Photosynthetic responses of four mixed-grass prairie species to elevated [Carbon dioxide] and warming during contrasting precipitation years

How rising atmospheric CO2 concentration and associated climate warming will interact to influence plant photosynthesis in the future is uncertain. I investigated effects of these combined global changes on light-saturated photosynthesis (Asat) and related parameters in four dominant plant species of a native prairie ecosystem near Cheyenne, WY. I hypothesized that the magnitude of photosynthetic stimulation by elevated [CO2] and warming would depend on precipitation and feedbacks to soil moisture availability. Photosynthesis in a C3 sub-shrub (Artemisia frigida) and forb (Sphaeralcea coccinea) were stimulated by elevated CO2 and warming, individually and in combination, depending on soil water content. Photosynthetic capacity of a C3 grass ( Pascopyrum smithii) was reduced under elevated [CO2], which moderated Asat in this dominant species. My results demonstrate that species are likely to differ greatly in their photosynthetic response to global change and that water was the principal factor modulating photosynthetic stimulation in this temperate grassland ecosystem.