title: Species and functional group diversity independently influence biomass accumulation and its response to CO2 and N.
abstract: The characteristics of plant assemblages influence ecosystem processes such as biomass accumulation and modulate terrestrial responses to global change factors such as elevated atmospheric CO(2) and N deposition, but covariation between species richness (S) and functional group richness (F) among assemblages obscures the specific role of each in these ecosystem responses. In a 4-year study of grassland species grown under ambient and elevated CO(2) and N in Minnesota, we experimentally varied plant S and F to assess their independent effects. We show here that at all CO(2) and N levels, biomass increased with S, even with F constant at 1 or 4 groups. Likewise, with S at 4, biomass increased as F varied continuously from 1 to 4. The S and F effects were not dependent upon specific species or functional groups or combinations and resulted from complementarity. Biomass increases in response to CO(2) and N, moreover, varied with time but were generally larger with increasing S (with F constant) and with increasing F (with S constant). These results indicate that S and F independently influence biomass accumulation and its response to elevated CO(2) and N.
authors.affiliation: Department of Forest Resources, University of Minnesota, St. Paul, 55108, USA. preich@umn.edu
authors.forename: Peter B
authors.initials: PB
authors.lastname: Reich
authors.forename: David
authors.initials: D
authors.lastname: Tilman
authors.forename: Shahid
authors.initials: S
authors.lastname: Naeem
authors.forename: David S
authors.initials: DS
authors.lastname: Ellsworth
authors.forename: Johannes
authors.initials: J
authors.lastname: Knops
authors.forename: Joseph
authors.initials: J
authors.lastname: Craine
authors.forename: David
authors.initials: D
authors.lastname: Wedin
authors.forename: Jared
authors.initials: J
authors.lastname: Trost
mesh_terms: D044822:Biodiversity; D018533:Biomass; D002245:Carbon Dioxide / Q000494:pharmacology*; D009584:Nitrogen / Q000494:pharmacology*; D006109:Poaceae / Q000254:growth & development*
chemical_list: D002245:Carbon Dioxide; D009584:Nitrogen