1. 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

2. Arctic(a) vs. Antarctica  land: 8 X 10 6 km 2 (30% ice)  substantial terrestrial food  land mammals  herbivorous & insectivorous birds  land: 14 X 10 6 km 2 (97% ice)  no terrestrial food  no land mammals  no herbivorous or insectivorous birds

3. 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

4. Tundra ecosystems “tundra” = treeless barrens

5. Global distribution of tundra

6. Arctic ecosystems in Canada N.Arctic = polar desert S.Arctic = tundra

7. Tundra ecosystems PTundra 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.

8. Tundra ecosystems PLow species diversity may promote instability. This is expressed by highly cyclic behaviour. PArctic communities are geologically-recent developments in the planetary biome landscape.

9. Day-length and insolation at top of atmosphere Equator 40°N 60°N 90°N Insolation (w m -2 ) 0 100 200 300 400 500 600 daylength ( North Pole) 0h 12h 24h 12h 0h J M J S D

10. Tundra climate stations Barrow Churchill Iqaluit Svalbard Tiksi Gulf Stream Treeline 60°N 75°N

11. Mean monthly temperatures, tundra climate stations

12. Mean monthly precipitation tundra climate stations

13. Synoptic climatology (after Reid Bryson) Treeline Mean position of Polar Front (July) ARCTIC airmass Bering Sea ice

14. Frost-free days Treeline

15. Mean annual snowfall (mm) Treeline

16. Permafrost distribution (note transect lines and presence of sub-sea permafrost)

17. Alaska Siberia

18. Boreal forest Tundra Permafrost patchy discontinuous continuous 120 30 mean #d >10°C mean location Polar Front JulyJan 150 240 mean #d <0°C tree growth pollen/seed viability 150 60 frost-free days

19. The critical thaw period Data from Barrow, AK ~70 d ~40 d

20. Microclimatology: slope and aspect forest?

21. Vigorous tree growth on south- facing slopes near treeline

22. Polar montane environments: freeze-thaw weathering - felsenmeer and talus cones

23. Polar uplands: thaw-layer dynamics and solifluction

24. Polar lowlands

25. Cryoturbation and patterned ground dwarf shrubs, grasses sedges, lichens

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

27. 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 highlands of NE Asia

29. Tundra vegetation-soil catenas Sedge Shrub Sedge Tussock Heath 0 organics sandy soil permafrost rocky soil silty soil Depth (m) 1 2 Felsen- meer

30. Felsenmeer vegetation dominated by lichens

31. Evergreen heath tundra Dominated by Ericaceae (heaths), such as Cassiope

32. Heath tundra is floristically more diverse than other tundra types

33. Tussock tundra (dominated by Eriophorum) [cotton grass]

34. Wet sedge tundra: dominated by graminoids (e.g. Carex, Dupontia)

35. Animal life

36. Surviving winter Strategy Organisms  Distant migration  Local migration  Above snow-pack heavy insulation protective colouring  Below snow-pack  Hibernation  Dormant phase birds caribou ground squirrels plants, insects muskox, polar bear lemmings, voles arctic fox, ptarmigan

37. 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

38. Lemming distribution

39. The tundra phosphorus cycle lemmings/ha 2-12 2-12 40-50 180-200 jaegers uncommon uncommon breeding breeding (pairs/km 2) no breeding no breeding 10 40-50 snowy owls scarce scarce breeding breeding (pairs/km 2) no breeding no breeding 0.1 0.2 shorteared absent absent 1 record 10/km 2 owls Active layer Permafrost Ca N N N N P P P P KK K K Forage (%P) 0.2 0.2 0.3 0.6 quality Litter layer thin thick

40. Caribou dynamics The ANWR debate

42. Porcupine herd migrations : radio-collared females at calving grounds on Arctic Alaska coastal plain

43. Winter feeding grounds in Yukon, Porcupine caribou herd (1998-99) 300 km

44. Snow goose dynamics Lesser snow goose flock ~4 M geese breed in the marshes of the Canadian Arctic birds devegetated area Jeffries et al., 2006. J. Ecol. 94, 234-242.

45. Impacts of snow goose overgrazing drying of surface soil increased soil salinity reduced graminoid growth reduced graminoid biomass Intense grubbing and grazing by snowgeese

46. Effects of snow goose grazing and grubbing (James Bay) Salicornia Puccinellia

47. Potential effects of climate change PIs climate change occurring in Arctic environments? - climate records short - biotic data fragmentary  Simulation models  Field experiments

48. 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

49. Climate change

50. Climate change in the western Canadian arctic Data: Environment Canada

51. Climate change in the western Canadian arctic Data: Environment Canada

52. Climate change in the eastern Canadian arctic Data: Environment Canada

53. Climate change in the eastern Canadian arctic Data: Environment Canada

54. Source: www.metoffice.gov.uk/.../ images/figure5.jpg Sea-ice extent, Arctic and Antarctic oceans

55. Source: Arctic Climate Impact Assessment website

56. The Arctic of the future

59. Field experiments: ITEX sites

60. Impacts of climatic warming (ITEX results [1997]) inc. seed weight and viability increased graminoid abundance reduced evergreen shrub competitiveness increased plant productivity Increased air temperature reduced plant diversity