1.3- Factors Driving Change In The Magnitude Of Carbon Stores

Question 1

On a global level, is the carbon cycle an open or closed system?

Answer 1

Closed

Question 2

On a local level, is the carbon cycle e.g a forest carbon cycle an opened or closed system?

Answer 2

Open, due to inputs and outputs

Question 3

What are transfers in carbon cycles, and why are they important?

Answer 3

• transfers are processes which move carbon between stores; this may include a change in state
• an example in photosynthesis as carbon dioxide is removed from the atmosphere and converted into carbohydrates such as glucose within plants

Question 4

The size of transfers controls the size of

Answer 4

Stores

Question 5

What are the main transfers operating in the carbon cycle?

Answer 5

1- photosynthesis 
2- respiration 
3- decomposition 
4- combustion 
5- burial and compaction 
6- carbon sequestration 
7- weathering

Question 6

Explain the process of photosynthesis

Answer 6

• process whereby plants utilise carbon dioxide and light energy from the sun to produce carbohydrates in the form of glucose
• green plants absorb the light usiate chlorophyll in chloroplasts often within palisade cells in their leaves
• absorbed light energy converts carbon dioxide in the air and water from soil into glucose, releasing oxygen into the air
• some glucose is utilised as a respiratory substrate, but the rest is converted into starch, an insoluble storage molecule that can be hydrolysed back to glucose for respiration

Question 7

Explain the process of respiration

Answer 7

• vital chemical process that occurs in both animals and plants where most commonly, glucose is converted into ATP (energy currency) used to maintain life (movement, of control of body temperature in mammals)
• carbon dioxide is then returned to the atmosphere mostly by exhaled air

Question 8

Explain process of decomposition

Answer 8

• when organisms die, they are consumed by decomposers such as bacteria, fungi and earthworms
• during process of decomposition, carbon from their bodies is returned to the atmosphere as carbon dioxide, but some may transfer to the soil where it may be stored for hundreds of years

Question 9

Explain the process of combustion

Answer 9

• organic material contain carbon
• when it is burned in the presence of oxygen e.g. coal in a power station, it is converted into energy, carbon dioxide and water = combustion
• carbon dioxide released back into the atmosphere, returning carbon that might have been stored in rocks for millions of years

Question 10

Explain the process of burial and compaction

Answer 10

• where organic matter is buried by sediments and becomes compacted
• over millions of years, these organic sediments containing carbon may form hydrocarbons such as coal and oil
• corals and shelled organisms take up carbon dioxide from the water and convert it into calcium carbonate, used to build their shells
• when they die, the shells accumulate on the seabed- some of the carbonates dissolve releasing carbon dioxide
• the rest become compacted to form limestone, storing limestone for millions of years

Question 11

Explain process of carbon sequestration

Answer 11

• umbrella term used to describe the transfer of carbon from the atmosphere to plants, soils, rock formations and oceans
• sequestration both a natural and a human process
• carbon capture storage is a recent term used to describe the technological ‘capturing’ of carbon emitted from power stations
• smaller-scale sequestration can also take place e.g. by a change in farming practices

Question 12

Explain the process of weathering

Answer 12

• involves the breakdown or decay of rocks in situ or close to the surface
• when carbon dioxide is absorbed by rainwater it forms a mildly acidic carbonic acid
• through a series of complex chemical reactions, rocks will slowly dissolve with the carbon being held in solution
• transported via the water cycle to the oceans; this carbon can then be used to build the shells of marine organisms

Question 13

Summarise carbon cycle of a tree

Answer 13

• tree acts as a carbon sink- wood is about 50% carbon
• flows include photosynthesis, leaf litter, decomposition, respiration by decomposers and general plant respiration
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Question 14

Regarding a terrestrial carbon cycle: the lithosphere, explain the sequence of changes which is classed as vegetation succession:

Answer 14

• when rock is exposed for the first time, say after glacial retreat, it is vulnerable to processes of weathering
• as the rock is slowly broken down, carbon may released often dissolved in water
• over time, vegetation such as lichen and moss grows on bare rock and carbon exchange starts to take place involving photosynthesis and respiration
• gradually, as organic matter to the broken fragments of rock, a soil develops that can support a wide range of plants (soil important bc it can absorb and store carbon over moderate periods of time)
• over hundreds of years, the plant species become more diverse, benefitting from the supply of carbon in the soil- a number of different habitats are established and wildlife becomes abundant
• this sequence of changes = vegetation succession

Question 15

A succession that relates to a specific environment=

Answer 15

A sere and each stage in succession can be referred to as a seral stage

Question 16

A lithosphere is a vegetation succession that occurs on bare rock- other seres include:

Answer 16

• hydrosphere (water- freshwater pond)
• halosphere (salt-coastal salt marsh)
• psammosere (coastal sand- sand dunes)

Question 17

Eventually, a final stage of sere is reached when a state of environmental equilibrium or balance is achieved, termed

Answer 17

Climatic climax

Question 18

The climax vegetation for a lithosphere in the uk will usually be

Answer 18

A deciduous woodland