Please enable JavaScript.

Coggle requires JavaScript to display documents.

THE AMAZON RAINFOREST (Carbon Cycle (Background (Biomass - 400-700…

- - - - Leached + acidic soils contain only limited C and nutrient stores
        
        But these poor soils support a biome with the highest NPP and biomass of all terrestrial ecosystems
        
        This emphasises the speed with which organic matter is broken down, mineralised and recycled
      - Accumulates temporarily at the soil surface and within rainforest soils
      - Soil C stores average 90-200 tonnes/ha
    - - Dominate the biomass of the Amazon Basin
      - Main C store
      - 60% of rainforest C is stored in the above ground biomass of tree stems, branches and leaves; remainder is below ground, as roots and soil organic matter
      - Leaf forest trees typically store around 180 tonnes C/ha above ground, and a further 40 tonnes C/ha in their roots
  - - - High temps., high rainfall and intense sunlight stimulate primary production
      - Connects the rainforest to the atmosphere C stores
    - - Decomposition releases nutrients to the soil for immediate take-up by tree-root systems and emits Co2 to the atmosphere
      - High temp. and humid conds. promote rapid decomposition of organic litter by bacteria, fungi and other soil organisms
      - Releases 1.7 billion tonnes CO2/year thru decompostion
  - - - = rapid exchanges of C between atmosphere, biosphere and soil
    - - = high rates of phtotsynthesis = high rates of fixation
    - - Carbonates are largely absent from the mineral composition of these rocks
      - In western parts of the basin, nearer the Andes, there are outcrops of limestone
        
        Significant regional C store in SLOW C cycle
  - - - In primary forest, unaffected by human activity, tree biomass = 60% of all C in the ecosystem
      - Exhausts the C biomass store
      - Croplands and pasture contain a small amount of C
      - Reduces inputs of organic material to the soils
        
        Soils depleted of C and exposed to strong sunlight support fewer decomposers, thus reducing flow of C form soil to atmosphere
      - Destroys the nutrient store (the forest trees) and removes most nutrients from the ecosystem
        
        Principal store of plant nutrients is in forest trees
        
        Soils contain only a small reservoir of essential nutrients and the forest is only sustained by a rapid nutrient cycle
        
        Nutrients no longer taken up by the root systems of trees are washed out of soils by rainwater
- - - - Due to the intense insolation year-round
      - Extreme cloud cover means that temps. do not reach that of sub-Saharan Africa
    - - Convectional rainfall
      - Most areas experience at least one drier period
  - - - High annual rainfall
      - Rainfall fairly evenly distributed around the year
      - Short drier seasons occur in some places
      - High-intensity, convectional rainfall
      - 10% of rainfall intercepted - high
      - Intercepted rainfall accounts for 20-25% of all evaporation
    - - High rates of evaporation and transpiration bc of high temperatures, abundant moisture + dense vegetation
      - Strong evapotransp.-precip. feedback loops sustain high rainfall totals
      - Around 1/2 rainfall is returned to atmosphere by evapotransp.
      - Most evap. is from intercepted moisture from leaf surfaces
      - Moisture lost in transpiration is derived from the soil via tree roots.
    - - Rapid runoff related to high rainfall, intensive rainfall events and well-drained soils
      - River discharge may peak in 1 or 2 months of the year due to seasonal distribution of rainfall
    - - High temps. allow the atmosphere to store large amounts of moisture (i.e. absolute humidity is high)
      - Relative humidity is also high
    - - Abundant rainfall and deep tropical soils = significant water storage in soils and aquifers
    - - Rainforest trees play a crucial role in the water cycle
      - The trees absorb and store water from the soil
      - They release water through trnspiration
    - - This loss is made good by an inward flux of moisture from the Atlantic Ocean
  - - - Impermeable catchments have minimal water storage capacity = rapid runoff
        
        Large parts of the Amazon Basin are an ancient shield area comprising impermeable, crystaline rocks
      - Permeable and porous rocks e.g. limestone and sandstone store rainwater and slow run-off
    - - Most of the Amazon Basin comprises extensive lowlands
      - In areas of gentle relief water moves across the surface (overland flow) or horizontally thru soil (throughflow) to streams and rivers
      - In the west the Andes create steep-catchments w rapid runoff
      - Annual widespread inundation across extensive floodplains - stores water for several months and slows into movement into rivers
    - - High temps. year-round = high rates of evapotransp.
      - Strong convection = high atmospheric humidity, thunderstorm clouds + intense precipitation
      - Water is cycled continually between land surface, forest trees and atmosphere by evaporation, transpiration and precipitation
  - - - Deforestation
        
        General
        
        Rates of deforestation have slowed in recent years
        
        Almost 1/5 of primary forest destroyed/degraded since 1970
        
        Reduced water storage in:
        
        Trees
        
        Soils
        
        Have been eroded
        
        Permeable rocks
        
        BC of rapid runoff
        
        Atmosphere
        
        Fewer trees = less evapotransp.
        
        Increased total runoff + runoff speeds = increased flood risks throughout basin
        
        Averaged 17,500 km2/year between 1970 and 2013
        
        Significant impacts - could change the climate at local and regional scales
        
        Converting rainforest to grassland increases runoff by a factor of 27
        
        Half of all rain falling on grassland goes directly into rivers
        
        Rainforest trees are crucial to the water cycle
        
        Extract moisture from the soil
        
        Intercept rainfall
        
        Release water into atmosphere thru transpiration
        
        Stabilise forest albedo and ground temps.
        
        Its water cycle sustains high atmospheric humidity, which is responsible for cloud formation and heavy convectional rainfall
        
        Deforestation breaks that cycle = permanent climate change
        
        Future predictions
        
        Projections of future deforestation in Amazonia predict 20% decline in regional rainfall
        
        Disruption of regional water cycle = forests 000s km downwind of degraded sites are affected too
        
        Deforestation at Bolivia and Peru was the main driver of the floods, despite the torrential rains in the upper basin of the Madeira River
        
        2000-2012: 30,000 km2 of Bolovian rainforest cleared for subsistence farming + cattle ranching
        
        Mostly occurred on steep lower slopes of Andes
        
        Resulted in massive reduction in water storage + accelerated runoff
      - Flooding
        
        Devastating floods in April 2014, Mandeira River (largest tributary of Amazon River)
        
        At Port Velho the river reached record levels of 19.68m above normal
        
        Much inundation
        
        60 dead
        
        68,000 families evacuated
        
        Outbreaks of cholera
      - Human activity has modified stores and flows of the water cycle
- - - - Brazil is committed to restoring 120,000 km2 of rainforest by 2030
    - - Indigenous people have lived sustainably in rainforests for thousands of years as shifting cultivators
      - Commercial farming, logging and mining of the past 50 years is expolitative
    - - Protection through legislation of large expanses of primary forest so far unaffected by commercial developments
        
        Since 1998, Brazilian gov. has established many forest conservation areas
        
        Amazon Regional Protected Areas - 20 times the size of Belgium
        
        2015 - 44% of Brazilian Amazon comprised national parks, wildlife reserves and indigenous reserves where farming is banned
      - Projects to reforest areas degraded/destroyed by subsistence farming, cattle ranching, logging and mining
        
        Reforestation projects sponsored by local authorities, NGOs and businesses
        
        Slow progress
        
        Parica Project, Rhondonia, W Amazon
        
        The sustainable forestry scheme aims to develop a 1000 km2 commercial timber plantations on government-owned, deforested land
        
        Plan to plant 20 million fast-growing tropical hardwoods on 400 smallholdings, to mature over 25 years
        
        Financial assistance given to smallholders
        
        Is a monoculture and cannot replicate the BD of the rainforest - but is sustainable
        
        Sequesters C in the trees and soil
        
        Reduces CO2 emissions from deforestation
        
        Re-established water and C cycles
        
        Reduces runoff and loss of plant nutrients + C from the soils
      - Improving agricultural techniques to make permanent cultivation possible
        
        Scheme for the Surui people
        
        To protect primary forest from logging and reforest areas
        
        The Suri plant seedlings bred in local nurseries in deforested areas around their villages
        
        Native species planted are chosen to provide them with timber for construction, food crops, and a sustainable source of income thru logging
        
        NB: 2009 - Suri were first indigenous group to join UN's REDD scheme
        
        This scheme provides payment to the tribe for protecting the rainforestt and abandoning logging
        
        Is a market-based approach involving the granting of C credits to Surui
        
        These credits can be purchased by international companies that have exceeded their annual C emission quotas
    - - Farming is main cause of deforestation in Amazonia
      - Low fertility soils meant that permanent cultivation has been unsustainable
      - Smallholders will abandon their plots after a few years when converted to low quality grassland
      - Extensive ranching enterprises could scarcely support stocking levels of one head of cattle per hectre
      - Diversification
        
        Soil fertility can be maintained by rotational cropping and combining livestock and arable operations
        
        Integrating crops and livestock could allow a fivefold increase in ranching productivity and help slow rates of deforestation
      - Soils-recreation
        
        Human-engineered dark soils are made from charcoal, waste and human manure
        
        Charcoal attacks micro-organisms and fungi and allows these soils to maintain fertility long-term
        
        If these dark soils can be successfully recreated, they would allows intensive and permanent cultivation which would drastically reduce deforestation and C emissions