Contribution of terrestrial ecosystems to carbon sequestration.

Contribution of terrestrial ecosystems to carbon sequestration. This article focuses on the contribution of natural ecosystems (forests, grasslands) and agrosystems to carbon sequestration either in biomass or in soil. Carbon stocks are important (650 Gt in biomass, 1500 to 2000 Gt in soils as compared with 750 for atmospheric CO2), and also fluxes that led to CO2 emissions in the past (due to deforestation or cultivation) and which now turn to carbon sequestration (2 Gt(C)/year). This article shows great spatial variations in stocks and fluxes and great measurement difficulties, especially for stock variations. Anthropic actions such as reforestation (mainly in the North), changes in land use or in crop management, can increase carbon sequestration in biomass or soil, with a residence time of several decades, which is not insignificant with respect to the Kyoto protocol and which also has other environmental (C) 2003 Academie des sciences. Publie par Editions scientifiques et medicales Elsevier SAS.