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The influence of increasing temperature and CO2 concentration on recent growth of old-growth larch: contrasting responses at leaf and stem processes derived from tree-ring width and stable isotopes

Weigt, Rosemarie B. ; Streit, Kathrin ; Saurer, Matthias ; Siegwolf, Rolf T W.

In: Tree Physiology, 2018, vol. 38, no. 5, p. 706-720

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    Titre
    • The influence of increasing temperature and CO2 concentration on recent growth of old-growth larch: contrasting responses at leaf and stem processes derived from tree-ring width and stable isotopes
    Auteur
    • Weigt, Rosemarie B.. Laboratory of Atmospheric Chemistry, Ecosystem Fluxes, Paul Scherrer Institute, 5232 Villigen, Switzerland
    • Streit, Kathrin. Swiss Federal Institute for Forest, Snow and Landscape Research WSL, 8903 Birmensdorf, Switzerland
    • Saurer, Matthias. Laboratory of Atmospheric Chemistry, Ecosystem Fluxes, Paul Scherrer Institute, 5232 Villigen, Switzerland
    • Siegwolf, Rolf T W.. Laboratory of Atmospheric Chemistry, Ecosystem Fluxes, Paul Scherrer Institute, 5232 Villigen, Switzerland
    Type de document
    • Postprint
    Langue
    • Inglese
    Publié dans
    • Tree Physiology, 2018, vol. 38, no. 5, p. 706-720. Oxford University Press
    Autre version électronique
    Identifiant OAI-PMH
    • oai:doc.rero.ch:332089
    Summary
    Time series of tree-ring growth show significant increases since the early 1970s at the alpine tree line, with simultaneously increasing temperatures and atmospheric CO2 concentration. For a comprehensive understanding of this growth change, the physiological response patterns at both the leaf and stem level need to be separately analyzed and identified, and can be retrieved from tree-ring growth and isotope (δ13C, δ18O) series. In this study, we assessed the relative contribution of environmental factors to interannual tree-ring variability by multivariate linear mixed-effects models and the dual isotope approach on a dataset of tree-ring records of ~400-year-old larch (Larix decidua Mill.) from a non-water-limited high-elevation site in the Swiss Alps. The models suggest that summer temperatures and the recent lack of larch budmoth outbreaks were most important for explaining growth variations and trends, while a significant direct effect of the continuously increasing CO2 concentration could not be confirmed. In contrast, δ13C and δ18O, which are strongly influenced by fractionation changes in the leaf, clearly reflected the impact of air humidity (precipitation and vapor pressure deficit) and CO2 concentration: the increase in (δ13C-derived) intrinsic water-use efficiency over the second half of the 20th century suggests an increase in carbon assimilation as a result of enhanced CO2 concentration. The tree-ring δ18O largely reflected recent precipitation as source water, thus indicating a low variability in stomatal conductance, which was confirmed by the dual isotope approach. These leaf-level effects were not reflected in stem growth as they may have been masked by the temperature-caused growth limitation controlling the allocation of increased amounts of photosynthates into wood growth. Our approach demonstrates that the identification of different roles of environmental factors on leaf and stem processes helps to improve the assessment of site-specific changes of carbon fluxes and growth performance under future environmental conditions.