Do species and functional groups differ in acquisition and use of C, N and water under varying atmospheric CO₂ and N availability regimes? A field test with 16 grassland species

Authors

Peter B. Reich, University of Minnesota, St. Paul, MN
David Tilman, University of Minnesota, St. Paul, MN
Joseph Craine, University of California, Berkeley, CA
David Ellsworth, Brookhaven National Laboratory, Upton, NY
Mark G. Tjoelker, University of Minnesota, St. Paul, MN
Johannes M. H. Knops, University of Nebraska-LincolnFollow
David A. Wedin, University of Nebraska-LincolnFollow
Shahid Naeem, University of Washington, Seattle, WA
Dan Bahauddin, University of Minnesota, St. Paul, MN
Jenny Goth, University of Minnesota, St. Paul, MN
Wendy Bengtson, University of Minnesota, St. Paul, MN
Tali D. Lee, University of Minnesota, St. Paul, MN

Date of this Version

3-30-2001

Comments

Published in New Phytologist (2001) 150 : 435–448.

Abstract

Summary:

• 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.