Evidence from chronosequence studies for a low carbon-storage potential of soils

Data from chronosequence studies are used here to show that the production of refractory humus substances in soils sequesters only about 0.4 x 10 to the 15th g C/yr from the atmosphere, accounting for just 0.7 percent of terrestrial net primary production of C. Moreover, agricultural practices tend, on balance, to cause a release of soil carbon to the atmosphere. Thus, if the terrestrial biosphere is indeed to act as a carbon sink under future elevated levels of CO2, this would be more likely to be the result of changes in the distribution and biomass of terrestrial vegetation than of changes in the accumulation of soil organic matter.