We will perform a scaling analysis of terrestrial carbon exchange using several of the NIGEC flux sites in different biomes (forest, C4 grassland, C3 agriculture), using a numerical model of the biophysics and biogeochemistry of plants and soils (SiB2), which includes calculations of the surface fluxes of CO2, energy, and moisture. This model will be used to analyze local fluxes at each site based on observed meteorology and soil conditions, and then the site-calibrated model will be coupled to a series of atmospheric models on increasing spatial scales and with decreasing reliance on a knowledge of local conditions. These atmospheric models will include a 1-dimensional model of PBL turbulence with a grid spacing of about 10 m, a 3-D mesoscale model (RAMS) with a grid spacing of about 6 km, and a global atmospheric general circulation model (CSU GCM), with a grid spacing of about 400 km. This spectrum of atmospheric calculations will provide insight into the coupling between atmospheric transport and terrestrial ecosystem metabolism over a range of spatial scales. Our results will allow the tower flux measurements to be generalized in both space and time, providing a means for NIGEC to leverage its investment in the data collection and to obtain regional and global estimates of sources and sinks of CO2, and will be useful in understanding the processes controlling land surface climate and CO2 flux.