Legume species identity and soil nitrogen supply determine symbiotic nitrogen-fixation responses to elevated atmospheric [CO2].
In nitrogen (N)-limited systems, the response of symbiotic N fixation to elevated atmospheric [CO2] may be an important determinant of ecosystem responses to this global change. Experimental tests of the effects of elevated [CO2] have not been consistent. Although rarely tested, differences among legume species and N supply may be important. In a field free-air CO2 enrichment (FACE) experiment, we determined, for four legume species, whether the effects of elevated atmospheric [CO2] on symbiotic N fixation depended on soil N availability or species identity. Natural abundance and pool-dilution 15N methods were used to estimate N fixation. Although N addition did, in general, decrease N fixation, contrary to theoretical predictions, elevated [CO2] did not universally increase N fixation. Rather, the effect of elevated [CO2] on N fixation was positive, neutral or negative, depending on the species and N addition. Our results suggest that legume species identity and N supply are critical factors in determining symbiotic N-fixation responses to increased atmospheric [CO2].
Department of Ecology, Evolution and Behavior, University of Minnesota, St Paul, MN, USA. jwest@biology.utah.edu
Jason B
JB
West
Janneke
J
HilleRisLambers
Tali D
TD
Lee
Sarah E
SE
Hobbie
Peter B
PB
Reich
D001272:Atmosphere / Q000032:analysis; D002245:Carbon Dioxide / Q000378:metabolism*; D007887:Fabaceae / Q000254:growth & development / Q000378:metabolism* / Q000382:microbiology; D008910:Minnesota; D009584:Nitrogen / Q000032:analysis; D009586:Nitrogen Fixation; D012987:Soil / Q000032:analysis; D013045:Species Specificity; D013559:Symbiosis
D012987:Soil; D002245:Carbon Dioxide; D009584:Nitrogen