title: How do climate warming and species richness affect CO2 fluxes in experimental grasslands?
abstract: This paper presents the results of 2 yr of CO(2) flux measurements on grassland communities of varying species richness, exposed to either the current or a warmer climate. We grew experimental plant communities containing one, three or nine grassland species in 12 sunlit, climate-controlled chambers. Half of these chambers were exposed to ambient air temperatures, while the other half were warmed by 3 degrees C. Equal amounts of water were added to heated and unheated communities, implying drier soils if warming increased evapotranspiration. Three main CO(2) fluxes (gross photosynthesis, above-ground and below-ground respiration) were measured multiple times per year and reconstructed hourly or half-hourly by relating them to their most important environmental driver. While CO(2) outputs through respiration were largely unchanged under warming, CO(2) inputs through photosynthesis were lowered, especially in summer, when heat and drought stress were higher. Above-ground CO(2) fluxes were significantly increased in multispecies communities, as more complementary resource use stimulated productivity. Finally, effects of warming appeared to be smallest in monocultures. This study shows that in a future warmer climate the CO(2) sink capacity of temperate grasslands could decline, and that such adverse effects are not likely to be mitigated by efforts to maintain or increase species richness.
authors.affiliation: Research Group of Plant and Vegetation Ecology, Department of Biology, Universiteit Antwerpen (Campus Drie Eiken), Universiteitsplein 1, B-2610 Wilrijk, Belgium.
authors.forename: Hans J
authors.initials: HJ
authors.lastname: De Boeck
authors.affiliation: Research Group of Plant and Vegetation Ecology, Department of Biology, Universiteit Antwerpen (Campus Drie Eiken), Universiteitsplein 1, B-2610 Wilrijk, Belgium.
authors.forename: Catherine M H M
authors.initials: CMHM
authors.lastname: Lemmens
authors.affiliation: Research Group of Plant and Vegetation Ecology, Department of Biology, Universiteit Antwerpen (Campus Drie Eiken), Universiteitsplein 1, B-2610 Wilrijk, Belgium.
authors.forename: Sara
authors.initials: S
authors.lastname: Vicca
authors.affiliation: Research Group of Plant and Vegetation Ecology, Department of Biology, Universiteit Antwerpen (Campus Drie Eiken), Universiteitsplein 1, B-2610 Wilrijk, Belgium.
authors.forename: Joke
authors.initials: J
authors.lastname: Van den Berge
authors.affiliation: Research Group of Evolutionary Biology, Department of Biology, Universiteit Antwerpen (Campus Groenenborger), Groenenborgerlaan 171, B-2020 Antwerpen, Belgium.
authors.forename: Stefan
authors.initials: S
authors.lastname: Van Dongen
authors.affiliation: Research Group of Plant and Vegetation Ecology, Department of Biology, Universiteit Antwerpen (Campus Drie Eiken), Universiteitsplein 1, B-2610 Wilrijk, Belgium.
authors.forename: Ivan A
authors.initials: IA
authors.lastname: Janssens
authors.affiliation: Research Group of Plant and Vegetation Ecology, Department of Biology, Universiteit Antwerpen (Campus Drie Eiken), Universiteitsplein 1, B-2610 Wilrijk, Belgium.
authors.forename: Reinhart
authors.initials: R
authors.lastname: Ceulemans
authors.affiliation: Research Group of Plant and Vegetation Ecology, Department of Biology, Universiteit Antwerpen (Campus Drie Eiken), Universiteitsplein 1, B-2610 Wilrijk, Belgium.
authors.forename: Ivan
authors.initials: I
authors.lastname: Nijs
mesh_terms: D044822:Biodiversity; D002245:Carbon Dioxide / Q000378:metabolism*; D002980:Climate; D017753:Ecosystem; D017752:Greenhouse Effect; D006109:Poaceae / Q000378:metabolism*; D012621:Seasons; D012987:Soil; D014867:Water / Q000378:metabolism
chemical_list: D012987:Soil; D014867:Water; D002245:Carbon Dioxide