We focussed on the potential and limits of NOAA-AVHRR 5-day composite data for monitoring the phenology and the fluxes of temperate forests at regional scale. The spatio-temporal variability ofkm2 Normalised Difference Vegetation Index (NDVI) was large, and primary varied with the deciduous/ coniferous mixture. It could provide the phenological cycle of deciduous ecosystems. For the large coniferous Landes forest, it characterised the different ecotypes, and was sensitive to land use (age of the pine stands) and understorey vegetation. Relationships between NDVI, TS and rainfall confirmed the ability of km2 thermal infrared data to infer the water status of this forest.