Growth of blue grama (Bouteloua gracilis) in response to atmospheric CO2 enrichment

Blue grama (Bouteloua gracilis (HBK.) Griffiths), an important C 4 species in the Great Plains grasslands of the north-central United States, was grown under three concentrations of CO 2 : 350, 675, and 1000 μL∙L −1 . Growth of blue grama was significantly enhanced by enrichment to 675 but not to 1000 μL∙L −1 . At the end of the experiment, 7 weeks after planting, plants grown at 675 μL∙L −1 had 35% more total biomass and nearly 90% greater leaf area than controls grown at 350 μL∙L −1 . This growth enhancement is large for a C 4 species, but is modest compared with the response typical of C 3 species. It is concluded that blue grama may experience increasing competition from its C 3 , associates if atmospheric CO 2 continues to increase in the future.