Biogeosciences www.biogeosciences.net 1726-4170 1726-4189 5 2 2008 10.5194/bg-5-585-2008 http://www.biogeosciences.net/5/585/2008/ http://www.biogeosciences.net/5/585/2008/bg-5-585-2008.html http://www.biogeosciences.net/5/585/2008/bg-5-585-2008.pdf 585 594 2008-04-21 Biomass production in experimental grasslands of different species richness during three years of climate warming H. J. De Boeck hans.deboeck@ua.ac.be C. M. H. M. Lemmens C. Zavalloni B. Gielen S. Malchair M. Carnol R. Merckx J. Van den Berge R. Ceulemans I. Nijs Research Group of Plant and Vegetation Ecology, Department of Biology, Universiteit Antwerpen (Campus Drie Eiken), Universiteitsplein 1, B-2610 Wilrijk, Belgium Division Soil and Water Management, Faculty of Bioscience Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20, B-3001 Leuven/Heverlee, Belgium Lab. of Plant and Microbial Ecology, Institute of Plant Biology B22, Univ. of Liège, Sart Tilman, B-4000 Liège, Belgium Here we report on the single and combined impacts of climate warming and species richness on the biomass production in experimental grassland communities. Projections of a future warmer climate have stimulated studies on the response of terrestrial ecosystems to this global change. Experiments have likewise addressed the importance of species numbers for ecosystem functioning. There is, however, little knowledge on the interplay between warming and species richness. During three years, we grew experimental plant communities containing one, three or nine grassland species in 12 sunlit, climate-controlled chambers in Wilrijk, Belgium. Half of these chambers were exposed to ambient air temperatures (unheated), while the other half were warmed by 3°C (heated). Equal amounts of water were added to heated and unheated communities, so that warming would imply drier soils if evapotranspiration was higher. Biomass production was decreased due to warming, both aboveground (–29%) and belowground (–25%), as negative impacts of increased heat and drought stress in summer prevailed. Complementarity effects, likely mostly through both increased aboveground spatial complementarity and facilitative effects of legumes, led to higher shoot and root biomass in multi-species communities, regardless of the induced warming. 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