Tundra and Polar Ecosystems - Summary

Tundra and Polar Ecosystems

Temperature and Precipitation

Tundra ecosystems are found in areas with extreme near-polar climates, limiting productivity and biodiversity. The distribution of tundra includes Arctic, Alpine, and Antarctic regions.

Arctic vs. Antarctica

  • Arctic: Less geographically isolated, has glacial refuges, ice-free coastal zones in summer, and higher plant and animal diversity.
  • Antarctica: Geographically isolated, lacks glacial refuges, has restricted ice-free coastal zones, and low plant and animal diversity.

Tundra Types and Distribution

Tundra is a Finnish word meaning 'treeless plain.' Arctic tundra is located north of the Arctic Circle, while Alpine tundra is found in high mountain areas. Global distribution includes areas in North America, Europe, and Asia.

Climate and Permafrost

Tundra ecosystems are characterized by:

  • Areas of extreme near-polar climate that limits productivity and biodiversity.
  • Permafrost: continuous, discontinuous, sporadic, and alpine.
  • Active layer: the top layer of soil that thaws in summer (0.15-0.6 m thick in continuous permafrost areas).

Landscape Features

  • Cryoplanation: Soil movement down slopes due to freeze-thaw, creating a rolling landscape.
  • Patterned ground: Symmetrical landforms from frost action, including cryoturbation (soil movement from freeze-thaw).
  • Frost polygons: Unvegetated boils where mud is pushed up, with stones pushed to edges and standing water in cracks.

Vegetation

Arctic vegetation is structurally simple, with few layers, a low number of species, and low growth rates. Plants are mainly perennial and reproduce vegetatively. Common vegetation types include:

  • Sedge
  • Shrub
  • Heath
  • Tussock
  • Fellfields ('rock deserts'): Higher, drier areas 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).

Fauna

Animals adapt to the winter through:

  • Distant migration (birds, reindeer)
  • Local migration (ground squirrels)
  • Above snow-pack survival with heavy insulation and protective coloring (muskox, polar bear)
  • Below snow-pack survival (lemmings, voles, arctic fox, ptarmigan)
  • Hibernation (ground squirrels)
  • Dormant phase (plants, insects)

Population Dynamics

Low species diversity may promote instability, leading to cyclic behavior in populations, such as voles and lemmings.

Climate Change Impacts

  • Reduction in sea ice extent and thickness
  • Northward treeline shifts
  • Increased lake productivity
  • Range expansions of species
  • Ice shelf disintegration
  • Spread of flowering plants and colonization by new lichen species

Climatic warming impacts include increased seed weight and viability, increased graminoid abundance, reduced evergreen shrub competitiveness, increased plant productivity, and reduced plant diversity.

Tundra Characteristics

  • Very cold permafrost, leading to poorly drained, peaty soils with lakes and bogs.
  • Short growing season, with winter temperatures potentially reaching -10 to -50°C.
  • Limited soil microbial activity.
  • Plants propagate vegetatively, with a lot of below-ground biomass.
  • Exposure is a significant challenge, resulting in perennial, low-growing plants, cushion formers, and lichens.
  • Common migratory birds and predatory birds affect the ecological balance.
    *Few animals all year round that move up from southern forests.
    *Low productivity overall, but highly productive during growing season.