Wc24 - tropical rainforest carbon and water

• components of the tropical rainforest water cycle


  -open system

  -25% of rainfall is evaporated

  -75% of rainfall is intercepted by the canopy

  
• characteristics of tropical rainforests


  -over 2000mm of rainfall a year

  -between the tropics

  -under or near inter tropical convergence zone

  -low pressure system

  -convectional clouds (cumulonimbus) dominate
• formation of recycled rainfall

  1. trees draw up water from ground water stores

  2. water released by evapotranspiration

  3. humidity increased by 20-30%

  4. water vapour condenses forming convectional cloud formations

  5. 25-50% of rainfall is recycled
• impacts of deforestation on the water cycle


  -evapotranspiration decreases, so recycled rainfall no longer takes place

  -soil is exposed, increased soil erosion, less infiltration, increased runoff, increased flood risk

  -reduced rate of evapotranspiration, reduced cloud formation, less rainfall, risk of drought
• how are tropical rainforests important for the carbon cycle?


  -1-3 giga-tonnes of carbon sunk into all global rainforests annually

  -20% of total biospheric carbon stored in amazonian trees

  -120 billion tonnes of carbon stores in the amazon rainforest
• impacts of deforestation on the carbon cycle


  -total carbon emissions from respiration, combustion, decay and soil erosion higher than absorption by photosynthesis

  -decrease in plant and animal respiration

  -decomposers absent

  -ash increases carbon content of soil