To determine the long‐term impact of elevated CO 2 on primary production of native tallgrass prairie, we compared the responses of tallgrass prairie at ambient and twice‐ambient atmospheric CO 2 levels over an 8‐year period. Plots in open‐top chambers (4.5 m diameter) were exposed continuously (24 h) to ambient and elevated CO 2 from early April to late October each year. Unchambered plots were monitored also. Above‐ground pea...

We measured leaf‐level stomatal conductance, xylem pressure potential, and stomate number and size as well as whole plant sap flow and canopy‐level water vapour fluxes in a C4‐tallgrass prairie in Kansas exposed to ambient and elevated CO 2 . Stomatal conductance was reduced by as much as 50% under elevated CO 2 compared to ambient. In addition, there was a reduction in stomate number of the C4 grass, Andropogon gerardii Vitma...