THE CARBON BUDGET IN SOILS.

The global soil C reservoir, ∼1500 Gt of C (1 Gt = 10[sup 12] kg of C), is dynamic on decadal time scales and is sensitive to climate and human disturbance. At present, as a result of land use, soil C is a source of atmospheric CO2 in the tropics and possibly part of a sink in northern latitudes. Here I review the processes responsible for maintaining the global soil C reservoir and what is known about how it responds to direct and indirect human perturbations. “I am fire and air; my other elements I give to baser life” —William Shakespeare, Antony and Cleopatra [ABSTRACT FROM AUTHOR]