amazon rainforest Flashcards
The Amazon Rainforest
- South America
- 6 million km^2
- 70% in Brazil, but forest also extends into parts of Peru, Ecuador, Venezuela, Columbia, Bolivia and Guyana
The Amazon Rainforest - Water Cycle
- high average annual temperatures 25-30-> intense insolation
- however, significant cloud cover ensures max temps don’t reach extremes of subtropical climates
- small seasonal variations in temperature
The Amazon Rainforest - Water Cycle
high average annual rainfall (>2000mm)
- no dry season
- 50-60% precipitation recycled by evapotranspiration - water loss by river flows and export atmospheric vapour
- loss made good by inward flux of moisture from Atlantic
The Amazon Rainforest - Precipitation
- high av rainfall (<2000mm)
- rainfall evenly distributed/yr
- short dry season in some places
- high-intensity, convectional rainfall
- 10% precipitation intercepted by trees
- intercepted rainfall accounts for 20-25% evaporation
The Amazon Rainforest - Evapotranspiration
- high rates due to high temp, abundant moisture, dense vegetation
- strong feedback loops sustain high rainfall totals
- 1/2 rainfall returned to atmosphere most evaporation - intercepted moisture from leaves
- moisture lost in transpiration derived from soil via roots
The Amazon Rainforest - Run-off
- rapid rates relates to high rainfall, intensive rainfall events and well drained soils
- depending on seasonal distribution, river discharge may peak in 1-2 months of the year
The Amazon Rainforest - Atmosphere
- high temp allows to store large amounts of moisture e.g. absolute and relative humidity high
The Amazon Rainforest - Soil/Groundwater
abundant rainfall and deep tropical soils lead to significant water in storage in soils and aquifers
The Amazon Rainforest - Vegetation
- trees play crucial role in water cycle, absorbing and storing water from soil and releasing through transpiration
The Amazon Rainforest - Carbon Cycle
- humid climate perfect for plant growth
- net primary productivity high: 2500g^2/yr and bio mass between 400-700 tonnes
- large trees store 220 tonnes
- major global reservoir: absorbs 2.4 billion tonnes/yr
The Amazon Rainforest - Carbon Cycle
- exchanges between atmosphere, biosphere, soil rapid - humid: quick decomposition and release of co2
- carbon fixation through photosynthesis
- high acidic soil contains limited carbon and nutrient stores
- poor soil emphasis speed organic matter broken down, mineralised and recycled
The Amazon Rainforest - Geology
- impermeable catchments e.g. crystalline rocks, have minimal water storage and capacity resulting in rapid runoff
- permeable rocks and prosperous rocks e.g. limestone store rainwater and slow run off
The Amazon Rainforest - Relief (Slopes)
- mostly lowlands, water moves along surface (overland) or horizontally (through) to streams and rivers
- west: Andes create steep catchments with rapid run-off
- widespread inundation across extensive floodplains e.g. Pantanal occurs annually, storing water for several months, slowing movement into rivers
The Amazon Rainforest - Temperature
- high temp: high evapotranspiration
- convection strong, causing high atmospheric humidity (e.g. intense rainfall)
- water cycled continuously between land surface, forest trees and atmosphere by evaporation, transpiration, precipitation
The Amazon Rainforest - Physical factors affecting the stores and flows of carbon
- 100 billion tonnes trapped
- 1.7 billion/yr released through decomposition
- 60% stored in above ground biomass e.g. trees, remainder below e.g. soil organic matter
- photosynthesis connects rainforest to atmosphere carbon stores
- high temp, rainfall and intense sunlight stimulate primary production, accounts for 15-20% all NPP in terrestrial ecosystems
The Amazon Rainforest - Physical factors affecting the stores and flows of carbon
- dead organic matter accumulates temporarily at soil surface and within soil high temp promotes rapid decomposition by fungi, releases nutrients that are taken up by tree roots and emits co2 which returns to atmosphere
- rocks significant in carbon store
The Amazon Rainforest - Human factors affecting the stores and flows of water
- deforestation around 17,500km^2/yr
- since 1970, 1/5 rainforest destroyed/ degraded
- april 2014: floods on Madeira river (largest tributary), river reached reread levels of 19.68m above normal: 60 died, 68,000 families evacuated, outbreak of cholera
The Amazon Rainforest - Human factors affecting the stores and flows of water
- upper Madeira drainage basin: human activity; deforestation reduced water storage in trees and soil (eroded), permeable rocks (rapid runoff) and atmosphere
- fewer trees -> less evapotranspiration -> less precipitation run off and speed increased, raising flood risk
The Amazon Rainforest - Human factors affecting the stores and flows of water
- 2000-12, 30,000 km^2 Bolivian rainforest cleared for cattle and subsistence farming
- much occurred on steep lower slopes of Andes, resulting in reduction in water storage and accelerated run off
The Amazon Rainforest - Human factors affecting the stores and flows of water
- potential to change climate
- increased run off by factor of 27 1/2
- all rain falling onto grassland goes directly into rivers
- trees: crucial; extract moisture from soil, incept rainfall and release it into atmosphere (transpiration), stabilises albedo and ground temps -> cycle sustains high atmospheric humidity, helps cloud formation and heavy convectional rainfall
The Amazon Rainforest - Human factors affecting carbon and nutrient flows and stores
- deforestation destroys main nutrient store (forest trees) and removes most nutrients from ecosystem - nutrients no longer taken up by root systems of trees - washed out of soils by rain; and soils, without protective cover of trees, quickly eroded by run off
The Amazon Rainforest - Strategies to manage tropical rainforests and positive effects on the carbon and water cycles
- protection through legislation of large expanses of primary forest not affected by commercial developments
- projects to reforest areas degraded or destroyed by subsistence farming, cattle ranching, logging, mining improving agricultural techniques to make permanent cultivation possible
The Amazon Rainforest - Regional protected areas
- 1989, Brazilian government began to establish forest conservation areas
- now cover an area 22x larger than Belgium
- By 2015, 44% Brazilian amazon comprised national parks, wildlife reserves and indigenous reserves where farming is banned
The Amazon Rainforest - Improved agricultural techniques
- low fertility of soils meant permanent cultivation proved unsuitable after a few years
- small holders abandoned plots which were converted to low quality grassland
- extensive ranching enterprises could scarcely support stocking levels of one head of cattle/ hectare
