title: Effects of climate warming and species richness on photochemistry of grasslands.
abstract: In view of the projected climatic changes and the global decrease in plant species diversity, it is critical to understand the effects of elevated air temperature (T(air)) and species richness (S) on physiological processes in plant communities. Therefore, an experiment of artificially assembled grassland ecosystems, with different S (one, three or nine species), growing in sunlit climate-controlled chambers at ambient T(air) and ambient T(air) + 3 degrees C was established. We investigated whether grassland species would be more affected by midday high-temperature stress during summer in a warmer climate scenario. The effect of elevated T(air) was expected to differ with S. This was tested in the second and third experimental years by means of chlorophyll a fluorescence. Because acclimation to elevated T(air) would affect the plant's stress response, the hypothesis of photosynthetic acclimation to elevated T(air) was tested in the third year by gas exchange measurements in the monocultures. Plants in the elevated T(air) chambers suffered more from midday stress on warm summer days than those in ambient chambers. In absence of severe drought, the quantum yield of PSII was not affected by elevated T(air). Our results further indicate that species had not photosynthetically acclimated to a temperature increase of 3 degrees C after 3 years exposure to a warmer climate. Although effects of S and T(air) x S interactions were mostly not significant in our study, we expect that combined effects of T(air) and S would be important in conditions of severe drought events.
authors.affiliation: Research Group of Plant and Vegetation Ecology, Department of Biology, University of Antwerp, Campus Drie Eiken, Universiteitsplein 1, B-2610 Wilrijk, Belgium. birgit.gielen@ua.ac.be
authors.forename: Birgit
authors.initials: B
authors.lastname: Gielen
authors.forename: Kim
authors.initials: K
authors.lastname: Naudts
authors.forename: David
authors.initials: D
authors.lastname: D'Haese
authors.forename: Catherine M H M
authors.initials: CM
authors.lastname: Lemmens
authors.forename: Hans J
authors.initials: HJ
authors.lastname: De Boeck
authors.forename: Eddy
authors.initials: E
authors.lastname: Biebaut
authors.forename: Roger
authors.initials: R
authors.lastname: Serneels
authors.forename: Roland
authors.initials: R
authors.lastname: Valcke
authors.forename: Ivan
authors.initials: I
authors.lastname: Nijs
authors.forename: Reinhart
authors.initials: R
authors.lastname: Ceulemans
mesh_terms: D000064:Acclimatization; D002734:Chlorophyll / Q000378:metabolism; D002980:Climate; D017753:Ecosystem; D004780:Environment, Controlled; D017752:Greenhouse Effect; D010777:Photochemistry; D010788:Photosynthesis / Q000528:radiation effects; D018515:Plant Leaves / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects; D006109:Poaceae / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects; D013472:Sunlight; D013696:Temperature
chemical_list: D002734:Chlorophyll