Polar ecosystems

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. 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 Arctic(a) vs. Antarctica

3. 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 Arctic(a) vs. Antarctica

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 • 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.

8. 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.

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

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

11. Mean monthly temperatures,tundra climate stations

12. Mean monthly precipitationtundra climate stations

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

14. Frost-free days Treeline

15. Mean annual snowfall (mm) Treeline

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

17. Alaska Siberia

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

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

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 sedges, lichens dwarf shrubs, grasses

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? Plio-Pleistocene migration Alpine highlands of NE Asia Plio-Pleistocene migration Davis Strait “gap” (major floristic contrast)

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

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. Distantmigration Local migration Above snow-packheavy insulation protective colouring Below snow-pack Hibernation Dormant phase birds caribou Surviving winterStrategyOrganisms muskox, polar bear arctic fox, ptarmigan lemmings, voles ground squirrels plants, insects

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 Forage (%P) 0.2 0.2 0.3 0.6 quality •• •• •• Litter layer thin thick K N Ca K P Ca K N Ca N P Active layer K P 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

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

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

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

47. Potential effects of climate change • Is 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