2.3.6—Ecosystems as carbon stores/sinks/sources
- Syllabus
- First assessment 2026
- Objective
- 2.3.6
- Level
- SL
Classify a Forest by Photosynthesis and Respiration
Compare photosynthetic uptake P with total release R: P>R is a sink, P≈R is balanced, and R>P is a source.
Young growth can fix carbon faster than it respires; fire, drought or decay can reverse the balance. These are rate comparisons, not permanent labels for an ecosystem type.
If a forest fixes 100 units and releases 70, net uptake is 30; if fire raises release to 130, net release is 30.
No. Measure P and R for the stated period; age is only a clue, not the calculation.
Do not equate high biomass with current net uptake; a large old stock can be near balance or a source.