The experimental site of Guyaflux in the Paracou forest (Sinnamary, French Guiana) has been created in 2003 and is set up for at least 20 years. Guyaflux has several aims : 1. to characterise the greenhouse gases exchanges between the forest ecosystem and the atmosphere. 2. to assess the contribution of Guianese tropical humid forest ecosystem to the biospheric carbon sink. 3. to assess the impact of environmental constraints on carbon footprint. 4. to analyze the contribution of different compartments of the ecosystem (soil, subsoil, canopy) to storage and water and carbon flows. 5. to model the primary productivity of this ecosystem by linking carbon flow and tree growth. 6. to assess interactions between water cycle, carbon cycle and major soil minerals (nitrogen and phosphorus) The experimental set-up is composed of a 55m-high flux tower, which measures gases exchanges in real-time.Several data types are registrated : microclimatic data, carbon and water flows between forest ecosystem and atmosphere, CO2, CH4, H2O, water content of the soil, trees growth, evapo-transpiration from the trees...To obtain the flows of water and carbon, the turbulent correlations method is used. The project owner is Institut national de la recherche agronomique (INRA). NORELEC is the master builder of the tower. The Guyaflux project received 55% of its funding by INRA and 45% by Ministry of Research and European Union.