
(so-called northern unicentric species). Only ( D) is a southern unicentric type of species
multiply in the same catastrophic manner.
It
seems that outbreaks of such
dimensions are only possible under the special set of conditions prevailing on the
northern limits of the birch forest. The summer temperatures are still high enough
for the mass increases but the fauna is no longer of sufficient diversity to exert a
buffering action against the vast numbers of moths. No mass outbreaks of
inchworm have been reported from Tromso, so that a reinvestigation at this point
would probably bring interesting results. Anthills (Formica) in sufficient density
suppress outbreaks of Oporinia (Laine and Niemela, 1980).
[ Pobierz całość w formacie PDF ]