Changes in Soil Carbon Storage and Associated Properties with Disturbance and Recovery

Organic matter in the world’s soils contains about three times as much carbon as the land vegetation. Soil organic matter is labile and is likely to change as a result of human activities. Agricultural clearing, for example, results in a decline in soil organic matter. At the present time, there may be a net release of 0.85 × 1015 g C • yr−1 from soils of the world due to agricultural clearing (Houghton et al. 1983; Schlesinger 1984), or about 15% of the annual release from fossil fuels. The release of carbon may have been greater near the turn of the century as a result of more rapid agricultural expansion into virgin areas (Stuiver 1978, Wilson 1978). It is the purpose of this chapter (1) to review briefly the present estimates of the size of the pool of carbon in world soils and (2) to offer a review and analysis of what is known about the effects of agriculture on soil carbon storage.