Terrestrial biological carbon cycle

[2] Carbon is cycled through the terrestrial biosphere with varying speeds, depending on what form it is stored in and under which circumstances.

Autotrophs, such as trees and other green plants, use photosynthesis to convert carbon dioxide during primary production, releasing oxygen in the process.

If oxygen is not present, e.g. as is the case in marshes or in animals' digestive tracts, anaerobic respiration can occur, which produces methane.

Part of the net primary production, or the remaining carbon absorbed by the biosphere, is emitted back into the atmosphere through fires and heterotrophic respiration.

Human activity has large effects on the terrestrial biosphere, changing the way that it acts as a carbon reservoir.

Indirectly, human-induced changes in the global climate cause widespread modifications to the terrestrial ecosystem's function in the carbon cycle.

For example, warming in the Arctic has caused stress in North American boreal forests,[5] thus decreasing primary production and carbon uptake, while the same warmer temperatures have led to increased shrub growth in the same areas,[6] producing an opposite effect.

Higher CO2 levels in the atmosphere can cause photosynthesis to take place more efficiently, thus increasing plant growth and primary production.

How long this carbon would remain sequestered in the terrestrial biosphere before being rereleased into the atmosphere is unclear, however, and it is likely that other limiting factors (e.g. nitrogen availability, moisture, etc.)