Tundra

 
  • The tundra is a frozen plain that is located at the highest latitudes of the Northern Hemisphere
    • Tundra has up to 100 percent plant cover and wet to moist soils
    • Polar desert has less than 5 percent plant cover and dry soil
       

 

 

 

 

 

 

  • Three forces interact to form the conditions unique to the Arctic tundra
    • Permanently frozen deep layer of permafrost
    • Overlaying active layer of organic matter and mineral soil that thaws each summer and freezes the following winter
    • Vegetation that reduces warming and retards thawing in summer
       

 

  • The alternate freezing and thawing of the upper layer of soil pushes stones and other material upward and outward from the mass to form a patterned surface
    • Frost hummocks, frost boils, earth stripes, stone polygons
  • Solifluction terraces or "flowing soil" form on sloping ground
    • Creep, frost thrusting, downward flow of supersaturated soil over the permafrost
       

 

 

 

 

  • The vegetation structure of the tundra is simple few species and slow growth
    • Only species that can withstand constant soil disturbance, buffeting by the wind, and abrasion by wind-carried particles of soil and ice can survive
  • Arctic plants propagate by vegetative means
     

 

 

  • Low ground vegetation
    • Cotton grasses, sedges, and Sphagnum
  • Well-drained sites
    • Heath shrubs, dwarf willows, birches, herbs, mosses, and lichens
  • Driest and most exposed sites
    • Scattered heaths, crustose and foliose lichen
       

 

 

  • Tundra plants are photosynthetically active about three months out of the year
    • They maximize use of the growing season and light by photosynthesizing during the 24-hour daylight period
    • Erect leaves allow for almost complete interception of solar radiation
  • Most of the photosynthate goes into the production of new growth
    • At the end of the season, resources are allocated to the roots
       

 

  • Most of the tundra vegetation is underground
    • Root-to-shoot ratios range from 3:1 to 10:1
  • Roots are concentrated in the upper soil that thaws during the summer
     

 

  • Animal diversity in the tundra is low
  • Invertebrates are concentrated near the surface
    • Segmented whiteworms, collembolas, and flies
  • Dominant vertebrates are herbivores
    • Caribou
    • lemmings
    • Arctic hares
    • musk oxen
  • Carnivore
    • Wolf
    • Arctic fox
    • snowy owls
    • jaegers, and other birds
  • Animals of the Tundra
     

 

 

  • Alpine tundra occurs in the higher mountains of the world and is a severe environment of rock-strewn slopes, bogs, meadows, and shrubby thickets
     

 

 

 

  • Strong winds, snow, cold, and widely fluctuating temperatures dominate these mountainous areas
    • Because the atmosphere is thin at high elevations, ultraviolet light is especially intense on clear days
    • Summer soil temperature ranges from 40C to 0C!
    • These areas receive precipitation but the steep topography induces rapid runoff (and loss) of water
       

 

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Newfoundland