During the second stage of FLUXNET the research priority involved the decomposition of NEE measurements into component fluxes such as GPP and ecosystem respiration, R eco. This step is required for FLUXNET to be a successful tool for validating MODIS-based estimate of terrestrial carbon exchange; algorithms driven by satellite-based remote sensing instruments are unable to assess NEE directly, and instead compute GPP or NPP. In the intervening years, FLUXNET scientists have used the flux-component datasets (GPP, R eco) to assess how canopy photosynthesis and ecosystem respiration vary as a function of: 1) season; 2) plant functional type; and 3) environmental drivers.