4.2 How do the Water and Carbon Cycles Operate in Contrasting Locations? Flashcards
What area does the Amazon rainforest occupy?
The Amazon rainforest in South America occupies an area of more than 6 million km. The majority-70 per cent-of the rainforest is in Brazil, but the forest also extends into parts of neighbouring Peru, Ecuador Venezuela, Colombia, Bolivia and Guyana.
What are the climatic features of the Amazon rainforest?
The rainforest water cycle Amazonia is the world’s largest tract of rainforest. Dominated by tall, evergreen, hardwood trees, its climatic features are:
- high average annual temperatures between 25°C and 30°C
- small seasonal variation in temperature
- high average annual rainfall (>2000 mm) with no dry season.
High average temperatures are a response to intense insolation throughout the year. However, significant cloud cover ensures that maximum temperatures do not reach the extremes of sub- tropical desert climates. Seasonal differences in temperature are small and convectional rain falls all year round, though most areas experience at least one drier period Between 50 and 60 per cent of precipitation in Amazonia is recycled by evapotranspiration (Figure 4.13. page 114) Water losses from the Amazon Basin result from river flow and export of atmospheric vapour to other regions. This loss is made good by an inward flux of moisture from the Atlantic Ocean.
What is precipitation like in the Amazon rainforest?
High average annual rainfall (>2000mm) Rainfall fairly evenly distributed throughout the year though drier season occurs in some places. High-intensity convectional rainfall interception by forest trees is high (around 10% of precipitation). Intercepted rainfall accounts for 20-25 per cent of all evaporation.
What is evapotranspiration like in the Amazon?
High rates of evaporation and transpiration due to high temperatures, abundant moisture and dense vegetation. Strong evapotranspiration-precipitation feedback loops sustain high rainfall totals. Around a half of incoming rainfall is returned to the atmosphere by evapotranspiration. Most evaporation is from intercepted moisture from leaf surfaces. Moisture lost in transpiration is derived from the soil via tree roots.
What is run off like in the Amazon?
Rapid run-off related to high rainfall, intensive rainfall events and well-drained soils. Depending on seasonal distribution of rainfall, river discharge may peak in one or two months of the year.
What is the atmosphere like in the Amazon?
High temperatures allow the atmosphere to store large amounts of moisture (e.g. absolute humidity is high). Relative humidity is also high
What is the vegetation like in the Amazon?
Rainforest trees play a crucial role in the water cycle, absorbing and storing water from the soil and releasing it through transpiration.
What is the soil/groundwater like in the Amazon?
Abundant rainfall and deep tropical soils leads to significant water storage in soils and aquifers.
What is the rainforest carbon cycle like?
Amazonia’s humid equatorial climate creates ideal conditions for plant growth Net primary productivity (NPP) is high, averaging 2500 grams/m//year and the biomass is between 400 and 700 tonnes/ha Large forest trees typically store around 180 tonnes Cha above ground, and a further 40 tonnes Cha in their roots Soil carbon stores average between 90 and 200 tonnes/ha The Amazon rainforest is a major global reservoir of stored carbon, absorbing 2.4 billion tonnes a year.
Compared to other forest ecosystems, exchanges of carbon between the atmosphere, biosphere and soil are rapid. Warm, humid conditions ensure speedy decomposition of dead organic matter and the quick release of CO. Meanwhile, rates of carbon fixation through photosynthesis are high.
Amazonia’s leached and acidic soils 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, emphasises the speed with which organic matter is broken down, mineralised and recycled.
What physical factors affect stores and flows of water?
Physical factors such as geology, relief and temperature affect flows and stores of water in the Amazon rainforest and other environments.
What is the impact of geology on flows and stores of water?
Impermeable catchments (e.g. large parts of the Amazon Basin are an ancient shield area comprising impermeable, crystalline rocks) have minimal water storage capacity resulting in rapid run-off. Permeable and porous rocks such as limestone and sandstone store rainwater and slow run-off
What is the impact of relief on flows and stores of water?
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 run-off Widespread inundation across extensive floodplains (eg, the Pantanal occurs annually storing water for several months and slowing its movement into rivers
What is the impact of temperature on flows and stores of water?
High temperatures throughout the year generate high rates of evapotranspiration. 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.
What are the physical factors affecting flows and stores of carbon?
Forest trees dominate the biomass of the Amazon B and are the principal carbon store. In total approximately 100 billion tonnes of carbon is locked up in the Amazon rainforest. Absorbing around 2.4 billion tonnes of CO2 a year and releasing 1.7 billion tonnes through decomposition the rainforest is a carbon sink of global importance. Sixty per cent of rainforest carbon is stored in the above ground biomass of tree stems, branches and leaves. The remainder is below ground, mainly as roots and soil organic matter. Carbon cycles between the forest and other living organisms, the soil and the atmosphere. Photosynthesis connects the rainforest to the atmosphere carbon stores. High temperatures, high rainfall and intense sunlight stimulate primary production, NPP averages about 2500 grams/m/year. Amazonia alone accounts for 15-25 per cent of all NPP in terrestrial ecosystems
Leaf litter and other dead organic matter accumulates temporarily at the soil surface and within rainforest soils. High temperatures and humid conditions promote rapid decomposition of organic litter by bacteria, fungi and other soil organisms. Decomposition releases nutrients to the soll for immediate take-up by tree root systems, and emits CO, which is returned to the atmosphere.
The geology of the Amazon Basin is dominated by ancient igneous and metamorphic rocks. Carbonates are largely absent from the mineral composition of these rocks.
However, in the western parts of the basin, close to the Andes, outcrops of limestone occur. In the context of the slow carbon cycle they are significant regional carbon stores.
What are the human factors affecting stores and flows of water?
Deforestation in Amazonia averaged around 17,500 km2/year between 1970 and 2013. Since 1970 almost one-fifth of the primary forest has been destroyed or degraded. Since 2009 annual rates have been lower than the average but have started to rise again in recent years.
In April 2014 devastating floods occurred on the Madeira River, the largest tributary of the Amazon River. At Porto Velho the river reached record levels of 19.68m above normal Vast expanses of floodplain were inundated 60 people died: 68,000 families were evacuated and there were outbreaks of cholera and leptospirosis.
In the Upper Madeira drainage basin human activity has modified stores and flows in the water cycle. Deforestation has reduced water storage in forest trees, soils (which have been eroded), permeable rocks (due to more rapid run-off) and in the atmosphere. At the same time fewer trees mean less evapotranspiration and therefore less precipitation Meanwhile total run-off and run-off speeds have increased raising flood risks throughout the basin.
Despite torrential rains in the upper basin of the Madeira River the main driver of the foods was deforestation in Bolivia and Peru Between 2000 and 2012, 30000 km of Bolivian rainforest was cleared for subsistence farming and cattle ranching Much of this deforestation occurred on steep lower slopes of the Andes. The result was a massive reduction in water storage and accelerated run-off.
Deforestation has a huge impact on the water cycle and has the 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 a crucial part of the water cycle, extracting moisture from the soll, intercepting rainfall and releasing it to the atmosphere through transpiration, as well as stabilising forest albedo and ground temperatures This cycle sustains high atmospheric humidity which is responsible for cloud formation and heavy conventional rainfall Deforestation breaks this cycle and can lead to permanent climate change.
However, the impact of deforestation on water cycles is not just local Projections of future deforestation in Amazonia predict a 20 per cent decline in regional rainfall as the rainforest dies out and forest trees are gradually replaced by grassland Nor is it just deforested areas that experience a reduction in rainfall: disruption of the regional water cycle means that forests hundreds of kilometres downwind of degraded sites are affected too.
What are the human factors affecting carbon and nutrient flows and stores?
Present-day deforestation is most severe in the tropica rainforest. In primary rainforest, unaffected by human activity, the biomass of trees represents about 60 per cent of all the carbon in the ecosystem. The above god carbon biomass in the rainforest is approximately 180 tonnes/ha. Most of the remaining carbon is found in the soil as roots and dead organic material
Deforestation exhausts the carbon biomass store Croplands and pasture contain only a small amount of carbon compared to forest trees. For example, the of grasslands in areas of former rainforest is 16.2 tone has and for soya cultivation it is just 2.7 tonnes/ha same time, deforestation drastically reduces inputs of organic material to the soil. Soils, depleted of carbon exposed to strong sunlight, support fewer decomposer organisms, thus reducing the flow of carbon from the to the atmosphere.
In tropical rainforests, the principal store of plant n such as calcium, potassium and magnesium is for Rainforest soils contain only a small reservoir of e nutrients and the forest is only sustained by a rapid nutrient cycle. Deforestation destroys the main nutrient store-the forest trees-and removes most nutrients from the ecosystem. Nutrients no longer taken up by root systems of trees are washed out of soils by rainwater and soils, without the protective cover of trees, are quickly eroded by run-off.
What are the strategies to manage the amazon?
The degrading or outright destruction of large areas of Amazon rainforest is an issue of international as well as national concern. This is because deforestation has implications for global climate change. Brazil is committed to restoring 120,000 km of rainforest by 2030
Indigenous people have lived sustainably in the rainforest for thousands of years, maintaining the water balance, carbon cycle and the forest’s biodiversity. These people survived as hunter-gatherers and shifting cultivators in stark contrast to exploitative commercial farming, logging and mining of the past 50 years, indigenous people pursued a way of life perfectly adapted to the limited resources and fragility of the rainforest.
Modern strategies to manage the Amazon rainforest sustainably fall into three categories:
- Protection through legislation of large expanses of primary forest so far unaffected by commercial developments
- Projects to reforest areas degraded or destroyed by subsistence farming, cattle ranching, logging and mining
- improving agricultural techniques to make permanent cultivation possible
What are the examples of protection through legislation in the Amazon?
Since 1998, the Brazilian government has established many forest conservation areas. These Amazon Regional Protected Areas now cover an area twenty times the size of Belgium By 2015, 44 per cent of the Brazilian Amazon comprised national parks, wildlife reserves and indigenous reserves where farming is banned
What are examples of protection through reforesting in the amazon?
Several reforestation projects, sponsored by local authorities, non-governmental organisations (NGOs) and businesses, are underway but so far progress has been slow. One such example is the Parica project in Rondônia in the western Amazon. This sustainable forestry scheme aims to develop a 1000 km commercial timber plantation on government-owned, deforested land. The plan is for 20 million fast- growing, tropical hardwood seedlings, planted on 4000 smallholdings, to mature over a period of 25 years Financial assistance is given to smallholders for land preparation, planting and the maintenance of plots. Tree nurseries provide them with seedlings. Timber will be exported along the Amazon and its tributaries through Manaus or Port Velho
Although this project is a monoculture and cannot replicate the biodiversity of the primary rainforest, it is sustainable. It also sequesters carbon in the trees and soil reduces CO, emissions from deforestation re-establishes water and carbon cycles; and reduces run-off and the loss of plant nutrients and carbon from the soil
What is the importance of the surui people in protection of the amazon?
Also in Rondônia, the indigenous Surui people participate in a scheme that aims to protect primary rainforest on tribal lands from further illegal logging, and reforest areas degraded by deforestation in the past 40 years. The Surui plant seedings bred in local nurseries in deforested areas around their villages. The native species planted are chosen to provide them with timber for construction, food crops and, through logging sustainable source of income
In 2009 the Surui were the first indigenous in Amazonia to join the UN’s Reducing Emissions from Deforestation and Degradation (REDD) scheme. This scheme provides payment to the tribe for protecting rainforest and abandoning logging, it is a ma approach involving granting of carbon credits to the Surul. These credits can be purchased by internation companies which have exceeded their annual carbo emissions quotas. In 2013, Natura, a large cosmetics transnational corporation (TNC), purchased 120000 tonnes of carbon credits from the Surui. This was the carbon credit sale by indigenous people in Amazonia.
What are the examples of improved agricultural techniques in the amazon?
Farming has been the main cause of deforestation in Amazonia. However, the low fertility of soils meant that permanent cultivation proved unsustainable Afe a few years, smallholders abandoned their plots which were then converted to low quality grassland. Extensive ranching enterprises could scarcely support stocking levels of one head of cattle per hectare.
One response to improve agriculture has been 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 so rates of deforestation.
European explorers observed that the Amazon rainforest as late as the sixteenth century, supported high population densities, and many large urban centres. This appears to contradict the view that natural resources for farming in the region are too poor to support settled, permanent cultivation. The explanation is thought to be human engineered soils: so-called dark soils made from inputs of charcoal, waste and human manure. Charcoal in these so attracts micro-organisms and fungi and allows the so to retain their fertility long-term. Scientists are currently investigating these dark soils. If they can be successfully recreated they would allow intensive and permanent cultivation which would drastically reduce deforestation and carbon emissions
What are the climatic conditions of the Alaskan tundra and what is it?
Arctic tundra occupies some 8 million km in northern Canada Alaska and Siberia. It extends from the northern edge of the boreal coniferous forest to the Arctic Ocean and its southern mit approximates the 10°C July isotherm [i.e. climatic limit of the tree line) Climatic conditions in the Alaskan tundra are severe with mean temperatures below-15 °C. For eight or nine months a year the tundra has a negative heat balance with average monthly temperatures below freezing. As a result the ground is permanently frozen with only the top metre or so thawing during the Arctic summer.
Permafrost underlies much of the Alaskan tundra and is an important feature of the region’s water cycle. In winter, when for several weeks the Sun remains below the horizon, temperatures can plunge below -40°C. Long hours of daylight in summer provide some compensation for brevity of the growing season. Mean annual precipitation is low.
Few plants and animals have adapted to this extreme environment, biodiversity is low and apart from a few dwarf species, the ecosystem is treeless in the southern areas-the Low Arctic-conditions are less severe, and vegetation provides a continuous ground cover. Further north in the High Arctic, plant cover is discontinuous with extensive areas of bare ground
What are the main features of the water cycle in the tundra?
The main features of the water cycle in the Alaskan tundra are:
- Low annual precipitation (less than 100 mm in most places) with most precipitation falling as snow
- Small stores of moisture in the atmosphere owing to low temperatures which reduce absolute humidity.
- Limited transpiration because of the sparseness of the vegetation cover and the short growing season of only about three months.
- Low rates of evaporation. Much of the Sun’s energy in summer is expended melting snow so that ground temperatures remain low and inhibit convection. Also, surface and soil water are frozen for most of the year.
- Limited groundwater and soil moisture stores. Permafrost is a barrier to infiltration, percolation, recharge and groundwater flow.
- Accumulation of snow and river/lake ice during the winter months. Melting of snow, river and lake ice, and the uppermost active layer of the permafrost in spring and early summer, results in a sharp increase in river flow. The Yukon River has a minimum discharge of 340 cumecs in winter and a maximum of 24.600 cumecs in summer.
- Extensive wetlands, ponds and lakes on the tundra during summer. This temporary store of liquid water is due to permafrost which impedes drainage Alaska has over 3 million lakes and extensive wetlands lie in valleys, such as the Yukon River in deltas and along the coast, especially off the Bering Sea.
What is the carbon cycle like in the tundra?
The permafrost is a vast carbon sink Globally it is estimated to contain 1600 GT of carbon. The accumulation of carbon is due to low temperatures which slow decomposition of dead plant material Overall, the amount of carbon in Alaskan tundra soils is five times greater than in the above-ground biomass.
The flux of carbon is concentrated in the summer months when the active layer thaws Plants such as w crowberry and moss grow rapidly in the short summer hours of daylight allow them to flower and fruit within je a few weeks. Nonetheless, net primary productivity is less than 200 grams/m/year. Consequently the Alaskan tundra biomass is small, ranging between 4 and 29 tonnes/ha depending on the density of vegetation cover.
During the growing season tundra plants input carbon-rich litter to the soil. The activity of m organisms increases, releasing CO, to the atmosphere through respiration. However, CO, (and methane ( emissions are not just confined to the summer. Even in winter, pockets of unfrozen soil and water in the permafrost act as sources of CO, and CH, Meanwhile snow cover may insulate microbial organisms and lo some decomposition despite the low temperatures.
In the past the permafrost functioned as a carbon sink But today, global warming has raised concerns in Alaska that it is becoming a carbon source. At the moment the evidence is unclear. While outputs of carbon from the permafrost have increased in recent decades, higher temperatures have stimulated plant growth in the tundra and greater uptake of CO2. This in turn has increased the amount of plant litter entering store. it is possible there that despite the warming Alaskan climate, the carbon budget in the tundra today remains close to balance
