Long-term changes in alpine plant communities in Norway and Finland


Virtanen, R.; Eskelinen, A.; Gaare, E.

Alpine diversity in Europe: 411-422

2003


Long-term changes in species composition, abundance and diversity of alpine plant communities were analysed by using data sets from central Norway and NW Finland sampled in the 1920s and 1990s. Comparisons were made for seven sites representing heath, snowbed and soligenous mire vegetation. The cover and number of lichens declined in most communities probably owing to increased reindeer grazing and trampling. In heath, the cover of some bryophytes and dwarf shrubs increased on the Norwegian sites. Herbs and grasses increased in snowbed communities, while some typical snowbed plants disappeared or decreased. The data for snowbeds suggests that these communities may have responded to changes in snow cover as a result of the observed warmer climate in the 1990s. The species that showed a significant decline or increase may be considered for use in monitoring as indicators of environmental change.

25
Long
-Term
Changes
in
Alpine
Plant
Communities
in
Norway
and
Finland
R.
VIRTANEN,
A.
ESKELINEN
and
E.
GAARE
25.1
Introduction
High
-mountain
environments
are
regarded
as
susceptible
to
environmental
change
such
as
the
global
warming
of
climate
(Grabherr
et
al.
1995;
Korner
1999).
It
has
been
predicted
that,
in
a
warmer
climate,
lowland
plants
would
migrate
upwards
and
plant
communities
typically
found
in
areas
with
late
or
moderate
snow
cover
would
be
invaded
by
plant
species
characteristic
of
more
favourable,
lowland
habitats
(Holten
and
Carey
1992).
Grabherr
et
al.
(1994)
presented
evidence
of
upward
migration
of
plants
on
mountain
tops.
Although
migration
may
increase
species
richness
in
some
habitats,
else-
where
it
may
pose
a
threat.
Some
mountain
plants
are
expected
to
decrease
due
to
increased
competition
and
changes
in
environmental
conditions
(Saetersdal
and
Birks
1997).
Recent
experiments
have
shown
that
temperature
conditions
strongly
affect
plant
performance
in
alpine
environments
(Galen
and
Stanton
1993;
Molau
and
Alatalo
1998;
Totland
and
Nylehn
1998);
how-
ever,
short-term
experiments
may
give
insufficient
information
on
long-term
vegetation
changes.
The
objective
of
this
study
was
to
analyse
changes
in
plant
species
compo-
sition
over
70
years
at
seven
sites
in
two
alpine
areas
in
Finland
and
Norway.
In
particular,
we
compared
species'
abundances
and
composition
reported
in
the
literature
(Nordhagen
1928;
Lippmaa
1929)
with
those
recorded
in
1998
and
1999.
We
interpret
the
observed
changes
in
relation
to
changes
in
reindeer
grazing
and
temperature.
An
increasing
trend
of
annual
mean
temperatures
from
the
1920s
to
the1990s
has
been
observed
near
Kilpisjarvi,
Finland
(Hoof-
gaard
1999).
Annual
mean
temperatures
in
the
Norwegian
mountains
declined
by
0-0.5
°C
between
1925-1944
followed
by
an
increase
of
ca.
1-2
°C
between
1978-1999
(Gronas
1999;
Jones
et
al.
1999;
Kullman
2002).
The
dura-
tion
of
snow
lie
decreased
during
1950-1990s
by
about
10
%
(E.
Gaare,
unpubl.
data).
It
has
also
been
known
for
some
time
that
reindeer
grazing
can
have
Ecological
Studies,
Vol.
167
L.
Nagy,
G.
Grabherr,
Ch.
Korner,
D.B.A.
Thompson
(Eds.)
Alpine
Biodiversity
in
Europe
Sprin
ger-Verlag
Berlin
Heidelberg
2003
412
R.
Virtanen,
A.
Eskelinen
and
E.
Gaare
considerable
impact
on
vegetation
on
mountains
(Gaare
1968)
and
it
has
to
be
considered
when
interpreting
detected
vegetation
responses.
25.2
Study
Areas
Two
mountain
areas
of
the
Scandes
with
detailed
data
on
their
alpine
plant
communities
were
re
-sampled
in
1998-1999,
using
identical
methodology
to
the
earlier
sampling
about
70
years
earlier.
The
first
area,
Mt.
Sylfjellet,
central
Norway
(63°00'N,
12°10'E),
was
recorded
by
R.
Nordhagen
in
the
1920s
(Nord-
hagen
1928).
Mount
Sylan,
the
highest
mountain
of
the
area,
reaches
1762
m
a.s.l.
and
has
a
mountain
birch
(Betula
pubescens
subsp.
czerepanovii)
treeline
at
an
altitude
of
800
m
a.s.l.
Apart
from
the
construction
of
a
water
reservoir
in
the
1960s
between
706-729
m
a.s.l.,
the
mountains
in
the
area
have
remained
in
a
near
-natural
condition
and
human
impact
is
still
small.
The
reindeer
population
nearly
doubled
from
about
2100
in
the
1890s
to
3400-4000
in
the
1990s
(H.
Staaland,
pers.
comm.).
Moreover,
the
seasonal
pattern
of
grazing
has
changed:
the
formerly
prevalent
winter
grazing
has
declined
while
summer
grazing
increased
(T.
Brandfjeld,
pers.
comm.).
Nord-
hagen
(1928)
mentioned
no
sheep
grazing
and
we
observed
no
signs
of
sheep
grazing
in
the
area
in
the
summer
of
1999.
The
second
area
was
the
Kilpisjarvi
region,
NW
Finnish
Lapland
(69°03'N,
20°50'E),
where
T.
Lippmaa
studied
the
vegetation
in
the
late
1920s
(Lippmaa
1929).
The
highest
mountains
of
the
area
reach
above
1000
m
a.s.l.
The
tree
-
line
formed
by
mountain
birch
lies
at
ca.
600
m
a.s.l.
In
the
Kilpisjarvi
region,
the
density
of
the
reindeer
population
has
ranged
from
about
1.5
reindeer
km
-2
to
3.5
reindeer
km
-2
in
1991
(Kojola
et
al.
1993).
There
is
little
informa-
tion
available
about
the
reindeer
from
the
1920s,
and
it
is
believed
that
their
long-term
average
densities
have
remained
relatively
unchanged.
For
the
Sib-
baldia
procumbens-Trisetum
spicatum
snowbed
site
changes
in
reindeer
grazing
are
likely
to
have
been
small
because
the
site
is
located
in
the
Malla
Nature
Reserve
where
reindeer
are
not
allowed
to
graze.
Nevertheless,
some
stray
animals
have
been
sighted.
25.3
Data
Collection
and
Analysis
We
re
-sampled
the
vegetation
using,
as
much
as
possible,
identical
methods
and
numbers
of
vegetation
quadrats
to
those
used
in
the
original studies.
At
Mt.
Sylfjellet,
we
relocated
five
of
Nordhagen's
(1928)
sampling
sites
rep-
resenting
four
community
types
(Loiseleuria
procumbens
wind-swept
heath,
Vaccinium
myrtillus
heath,
Deschampsia
fl
exuosa-Anthoxanthum
odoratum
Long
-Term
Changes
in
Alpine
Plant
Communities
in
Norway
and
Finland
413
snowbed
community
and
Kobresia
simpliciuscula-Carex
microglochin
alpine
mire
community).
Following
Nordhagen
(1928),
the
cover
of
vascular
plants,
bryophytes
and
lichens
was
estimated
using
the
Hult-Sernander
scale.
At
Kilpisjarvi,
we
relocated
two
of
the
sites
sampled
by
Lippmaa
(1929).
The
vegetation
types
included
Vaccinium
myrtillus
heath
and
Sibbaldia-Trisetum
snowbed.
Following
Lippmaa
(1929),
the
shoots
of
individual
plants
were
counted
or
their
percentage
cover
class
(75,
50,
40,
25,
13, 10,
6,
3
and
<3)
was
estimated
in
each
of
ten
0.25-m
2
quadrats
in
both
vegetation
types.
The
quadrats
were
placed
randomly
by
throwing
a
rod
within
the
sampling
area.
The
nomenclature
of
bryophytes
is
according
to
Soderstrom
et
al.
(1992),
that
of
lichens
follows
Vitikainen
et
al.
(1997),
and
that
of
vascular
plants
is
after
Hamet-Ahti
et
al.
(1998).
We
aimed
to
separate
the
significant
changes
in
plants'
abundances
and
occurrences
between
the
1920s
and
1990s
from
those
that
could
have
been
the
result
of
chance.
The
tests
can
be
regarded
as
planned
a
priori
contrast
analy-
ses,
where
each
data
set
is
tested
only
once.
For
this
reason,
type
I
error
levels
do
not
need
to
be
corrected
(Sokal
and
Rohlf
1995).
For
plant
species
that
occurred
regularly
in
the
quadrats,
t
-tests
for
independent
samples
were
made.
Before
these
tests,
the
original
cover
classes
were
transformed
to
corre-
sponding
percent
cover
values
using
geometric
means
of
each
cover
class
(Oksanen
1976).
The
comparison
of
cover
changes
was
not
suitable
for
more
infrequent
and
subordinate
species
occurring
in
the
lowest
cover
classes.
The
changes
in
species
frequencies
were
tested
by
using
chi
-squared
tests.
25.4
Changes
in
Species
Composition
and
Abundance
25.4.1
Heath
Vegetation
In
wind
-exposed
Loiseleuria
heath
at
Sylfiellet,
reindeer
lichens
(Cladina
spp.)
and
Flavocetraria
nivalis
declined
(Table
25.1)
and
Solorina
crocea
dis-
appeared.
By
contrast,
the
cover
values
of
Empetrum
nigrum
ssp.
hermaphro-
ditum,
Salix
herbacea
and
bryophytes,
notably
Gymnomitrion
spp.
and
Racomitrium
lanuginosum,
were
higher
in
1999
than
in
the
1920s.
An
annual
vascular
plant,
Euphrasia
frigida,
present
in
the
1920s,
was
not
recorded
in
1999.
In
the
snow
-protected
Vaccinium
myrtillus
heath
on
Mt.
Sylfjellet
(Table
25.1),
lichen
species,
mostly
Cladina
spp.,
declined
or
disappeared.
By
contrast,
the
cover
of
Empetrum
nigrum
and
the
bryophytes
Barbilophozia
spp.
and
Pleurozium
schreberi
were
higher
in
1999
than
in
the
1920s.
Calluna
vulgaris,
not
recorded
in
the
1920s,
was
present
in
one-third
of
the
quadrats
in
1999.
At
Kilpisjarvi,
in
the
Vaccinium
myrtillus
heath
reindeer
lichens
have
declined,
414
R.
Virtanen,
A.
Eskelinen
and
E.
Gaare
Table
25.1.
Changes
in
plant
species
abundance
in
heath
vegetation
at
Mt.
Sylfjellet
and
Kilpisjarvi
in
the
1920s
and
1999.
Loiseleuria
procumbens
heath
n=15;
Vaccinium
myr-
tillus
heath,
Sylfjellet
n=25;
and
Vaccinium
myrtillus
heath,
Kilpisjarvi
n=10.
t
-test
and
X
.
2
results
(*
p<0.5,
**
p<0.01,
***
p<0.005)
Loiseleuria
procumbens
heath
(Sylene)
Mean
cover
(%)
Frequency
1920s
1999
1920s
1999
Decreased
Arctostaphylos
alpina
7.6
0.2***
0.8
0.0***
Loiseleuria
procumbens
66.0
28.9***
1.0
1.0
Vaccinium
myrtillus
Vaccinium
vitis-idaea
4.4
0.7***
1.0
0.2***
Salix
herbacea
Carex
bigelowii
Deschampsia
fl
exuosa
Diphasiastrum
alpinum
Euphrasia
frigida
2.0
0.0
0.6
0.0**
Hieracium
alpinum
Trientalis
europaea
Polytrichum
piliferum
Alectoria
nigricans
4.4
1.1***
0.8
0.3
Alectoria
ochroleuca
12.2
2.2***
1.0
0.7
Cetraria
ericetorum
12.0
3.1***
1.0
0.9
Cladina
arbuscula
(incl.
C.
mitis)
8.2
2.9***
1.0
0.9
Cladonia
coccifera
3.3
1.3***
1.0
0.4**
Cladonia
deformis
(+C.
sulphurina)
Cladonia gracilis
3.4
2.2*
0.9
0.7
Cladonia
pyxidata
(+C.
chlorophaea)
2.0
0.7*
0.6
0.2
Cladonia
uncialis
Flavocetraria
cucullata
10.2
0.9***
0.9
0.3*
Flavocetraria
nivalis
17.7
4.9***
1.0
0.9
Solorina
crocea
2.6
0.0
0.8
0.0***
Stereocaulon
spp.
8.0
0.7***
1.0
0.2***
Thamnolia
vermicularis
7.0
3
.3
***
1.0 1.0
Increased
Calluna
vulgaris
Empetrum
nigrum
ssp.
hermaphroditum
11.8
19.9*
1.0
1.0
Salix
herbacea
0.7
2.4***
0.2
0.7*
Vaccinium
uliginosum
Melampyrum
pratense
Andreaea
rupestris
0.0
1.5
0.0
0.5*
Barbilophozia
spp.
Gymnomitrion
spp.
1.2
10.7***
0.3
0.9***
Polytrichum
juniperinum
Pleurozium
schreberi
Ptilidium
ciliare
0.0
1.3
0.0
0.4
Racomitrium
lanuginosum
2.8
15.8***
0.7
0.9
Cetraria
islandica
Cetrariella
delisei
0.0
1.3
0.0
0.4
Cladonia
subfurcata
Long
-Term
Changes
in
Alpine
Plant
Communities
in
Norway
and
Finland
415
Vaccinium
myrtillus
heath
(Sylene)
Mean
cover
(%)
Frequency
Vaccinium
myrtillus
heath
(Kilpisjarvi)
Mean
cover
(%)
Frequency
1920s
1999
1920s
1999
1920s
1999
1920s
1999
40
26*
1.0 1.0
5.5
2.0***
0.7
0.6
4.6
0.5**
0.4
0.2
6.9
3.1***
1.0
0.6
7.3
3.8***
1.0
0.9
2.9
0.7*
0.6
0.2
3.7
0.9***
0.9
0.3**
2.2
0.9***
0.7
0.3
1.9
0
0.8
0***
7.8
1.4***
1.0
0.4**
30.1
11.4***
1.0
1.0
1.8
0.3*
1.0
0.6
7.1
1.2***
1.0
0.4
3.9
1.2*
1.0
0.8
3.1
0.1***
0.9
0.1***
15.2
3.6***
1.0
0.9
11.3
1.8***
1.0
0.6
0.9
0.3**
0.9
0.7
3.1
0.8*
0.4
0.2
0
0.9
0
0.3*
4.5
27.4***
0.7
1.0
1.4
10.3***
0.3
0.4
0.1
0.9*
0.1
0.3
4.4
9.6*
0.7
1.0
0.5
7.6*
0.8
0.6
0.7
4.8***
0.2
0.8***
0.7
2.7***
0.7
1
0.0
0.9
0
0.3*
416
R.
Virtanen,
A.
Eskelinen
and
E.
Gaare
Table
25.2.
Changes
in
plant
species
abundances
in
snowbed
vegetation
at
Mt.
Sylfjellet
and
Kilpisjarvi
in
the
1920s
and
in
1998/1999
(Deschampsia
fl
exuosa-Anthoxanthum
odoratum
snowbed;
n=20;
Trisetum
spicatum-Sibbaldia
procumbens
snowbed,
n=10).
t
-test
and
X
2
results
(*
p<0.5,
**
p<0.01,
***
p<0.005).
Values
in
italics
are
numbers
of
shoots
0.25
m
-2
Deschampsia
fl
exuosa-
Anthoxanthum
odoratum
snowbed
Trisetum
spicatum-
Sibbaldia
procumbens
snowbed
Mean
cover
(%)
1920s
1999
Frequency
1920s
1999
Mean
cover
(%)
1920s
1998
Frequency
1920s1998
Decreased
Salix
herbacea
51
25.4**
1.0
1.0
Carex
bigelowii
14.3
0.7***
1
0.2***
Carex
lachenalii
2.5
0
0.5
0**
Carex
vaginata
2.2
0
0.5
0**
Gnaphalium
supinum
4.7
1.5**
0.7
0.5
Rumex
acetosa
3.0
1.0***
0.9
0.3***
Salix
herbacea
27.4
13.9**
1
0.9
Trientalis
europaea
6.2
0.8***
0.7
0.3
Barbilophozia
spp.
8.6
5.0*
1
0.9
Kiaeria
starkei
2.9
0.6*
0.5
0.1
Moerckia
blyttii
3.4
0
0.5
0**
Pleurocladula
albescens
3.1
0
1.0
0***
Polytrichastrum
alpinum
3.8
0.2***
0.6
0.1**
Cetraria
islandica
5.4
1.8***
1
0.6**
1.8
0.2**
1.0
0.2**
(+
C.
ericetorum)
Cetrariella
delisei
0.7
0
0.7
0*
Cladonia
coccifera
1.6
0
0.8
0**
Cladonia
gracilis
11.7
2.0***
1.0
0.6
1.3
0.2*
0.9
0.3
(+C.
ecmocyna)
Cladonia
bellidiflora
8.3
0
0.9
0***
Increased
Agrostis
mertensii
0
15.6
0
1.
0***
Alchemilla
alpina
0.2
5.6***
0.1
0.7***
Bartsia
alpina
0
1.2
0
0.4*
Bistorta
vivipara
1.0
4.0***
0.3
1.0***
Deschampsia
cespitosa
0.2
2.6*
0.1
0.4
Deschampsia
fl
exuosa
3.1
43.5**
0.2
0.8
Empetrum
nigrum
0.3
6.3***
0.1
0.8***
Euphrasia
frigida
0
1.8
0
0.6***
Long
-Term
Changes
in
Alpine
Plant
Communities
in
Norway
and
Finland
417
Table
25.2.
(Continued)
Deschampsia
fl
exuosa-
Anthoxanthum
odoratum
snowbed
Trisetum
spicatum-
Sibbaldia
procumbens
snowbed
Mean
cover
(%)
Frequency
Mean
cover
(%)
Frequency
1920s
1999
1920s
1999
1920s
1998
1920s
1998
Geranium
sylvaticum
0
1.7
0
0.5**
Luzula
multiflora
ssp.frigida
0
1.8
0
0.5**
Phleum
alpinum
0.8
2.1*
0.3
0.6
Pyrola
minor
0
1.5
0
0.5**
Ranunculus
acris
0
2.6
0
0.6***
Sibbaldia
procumbens
0.5
1.7*
0.2
0.5
Solidago
virgaurea
0.8
2.9**
0.3
0.7*
Taraxacum
sp.
0
1.4
0
0.6*
Vaccinium
myrtillus
0.2
13.3***
0.2
0.8***
Veronica
alpina
0
2.3
0
0.7***
1.3
4.9*
0.4
0.8
Polytrichum
juniperinum
0
1.5
0
0.5**
Sanionia
uncinata
0
2.3
0
0.6***
Cladina
arbuscula
0
1.5
0
0.5**
similarly
to
the
Sylfjellet
site.
However,
the
response
was
different,
with
Vac-
cinium
myrtillus
having
a
lower
cover
in
1999
than
in
the
1920s.
Of
the
mosses,
Polytrichum
piliferum,
regularly
present
in
the
1920s,
was
not
found
in
1999.
25.4.2
Snowbed
Vegetation
In
the
Deschampsia
fl
exuosa-Anthoxanthum
odoratum
community
on
Mt.
Sylfjellet,
typical
snowbed
plants
such
as
Carex
lachenalii,
Gnaphalium
supinum,
Kiaeria
starkei,
Moerckia
blyttii
and
Salix
herbacea
declined
between
the
1920s
and
1999
(Table
25.2)
and
herbaceous
species
of
grasslands
or
less
extreme
snowbed
sites,
such
as
Bistorta
vivipara
and
Solidago
virgau-
rea,
increased.
At
Kilpisjarvi,
in
the
Trisetum
spicatum-Sibbaldia
procumbens
snowbed
community
a
similar
trend
was
found.
Snowbed
plants
(Pleuro-
cladula
albescens,
Salix
herbacea,
and
Veronica
alpina)
declined
and
grasses
(Agrostis
mertensii
and
Deschampsiaflexuosa)
and
Taraxacum
spp.
(mainly
T.
croceum)
increased.
In
both
areas,
dwarf
-shrub
species,
e.g.
Vaccinium
myr-
tillus,
normally
absent
from
snowbed
sites,
had
established.
418
R.
Virtanen,
A.
Eskelinen
and
E.
Gaare
25.4.3
Alpine
Soligenous
Mires
The
species
-rich
Kobresia
simpliciuscula-Carex
microglochin
mire
communi-
ties
on
Mt.
Sylfjellet
were
studied
at
low
(860
m
a.s.1.,
Storbekken)
and
high
altitude
(1200
m
a.s.l.,
Storsola).
Lichens,
albeit
not
dominant
in
1920s,
showed
a
significantly
lower
abundance
in
1999
compared with
the
1920s
(Table
25.3).
At
high
altitude
there
was
a
decline
in
vascular
plant
species,
including
dwarf
shrubs,
small
herbs,
and
rosette
species.
Only
Juncus
biglumis
had
a
greater
cover
in
1999
than
in
the
1920s.
On
the
lower
altitude
site,
species
typically
found
at
high
altitudes,
e.g.
Carex
bigelowii,
declined.
Of
the
mosses,
Blindia
acuta
and
Scorpidium
cossoni
showed
some
increase.
Table
25.3.
Changes
in
plant
species
abundance
in
the
Kobresia
simpliciuscula-Carex
microglochin
communities
in
Storsola
(1205
m
a.s.1.)
and
in
Storbekken
(860
m
a.s.l.)
at
Mt.
Sylfjellet
in
the
1920s
and
1999
(in
each
site
n=10).
t
-test
and
X
2
results
(*
p<0.5,
**
p<0.01,
***
p<0.005)
Storsola
Storbekken
Mean
cover
(%)
1920s
1999
Frequency
1920s
1999
Mean
cover
(%)
1920s
1999
Frequency
1920s
1999
Decreased
Polygonum
viviparum
10.6
3.3***
1
1
5.5
2.3**
1.0
0.7
Carex
atrofusca
4.8
1.7*
0.8
0.5
5.0
2.0**
1
0.6
Carex
bigelowii
6.1
0.7
0.9
0.2*
Carex
capillaris
8.3
2.3***
1.0
0.7
Carex
microglochin
28.3
13.7*
1.0
0.8
Carex
rupestris
8.8
2.5*
0.6
0.6
Carex
vaginata
13.3
5.2**
1
0.7
Diapensia
lapponica
2.9
0
0.7
0*
Empetrum
nigrum
6.4
0.3***
1
0.1***
Euphrasia
frigida
3.0
1.0***
0.9
0.3
Festuca
vivipara
6.6
2.0***
1.0
0.6
Juncus
triglumis
3.9
1.3***
1.0
0.4
Pedicularis
oederi
6.6
2.0***
1
0.6
Pinguicula
vulgaris
3.3
1.3***
1
0.4*
3.3
1.3***
1.0
0.4
Vaccinium
uliginosum
2.9
0
0.7
0*
4.4
2.0*
1.0
0.6
Aulacomnium
turgidum
8.3
1.0***
0.8
0.3
Hypnum
bambergeri
10.9
0
1.0
0
Hypnum
hamulosum
6.0
1.0*
0.7
0.3
(+H.
callichroum)
Ptilidium
ciliare
2.3
0.7*
0.7
0.2
Racomitrium
lanuginosum
6.1
0
1
0***
Scorpidium
cossoni
5.1
1.7*
0.7
0.5
(+S.
revolvens)
Cetraria
islandica
3.3
0.3***
1
0.1***
3.3
0.3
1.0
0.1***
Long
-Term
Changes
in
Alpine
Plant
Communities
in
Norway
and
Finland
419
Table
25.3.
(Continued)
Storsola
Storbekken
Mean
cover
(%)
Frequency
Mean
cover
(%)
Frequency
1920s
1999
1920s
1999
1920s
1999
1920s
1999
Cladina
arbuscula
3.3
0.7***
1
0.2***
3.3
0.7
1.0
0.2***
Cladonia
pyxidata
Flavocetraria cucullata
3.3
1.3***
1
0.4*
Flavocetraria
nivalis
3.3
0.3***
1
0.1***
3.0
0
0.9
0***
Thamnolia
vermicularis
2.6
0.7**
0.8
0.2
Nostoc
commune
9.6
0.3
1
0.1***
Increased
Juncus
biglumis
1.3
3.0*
0.4
0.9
Blindia
acuta
0
8.0
0
1***
Hypnum
bambergeri
0
2.3
0
0.7*
Scorpidium
cossoni
0
2.9
0
0.7*
25.5
Discussion
The
long-term
comparative
data
show
a
number
of
changes
in
the
species
composition
and
abundance
of
plant
species
in
several
sites
of
the
Scandes.
The
observed
vegetation
changes
can
result
from
different
factors
and
they
need
careful
interpretation.
Causal
links
between
observational
data
and
processes
rely
on
weak
inference.
However,
we
recognise
that
information
obtained
from
long-term
observational
data
is
important
to
complement
an
experimental
approach
to
vegetation
change,
which
often
suffers
from
time-
lag
deficiencies
and
unrealistic
designs.
A
possible
reason
for
the
decline
in
lichen
cover
in
heath
vegetation
at
Mt.
Sylfiellet
is
the
increased
summer
grazing,
as
opposed
to
mainly
winter
graz-
ing
earlier.
Summer
grazing
and
trampling
are
known
to
reduce
lichen
cover
(Gaare
1968;
Grabherr
1982;
Haapasaari
1988)
and
recovery
is
slow
after
heavy
lichen
depletion
(Gaare
1998).
However,
Cornelissen
et
al.
(2001)
found
that
an
increase
in
dwarf
shrubs
could
lead
to
a
decrease
in
lichens.
In
the
heath
site
at
Kilpisjarvi,
the
cover
of
lichens
had
declined
which
suggests
that
the
levels
of
reindeer
trampling
and
grazing
have
become
more
intense
dur-
ing
the
last
decades.
The
increased
cover
of
heath
dwarf
shrubs
at
Mt.
Sylfjellet
could
be
a
response
to
the
observed
climatic
warming
(Holten
and
Carey
1992).
Mean-
while,
the
decline
in
the
cover
of
the
dominant
dwarf
shrub
Vaccinium
myr-
tillus
at
the
Kilpisjarvi
heath
site
is
most
likely
to
have
resulted
from
grazing
420
R.
Virtanen,
A.
Eskelinen
and
E.
Gaare
by
the
Norwegian
lemming.
Lemmings
cut
V
myrtillus
shoots
during
their
population
peak
in
the
winter
of
1997-1998
(R.
Virtanen,
pers.
obs.).
A
general
trend
of
the
change
in
snowbed
sites
was
that
the
abundance
of
grassland
and
heath
species
increased
while
snowbed
plants
declined.
Such
changes
in
snowbed
vegetation
are
unlikely
to
be
related
to
changes
in
reindeer
grazing
pressure.
In
fact,
heavy
reindeer
grazing
would
favour
narrow
-leaved
graminoids
and
prostrate
plants,
whereas
taller
herbs
and
shrubs
would
increase
under
light
grazing
(Gaare
1968;
Oksanen
and
Moen
1994;
Moen
and
Oksanen
1998;
Virtanen
1998).
Rather,
the
changes
in
vegetation
composition
suggest
that
the
sites
with
formerly
late
-lying
snow
became
snow
-free
earlier
and
that
the
vegetation
had
already
responded
to
such
a
lengthening
of
the
growing
season.
Unfortunately,
we
cannot
relate
the
observed
changes
in
snowbed
vegetation
to
direct
observations
of
snow
duration
in
the
two
areas;
however,
they
are
in
accordance
with
the
observed
increase
in
surface
temper-
atures
and
shorter
duration
of
snow
cover,
particularly
in
the
mountains
of
southern
Norway
(see
also
Klanderud
and
Birks
2003).
The
species
-rich
alpine
mires
at
Mt.
Sylfjellet
with
rare
mountain
plants
did
not
show
any
strong
signs
of
vegetation
change
over
70
years.
The
decline
of
lichens
may
reflect
the
observed
changes
in
reindeer
grazing
discussed
above.
Current
grazing
regime
may
be
responsible
for
the
increase
of
the
moss
Blindia
acuta
and
the
graminoid
Juncus
biglumis.
The
rarer
plants
are
still
regularly
found
and
their
abundance
changed
only
a
little.
These
communi-
ties
are
found
in
small
habitat
patches
where
ground
water
seeps
onto
the
ground.
The
conditions
in
these
habitat
patches
have
remained
stable
and
therefore
no
marked
change
in
plant
cover
can
be
detected.
A
potential
threat
to
mires,
particularly
on
lowland
sites,
is
the
invasion
of
some
plants
which
by
dominating
the
space
can
exclude
low
-stature
mountain
plants.
It
is
notewor-
thy
that
Molinia
caerulea
hardly
recorded
in
the
1920s
now
has
a
cover
of
ca.
5
%,
suggesting
that
it
may
have
increased
in
this
site.
Its
further
expansion
has
to
be
considered
as
a
potential
threat
to
these
rich
alpine
mires.
25.6
Conclusions
1.
Long-term
changes
in
species
composition,
abundance
and
diversity
of
alpine
plant
communities
were
analysed
by
using
data
sets
from
central
Norway
and
NW
Finland
sampled
in
the
1920s
and
1990s.
Comparisons
were
made
for
seven
sites
representing
heath,
snowbed
and
soligenous
mire
vegetation.
2.
The
cover
and
number
of
lichens
declined
in
most
communities
probably
owing
to
increased
reindeer
grazing
and
trampling.
In
heath,
the
cover
of
some
bryophytes
and
dwarf
shrubs
increased
on
the
Norwegian
sites.
Long
-Term
Changes
in
Alpine
Plant
Communities
in
Norway
and
Finland
421
Herbs
and
grasses
increased
in
snowbed
communities,
while
some
typical
snowbed
plants
disappeared
or
decreased.
The
data
for
snowbeds
suggests
that
these
communities
may
have
responded
to
changes
in
snow
cover
as
a
result
of
the
observed
warmer
climate
in
the
1990s.
3.
The
species
that
showed
a
significant
decline
or
increase
may
be
consid-
ered
for
use
in
monitoring
as
indicators
of
environmental
change.
Acknowledgements.
The
Finnish
Research
Council
of
Natural
Resources
and
Environ-
ment
and
European
Science
Foundation
through
the
ALPNET
network
financially
sup-
ported
the
study.
M.
Zobel
helped
in
interpreting
Lippmaa's
cover
classes.
H.
Staaland
gave
useful
information
on
reindeer
population
at
the
Mt.
Sylfjellet
area.
L.
Nagy
and
an
anonymous
referee
improved
the
presentation.
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