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A Level Global Systems > 7 - carbon stores in different biomes ✅ > Flashcards

7 - carbon stores in different biomes ✅ Flashcards

1
Q

what are the main reservoirs of carbon

A

mantle - 2,500,000 gigatonnes
crust - 1,425,000 gigatonnes
oceans - 9,500 gigatonnes

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2
Q

where is carbon primarily stored in forests

A

in the biomass of the trees but thick litter layers on the forest floor can also be significant

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3
Q

how have forest landscapes been an important resource for human populations and why has this caused issues to carbon cycling

A
  • deforestation for agriculture etc has major ecosystem impact and amount of carbon stored
  • forest growth leads to sequestration of carbon from atmosphere whilst forest clearance can lead to carbon emissions to atmosphere through burning or decomposition of biomass
  • and through changes in soil organic carbon storage associated with forest clearances
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4
Q

how have impacts on carbon balance been variable in time and space

A
  • clearance of tropical forests for settlements/agriculture = significant increases in carbon emissions from tropics
  • in contrast N. America forest regrowth due to agricultural abandonment after the great depression of the 1930s lead to increases in carbon sequestration by forest land
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5
Q

where is the largest carbon store

A

FORESTS hold largest carbon stores of all the terrestrial based ecosystems

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6
Q

what differs Boreal (coniferous) forest stores from tropical rainforests

A
  • Boreal forest stores hold more carbon globally than TRFs due to it being larger
  • however TRF has greater biomass per unit area than the Boreal Forest
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7
Q

how do boreal forests differ from TRFs in carbon store %

A

BOREAL = 26%
TRF = 20%

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8
Q

what is the importance of carbon in biomass

A
  • to grow and create new organic matter plants require a variety of nutrients
  • carbon is essential plant macronutrient and makes up about 44% of dry weight of plant biomass
  • potassium and calcium amount to less than 1%
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9
Q

how much carbon is in the biosphere

A

20% of all carbon in biosphere, most stored above ground in TRFs

animals hold minimal carbon
litter is also minimal carbon

soil, humus, is very rich in carbon. land use management to develop humus is seen as a carbon sequestration approach

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10
Q

where are the major rainforests in the world

A
  • olympic rainforest (temperate)
  • rainforests of central america
  • amazon rainforest
  • madagascar rainforest
  • congo river basin rainforest
  • rainforests of southeast Asia
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11
Q

what are the physical factors affecting plant growth and carbon storage in TRFs

A
  1. LIGHT
  2. TEMPERATURE
  3. PRECIPITATION
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12
Q

how does light affect plant growth and carbon storage in TRFs

A

suns rays concentrated at this latitude with little seasonal variation resulting in all year growth and carbon sequestration

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13
Q

how does temperature affect plant growth and carbon storage in TRFs

A
  • high average annual temperatures between 25 and 30 degrees with only small seasonal variations
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14
Q

how does precipitation affect plant growth and carbon storage in TRFs

A
  • very heavy convectional rainfall (2000-3000mm/year)
  • no dry season although some areas such as Manaus have drier season
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15
Q

what are the effects of physical factors

A
  • high and constant rainfall with warm temperatures provides optimum conditions for terrestrial plant growth and biomass
  • competition for light and water created 5 tier structure
  • plants are evergreen with large leaves to maximise transpiration and growth
  • carbon stores in animals high in TRFs as wide range of animal habitats
  • carbon stores in plants also high in TRFs as nearly 2/3 of world’s plant species located there
  • in the Napo region of Peru, 283 tree species were found in 1 hectare (size of a football pitch)
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16
Q

what is the 5 tier structure of a tree

A
  1. field layer
  2. shrub layer
  3. under-canopy
  4. canopy
  5. emergent layer
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17
Q

how much carbon is held in TRFs compared to forest trees

A
  • in total, 550 gigatonnes of carbon is stored in TRFs
  • large forest trees store 180 tonnes of carbon per hectare above ground + 40 in roots
  • soil carbon store averages 100 tonnes per hectare
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18
Q

how does the climate affect rainforest carbon stores

A
  • warm, humid conditions allow rapid decomposition of organic material, litter store is smaller than in temperate grasslands
  • heavy rainfall = soils leached and low amounts of organic carbon stored in humus layer
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19
Q

where are temperate grasslands found

A
  • midlatitude temp. grasslands found on periphery of mid-latitude deserts, 30-50 degrees north of equator
  • the leeward side of mountain systems and several extensive non-coastal systems
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20
Q

where are temperate grasslands located

A
  • north american prairies
  • eurasian steppes (ukraine eastwards through Russia and Mongolia)
  • south africas veld landscape
  • south american pampas
21
Q

what is the impact of rainfall on tree growth

A
  • lack of rainfall is major limiting factor to tree growth
  • short perennial (long lived) grasses dominate landscape
  • grasses have their growth buds at or just below the surface and are well adapted to drought or fire
22
Q

what are the physical factors affecting plant growth and carbon storage

A
  • light
  • temperature
  • precipitation
23
Q

how does light affecting plant growth and carbon storage

A
  • sun’s rays are concentrated during summer at these latitudes, but are weaker in winter when there may be less than 6 hours of light a day
  • = pronounced variations in plant growth and biomass carbon storage
24
Q

how does temperature affect plant growth and carbon storage

A
  • in Mariupol (Ukraine) mean monthly temperatures range from 22 to -5 degrees c
  • temperate grasslands at high altitude may experience even greater extremes
  • encourages large seasonal changes in stored biomass carbon
25
Q

how does precipitation affect plant growth and carbon storage

A
  • low average annual rainfall of 500mm or less in Biome is spread relatively evenly throughout the year
  • there is a large build up of snow in winter months in northernly latitudes
  • limits plant growth and encourages some variations in seasonal biomass carbon
26
Q

what are two common grasses

A

1 - TURF GRASSES: with rhizomes (underground stems) from which new plants grow found in more humid parts of the biome
2 - BUNCH GRASSES: without rhizomes that reproduce by seed found in the drier parts of the biome

27
Q

what are animal biodiversity levels like in temperate grasslands

A
  • animal biodiversity and biomass relatively low
  • no more than 2/3 species of large grazing mammals eg bison
  • simple structure of biome in terms of climate and vegetation
28
Q

what is the importance of earthworms

A
  • a sq.m patch of underground may contain up to 500 earthworms
  • they consume organic matter and excrete waste playing a key role in carbon cycling movements for the biome
  • in 10 years entire top 15cm of soil may be passed through earthworm guts
29
Q

what is the importance of the temperate grasslands in carbon storage and flows

A
  • grassland biomes and soil store 185 gigatonnes of carbon
  • temperate grasslands typically store 2-10 tonnes of carbon per hectare above ground, double found below ground
  • 2/3 of the root biomass is found in the top 30cm of soil
30
Q

what is the size of the soil carbon store and litter layer

A

averages around 100-200 tonnes of carbon per hectare

warm, humid conditions in autumn ensure rapid decomposition of dead grass matter and quick release of CO2 so litter layer is small

31
Q

how do the seasons affect carbon exchanges

A
  • carbon exchanges between atmosphere, biosphere and soil vary greatly according to season
  • in winter, grasses die back to their roots and photosynthesis ceases
  • plants can continue to respire through their roots however especially once the soil begins to warm in spring
32
Q

what has accelerated rainforest removal

A
  • rainforest timber harvesting (mahogany and teak)
  • recently, large scale land use changes carried out by agribusiness has accelerated this
33
Q

what are the effects of deforestation

A
  • deforestation in Amazonia averaged around 17,500 sq.km/year between 1970 and 2013 crops (soya beans) are grown
  • 1/3 of cleared rainforest land used for cattle ranching
  • increasingly affluent global population = greater food demand
  • oil palm cultivation threatening TRFs through forest fires in Sumatra and Kalimantan = toxic haze spreading across SE Asia
  • clearance of TRFs for settlement and agriculture = increase in carbon emissions
34
Q

what does deforestation do

A
  • removes carbon biomass store (2.7 tonnes with soya crop, 180 tonnes for virgin TRF)
  • reduces organic input into the soil and increased overland flow = soil erosion and loss of carbon storage capacity (links water/carbon cycles)
35
Q

what has happened to above ground biomass

A
  • above ground biomass of surviving rainforest increased due to increased CO2 sequestration (increased concentration)
  • example of negative feedback in carbon cycle system
36
Q

what is afforestation

A

AFFORESTATION involves planting trees in deforested places. new trees act as carbon sinks and help climate change mitigation

37
Q

what is the effect of afforestation

A

can reduce the flood risk which might erode the carbon capacity of the surface layer

38
Q

what is an example of an afforestation scheme

A

REDD (UN Reducing Emissions from Deforestation and forest Degradation)

this scheme provides incentives for developing countries to conserve rainforests by placing monetary value on conservation

39
Q

what is the monoculture of commercial trees

A
  • monoculture of commercial trees eg pine plantations in UK can increase carbon storage if it replaces grassland
  • but it may store less carbon than a natural forest due to a relative lack of biodiversity in plantations
40
Q

what is carbon offsetting

A
  • carbon offsetting is a way for an individual/business to offset their carbon emissions in activities eg flying, driving, consuming energy by funding equivalent CO2 emissions elsewhere
  • paying to plant new trees is a commonly accepted carbon offsetting principle
41
Q

what is the effect of agriculture

A
  • agriculture affects both biomass carbon storage of land and amount of soil organic carbon (SOC) eg humus made up of decomposed plants/animal materials
  • globally, clearing natural vegetation for agriculture = reduction in SOC levels
  • historically, excessive cultivation using inappropriate methods has resulted in soils being ‘overworked’ = land degradation and soil erosion problems
42
Q

what is an example of the effects of soil erosion

A
  • in 1920s/30s soil erosion in the USA led to the ‘dust bowl’
  • in Great Plains, wind erosion stripped 65 million hectares of over-cultivated land
  • there was an enormous loss of soil carbon storage capacity
43
Q

how has agriculture been positively changed

A
  • the addition of manure, plant debris, composts and biosolids from sewage to agricultural soils
  • all are high in organic carbon and represent additional carbon inputs to the soil subsystem
44
Q

what crop management can increase soil carbon storage

A
  • irrigation
  • improved crop rotation
45
Q

what are examples of pasture management that might increase soil carbon storage

A
  • fertiliser management
  • grazing management
  • earthworm introduction
  • introduction of legumes
46
Q

what organic amendments increase soil carbon storage

A
  • animal manure
  • recycled plant remains
47
Q

how can we get long term trends in atmospheric concentrations of CO2

A
  • ice core data
  • CO2 gas bubbles frozen in glacial ice
  • CO2 in the cryosphere
48
Q

what has caused changes in ice core data over the past 800,000 years

A

changes in the eccentricity of Earth’s orbit around Sun have 100,000 year cycles and likely influenced CO2 levels and glaciations

during glaciations CO2 levels were lower. during warmer interglacial periods, CO2 levels were higher

49
Q

consequences of increasing CO2 and global temperature

A
  • melting glaciers and polar ice caps
  • sea level rise and flooding of low lying coastal areas by salt water
  • ecosystems change, the range of plants, animals and diseases change impacting agriculture, migration of organisms and health
  • increase in severe weather events
  • disruption of global oceanic circulation

A Level Global Systems (10 decks)

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