Date of this Version
• To evaluate whether functional groups have a similar response to global change, the responses to CO2 concentration and N availability of grassland species from several functional groups are reported here.
• Sixteen perennial grassland species from four trait-based functional groups (C3 grasses, C4 grasses, non-leguminous forbs, legumes) were grown in field mono-cultures under ambient or elevated (560 μmol mol-1) CO2using free-air CO2enrichment (FACE), in low N (unamended field soil) or high N (field soil + 4 g N m-2 years-1) treatments.
• There were no CO2 x N interactions. Functional groups responded differently to CO2 and N in terms of biomass, tissue N concentration and soil solution N. Under elevated CO2, forbs, legumes and C3grasses increased total biomass by 31%, 18%, and 9%, respectively, whereas biomass was reduced in C4-grass mono-cultures. Two of the four legume species increased biomass and total plant N pools under elevated CO2, probably due to stimulated N-fixation. Only one species markedly shifted the proportional distribution of below- vs aboveground biomass in response to CO2 or N.
• Although functional groups varied in responses to CO2and N, there was also substantial variation in responses among species within groups. These results suggest that current trait-based functional classifications might be useful, but not sufficient, for understanding plant and ecosystem responses to elevated CO2and N availability.