UNDERSTANDING THE FEEDBACKS ASSOCIATED WITH CLIMATE CHANGE IN NORTHERN BOREAL FORESTS IS CRITICAL FOR PREDICTING HOW THESE ECOSYSTEMS WILL CHANGE INTO THE FUTURE. WE PROPOSE TO LINK OBSERVATIONS OF VEGETATION REFLECTANCE AND SIF COLLECTED AT HIGH TEMPORAL RESOLUTION (CONTINUOUS GROUND-BASED HYPERSPECTRAL REFLECTANCE AND SIF WITH CUSTOM PHOTOSPEC SPECTROMETERS) AND HIGH SPATIAL RESOLUTION (AIRBORNE DATA CFIS AVIRISNG) WITH CARBON FLUXES ACROSS A RANGE OF HYDROLOGIC AND CLIMATE REGIMES IN THE NORTHERN BOREAL FOREST. THIS MULTI-SCALE APPROACH WILL INFORM SATELLITE OBSERVATIONS FROM MODIS OCO-2 AND TROPOMI TO SCALE GPP ESTIMATES ACROSS THE BOREAL REGION. OUR PRIMARY OBJECTIVES ARE AS FOLLOWS: 1) ESTABLISH A QUANTITATIVE FRAMEWORK TO DESCRIBE THE ECOPHYSIOLOGICAL AND PHYSICAL MECHANISMS LINKING SURFACE MEASUREMENTS OF SIF AND VEGETATION REFLECTANCE TO GPP AT ESTABLISHED TOWER SITES AND COINCIDENT AIRBORNE CAMPAIGNS. 2) REDUCE UNCERTAINTIES IN SATELLITE-BASED ESTIMATES OF GPP ACROSS THE BOREAL REGION BY APPLYING A PROCESS-BASED UNDERSTANDING OF BOTH THE TEMPORAL AND SPATIAL DYNAMICS OF SIF AND VEGETATION REFLECTANCE AT FINE SCALES.