title: Long-term responsiveness to free air CO2enrichment of functional types, species and genotypes of plants from fertile permanent grassland.
abstract: To test inter- and intraspecific variability in the responsiveness to elevated CO2, 9-14 different genotypes of each of 12 perennial species from fertile permanent grassland were grown in Lolium perenne swards under ambient (35 Pa) and elevated (60 Pa) atmospheric partial pressure of CO2(pCO2) for 3 years in a free air carbon dioxide enrichment (FACE) experiment. The plant species were grouped according to their functional types: grasses (L. perenne, L. multiflorum, Arrhenatherum elatius, Dactylis glomerata, Festuca pratensis, Holcus lanatus, Trisetum flavescens), non-legume dicots (Rumex obtusifolius, R. acetosa, Ranunculus friesianus), and legumes (Trifolium repens, T. pratense). Yield (above a cutting height of 4.5 cm) was measured three times per year. The results were as follow. (1) There were highly significant differences in the responsiveness to elevated pCO2between the three functional types; legumes showed the strongest and grasses the weakest yield increase at elevated pCO2. (2) There were differences in the temporal development of responsiveness to elevated pCO2among the functional types. The responsiveness of the legumes declined from the first to the second year, while the responsiveness of the non-legume dicots increased over the 3 years. During the growing season, the grasses and the non-legume dicots showed the strongest response to elevated pCO2during reproductive growth in the spring. (3) There were no significant genotypic differences in responsiveness to elevated pCO2. Our results suggest that, due to interspecific differences in the responsiveness to elevated pCO2, the species proportion within fertile temperate grassland may change if the increase in pCO2continues. Due to the temporal differences in the responsiveness to elevated pCO2among species, complex effects of elevated pCO2on competitive interactions in mixed swards must be expected. The existence of genotypic variability in the responsiveness to elevated pCO2, on which selection could act, was not found under our experimental conditions.
authors.affiliation: Institute of Plant Sciences, Swiss Federal Institute of Technology, CH-8092 Zurich, Switzerland, , , , , , CH.
authors.forename: A
authors.initials: A
authors.lastname: Lüscher
authors.affiliation: Department of Applied Science, Brookhaven National Laboratory, Upton, Long Island, NY 11973, USA phone: ++41/1/6323890 Fax: ++41/1/632 11 53; e-mail: andreas.luescher@ipw.agrl.ethz.ch, , , , , , IS.
authors.forename: G R
authors.initials: GR
authors.lastname: Hendrey
authors.affiliation: Institute of Plant Sciences, Swiss Federal Institute of Technology, CH-8092 Zurich, Switzerland, , , , , , CH.
authors.forename: J
authors.initials: J
authors.lastname: Nösberger
keywords: Elevated CO2; Fertile permanent grassland; Intraspecific variability; Key words Interspecific variability; Perennial species