The Amazon Rainforest (not in specified) Flashcards
characteristics of the rainforest
- 6 million km2
- high amounts of precipitation, high humidity + high temps
- high avg temp are a response to intense insulation through heat
- conventional rainfall all year
flows + states in the water cycle
- precipitation
- evapotranspiration
- run - off
- atmosphere
- soil, groundwater
- vegetation
precipitation
- Between 50-60% of precipitation in Amazonia is recycled by evapotranspiration
- High average annual rainfall (more than 2000 mm)
Evapotranspiration
- High rated of evaporation and transpiration due to high temperatures, lots of moisture and dense vegetation.
- Strong evapotranspiration-precipitation feedback loops sustain high rainfall totals.
- Half of incoming rainfall is returned to the atmosphere by evapotranspiration
- Majority of evaporation is from intercepted moisture from the surface of leaves.
run off
Rapid run-off is caused by intensive rainfall events and well-drained soils
atmosphere
- High temperatures allow atmosphere to store huge amounts of moisture
- Absolute humidity is high
- Relative humidity is also high
vegetation
Rainforest trees are crucial; they absorb and store water from the soil and release it through transpiration
losses
- Water losses result from Amazon basin result from river flow and export of atmospheric. Vapour to other regions
- The losses are replenished by an inward flux of moisture from the Atlantic
physical factors and how they effect flood hydrograph
geology - Impermeable catchments have minimal water storage capacity therefore resulting in rapid run-off. Permeable and porous rocks eg. Limestone and sandstone store rainwater and slow run-off.
relief - In areas with gentle relief, water moves across the surface (overland flow) or horizontally through the soil (throughflow) to stream and rivers. In the West, the Andes create steep catchments with rapid run-off. Widespread inundation (intentional flooding) across extensive flood plains occurs annually, storing water for months at a time and slowing its movement into rivers.
temperature - High temperatures = high rates of evapotranspiration. Convection is strong leading to high atmospheric humidity, the development of thunderstorm clouds and intense precipitation.
human factors affecting flows + stores of water
- Deforestation in Amazonia avg = 17,500km2 per year between 1970 and 2013
- Since 1970 a third of primary forest has been destroyed or degraded
- April 2014 floods on Madeira River (largest tributary of Amazon) reaches record levels of 19.68m above normal level - 68 people died and 68,000 families were evacuated plus outbreaks of cholera and leptospirosis
- Deforestation has reduced water storage in forest trees, soils, permeable rocks and in the atmosphere. Fewer trees mean less evapotranspiration so less precip. Total run-off and run-off speeds have increased, raising flood risks through basin
how does deforestation affect the climate?
Deforestation has potential to change the climate at local and regional scales - converting rainforest to grassland increases run-off by a factor of 27, and half of all rain falling on grassland goes directly into rivers. Rainforest trees are crucial in extracting moisture from soil, intercepting rainfall and releasing it into atmosphere by transportation as well as stabilising forest albedo and ground temperatures - cycle sustains high atmospheric humidity which is responsible for cloud formation and heavy conventional rainfall so with deforestation the cycle can break and leads to permanent climate change
what are the improved agricultural techniques?
DIVERSIFICATION = one improvement as soil fertility can be maintained by rotational cropping and combining livestock and arable operations which would increase ranching productivity fivefold and help slow rates of deforestation
rain forest carbon cycle
- The humid equatorial (near equator) climate creates idea conditions for plant growth
- Net primary productivity (rate at which energy is stored as biomass) = high, avg 2500 grams/m2/year, biomass = 400-700 tonnes/ha.
- Large forest trees typically store around 180 tonnes C/ha above ground, further 40 C/ha in roots
- Soil carbon stores = avg 90 - 200 tonnes/ha.
- Amazon = major global reservoir stored carbon, absorbing 2.4 billion tonnes a year
- Compared to other forest ecosystems, transfer of carbon between the stores are rapid. The warm, humid conditions ensure speedy decomposition of dead organic matter + quick release of CO2. Rates of carbon fixation* through photosynthesis are high.
physical factors affecting stores + flows
- Forest trees = principal carbon stores. Approx 100 billion tonnes of carbon are stored in rainforest, 2.4 billion tonnes are absorbed of CO2 + release 1,7 billion tonnes through decomposition. Rainforest = carbon sink of global importance. 60% of rainforest carbon is stored in above ground biomass
- Photosynthesis connects rainforest -> atmosphere carbon stores. High temp, high rainfall + intense sunlight: stimulate primary production. NPP avgs 2500 grams/m2/year - Amazonia alone amounts for 15-25% of all NPP in terrestrial ecosystems
- Leaf litter + dead organic matter accumulate temporarily at soil surface + within soils. High temp + humid conditions speed up decomposition of organic litter by bacteria, fungi. Decomposition releases nutrients to soil which is immediately taken up by tree root systems + emits CO2 which is returned to atmosphere.
- Geology: dominated by ancient igneous + metamorphic rocks. Carbonates largely absent from mineral composition of these rocks. But, in western parts of basin, close to Andes, outcrops of limestone occur. In cxt of slow carbon cycle = significant regional carbon stores.
human factors and how they affect stores + flows carbon
- Deforestation exhausts the carbon biomass store. Croplands + pasture contain only small amount of carbon compared to forest trees. Eg biomass of grasslands in areas of former rainforest is 16.2 tonnes/ha. At same time deforestation drastically reduces inputs of organic material to the soil. Soils, depleted of carbon + exposed to strong sunlight, support fewer decomposer organisms -> reducing flow of carbon from soil to atmosphere.
- Deforestation destroys main nutrient store + removes most nutrients from ecosystem. No longer taken up by root systems of trees, they are washed out by rainwater + soils, without protective cover of trees are quickly eroded by run off.
