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How do forests act as carbon reservoirs?

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A labeled diagram of the periodic table entry for carbon, showing its atomic number 6, symbol C, electron configuration, atomic weight range, solid physical state, hexagonal crystal structure, and weakly acidic oxide properties. Color coding and icons indicate it is a nonmetal, solid at room temperature, with hexagonal structure and weak acidity. — carbon Carbon and its properties.

Forests serve as vital carbon reservoirs by acting as terrestrial carbon sinks, where they store carbon in both aboveground biomass and soils.12

How Forests Store Carbon

Photosynthesis: Through photosynthesis, trees and other vegetation extract carbon dioxide (CO₂) from the atmosphere and convert it into organic compounds, which are then stored in their tissues, such as wood, leaves, and roots.32
Soil Accumulation: Carbon that is not stored in living plant tissues often enters the soil as litter, where it is eventually incorporated into soil humus.4
Scale of Storage: Forests are the largest terrestrial carbon reservoirs, holding up to 80 percent of aboveground carbon and approximately one-third of belowground carbon in terrestrial communities.2

The Balance of Carbon

While forests sequester carbon, they can also become carbon sources if that stored carbon is released back into the atmosphere. This occurs through decomposition by microorganisms or combustion caused by fires. Human activities, particularly deforestation, disrupt this balance by removing the vegetation that sequesters carbon and accelerating the release of stored carbon into the atmosphere.3142