Soil is a vital national resource and soil carbon is an integral component of soil structure and function. Soil is the largest terrestrial reservoir of carbon, containing an estimated 1550 Pg of organic carbon in the top meter alone. Soil contains twice as much carbon as the atmosphere (800 Pg in 2007), and three times that in global vegetation (~500 Pg). Although the global stock of soil carbon is immense, it is not static: about 120 Pg of carbon moves annually between soil and the carbon reservoirs in the atmosphere and vegetation. Soil carbon may thus play a singular but uncertain role in climate forcing during the coming decades, with significant net losses contributing to positive feedbacks, or significant sequestration helping to mitigate climate forcing.
Though important, climate regulation is not the only service provided by soil carbon. In fact, carbon held in soils provides a number of essential other services (i.e., ecosystem services) that either directly or indirectly support human well-being. For example, carbon held in soils plays a vital role in the improvement soil tilth, retention and supply of plant nutrients, isolation and decomposition of wastes and toxic substances, production of food and fiber, water retention and supply, flood protection, reduction of wind and water erosion, and maintenance of biodiversity. The loss of soil carbon or disruption of its cycling may impair the ecosystem services it provides, with consequent negative impacts on society.
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