amazon rainforest - carbon cycle

Question 1

carbon cycle flows and stores

Answer 1

• Loss is made good by an inward flux of moisture from the Atlantic Ocean
• Net primary productivity = high – 2500 grams/m2/year biomass = 400-700 tonnes/ha
• Large trees store 180 tonnes C/ha above ground and +40 tonnes C/ha in roots
• Soil carbon stores 90-200 tonnes/ha
• Conditions = speedy decomposition of dead organic matter = quick release of carbon
• Rates of Carbon fixation high via photosynthesis
• Amazon rainforest is a major global reservoir of stored carbon – absorbing 2.4 billion tonnes annually
• Exchanges of carbon between atmosphere, biosphere and soil = rapid
• Amazonia’s leached and acidic soils contain only limited carbon and nutrient stores
• Poor soils support a biome with the highest NPP and biomass of all terrestrial ecosystems, emphasises the speed organic matter is broken down, mineralised and recycled

Question 2

physical factors affecting carbon cycle in amazon

Answer 2

trees
photosynthesis
decomposition
geology

Question 3

trees

Answer 3

• Forests trees dominate the biomass = main carbon store
• Approximately 100 billion tonnes of carbon is locked up in the Amazon
• Absorbing 2.4billion tonnes of CO2 a year and releasing 1.7billion tonnes through decompositions
• Rainforest = carbon skin of global importance
• 60% of rainforest carbon is stored in the above ground biomass of tree stems, branches and leaves
• Below biomass = roots and soil organic matter

Question 4

photosynthesis

Answer 4

• Photosynthesis connects rainforest to atmosphere carbon stores
• High temperatures, high rainfall and intense sunlight stimulate primary production – NNP = 2500 grams/m2/year.
• Amazonia = 15-25% of all NNP in terrestrial ecosystems

Question 5

decomposition

Answer 5

• Leaf litter and dead organic matter accumulates temporarily at the soil surface & within rainforest soils
• High temperatures and humid conditions promote rapid decomposition of organic litter (bacteria, fungi)
• Decomposition releases nutrients to the soil for immediate take-up by tree root systems, emits CO2 – returned to the atmosphere

Question 6

geology

Answer 6

• Geology dominated by ancient igneous and metamorphic rocks
• Carbonates are largely absent from the mineral composition of these rocks
• Western parts of basin (close to Andes) outcrops of limestone occurs
• Slow carbon cycle – significant regional carbon stores

Question 7

human factors affecting carbon cycle

Answer 7

deforestation

Question 8

deforestation

Answer 8

• Present day deforestation = most severe in tropical rainforest
• the biomass of trees represents 60% of all carbon in ecosystems
• Above ground carbon biomass = 180 tonnes/ha
• Deforestation exhausts the carbon biomass store
• Crop lands and pasture contain small amount of carbon > forest trees
  Example – the biomass of grasslands in post deformation = 16.2 tonnes/ha and soya cultivation is 2.7 tonnes/ha
• Deforestation drastically reduced inputs of organic material to soil
• Solid depleted of carbon and exposed to strong sunlight , support fewer decomposed organisms = reducing the flow of carbon from soil to atmosphere
• Principle store of plant nutrients (calcium, potassium and magnesium) is forest trees
• Rainforest soils contain small reservoir of essential nutrients & forest sustained by a rapid nutrient cycle
• Deforestation destroyed main nutrient store and removes most nutrients from ecosystems
• Nutrients no ,longer taken up by the root systems of trees are washed out of solid by rainwater
• Soils without the protective cover of trees = eroded by run-off