CASE STUDY: The Amazon Rainforest

Between 50 - 60% of precipitation is recyled in the Amazon by evapotranspiration

NPP is high - averaging 2500grams/m^2/year and the biomass is between 400 and 700 tonnes/ha

Rainforest absorbs 2.4 billion tonnes of carbon a year 

Carbon exchanges are rapid: 

• warm humid conditions = speedy decomposition od dead organic matter and quick release of CO2. 
• rates of carbon fixation through photosynthesis are high

Amazon's leached and acidic soils contain only limited carbon and nutrient stores. The fact that such poor soils support a biome with the highest NPP and biomass of all terrestrial ecosystems suggests the speed with which organic matter is decomposed, mineralised and recycled. 

Physical factors affecting the water cycle

• geology, relief and temp affect flows and stores of water

Geology

• impermeable catchments have minimal water storage capacity resulting in rapid run-off. Permeable and porous rocks e.g. limestone and sandstone dtore rainwater and slow runoff

Relief 

• Most of the Amazon is lowlands
• areas of gentle relief water moves across the surface (overland flow) or horizontally through the soil (throughflow) to streams and rivers
• In the west, the Andes creates steep catchments with rapid runoff 
• Widespread inundation across floodplains such as the Pantanal) occurs annually, storing water for several months and slowing its movement into rivers

Temperature

• high temperatures = high rates of evapotranspiration 
• convection is strong = high atmospheric fluidity, thunderstorm clouds and intense precipitation

Physical factors affecting the carbon cycle

• forest trees dominate the Amazon's principle carbon store
• approx. 100 billion tonnes of carbon is locked up in the Amazon rainforest 
• absorbs 2.4 billion and releases 1.7 billion through decomposition 
• 60% of…