5.9: Ecosystems and its Dependence on Carbons

Ecosystems

 Open systems where both matter and energy can enter/exit 

→ Carbon exits/enters mainly as CO₂using photosynthesis and respiration

Carbon Sink

Anything that absorbs more carbon from the atmosphere than it releases

• When more photosynthesis is occurring than respiration (less CO₂ is produced → Ecosystem acts as a carbon sink 

Carbon source

That releases an excessive amount of CO₂ into the atmosphere 

• When more respiration is occurring than photosynthesis (more CO₂ produced) → Acting as a carbon source 

Saprotrophs

• release carbon dioxide through respiration when they digest dead organic matter 

  • Some conditions might inhibit decomposition - less CO₂

    • Eg, Acidic/ anaerobic conditions in waterlogged habitats → Accumulates peat

Sequestration

• Removal of carbon from the cycle 

Fires

• Production of more CO₂ → natural and most species are adapted to it

  • Combustion: The process of carbon being released from carbon compounds in living/dead organism through fire 

Natural Gas and Oil

• Formed through deep burial under sediments of partially decomposed organic matter → High temperatures than create chemical changes to form oil 

  • Trapped in porous rocks

• When it is formed: Over the past 550 million years from the precambrian geological period 

Coal

• Formed through the accumulation of wood/plants in swamp areas 

  • They are then buried under other sediment

• When it is formed: From 325-250 million years ago  

Peat

• Formed through the incomplete decomposition of dead plant matter from acidic/anaerobic conditions of waterlogged regions

  • Waterlogged: Saturated/filled with water

• When it is formed: Mostly over the past 10000 years - since the last glaciation 

Biomass

• Formed through the photosynthesis of general plants and its transfer in food chains until its an animal biomass

• When it is formed: Wood accumulations over the years, other organic matter is recent

Flash Point

• Combustion occurs when this ignition temperature is reached 

  • Not possibly through natural weather but can be reached through volcanic activity or lighting strikes, fires etc

• Coal/ crude oil/ natural gas: Over 500^oC

• Dry wood: Over 400^oC 

Combustion today

•  Combustion of peat occurring through wildfires in areas of tundra (within the Arctic Circle) 

• Around 250 megatonnes of CO₂ emitted from these fires in 2020 :O 

• Around 3400 megatonnes of CO₂ emitted by humans through fossil fuel burning 

  • Today humans combusted like crazy = unbalanced

Keeling Curve

CO₂ concentrations measured in a region that is plotted showing 2 trends

• Started being used in Hawaii

Annual Fluctuation on a keeling curve

• Concentration of CO₂ increases between Oct-May and then falls from May-Oct

  • Photosynthesis will increases during the summer - especially for the northern hemisphere because it has more of earths plants

Long-Term Trend on a keeling curve

• Despite seeing a decrease near the end of the year, it is relatively higher than the original concentration of the year 

• Full Keeling Curve: Trend from 1959 where fossil fuel burning, anthropogenic factors by humans increase the concentration 

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