Tundra and Polar Ecosystem Notes

Tundra and Polar Ecosystems

Temperature and Precipitation

  • Tundra biome relating annual mean temperature and precipitation compared to other biomes such as desert, grassland, tropical forest, etc.

Arctic vs. Antarctica

  • Arctic:
    • Land: 8 X 106 km2 (30% ice)
    • Substantial terrestrial food web.
    • Land mammals and herbivorous & insectivorous birds.
    • Not geographically isolated
    • Glacial refuges and ice-free coastal zone in summer
    • Relatively high plant and animal diversity.
  • Antarctica:
    • Land: 14 X 106 km2 (97% ice)
    • No terrestrial food web.
    • No land mammals and no herbivorous or insectivorous birds.
    • Geographically isolated.
    • No glacial refuges and restricted ice-free coastal zone in summer
    • Low plant and animal diversity.

Tundra Distribution

  • Arctic tundra: North of the Arctic Circle.
  • Alpine tundra: High mountains.

Tundra Ecosystems

  • Associated with areas of extreme near-polar climate, limiting productivity and biodiversity through freeze-thaw dynamics.

Treeless Plain

  • Tundra characterized as a treeless plain with locations such as Churchill, Iqaluit, Barrow, Tiksi, and Svalbard.

Tundra Climate

  • Mean monthly temperatures for tundra climate stations (Barrow, Churchill, Iqaluit, Svalbard, Tiksi) indicating extreme cold.

Permafrost Distribution

  • Zones of continuous, discontinuous, and alpine permafrost in regions like Siberia and Alaska.

Permafrost

  • Diagrammatic cross-sections of permafrost in Alaska and Siberia showing active layer thickness and permafrost depth.

Permafrost and Tree Growth

  • Relationship between permafrost type (patchy discontinuous, continuous), mean number of days >10°C, polar front location, and tree growth.

Polar Uplands

  • Cryoplanation: Movement of soil down slopes due to freeze-thaw action, creating a rolling landscape.
    • More impact on landscape than erosion in Arctic.

Slope and Aspect

  • Tree growth influenced by slope and aspect at high latitudes, with south-facing slopes favoring growth near the tree line due to ground-sun angle and direct-beam radiation.

Patterned Landforms

  • Symmetrically patterned landforms result from frost action.
  • Cryoturbation: Movement of soil caused by freeze-thaw.
  • Landscape is patterned - topography dwarf shrubs, grasses sedges, lichens in polar lowlands.

Frost Polygons

  • Unvegetated boils where mud is pushed up as frozen soil expands, with large stones pushed to edges and standing water in cracks.

Arctic Vegetation

  • Structurally simple with few layers.
  • Low number of species.
  • Low growth and mainly perennial.
  • Reproduces vegetatively rather than by seed.

Tundra Vegetation Types

  • Sedge, shrub, tussock heath compositions in varying soil and depth conditions.

Fellfields

  • Rock deserts at higher, drier, wind-exposed locations dominated by lichens.

Evergreen Heath Tundra

  • Dominated by Ericaceae (heaths), adapted to dry, cold conditions.

Tussock Tundra

  • Dominated by Eriophorum (cotton grass).

Wet Sedge Tundra

  • Dominated by graminoids (e.g., Carex).

Tundra Types

  • Tundra type: Heath, Tussock, Wet sedge, Shrub relating topography, flora, thaw depth and organic layer.

Fauna Survival Strategies

  • Strategies for surviving winter: distant migration, local migration, above snow-pack insulation & protective coloring, below snow-pack hibernation/dormant phase.

Caribou Migration

  • Caribou migration patterns, calving in spring, and winter feeding grounds (Porcupine herd example).

Porcupine Caribou Diet

  • seasonal diet changes reflecting migration of Porcupine Caribou.

Arctic Ground Squirrel

  • Arctic ground squirrel can sustain body temp of -2.90C and has quick brain function restoration on awakening.

Population Cycles

  • Low species diversity may promote instability, seen in cyclic behavior of vole (N. Finland) and lemming (N. Norway) populations.

Population cycles

  • Population cycles in the snowshoe hare and lynx.

Climate Change

  • Evidence of climate change in Arctic environments is being studied through climate records, biotic data & models.

Recent Climate Change in Polar Regions

  • Arctic:
    • Reduction in sea ice extent and thickness.
    • Northward treeline shifts.
    • Increased lake productivity.
    • Range expansions (e.g. dragonflies).
  • Antarctic:
    • Ice shelf disintegration.
    • Spread of flowering plants (e.g. Antarctic hairgrass).
    • New lichen species colonizing recently deglaciated areas.

Sea-Ice Extent

  • Arctic and Antarctic sea-ice extent anomalies showing trends over time.

Impacts of Climatic Warming

  • Increased seed weight and viability.
  • Increased graminoid abundance.
  • Reduced evergreen shrub competitiveness.
  • Increased plant productivity.
  • Reduced plant diversity.

Polar Bears

  • Polar bear studies on field movements, body mass, RMR, feeding demands, and foraging success.

Arctic of the Future

  • Expected changes: ice melt, tundra thaw, tree growth, snow cover recession, vegetation shifts, warmer temperatures, more precipitation, and eroding coastlines.

Tundra Characteristics

  • Very cold permafrost – poorly drained, peaty soils (lakes, bogs).
  • Short growing season (winter min temp may be as low as -10 to -50deg C).
  • Little soil microbial activity.
  • Plants propagate by vegetative growth (not by seed spread) – a lot of below-ground biomass.
  • Exposure a problem – perennial, low growing plants, cushion formers, lichens.
  • Migratory birds, e.g. geese, Arctic tern, willow grouse, insectivorous birds (lots of mosquitoes!).
  • Predatory birds – feed on smaller birds and lemmings.

Tundra Animals

  • Few animals all year round – move up from southern forests e.g. reindeer, caribou, wolf, grizzly bear.
  • Exceptions e.g. Arctic fox, Musk ox – adapted (cold and camouflage).
  • Low species diversity - very extreme environment.
  • Low productivity overall, but highly productive during growing season.