Download PowerPoint Presentation - Polar and Arctic ecosystems

Polar ecosystems
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Arctic/Antarctic contrasts
Tundra - the physical template (climate,
landforms, soils)
Tundra plant and animal communities
Winter survival
Population cycles
Management issues
Responses to future climate change
Arctic(a) vs. Antarctica
 land: 8 X 106 km2
(30% ice)
 land: 14 X 106 km2
(97% ice)
\ substantial
\ no terrestrial food
\ land mammals
\ herbivorous &
\ no land mammals
\ no herbivorous or
terrestrial food
insectivorous
birds
insectivorous birds
Arctic(a) vs. Antarctica
 not geographically
isolated
 glacial refuges
 ice-free coastal
zone in summer
 relatively high
plant and animal
diversity
 geographically
isolated
no? glacial refuges
v. restricted icefree coastal zone in
summer
low plant and animal
diversity
Tundra ecosystems
“tundra” = treeless barrens
Global distribution of tundra
Arctic ecosystems in Canada
N.Arctic = polar desert
S.Arctic = tundra
Tundra ecosystems
 Tundra ecosystems are associated
with areas of extreme near-polar
climate which operates either
directly, or through a series of
environmental forcings (primarily
thaw-layer dynamics) to limit
productivity and biodiversity.
Tundra ecosystems
 Low species diversity may promote
instability. This is expressed by
highly cyclic behaviour.
 Arctic communities are
geologically-recent developments in
the planetary biome landscape.
Day-length and insolation
at top of atmosphere
Insolation
(w m-2)
600
500
Equator
400
300
40°N
200
60°N
100
0
90°N
J
daylength
0h
(North Pole)
M
J
S
12h
24h
12h
D
0h
Tundra climate stations
Barrow
Tiksi
Churchill
Iqaluit
Gulf Stream
Svalbard
Mean monthly temperatures,
tundra climate stations
15
10
5
0
-5
Barrow,AK
Churchill
Iqaluit
-10
Svalbard
Tiksi
-15
-20
-25
-30
-35
J
F
M
A
M
J
J
A
S
O
N
D
Mean monthly precipitation
tundra climate stations
70
60
50
40
Barro w,AK
Ti ksi
30
Churchil l
Iq alui t
Svalb ard
20
10
Svalb ard
Iq alui t
Churchil l
0
J
F
M
A
M
J
J
Ti ksi
A
S
Barro w,AK
O
N
D
Synoptic climatology
(after Reid Bryson)
Bering Sea
ice
ARCTIC
airmass
Treeline
Mean position of Polar Front (July)
Frost-free days
Treeline
Mean annual snowfall (mm)
Treeline
Permafrost
distribution
(note transect lines and
presence of sub-sea
permafrost)
Alaska
Siberia
Jan
120
150
150
tree
growth
pollen/seed
viability
July
mean location
Polar Front
30
mean #d >10°C
60
frost-free days
240
Boreal forest
patchy discontinuous
mean #d <0°C
Tundra
continuous
Permafrost
The critical thaw period
~40 d
~70 d
Data from Barrow, AK
Microclimatology: slope and aspect
forest?
Vigorous tree growth on southfacing slopes near treeline
Polar montane
environments:
freeze-thaw
weathering felsenmeer and
talus cones
Polar uplands:
thaw-layer
dynamics and
solifluction
Polar lowlands
Cryoturbation and patterned ground
Quick Time™ and a
TIFF (LZW) decompressor
are needed to see this picture.
dwarf shrubs,
grasses
sedges,
lichens
Frost polygons: note unvegetated
‘boils’ and standing water in cracks
Tundra floras
(product of late Tertiary cooling and
landbridges during glacial phases?
Centre-of-origin?
Alpine highlands
of NE Asia
Davis Strait “gap”
(major floristic contrast)
Topography Tundra
type
Flora
Thaw
depth
(m)
>2
rocky, well- Heath
evergreen
drained
shrubs
ridges
gently
Tussock Eriophorum 0.3-0.5
rolling
flat
Wet
graminoids 0.2-0.3
lowlands
sedge
wellShrub
deciduous
>1
drained
shrubs
alluvial
sites
Organic
layer (m)
<0.1
<0.3
0.1-0.5
thin?
Tundra vegetation-soil catenas
Sedge Shrub Sedge
FelsenTussock Heath meer
Depth (m)
0
1
2
organics
sandy
soil
permafrost
silty soil
silty soil
rocky
soil
Felsenmeer vegetation
dominated by lichens
Evergreen heath tundra
Dominated by Ericaceae (heaths), such as Cassiope
Heath tundra is floristically more
diverse than other tundra types
Tussock tundra
(dominated by
Eriophorum)
[cotton grass]
Wet sedge
tundra:
dominated by
graminoids (e.g.
Carex, Dupontia)
Animal life
Surviving winter
Strategy
 Distant migration
 Local migration
 Above snow-pack
heavy insulation
protective colouring
 Below snow-pack
 Hibernation
Dormant phase
Organisms
birds
caribou
muskox, polar bear
arctic fox, ptarmigan
lemmings, voles
ground squirrels
plants, insects
Are cyclical
population
dynamics
(~4 yr period)
a product of
simple food
webs?
(note difference in time
scales)
Vole data: N. Finland
Lemming data: N. Norway
Lemming distribution
The tundra phosphorus cycle
Forage (%P)
quality
Litter layer
0.2
0.2
0.3
0.6
••
thin
Ca
K
Active layer
P
N
N K
P
N
Ca
thick
P
K
••
••
Ca K
P N
Ca
Permafrost
lemmings/ha
jaegers
(pairs/km2)
snowy owls
(pairs/km2)
shorteared
owls
2-12
uncommon
no breeding
scarce
no breeding
absent
2-12
40-50
180-200
uncommon
no breeding
scarce
no breeding
absent
breeding
10
breeding
0.1
1 record
breeding
40-50
breeding
0.2
10/km2
Caribou dynamics
The ANWR
debate
Porcupine herd migrations:
radio-collared females at calving grounds on Arctic
Alaska coastal plain
Winter feeding grounds in Yukon,
Porcupine caribou herd (1998-99)
Snow goose dynamics
devegetated
area
birds
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Lesser snow goose flock
~4 M geese breed in the
marshes of the
Canadian Arctic
Jeffries et al., 2006. J. Ecol. 94, 234-242.
Impacts of snow goose overgrazing
Intense grubbing and
grazing by snowgeese
reduced
graminoid
growth
increased
soil salinity
reduced
graminoid
biomass
drying of
surface soil
Effects of snow goose grazing and grubbing
(James Bay)
Puccinellia
Salicornia
Potential effects of climate change
Is climate change occurring in Arctic
environments?
- climate records short
- biotic data fragmentary
Simulation models
Field experiments
Recent (post-1950) climate
change in polar regions
Arctic:
•
•
•
•
Reduction in sea ice extent and thickness
Northward treeline shifts (e.g. E. coast Hudson Bay)
Increased lake productivity (e.g. Ellesmere Island)
Range expansions (e.g. dragonflies - Inuvik - 2000)
Antarctic:
• Ice shelf disintegration (e.g. N. Larsen & Wordie Shelf)
• Spread of flowering plants (e.g. Antarctic hairgrass has
expanded its range 25-fold since 1964)
• New lichen species colonizing recently deglaciated areas
Climate
change
Climate change in the western Canadian arctic
Inuvik, NWT
30
Temperature (°C)
20
Monthly Max. Temp. (°C)
Mean Ann. Temp. (°C)
Monthly Min. Temp. (°C)
10
0
-10
-20
-30
-40
1950
1960
1970
1980
1990
2000
2010
Year
Data: Environment Canada
Climate change in the western Canadian arctic
Inuvik, NWT
400
350
Precipitation (mm)
300
250
200
150
100
50
Total Precip. (mm)
Snow (mm; water equivalent)
0
1950
1960
1970
1980
1990
2000
2010
Year
Data: Environment Canada
Climate change in the eastern Canadian arctic
Iqaluit, Nunavut
Monthly Max Temp (°C)
Mean Ann. Temp. (°C)
Monthly Min Temp (°C)
20
Temperature (°C)
10
0
-10
-20
-30
-40
1940
1950
1960
1970
1980
1990
2000
2010
Year
Data: Environment Canada
Climate change in the eastern Canadian arctic
Iqaluit, Nunavut
700
Total Precip. (mm)
Precipitation (mm)
600
Snow (mm; water
equivalent)
500
400
300
200
100
0
1940
1950
1960
1970
1980
1990
2000
2010
Year
Data: Environment Canada
Sea-ice
extent,
Arctic
and Antarctic
oceans
Source: www.metoffice.gov.uk/.../ images/figure5.jpg
Source: Arctic Climate Impact Assessment website
The
Arctic
of the
future
Field
experiments:
ITEX sites
Impacts of climatic warming
(ITEX results [1997])
reduced evergreen
shrub competitiveness
Increased air
temperature
increased
plant
productivity
increased
graminoid
abundance
inc. seed
weight and
viability
reduced
plant
diversity