ELSS Casestudy: Amazon Rainforest Flashcards
What are the climatic features of the Amazon rainforest?
- High annual average temperature between **25°-30°C
- Little seasonal variation in temperature
- High average annual rainfall >2000mm, with no dry season.
What type of rainfall occurs in the Amazon?
Convectional rainfall
What percent of precipitation in the Amazon is a result of evapotranspiration?
Between 50-60% of rainfall
Describe precipitation in the Amazon rainforest?
- There is high annual average rainfall of >2000mm
- Rainfall is evenly distributed throughout the year
- The rainfall is high intensity and convectional
- Interception by forest trees is high, accounting for around 10% of precipitation
- Intercepted rainfall accounts for 20-25% of all evaporation
Describe run-off in the Amazon rainforest
- There is rapid run-off related to high and intensive rainfall and well-drained soils.
How much carbon does the Amazon absorb per year?
2.4 billion tonnes - making it a major global resevoir of stored carbon.
Why is the soil store in the Amazon limited?
Amazonian soil stores are leached due to high rainfall
What are the 3 physical factors influencing flows and stores in the Amazon’s water cycle?
- Temperature
- Geology (rock permeability and porosity)
- Relief
In what ways does the physical factor of temperature affect the water cycle in the Amazon rainforest?
- High temperatures throughout the year generates high levels of evapotranspiration.
- High temperatures mean convection is strong, leading to high atmospheric humidity, the development of storm clouds and intense precipitation
- As a result, water is recycled continually between land surface, biosphere and the atmosphere through evapotranspiration and precipitation.
In what ways does the physical factor of geology affect the water cycle in the Amazon rainforest?
- There are large impermeable catchments (which are large parts of the Amazon basin that are an ancient shield area comprising impermeable, crystalline rocks).
- The impermeable catchments in the Amazon have minimal water storage capacity which results in rapid run-off
- There are spatial differences, as permeable and porous rocks such as limestone and sandstone store rainwater and slow run-off flows.
In what ways does the physical factor of relief affect the water cycle in the Amazon rainforest?
- The Amazon basin comprises of extensive lowlands.
- Areas of gentle relief facilitate water moving across the surface in overland flow, or horizontally through the soil in throughflow to streams and rivers.
- The West of the Amazon has the Andes creating steep catchments with rapid run-off due to gravity.
- Widespread inundation across extensive floodplains occurs annually, which stores water for several months and slows it’s movement into rivers.
What are the physical factors influencing flows and stores in the Amazon’s carbon cycle?
- Temperature
- Vegetation
- Mineral composition in rocks (geology)
- Organic matter in the soil
In what ways does the physical factor of temperature affect the carbon cycle in the Amazon rainforest?
- High temperatures and humid conditions promote rapid decomposition of organic matter by bacteria, fungi and other soil organisms.
- This inputs nutrients to soil for immediate uptake by roots, and when the vegetation respires - CO2 is released back into the atmosphere.
- Temperature provides optimal condition for plant growth from photosynthesis being accelerated - this stimulates primary production of biomass (vegetation store)
In what ways does the physical factor of vegetation affect the carbon cycle in the Amazon rainforest?
- Vegetation provides an intermediate store of carbon.
- Through photosynthesis, vegetation transfer carbon from the atmosphere (output) and input it into their biomass.
- Plants, when they die, are decomposed which return carbon to the atmosphere and soil.
In what ways does the physical factor of geology affect the carbon cycle in the Amazon rainforest?
- The geology of the Amazon basin is dominated by ancient igneous and metamorphic rocks.
- Carbonates are largely absent from mineral composition of Amazon rocks
- However, near the Andes in the Western parts of the Amazon basin there are outcrops of limestone. For the slow carbon cycle, these provide significant carbon stores.
Since 1970, what fraction of rainforest has been destroyed or degraded?
Almost 1/5 of primary forest
How has human activity affected the water cycle in the Upper Madeira drainage basin?
- Stores and flows have been modified stores and flows
- Deforestation has reduced water storage in forest trees, and subsequently soils that have been eroded.
- Total run-off and run-off speeds have increased, raising flood risks throughout the basin.
How does the human factor of deforestation impact evapotranspiration?
- Fewer trees means less evapotranspiration - and directly less precipitation
Cattle ranching and farming has led to deforestation in Bolivia, how does this affect the water cycle?
- This has led to deforestation and subsequent soil degradation - interrupting stores.
- Much of Bolivian deforestation occurred on the steep lower slopes of the Andes, so as a result, there is a massive reduction in water storage and runoff.
What event occurred due to a combination of human and natural factors in the Madeira basin?
- In April 2014, devastating floods occurred on the Madeira River - near Porto Velho.
- Vast expanses of floodplain was inundated
- 60 people died, 68000 families were evacuated and water-borne disease outbreak occurred.
What is the danger of converting rainforest into grassland?
- Run-off is increases by a factor of 27
- Half of all precipitation falling on grassland goes directly into rivers.
What is the role of rainforest trees in the water cycle?
- Extract moisture from soil store
- Intercept rainfall and release it to the atmosphere via evapotranspiration
- Stabilize forest albedo and ground temperatures.
What is evidence that deforestation is not local in effect?
- Projections of future deforestation in Amazonia predict a 20% decline in regional rainfall as the forest dries out and is replaced by grassland.
- Even forested areas will experience a reduction in rainfall: distribution of the regional water cycle means forests hundreds of kilometers away from degraded sites will be affected too.
In areas unaffected by human activity, what % of all carbon in the ecosystem does the biomass of trees represent?
60% of all carbon in the ecosystem
