Biome

• Tropical Rainforest Biome


  An example is the Amazon in South America
• Rainforests

  • Belong to the epicat camare group with high temperature and humidity levels
  • Located between 15 degrees north and south of the equator which results in constant, direct overhead sunshine
• Temperature

  • Generally high, ranging between 20 degrees and 34 degrees with an average of 27 degrees
  • The higher a rainforest gets in altitude, the lower the temperatures
• Diurnal range


  Greater than the seasonal change
• Temperature change with altitude

  Every 300m a rainforest goes up, the temperatures drop about 1.7°C
• Climate


  Generally one season, however in Monsoon areas a wet and dry Monsoon seasonal variation exists
• Rainfall


  • Averages 200 days per year
  • Varies from 2000mm per year to 5800mm per year
• Evaporation


  • Rates are high and condensation occurs at a rapid rate
  • Constant cloud cover keeps humidity levels high
• Trade winds


  The Northeast & Southeast trade winds meet at the equator and rise upwards to create a low-pressure belt
• Humidity


  • Averages 80-90%
  • Such conditions encourage high growth rates and denegation, therefore 50% of rainfall comes from evapo-transpiration
• Rainfall levels


  May be subjected to change because of human activities such as deforestation and agriculture
• Soil type


  Latosol soil
• Soil formation


  1. Produced by the process of leaching due to the high rainfall

  2. Infertile as the heavy rainfall washes the nutrients out of the soil

  3. A hardpan may frequently be found within this soil because of the leaching resulting in the soil becoming waterlogged
• Soil characteristics


  • Hot and wet conditions speed up the chemical weathering of the parent material which makes a very deep soil
  • Low in humus as plant litter decomposes rapidly due to the heat and humidity which is the nutrients to the plants instead of the soil
  • The large amount of decaying foliage results in many insects being able to camouflage themselves against the decaying foliage
• Soil colour


  • The heavy rainfall releases the Iron compounds contained within the soil to give it a dominant red/orange colour
  • Excessive leaching may result in laterisation, producing a Laterite soil which may bake hard when exposed to the hot temperatures
• Vegetation structure


  • Four layers: the emergent layer, the canopy, the understorey, and the forest floor
• Tree bark


  • Typically thin and smooth as the temperature throughout the year is typically 28°C on average, so they do not need protecting from the cold
  • The smooth surface allows water to run off easily to the soil so the tree can absorb the water
• Emergent layer


  • May grow to 40-70 metres in height to reach the sunlight first
  • Have wide structures on their roots called buttress roots, which support them in the wet soils caused by the heavy rainfall
  • Have small and waxy leaves to avoid drying out in warm winds and sunshine
• Canopy layer


  • Trees have large leaves with a drip tip so rainwater can run off quickly
  • Need to shed water to avoid the growth of fungus and bacteria
• Understorey


  • Vegetation has adapted by growing large and wide leaves to capture any light and moisture that trickles down
  • Some plants possess leaf stalks that turn as the light moves to absorb as much sunlight as possible
• Devil's Ivy plant


  • Leaves angle away from each other to avoid shading its own leaves to allow it to get more light
• Forest floor


  • Very little growth due to the lack of light
• Lianas


  • Have adapted to the dark conditions by having their roots in the ground and wrapping them around trees to climb towards the light