title: Growth cessation uncouples isotopic signals in leaves and tree rings of drought-exposed oak trees.
abstract: An increase in temperature along with a decrease in summer precipitation in Central Europe will result in an increased frequency of drought events and gradually lead to a change in species composition in forest ecosystems. In the present study, young oaks (Quercus robur L. and Quercus petraea (Matt.) Liebl.) were transplanted into large mesocosms and exposed for 3 years to experimental warming and a drought treatment with yearly increasing intensities. Carbon and oxygen isotopic (δ(13)C and δ(18)O) patterns were analysed in leaf tissue and tree-ring cellulose and linked to leaf physiological measures and tree-ring growth. Warming had no effect on the isotopic patterns in leaves and tree rings, while drought increased δ(18)O and δ(13)C. Under severe drought, an unexpected isotopic pattern, with a decrease in δ(18)O, was observed in tree rings but not in leaves. This decrease in δ(18)O could not be explained by concurrent physiological analyses and is not supported by current physiological knowledge. Analysis of intra-annual tree-ring growth revealed a drought-induced growth cessation that interfered with the record of isotopic signals imprinted on recently formed leaf carbohydrates. This missing record indicates isotopic uncoupling of leaves and tree rings, which may have serious implications for the interpretation of tree-ring isotopes, particularly from trees that experienced growth-limiting stresses.
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Zürcherstrasse 111, CH-8903 Birmensdorf, Switzerland Department of Environmental Systems Science, ETH Zurich, Universitätsstrasse 2, CH-8092 Zurich, Switzerland ellen.pflug@wsl.ch.
authors.forename: Ellen E
authors.initials: EE
authors.lastname: Pflug
authors.affiliation: Department of Environmental Systems Science, ETH Zurich, Universitätsstrasse 2, CH-8092 Zurich, Switzerland Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, CH-5232 Villigen, Switzerland.
authors.forename: R
authors.initials: R
authors.lastname: Siegwolf
authors.affiliation: Department of Environmental Systems Science, ETH Zurich, Universitätsstrasse 2, CH-8092 Zurich, Switzerland.
authors.forename: N
authors.initials: N
authors.lastname: Buchmann
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Zürcherstrasse 111, CH-8903 Birmensdorf, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Dobbertin
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Zürcherstrasse 111, CH-8903 Birmensdorf, Switzerland Department of Environmental Systems Science, ETH Zurich, Universitätsstrasse 2, CH-8092 Zurich, Switzerland Institute for Plant Production Sciences, Agroscope, CH-8820 Wädenswil, Switzerland.
authors.forename: T M
authors.initials: TM
authors.lastname: Kuster
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Zürcherstrasse 111, CH-8903 Birmensdorf, Switzerland.
authors.forename: M S
authors.initials: MS
authors.lastname: Günthardt-Goerg
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Zürcherstrasse 111, CH-8903 Birmensdorf, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Arend
mesh_terms: D058506:Cambium / Q000254:growth & development; D002247:Carbon Isotopes / Q000032:analysis; D055864:Droughts; D006358:Hot Temperature; D010103:Oxygen Isotopes / Q000032:analysis; D018515:Plant Leaves / Q000254:growth & development; D029963:Quercus / Q000254:growth & development*; D012621:Seasons; D013045:Species Specificity; D013557:Switzerland
chemical_list: D002247:Carbon Isotopes; D010103:Oxygen Isotopes
keywords: 13C; 18O; Quercus petraea; Quercus robur; dual isotope approach; water shortage; wood