Case Studies Flashcards
Amazon rainforest water cycle - precipitation
High average annual rainfall - >2000 mm
High intensity conventional rainfall
Interception by forest trees is high - 10% of precipitation account for 20-25% of all evaporation
Amazon rainforest - water cycle - evapotranspiration
High rates of evaporation and transpiration due to high temperatures, abundant moisture and dense vegetation
Around half of incoming rainfall is returned to the atmosphere by evaptranspiration
Most evaporation is from intercepted moisture from leaf surfaces
Moisture lost in transpiration is derived from the soil via tree roots
Amazon rainforest - water cycle - run-off
Rapid runoff due to high rainfall, intensive rainfall events and well-drained soils.
Amazon rainforest - water cycle - atmosphere
High temperatures allow the atmosphere to store large amounts of moisture
Absolute humidity and relative humidity is high
Amazon - water cycle - soil/groundwater
Abundant rainfall and deep tropical soils lead to significant water storage in soils leads to significant water storage in soils and aquifers.
Amazon - water - vegetation
Rainforest trees play a crucial role in the water cycle, absorbing and storing water from the soil and releasing it through transpiration.
Rainforest - carbon - climate
Humid equatorial climate creates ideal conditions for plant growth.
Net primary productivity is high, averaging 2500 grams/m squared/year.
Large forest trees typically store 180 tonnes c/ha above ground and a further 40 tonnes C/ha on their roots
Rainforest - carbon - exchanges
Exchanges between atmosphere, biosphere and soil is rapid
Warm humid conditions allow for decomposition of dead organic matter leading to the quick release of co2.
Rates of carbon fixation through photosynthesis are high
Rainforest - carbon - soil
Amazonia’s leached and acidic souls contain only limited carbon and nutrient stores.
The fact that such poor soils support a biome with the highest NPP and biomass of all terrestrial ecosystems, emphasising the speed with which organic matter is broken down, mineralised and recycled
Physical factors - amazon water cycle - geology
Impermeable catchments (eg large parts of the amazon basin are an ancient shield area comprising impermeable, crystalline rocks) have minimal water storage capacity resulting in rapid runoff.
Permeable rocks such as limestone and sandstone store rainwater and slow runoff
Physical factors - water - rainforest - relief
Most of the amazon basin comprises extensive lowlands
In areas of gentle relief water moves across the surface (overland flow) or horizontally through the soil (throughflow) to streams and rivers.
In the west the Andes create steep catchments with rapid runoff.
Physical factors - water - amazon - temperature
High temperature throughout the year generate high rates of evaporranspiration
Convection is strong leading to high atmospheric humidity, the development of thunderstorm clouds and intense precipitation.
Water is cycled continually between the land surface, forest trees and the atmosphere by evaporation, transpiration and precipitation
Physical factors - carbon - amazon - trees
100 billion tonnes of carbon is stored in the rainforest
60% of rainforest carbon is stored in above ground biomass of tree stems, branches and leaves.
Photosynthesis connects the rainforest to the atmosphere carbon stores
Physical factors - amazon - carbon - temperatures
Leaf litter and dead organic matter accumulates temporarily at the soil surface and within rainforest soils
High temperatures and humid conditions promote rapid decomposition or organic litter, releasing nutrients to the soil for immediate take up by tree root systems and emits co2 which is returned to the atmosphere
Physical factors - rainforest - carbon - geology
Dominated by ancient igneous and metamorphic rocks. Caribonates are largely absent from the mineral composition.
In west part of basin near Andes , outcrops of limestone occur
Human factors - amazon - water - floods
2014 - floods occurred in Madeira river due to deforestation
60 people died, 68,000 evacuated and outbreaks of cholera
Human factors - amazon - stores and flows of water cycle
Deforestation has reduced water storage in forest trees, permeable rocks (due to more rapid runoff)
Less evapotranspiration and therefore less precipitation.
Meanwhile total runoff and runoff speeds have increased, raising flood risks throughout basin
Floods of 2014
Between 2000 and 2012 30,000km of rainforest cleared for subsistence farming and cattle ranching. Much of this deforestation occurred on the steep slopes of the Andes.
Resulted in massive runoff and massive reduction in water storage
Future deforestation - amazon
20% decline in regional rainfall as the rainforest dries out and forest trees are replaced by grasslands.
Deforestation affect on carbon
Exhausts main store - grasslands only store 16.2 tonnes/ha
Reduces input of organic matter to the soil - reduces flow of carbon to the atmosphere
Protection through legislation- amazon
1998 Brazilian government has established many forest conservation areas.
By2015 44% of the Brazilian amazon comprised national parks, wildlife reserves and indigenous reserves where farming is banned
Projects to reforest areas - amazon
Parica project - aims to develop an1000km commercial timber plantation on government owned, deforested land.
Financial assistance is given to smallholders for land preparation, planting and the maintenance of plots.
Tree nurseries provide them with seedlings
Is sustainable and sequesters carbon in the trees, reducing the co2 emissions from deforestation and reduces runoff.
Indigenous surui peope
2009 - first indigenous people to join the UNs reducing emissions from deforestation and degradation scheme
Provides payment to the tribe for protecting the rainforest and abandoning logging - granting them carbon credit.
2013 - natura (tnc) purchased 120,000 tonnes of carbon credit from the surui
Improved agriculutural techniques
Diversification - soil fertility can be maintained by rotational cropping and integrating crops and livestock can help slow rates of deforestation
Tundra - water cycle - precipitation
Low annual precipitation with most of it falling as snow
Tundra - water cycle - atmosphere
Small stores of moisture in atmosphere lead to low temperatures which reduce absolute humidity
Water cycle - tundra - evapotranspiration
Limited transpiration - due to spare ness of vegetation cover
Low rates of evaporation - much of suns energy used melting snow in summer
Water cycle - tundra - river flows
Melting of active layer in spring results in sharp increase in river flows
Water cycle - tundra - groundwater
Limited ground water and soil moisture stores-permafrost is a barrier to infiltration, percolation, recharge and groundwater flow
Carbon cycle - tundra - storage
1600 GT of carbon - due to low temperatures which slow decomposition of dead plants
Carbon cycle - tundra - temperatures
Flux of carbon concentrated in summer months when active layer thaws
Plants grow rapidly in summer due to long hours of daylight
During growing season tundra plants input carbon-rich litter into soil. The activity of microorganisms increases, releasing co2 to atmosphere through respiration
In winter pockets of unfrozen soil in permafrost act as a source of co2 and ch4. Snow cover may insulate microbial organisms and allow some decomposition
Carbon cycle tundra - today
Now becoming a carbon source rather than a sink
More heat due to global warming leads to more plants - more decomposition
Physical factors - water - tundra - temperature
Below freezing temps means for most of the year water is stored as ground ice in permafrost layer
Summer - active layer melts and liquid water flows on surface forming pools and shallow lakes
This meltwater forms pools but there is poor drainage as water cannot infiltrate soil
Physical factors - water - tundra - evapotranspiration
Winter - no evapotranspiration due to sub zero temperatures
Summer - some evapotranspiration from standing water, soils and vegetation
Physical factors - water - tundra - geology
Permeability is low owing to the permafrost and the crystalline rocks which dominate the geology of the tundra in the arctic
Minimal relief and glacial deposits impede drainage and contribute to water logging during summer months
Physical factors - carbon - tundra - storage
Carbon is mainly stored as partly decomposed plant remains frozen in the permafrost
Physical factors - carbon - tundra - plant growth
Low temps, unavailability of liquid water and limited nutrients limits plant growth
Low temperatures slow decomposition and respiration and the flow of co2 to the atmosphere
Physical factors - carbon - tundra - geology
Owing to the impermeabilty of the permafrost, porosity and the mineral composition of rocks exert little influence over the carbon cycle
Oil and gas production
North slope of Alaska
1990s - north slope accounted for nearly a quarter of usas domestic oil production
Oil and gas production - melting
Construction and operation of oil and gas installations, settlements and infrastructure diffuses heat directly to the environment
Dust deposition along roadsides creates darkened snow surfaces, increasing absorption of sunlight
Removal of vegetation cover which stops the insulation of permafrost
Oil and gas production - permafrost melting releases co2 and methane
North slope - losses of co2 from permafrost vary from 7-40 million tonnes per year
Gas flaring and oil spillages emit co2
Destruction of tundra vegetation reduces photosynthesis and uptake of co2 from atmosphere
Thawing of soil increases microbial activity, decomposition and emissions of co2
Oil and gas production- affect on water
Increased runoff and river discharge - increased evaporation in summer
Strip mining of sand and gravel for construction creates artificial lakes which disrupt drainage and expose permafrost to further melting
Drainage networks disrupted by road construction
Water abstracted from creeks and rivers for industrial use and for building or ice roads in winter reduce runoff
Oil and gas production - management strategies
Insulated ice and gravel pads - roads and other infrastructural features can be constructed on insulating pads - prevents permafrost from melting
Buildings and pipelines elevated in piles - allows cola air to circulate beneath these structures
Building laterally beyond drilling platforms - new techniques allow oil and gas to be accessed kms from drilling sites
Refrigerated supports - trans Alaska pipeline - stabilise the temperature of permafrost
