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Carbon in the soil

Updated Sunday, 7th May 2000

The soil holds a lot of carbon - so how does it escape?

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Take rock fragments weathered by wind rain and rivers. Add dead organic matter from plants and animals. Now churn them around with the help of bacteria, fungi, worms and insects. What results is soil. Take a teaspoon of soil and you’ll find tens of millions of bacteria, fungi and also larger decomposers. All of these organisms release the carbon stored in plant and animal remains into the air as carbon dioxide gas.

Soil is a mixture of mineral and organic matter, and, in a huge variety of forms, it covers much of the Earth’s land surface. Organic matter gives soil its fertility. Fresh organic matter is devoured fairly quickly by decomposers and is quickly released as carbon dioxide. But a little of it is more resilient. Depending on its resistance to decomposition, organic carbon can stay in the soil for tens, hundreds, even thousands of years.

In wetlands the soil is flooded or saturated for at least part of the year. Wetlands include bogs, swamps, marshes and fens. They are among the most productive and diverse habitats on Earth. But because there is often little oxygen available, much of their carbon isn’t fully broken down in decomposition. So partly decomposed organic material accumulates.

Where do you find the carbon?

Dead organic matter and decomposers in soil, wetlands and freshwater sediments

What form of carbon?

Organic carbon

How long will the carbon remain?

Most decomposers within a few years, but some remain for thousands of years. The average is 25 years

How much carbon is there?

About 1500 x 10 12 kg

What processes will free the carbon?

Burning, lithification, respiration, river transport, sedimentation





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