Ecosystems as Carbon Sinks and Carbon Sources
- Ecosystems are open systems where both matter and energy can enter or exit.
- Carbon enters primarily as carbon dioxide through photosynthesis and exits through respiration.
- The balance between these processes determines whether an ecosystem acts as a carbon sink or source.
Definition
Carbon Sink
An ecosystem that absorbs more carbon than it releases.
Definition
Carbon source
An ecosystem that releases more carbon than it absorbs.
Role of Decomposition in Carbon Cycling
- In most ecosystems, saprotrophs break down dead organic matter, releasing carbon dioxide into the atmosphere through respiration.
- However, certain conditions can inhibit decomposition:
- Waterlogged Habitats: Acidic and anaerobic environments like bogs or swamps slow decomposition, leading to the accumulation of peat.
- Coal Formation: Over millions of years, peat can transform into coal, removing carbon from the cycle in a process called sequestration.
Natural Carbon Release: Fires in Ecosystems
- Periodic fires are a natural feature of many ecosystems.
- During a fire:
- Carbon stored in living organisms and organic matter is released as carbon dioxide.
- The ecosystem temporarily shifts to acting as a carbon source.
