The net ecosystem productivity (NEP) takes into account the soil respiratory flux originating from heterotrophic decomposition of soil organic matter. These carbon fluxes are quantified using the C-Fix model which is a remote sensed-based carbon balance product efficiency model wherein the evolution of the radiation absorption efficiency in the PAR (Photosynthetically Active Radiation) band (or fAPAR) of vegetation is directly inferred from space observations, SPOT-VEGETATION S10 (SPOT VGT S10) images, using the Normalized Difference Vegetation Index (NDVI).

Monitoring, understanding and modelling vegetation are crucial issues to asses the carbon dynamics of terrestrial ecosystems in the framework of global change and the Kyoto protocol. A vegetation area can be a net carbon sink or source. Using NPP/NEP, vegetation damage due to climatologic anomalies (late frost, long period of drought,...) and environmental pollution (ozone damage, heavy metal pollution,...) can be detected.