title: Effects of elevated CO₂, warming and drought episodes on plant carbon uptake in a temperate heath ecosystem are controlled by soil water status.
abstract: The impact of elevated CO₂, periodic drought and warming on photosynthesis and leaf characteristics of the evergreen dwarf shrub Calluna vulgaris in a temperate heath ecosystem was investigated. Photosynthesis was reduced by drought in midsummer and increased by elevated CO₂ throughout the growing season, whereas warming only stimulated photosynthesis early in the year. At the beginning and end of the growing season, a T × CO₂ interaction synergistically stimulated plant carbon uptake in the combination of warming and elevated CO₂. At peak drought, the D × CO₂ interaction antagonistically down-regulated photosynthesis, suggesting a limited ability of elevated CO₂ to counteract the negative effect of drought. The response of photosynthesis in the full factorial combination (TDCO₂) could be explained by the main effect of experimental treatments (T, D, CO₂) and the two-factor interactions (D × CO₂, T × CO₂). The interactive responses in the experimental treatments including elevated CO₂ seemed to be linked to the realized range of treatment variability, for example with negative effects following experimental drought or positive effects following the relatively higher impact of night-time warming during cold periods early and late in the year. Longer-term experiments are needed to evaluate whether photosynthetic down-regulation will dampen the stimulation of photosynthesis under prolonged exposure to elevated CO₂.
authors.affiliation: Biosystems Division, Risø DTU, Frederiksborgvej, Roskilde, Denmark. kria@risoe.dtu.dk
authors.forename: K R
authors.initials: KR
authors.lastname: Albert
authors.forename: H
authors.initials: H
authors.lastname: Ro-Poulsen
authors.forename: T N
authors.initials: TN
authors.lastname: Mikkelsen
authors.forename: A
authors.initials: A
authors.lastname: Michelsen
authors.forename: L
authors.initials: L
authors.lastname: Van Der Linden
authors.forename: C
authors.initials: C
authors.lastname: Beier
mesh_terms: D000064:Acclimatization; D029795:Calluna / Q000378:metabolism / Q000502:physiology*; D002244:Carbon / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism*; D002247:Carbon Isotopes / Q000032:analysis; D057231:Climate Change; D015536:Down-Regulation; D055864:Droughts; D017753:Ecosystem; D006358:Hot Temperature; D008027:Light; D009584:Nitrogen / Q000378:metabolism; D010788:Photosynthesis; D018515:Plant Leaves / Q000378:metabolism / Q000502:physiology; D018520:Plant Shoots / Q000502:physiology; D054046:Plant Stomata / Q000502:physiology; D012987:Soil / Q000737:chemistry; D014867:Water / Q000378:metabolism*
chemical_list: D002247:Carbon Isotopes; D012987:Soil; D014867:Water; D002245:Carbon Dioxide; D002244:Carbon; D009584:Nitrogen