Carbon Content in Soils

The next column lists carbon in soils. Boreal forests and tundra and alpine meadow contribute almost identical amounts to the planetary total soil carbon. Temperate grasslands and pasture contribute nearly as much total soil carbon as the boreal forest soils, but somewhat less on a per-hectare basis. The per-hectare values of the fourth and fifth columns can be expressed in kilograms per square meter by dividing these numbers by 10. Hence, tropical evergreen forests have about 17.7 kilograms per square meter of carbon in the vegetation, while the temperate grassland and pastures have about 0.7 kilogram per square meter. The most notable entry in this column is the enormous carbon density in soils of swamps and marshes, being over 2 1/2 times as much as the next largest entry.

Tillage of soil increases microbe activity in the soil and leads to rapid conversion of soil carbon to CO₂. The small marshes and wetlands (known as prairie potholes) that once covered the Iowa, Dakota, and southern Canada landscape, were rich in soil carbon as suggested by the carbon table. Draining and cultivating these regions has resulted in the loss of significant amounts of soil carbon. One of the benefits of modern minimum-tillage and no-tillage practices is that they increase amounts of carbon that are stored in the soil.

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