The enhanced understanding of the controlling mechanisms of carbon Cycling in European ecosystem is performed by executing: the partitioning of carbon fluxes in their constituents parts (assimilation, respiration, fossil fuel burning); the quantification of the effects of the management; the developments of ecosystem process models. The development of an observation system to detect changes of carbon stocks and carbon fluxes, related to the European commitments under the Kyoto Protocol is performed by: collecting atmospheric measurements to detect changes on CO2 concentration; outline a carbon accounting system, based on carbon fluxes and stock changes in soil and vegetation inventories.