CO2 uptake and ecophysiological parameters of the grain crops of midcontinent North America: Estimates from flux tower measurements

► We describe a net CO2 exchange partitioning method using PAR, soil temperature, and VPD. ► The curvature parameter of the VPD-response of photosynthesis is a measure of water stress limitation in grain crops of North America. ► Flux tower measurements show grain crops of the U.S. and Canada as local sinks for atmospheric CO2.