Fundamentals
Soil carbon stock
The total organic carbon held in soil to a defined depth, the largest terrestrial pool in many landscapes.
A stock estimate combines carbon concentration, bulk density, sampling depth and area. Each term carries uncertainty, and depth conventions differ between programmes, so comparability requires explicit statement.
Stocks are large and change slowly. That combination means small relative changes can be material in absolute terms, and also that detecting them requires careful design rather than a single sampling campaign.
Frequently asked questions
What depth is standard?
Commonly the top thirty centimetres, though deeper layers matter and should be stated when included.
Why is measurement so variable?
Spatial heterogeneity and density effects produce wide natural variation between nearby samples.