Wetlands And Carbon Cycling

Question 1

Methane is the …. most important greenhouse gas after …

Answer 1

Second

CO2

Question 2

How much human induced radiative forcing is methane responsible for?

Answer 2

18%

Question 3

How much more global warming potential does methane have compared to CO2

Answer 3

25 x

Question 4

Anthropogenic sources of CH4 emissions to atmosphere?

Answer 4

Livestock
Biomass burning
Landfills
Waste management 
Fossil fuel production
Rice agriculture

Question 5

Natural source of global CH4 emissions to the atmosphere?

Answer 5

Freshwater aquatic ecosystems

Wetlands

Question 6

….. are the single largest natural source of CH4

Answer 6

Wetlands

Question 7

What are rice fields

Answer 7

Agricultural wetlands with the same controls in CH4 emissions as natural wetlands

Question 8

What are wetlands?

Answer 8

Areas of land covered in, or saturated by water nearly all year round

Present in every climatic zone - from polar to tropics, from Hugh altitudes to dry regions

Question 9

Examples of wetlands?

Answer 9

Mangroves
Peat lands 
Marshes 
Rivers
Lakes
Deltas
Floodplains
Flooded forests 
Rice fields
Coral reefs

Question 10

Water inflows in wetlands/peat lands

Answer 10

Rainfall
Surface water
Groundwater

Question 11

Water outflows in wetlands and peat lands

Answer 11

Evapotranspiration
Surface water
Groundwater

Question 12

Water balance =

Answer 12

Inflow - outflow

Question 13

Explain the term hydrological regime

Answer 13

Describes the pattern of water storage and movement with and across the wetland boundary

It often has strong seasonal patterns arising from rainfall and sunshine intensity

Question 14

What is the hydrological regime determined by?

Answer 14

• timing of the presence of surface water
• how often the wetland floods and dries (frequency of flooding)
• the length of wet and dry periods (duration)
• how far the water spreads (extent)
• the depth of the surface water
• how far the water is below the ground (depth of water table)
• the waters source (rainfall, groundwater, river)
• the inter-annual variability of water levels

Question 15

What retirements the community of vegetation that will grow in a wetland?

Answer 15

The hydrological regime of the wetland

Question 16

Wetlands changes occur due to changes to the…

Answer 16

Wetland itself
Catchment surrounding the wetland
Climate change

Question 17

To accurately estimate the importance of wetlands for global emissions we need accurate data on…

Answer 17

The distribution of different wetland types

The areal coverage of different wetland types

Question 18

Atmospheric methane concentrations in 2000-2007

Answer 18

Constant atmospheric CH4 concentrations

i) increases in anthropogenic CH4 emissions
ii) dry conditions in northern wetland resulting in low CH4 emissions

Question 19

Atmospheric methane concentrations in 2007+

Answer 19

Atmospheric CH4 concentrations increase in response to
i) increases in anthropogenic CH4 emissions
ii)temperature increases leading to increase in emissions from;
Northern wetlands (2003-207)
Tropical wetlands (2007/8)
Boreal wetlands

Question 20

Uncertainties in the magnitude of CH4 emissions from wetlands

Answer 20

• controls of CH4 production, consumption and transport have not been adequately captured in models
• limited number of observations of fluxes and their associated environmental variables
• wetlands themselves are poorly mapped and very heterogeneous

Question 21

Peat lands

Answer 21

Wetland types including moors, bogs, mires, peat swamp forests and permafrost tundra

• characterised by water logged soil made up of dead and decaying plant material
• peatlands represent 50% of earths wetlands and cover 3% global land area

Question 22

Importance of peatlands?

Answer 22

Water - offer flood protection by absorbing rain and releasing water slowly

Food - herding cattle, catching fish and farming

Species - home to many rare and critically endangered species

Climate change - contain twice as much carbon as worlds forests however also a significant source of greenhouse emissions

Question 23

Peatlands and carbon storage ?

Answer 23

Carbon storage is an important ecosystem service provided by waterlogged, undisturbed peatlands where organic carbon input rates > organic carbon decomposition rates.

Question 24

How much carbon do peatlands contain?

Answer 24

500-700 billion tonnes of carbon

• more than the worlds tropical forests (360 Gt)
• more than half of the carbon stored in atmosphere (750 Gt)

Question 25

Peatlands carbon in and out cycle ?

Answer 25

Atmospheric CO2 taken in by plants and sites as plant tissue in the peat

Decay of plant litter and peat produces both CO2 and CH4

Carbon storage is ensured as long as peat remains water logged

Question 26

Environmental benefits of peatlands?

Answer 26

Carbon storage via plant uptake and litter production

Carbon sink / sequestration

Question 27

Environmental problems with peatlands?

Answer 27

Greenhouse gas emissions of CO2 and CH4

Waterborne carbon losses

Carbon source

Question 28

Organic matter degradation in peatlands

Answer 28

Lots of vegetation in peatlands - aquatic and terrestrial vegetation safe a key component

This vegetation is degrading under saturated soil conditions

Plant litter falls to the soil surface and encounters wet soil with low to no oxygen

Question 29

What conditions are decomposers must productive in?

Answer 29

Warm moist conditions providing sufficient oxygen is available

Question 30

When do decomposition rates decline?

Answer 30

At moisture content less than 30-50% dry mass because moisture films are small so dissolved organic matter cannot Efficiently diffuse to immobile bacteria

Question 31

What happens at higher moisture contents?

Answer 31

Air spaces filled with water - so low oxygen conditions

This restricts decomposition and leads to carbon accumulation e.g. peat soils in bogs and wetlands

Question 32

Decomposition as a reduction-oxidation (redox) process?

Answer 32

Microbial decomposition is a redox process that transfers electrons from organic matter to an electron acceptor.

During this process energy is released and ‘captured’ by the microbes in chemical energy.

Question 33

Methane production and oxidation in a wetland

Answer 33

Amount of methane emitted from a wetland is a balance between methane production and methane oxidation

Question 34

Factors controlling methane production in a wetland?

Answer 34

Hydrological regime - controls oxygen content of the substrate

Temperature - a higher temperature results in more methane being produced due to higher microbial activity

Organic matter content - the more organic matter the more methane can be produced

Organic matter quality - the organic matter must be labile (available to the Archaea)

Question 35

Carbon balance and water table patterns?

Answer 35

As you lower water table then lowland peatlands become net carbon source

As you raise water table you reach a critical point where CH4 emissions to the atmosphere start to become important

Net C balance still needs qualifying for many wetland types & management

Question 36

Globally peatlands store …% of carbon

Answer 36

30%

Question 37

How is carbon storage achieved ?

Answer 37

By photosynthesis of plants and subsequent storage of plant biomass in peat

Question 38

Measurements of carbon fluxes in fens?

Answer 38

Funnels to capture ebullition (bubbling) of methane from peat

Floating chambers to capture diffusion C fluxes from water

Static chambers to capture diffusive and plant mediated C fluxes

Question 39

What is ebullition controlled by?

Answer 39

Water level - higher the water level, more ebullition

Soil temperature - the higher the temperature, more ebullition

Plants - there was more ebullition when plant cover was lower