GLOSSARY

Fraction of Absorbed Photosynthetically Active Radiation (FAPAR): fraction of the solar radiation received on the surface which is absorbed by the canopy in the wavelength range used by photosynthesis (0.4-0.7 microns).

Leaf Area Index (LAI): leaf area per unit ground surface area. For example, an index of 5 m²/m² indicates that if one takes all the leaves above a surface of 1 m², one obtains 5 m² of leaves.

Meteorological forcing: ensemble of meteorological data that characterize the air in contact with the biosphere (temperature, moisture and winds) and quantify radiation and precipitation at the surface.

Net Ecosystem Productivity (NEP): net budget of the carbon exchanged between the atmosphere and the biosphere, by time and area units. It represents the difference between the activity of the photosynthesis, which absorbs CO₂, and that of respirations (respiration known as autotrophic of the working of the plants plus respiration known as heterotrophic related to the decomposition of the organic matter of the grounds), which emit CO₂ towards the atmosphere. On the figures, a negative value (green) indicates that overall the biosphere absorbs CO₂, a positive value (blue) states on the contrary that it rejects some.

Net Primary Productivity (NPP): quantity, by time and area units, of carbon absorbed by the plant and which produces biomass. It represents the difference between the activity of photosynthesis and that of autotrophic respiration. Autotrophic respiration is used to produce energy for the working of the plant and releases CO₂ towards the atmosphere. Annually, it is estimated that NPP accounts for approximately 50% of the assimilation.

Numerical model of the biosphere: computer code that simulates the evolution of the biosphere, mainly that of vegetation activity.