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Polar ecosystems 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

Polar ecosystems

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Polar ecosystems. 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. land: 8 X 10 6 km 2 (30% ice) - PowerPoint PPT Presentation

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Page 1: Polar ecosystems

Polar ecosystems 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

Page 2: Polar ecosystems

Arctic(a) vs. Antarctica

land: 8 X 106 km2 (30% ice)

substantial terrestrial food

land mammals

herbivorous & insectivorous birds

land: 14 X 106 km2 (97% ice)

no terrestrial food

no land mammals

no herbivorous or insectivorous birds

Page 3: Polar ecosystems

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 ice-free coastal zone in summer

low plant and animal diversity

Page 4: Polar ecosystems

Tundra ecosystems

“tundra” = treeless barrens

Page 5: Polar ecosystems

Global distribution of tundra

Page 6: Polar ecosystems

Arctic ecosystems in Canada

N.Arctic = polar desert

S.Arctic = tundra

Page 7: Polar ecosystems

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.

Page 8: Polar ecosystems

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.

Page 9: Polar ecosystems

Day-length and insolationat top of atmosphere

Equator

40°N

60°N

90°N

Inso

lati

on

(w m

-2)

0

100

200

300

400

500

600

daylength (North Pole) 0h 12h 24h 12h 0h

J M J S D

Page 10: Polar ecosystems

Tundra climate stations

Barrow

Churchill

IqaluitSvalbard

Tiksi

Gulf Stream

Treeline

60°N

75°N

Page 11: Polar ecosystems

Mean monthly temperatures,tundra climate stations

-35

-30

-25

-20

-15

-10

-5

0

5

10

15

J F M A M J J A S O N D

Barrow,AK

Churchill

Iqaluit

Svalbard

Tiksi

Page 12: Polar ecosystems

Mean monthly precipitationtundra climate stations

J F M A M J J A S O ND

Barrow,AK

Tiksi

ChurchillIqaluit

Svalbard0

10

20

30

40

50

60

70

Barrow,AK

Tiksi

Churchill

Iqaluit

Svalbard

Page 13: Polar ecosystems

Synoptic climatology(after Reid Bryson)

Treeline

Mean position of Polar Front (July)

ARCTIC airmass

Bering Sea ice

Page 14: Polar ecosystems

Frost-free days

Treeline

Page 15: Polar ecosystems

Mean annual snowfall (mm)

Treeline

Page 16: Polar ecosystems

Permafrost distribution(note transect lines

and presence of sub-sea

permafrost)

Page 17: Polar ecosystems

Alaska

Siberia

Page 18: Polar ecosystems

Boreal forest Tundra

Permafrost

patchy discontinuous continuous

120 30 mean #d >10°C

mean locationPolar FrontJulyJan

150 240 mean #d <0°C

treegrowth

pollen/seedviability

150 60 frost-free days

Page 19: Polar ecosystems

The critical thaw period

Data from Barrow, AK

~70 d

~40 d

Page 20: Polar ecosystems

Microclimatology: slope and aspect

Aspect Flat South-facing North-facingSlope (°)Ground-Sunangle (°)0 10 20 40 10 20 4045 55 65 85 35 25 5210Direct-beam radiation, solar noon, summer solstice, 68.5°N

forest?

Page 21: Polar ecosystems

Vigorous tree growth on south-facing slopes near

treeline

Page 22: Polar ecosystems

Polar montane environments:

freeze-thaw weathering -

felsenmeer and talus cones

Page 23: Polar ecosystems

Polar uplands:

thaw-layer dynamics

and solifluction

Page 24: Polar ecosystems

Polar lowlands

Page 25: Polar ecosystems

Cryoturbation and patterned ground

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

dwarf shrubs,grasses

sedges,lichens

Page 26: Polar ecosystems

Frost polygons: note unvegetated ‘boils’ and standing water in cracks

Page 27: Polar ecosystems

Tundra floras(product of late Tertiary cooling and landbridges during glacial phases?

Centre-of-origin?

Davis Strait “gap”(major floristic contrast)

Plio-Pleistocene

migration

Plio-Pleistocene

migration

Alpine highlandsof NE Asia

Page 28: Polar ecosystems

Topography Tundratype

Flora Thawdepth(m)

Organiclayer (m)

rocky, well-drainedridges

Heath evergreenshrubs

>2 <0.1

gentlyrolling

Tussock Eriophorum 0.3-0.5 <0.3

flatlowlands

Wetsedge

graminoids 0.2-0.3 0.1-0.5

well-drainedalluvialsites

Shrub deciduousshrubs

>1 thin?

Page 29: Polar ecosystems

Tundra vegetation-soil catenas

Sedge Shrub Sedge Tussock Heath

0 organics

sandysoil

permafrost

rockysoil

silty soilsilty soil

Depth (m)

1

2

Felsen-meer

Page 30: Polar ecosystems

Felsenmeer vegetation dominated by lichens

Page 31: Polar ecosystems

Evergreen heath tundra

Dominated by Ericaceae (heaths), such as Cassiope

Page 32: Polar ecosystems

Heath tundra is floristically more diverse than other tundra types

Page 33: Polar ecosystems

Tussock tundra

(dominated by Eriophorum)

[cotton grass]

Page 34: Polar ecosystems

Wet sedge tundra:

dominated by graminoids (e.g. Carex, Dupontia)

Page 35: Polar ecosystems

Animal life

Page 36: Polar ecosystems

Surviving winterStrategy Organisms

Distant migration Local migration Above snow-pack

heavy insulation

protective colouring

Below snow-pack Hibernation Dormant phase

birds caribou

ground squirrelsplants, insects

muskox, polar bear

lemmings, voles

arctic fox, ptarmigan

Page 37: Polar ecosystems

Are cyclical population dynamics

(~4 yr period)a product of simple food

webs?(note difference in time

scales)

Vole data: N. FinlandLemming data: N. Norway

Page 38: Polar ecosystems

Lemming distribution

Page 39: Polar ecosystems

The tundra phosphorus cycle

lemmings/ha 2-12 2-12 40-50 180-200 jaegers uncommon uncommon breeding breeding(pairs/km2) no breeding no breeding 10 40-50snowy owls scarce scarce breeding breeding(pairs/km2) no breeding no breeding 0.1 0.2shorteared absent absent 1 record 10/km2

owls

Active layer

Permafrost

CaCa

Ca

CaN

NN

N

P

PP

P

K KK

K

Forage (%P) 0.2 0.2 0.3 0.6quality

•• ••••Litter layer thin thick

Page 40: Polar ecosystems

Caribou dynamics

The ANWR debate

Page 41: Polar ecosystems
Page 42: Polar ecosystems

Porcupine herd migrations: radio-collared females at calving grounds on

Arctic Alaska coastal plain

Page 43: Polar ecosystems

Winter feeding grounds in Yukon, Porcupine caribou herd (1998-99)

300 k

m

Page 44: Polar ecosystems

Snow goose dynamics

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Lesser snow goose flock

~4 M geese breed in the marshes of the

Canadian Arctic

birds

devegetatedarea

Jeffries et al., 2006. J. Ecol. 94, 234-242.

Page 45: Polar ecosystems

Impacts of snow goose overgrazing

drying ofsurface soil

increasedsoil salinity

reduced graminoid

growth

reducedgraminoidbiomass

Intense grubbing andgrazing by snowgeese

Page 46: Polar ecosystems

Effects of snow goose grazing and grubbing (James Bay)

Salicornia

Puccinellia

Page 47: Polar ecosystems

Potential effects of climate change

Is climate change occurring in Arctic environments? - climate records short - biotic data fragmentary

Simulation modelsField experiments

Page 48: Polar ecosystems

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

Page 49: Polar ecosystems

Climate change

Page 50: Polar ecosystems

Climate change in the western Canadian arctic

Data: Environment Canada

Inuvik, NWT

-40

-30

-20

-10

0

10

20

30

1950 1960 1970 1980 1990 2000 2010

Year

Temperature (°C)

Monthly Max. Temp. (°C)Mean Ann. Temp. (°C)Monthly Min. Temp. (°C)

Page 51: Polar ecosystems

Climate change in the western Canadian arctic

Data: Environment Canada

Inuvik, NWT

0

50

100

150

200

250

300

350

400

1950 1960 1970 1980 1990 2000 2010

Year

Precipitation (mm)

Total Precip. (mm)

Snow (mm; water equivalent)

Page 52: Polar ecosystems

Climate change in the eastern Canadian arctic

Iqaluit, Nunavut

-40

-30

-20

-10

0

10

20

1940 1950 1960 1970 1980 1990 2000 2010

Year

Temperature (°C)

Monthly Max Temp (°C)Mean Ann. Temp. (°C)Monthly Min Temp (°C)

Data: Environment Canada

Page 53: Polar ecosystems

Climate change in the eastern Canadian arctic

Data: Environment Canada

Iqaluit, Nunavut

0

100

200

300

400

500

600

700

1940 1950 1960 1970 1980 1990 2000 2010

Year

Precipitation (mm)

Total Precip. (mm)

Snow (mm; waterequivalent)

Page 54: Polar ecosystems

Source: www.metoffice.gov.uk/.../ images/figure5.jpg

Sea-ice extent, Arctic

and Antarctic oceans

Page 55: Polar ecosystems

Source: Arctic Climate Impact Assessment website

Page 56: Polar ecosystems

The Arctic of the future

Page 57: Polar ecosystems
Page 58: Polar ecosystems
Page 59: Polar ecosystems

Field experiments:

ITEX sites

Page 60: Polar ecosystems

Impacts of climatic warming (ITEX results [1997])

inc. seedweight and

viability

increasedgraminoidabundance

reduced evergreen shrub competitiveness

increasedplant

productivity

Increased airtemperature

reducedplant diversity