Conifer Forests
Taiga or Boreal Forest

 
  • Conifer forests are found primarily in a broad circumpolar belt across the Northern Hemisphere and on mountain ranges
  • Low temperatures limit the growing season to a few months each year
    • Dominated by needle-leaf evergreen trees
       

 

 

  • The variable composition and structure of these forests reflect the wide range of climatic conditions in which they grow
  • Central Europe
    • Dominated by Norway spruce

 

 

 

 

 

  • North America Rocky Mountains
    • Subalpine forest Engelmann spruce, subalpine fir
    • Middle elevations Douglas fir
    • Low elevations ponderosa pine and lodgepole pine
       

 

 

 

  • North America California Sierra
    • Giant sequoia
  • North America Pacific Northwest
    • Highly productive coastal forest

 

 

  • The boreal forest (or taiga) is the largest expanse of conifer forest
    • This is the largest vegetation formation on Earth
  • The taiga encompasses the high latitudes of the Northern Hemisphere and covers 11 percent of the Earth's terrestrial surface (vs. 12% original tropical rainforest, now 5%)
  • The taiga primarily occupies formerly glaciated land and is a region of cold lakes, bogs, rivers, and alder thickets

     

 

  • The taiga is divided into three vegetation zones
    • Forest-tundra ecotone (pics)
    • Open lichen woodland (pics)
    • Main boreal forest this grades into the temperate forest (pics)
       

 

 

 

 

  • The taiga is dominated by a cold continental climate with strong seasonal variations
    • Summers are short, cool, and moist
    • Winters are long, harsh, and dry
  • Interior Alaska and central Siberia experience some of the most extreme seasonal temperature fluctuations (as much as 100C between min and max)
     

 

 

  • The permafrost is the perennially frozen subsurface that develops where the ground temperatures remain below 0C
  • Because the permafrost is impervious to water, it forces all water to remain and move above it
    • The ground stays soggy even though precipitation is low

       

 

  • During periods of drought, fires can affect a large portion of the taiga
  • Boreal species, broadleaf trees and conifers, are well adapted to fire
    • Fire is a source of regeneration
  • Many areas of boreal forest are being clear-cut because of global demand for timber and pulp
     

 

 

 

  • The boreal forest has a unique animal community
    • Herbivores include
    • caribou
    • moose
    • snowshoe hare
    • red squirrel
    • porcupine
    • Predators include wolf, lynx, pine martin, and owl
  • Nesting location of migratory neotropical birds (spend summers in US and Canada, winters in the tropics)
  • Herbivorous insects (e.g., spruce budworm)
     

 

 

  • Litter inputs are low but decomposition rates are slow, resulting in an accumulation of organic matter
  • Boreal forest soils
    • Spodosols characterized by a thick organic layer
  • Boreal forests have generally low net primary productivity
    • Limited by low nutrients, cooler temperatures, and a short growing season