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PowerPoint Presentation - Polar and Arctic 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
   Arctic(a) vs. Antarctica
 land: 8 X 106 km2    land: 14 X 106 km2
  (30% ice)             (97% ice)
\ substantial         \ no terrestrial food
   terrestrial food
\ land mammals        \ no land mammals
\ herbivorous &       \ no herbivorous or
   insectivorous        insectivorous birds
   birds
   Arctic(a) vs. Antarctica
 not geographically    geographically
  isolated              isolated
 glacial refuges      no? glacial refuges
 ice-free coastal     v. restricted ice-
  zone in summer        free coastal zone in
 relatively high       summer
  plant and animal     low plant and animal
  diversity             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
             600

             500                         Equator
Insolation




             400
 (w m-2)




             300
                                           40°N
             200

             100                            60°N
                                    90°N
               0
                   J   M      J     S               D
  daylength
             0h        12h   24h   12h             0h
(North Pole)
Tundra climate stations


                   Barrow

                              Tiksi

  Churchill


                   Svalbard
         Iqaluit




    Gulf Stream
              Mean monthly temperatures,
                tundra climate stations
 15


 10


 5


 0


 -5                                                   Barr ow,AK
                                                      Chur chill
-10                                                   Iqaluit
                                                      Svalbard
-15                                                   Tiksi


-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

                                                                               Ba rrow,AK
                                                                               Ti ksi
 30                                                                            Ch urchi l l
                                                                               Iqal ui t
                                                                               Sval bard
 20



     10



      0                                                            Sval bard
                                                                 Iqal ui t
          J   F
                  M                                            Ch urchi l l
                      A
                          M                                 Ti ksi
                              J
                                  J
                                      A                   Ba rrow,AK
                                          S
                                              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
                                             mean location
Jan        tree       July                    Polar Front
          growth
120                      30                mean #d >10°C
150                      60                frost-free days
        pollen/seed
150       viability   240                  mean #d <0°C

      Boreal forest              Tundra




  patchy discontinuous        continuous

                                Permafrost
The critical thaw period




                ~40 d



              ~70 d
                      Data from Barrow, AK
Microclimatology: slope and aspect

               forest?
Vigorous tree growth on south-
  facing 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


                                   QuickTime™ and a
                              TIFF (LZW) decompressor
                           are needed to see this pic ture.




                sedges,
dwarf shrubs,
                lichens
  grasses
 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      Flora     Thaw      Organic
            type                 depth    layer (m)
                                  (m)
rocky, well- Heath    evergreen    >2       <0.1
   drained             shrubs
    ridges
    gently   Tussock Eriophorum 0.3-0.5     <0.3
    rolling
      flat     Wet   graminoids 0.2-0.3    0.1-0.5
  lowlands    sedge
     well-    Shrub   deciduous    >1      thin?
   drained             shrubs
   alluvial
     sites
       Tundra vegetation-soil catenas
                                               Felsen-
       Sedge Shrub Sedge         Tussock Heath meer




Depth (m)
   0    organics
            sandy   silty soil      silty soil
             soil                                rocky
   1
                                                  soil

       permafrost
   2
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                   Organisms
 Distant migration        birds
 Local migration          caribou
 Above snow-pack
    heavy insulation
                           muskox, polar bear
    protective colouring
 Below snow-pack          arctic fox, ptarmigan
 Hibernation              lemmings, voles
Dormant phase             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)            0.2          0.2             0.3                    0.6
quality
Litter layer   thin
                                                     ••       thick
                                                                      ••         ••
                             K                  N         P            Ca K
                      Ca            N K              Ca
Active layer                                                            P N
                                        P        K
                             P     Ca
                      N

Permafrost

 lemmings/ha          2-12         2-12          40-50                180-200

 jaegers           uncommon      uncommon        breeding             breeding
(pairs/km2)       no breeding    no breeding      10                   40-50
snowy owls          scarce         scarce      breeding               breeding
(pairs/km2)       no breeding    no breeding      0.1                   0.2
shorteared          absent        absent       1 record               10/km2
       owls
           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 (Un compressed) decompressor
                            are neede d to see this picture.



Lesser snow goose flock
~4 M geese breed in the
    marshes of the           Jeffries et al., 2006. J. Ecol. 94, 234-242.
    Canadian Arctic
   Impacts of snow goose overgrazing
                           reduced
Intense grubbing and
grazing by snowgeese       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
                            Monthly Max. Temp. (°C)
                            Mean Ann. Temp. (°C)
                   20       Monthly Min. Temp. (°C)


                   10
Temperature (°C)




                    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


                     300
Precipitation (mm)




                     250


                     200


                     150


                     100

                              Total Precip. (mm)
                      50
                              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

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

                   10
Temperature (°C)




                    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)

                     600                                                  Snow (mm; water
                                                                          equivalent)


                     500
Precipitation (mm)




                     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                      increased   reduced
temperature                        graminoid   plant
                 increased         abundance   diversity
                    plant
                productivity
                                inc. seed
                               weight and
                                 viability

				
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