Abstract: CO2 and water vapor fluxes and ecosystem characteristics were measured at 24 sites along a 317-km transect from the Arctic coast to the latitudinal treeline in Alaska during the growing seasons of 1994-1996. The sites were stratified to sample the ranges of climate, physiography, soil moisture, and vegetation type within the region. Our main objective was to understand what factors control ... variations in CO2 and water vapor exchange across the region. We therefore developed a spatially extensive approach of documenting fluxes for 1-2 weeks at each of the sites in order to study as many sites as possible during the middle of the short arctic growing season, when plant phenology is most comparable among different vegetation types and climatic regions. This allowed us to compare, with some replication, a given vegetation type across different provinces and climatic zones, as well as multiple vegetation types within a given geographic area.