Friday, January 20, 2012

BIOMES: Coniferous Woodland

Coniferous or boreal forests occur in cold northern regions characterised by long cold winters and short summers. Although there is a lot of precipitation, most of it falls as snow.

Location and climate

This biome is found between 50° and 60° north of the equator and is characterised by evergreen coniferous trees with needles instead of leaves. It is also known as Taiga. Typical trees include spruce, pine and fir. Animals commonly found in the region are reindeer, voles and hares. At the most northern extent, summer temperatures rarely rise above 10°C. As you move further north, trees are shorter and less dense because of the shorter growing season. Winter temperatures can fall as low as minus 30°C. At its southern margins, the trees become taller and denser and merge with deciduous trees (those that lose their leaves). Temperatures here can rise as high as 20°C in the summer and can fall to minus 15°C in winter. Precipitation is 300–900 mm, and most falls as snow in winter.

Taiga climate graph
Adaptations of vegetation

Conifers in the snow

  • Coniferous trees have thick bark to protect against the cold. They are cone-shaped, with flexible branches which help them to cope with heavy snow fall.
  • Pine cones protect the seeds during the harsh winter.
  • The thin waxy needles reduce water loss.
  • Their evergreen nature means that the needles can photosynthesize whenever there is sufficient sunlight.
  • The dense forest creates warmth during the harsh winter.

Taiga soils
  • Soils are shallow due to lack of decomposition and weathering caused by the cold. They are acidic due to leaching from rainfall and they are also poor in nutrients.
  • The litter layer is thick with needles due to slow decomposition.
  • The humus (decomposed) layer is thin.
  • There are clear boundaries between the layers in the soil as there are few worms to mix it in the cold conditions.
  • Trees have shallow roots.
  • The typical soil is a podsol, which has a distinctive ash grey layer (or horizon) above a red layer, which is rich in iron.
Courtesy: BBC

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