title: Biomass responses in a temperate European grassland through 17 years of elevated CO2.
abstract: Future increase in atmospheric CO2concentrations will potentially enhance grassland biomass production and shift the functional group composition with consequences for ecosystem functioning. In the "GiFACE" experiment (Giessen Free Air Carbon dioxide Enrichment), fertilized grassland plots were fumigated with elevated CO2(eCO2) year-round during daylight hours since 1998, at a level of +20% relative to ambient concentrations (in 1998, aCO2was 364 ppm and eCO2399 ppm; in 2014, aCO2was 397 ppm and eCO2518 ppm). Harvests were conducted twice annually through 23 years including 17 years with eCO2(1998 to 2014). Biomass consisted of C3 grasses and forbs, with a small proportion of legumes. The total aboveground biomass (TAB) was significantly increased under eCO2(p = .045 and .025, at first and second harvest). The dominant plant functional group grasses responded positively at the start, but for forbs, the effect of eCO2started out as a negative response. The increase in TAB in response to eCO2was approximately 15% during the period from 2006 to 2014, suggesting that there was no attenuation of eCO2effects over time, tentatively a consequence of the fertilization management. Biomass and soil moisture responses were closely linked. The soil moisture surplus (c. 3%) in eCO2manifested in the latter years was associated with a positive biomass response of both functional groups. The direction of the biomass response of the functional group forbs changed over the experimental duration, intensified by extreme weather conditions, pointing to the need of long-term field studies for obtaining reliable responses of perennial ecosystems to eCO2and as a basis for model development.
authors.affiliation: Department of Plant Ecology, Justus Liebig University of Giessen, Giessen, Germany.
authors.forename: Louise C
authors.identifier: 0000-0002-4890-889X
authors.initials: LC
authors.lastname: Andresen
authors.affiliation: Department of Geography, Climatology, Climate Dynamics and Climate Change, Justus Liebig University of Giessen, Giessen, Germany.
authors.forename: Naiming
authors.initials: N
authors.lastname: Yuan
authors.affiliation: Department of Plant Ecology, Justus Liebig University of Giessen, Giessen, Germany.
authors.forename: Ruben
authors.initials: R
authors.lastname: Seibert
authors.affiliation: Department of Plant Ecology, Justus Liebig University of Giessen, Giessen, Germany.
authors.forename: Gerald
authors.initials: G
authors.lastname: Moser
authors.affiliation: Department of Plant Ecology, Justus Liebig University of Giessen, Giessen, Germany.|Department of Soil Science and Plant Nutrition, WG Climate Change Research for Special Crops, Hochschule Geisenheim University, Geisenheim, Germany.
authors.forename: Claudia I
authors.initials: CI
authors.lastname: Kammann
authors.affiliation: Department of Geography, Climatology, Climate Dynamics and Climate Change, Justus Liebig University of Giessen, Giessen, Germany.|Centre for International Development and Environmental Research, Justus Liebig University Giessen, Giessen, Germany.
authors.forename: Jürg
authors.initials: J
authors.lastname: Luterbacher
authors.affiliation: Department of Plant Ecology, Justus Liebig University of Giessen, Giessen, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Erbs
authors.affiliation: Department of Plant Ecology, Justus Liebig University of Giessen, Giessen, Germany.|School of Biology and Environmental Science, University College Dublin, Dublin, Ireland.
authors.forename: Christoph
authors.initials: C
authors.lastname: Müller
mesh_terms: D018533:Biomass; D002245:Carbon Dioxide / Q000032:analysis / Q000494:pharmacology*; D017753:Ecosystem; D007887:Fabaceae / Q000187:drug effects / Q000254:growth & development; D065948:Grassland; D006109:Poaceae / Q000187:drug effects / Q000254:growth & development; D012987:Soil
chemical_list: D012987:Soil; D002245:Carbon Dioxide
keywords: Giessen free air carbon dioxide enrichment; climate change; forbs; free air carbon dioxide enrichment; frost; grasses; long-term response; soil moisture