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Volume 6, issue 7
Biogeosciences, 6, 1167–1180, 2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 6, 1167–1180, 2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.

  15 Jul 2009

15 Jul 2009

Drought reduced monoterpene emissions from the evergreen Mediterranean oak Quercus ilex: results from a throughfall displacement experiment

A.-V. Lavoir1, M. Staudt1, J. P. Schnitzler2, D. Landais1, F. Massol3, A. Rocheteau4, R. Rodriguez1, I. Zimmer2, and S. Rambal1 A.-V. Lavoir et al.
  • 1DREAM team, Centre d'Ecologie Fonctionnelle et Evolutive – Centre National pour la Recherche Scientifique UMR 5175 (CEFE-CNRS), 1919 Rte de Mende, 34293 Montpellier Cedex5, France
  • 2Research Centre Karlsruhe, Institute for Meteorology and Climate Research (IMK-IFU), Kreuzeckbahnstrasse 19, 82467 Garmisch-Partenkirchen, Germany
  • 3UR HYAX, CEMAGREF, 3275, route de Cézanne – Le Tholonet, CS 40061, 13182 Aix-en-Provence cedex 5, France
  • 4CLIFA team, IRD (Institut pour la Recherche et le Développement) – CEFE-CNRS, 1919 Rte de Mende, 34293 Montpellier Cedex5, France

Abstract. The effects of water limitations on the emission of biogenic volatile organic compounds are not well understood. Experimental approaches studying drought effects in natural conditions are still missing. To address this question, a throughfall displacement experiment was set up in a natural forest of Quercus ilex, an evergreen Mediterranean oak emitting monoterpenes. Mature trees were exposed in 2005 and 2006 either to an additional drought, to irrigation or to natural drought (untreated control). In both years, absolute monoterpene emission rates as well as the respective standard factors of the trees exposed to normal and additional drought strongly declined during the drought periods. Monoterpene emissions were lower in year 2006 than in year 2005 (factor 2) due to a more pronounced summer drought period in this respective year. We observed a significant difference between the irrigation and additional drought or control treatment: irrigated trees emitted 82% more monoterpenes during the drought period 2006 than the trees of the other treatments. However, no significant effect on monoterpene emission was observed between normal and additional drought treatments, despite a significant effect on leaf water potential and photochemical efficiency. During the development of drought, monoterpene emissions responded exponentially rather than linearly to decreasing leaf water potential. Emissions rapidly declined when the water potential dropped below −2 MPa and photosynthesis was persistently inhibited. Monoterpene synthase activities measured in vitro showed no clear reduction during the same period. From our results we conclude that drought significantly reduces monoterpene fluxes of Mediterranean Holm oak forest into the atmosphere due to a lack of primary substrates coming from photosynthetic processes.

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