Martínez‐Sancho, Elisabet, Cernusak, Lucas A., Fonti, Patrick, Gregori, Alessandro, Ullrich, Bastian, Pannatier, Elisabeth Graf, Gessler, Arthur, Lehmann, Marco M., Saurer, Matthias, and Treydte, Kerstin (2023) Unenriched xylem water contribution during cellulose synthesis influenced by atmospheric demand governs the intra‐annual tree‐ring δ18O signature. New Phytologist. (In Press)

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Abstract

- The oxygen isotope composition (δ18O) of tree-ring cellulose is used to evaluate tree physiological responses to climate, but their interpretation is still limited due to the complexity of the isotope fractionation pathways.

- We assessed the relative contribution of seasonal needle and xylem water δ18O variations to the intra-annual tree-ring cellulose δ18O signature of larch trees at two sites with contrasting soil water availability in the Swiss Alps. We combined biweekly δ18O measurements of soil water, needle water, and twig xylem water with intra-annual δ18O measurements of tree-ring cellulose, xylogenesis analysis, and mechanistic and structural equation modeling.

- Intra-annual cellulose δ18O values resembled source water δ18O mean levels better than needle water δ18O. Large parts of the rings were formed under high proportional exchange with unenriched xylem water (pex). Maximum pex values were achieved in August and imprinted on sections at 50–75% of the ring. High pex values were associated with periods of high atmospheric evaporative demand (VPD). While VPD governed needle water δ18O variability, we estimated a limited Péclet effect at both sites.

- Due to a variable pex, source water has a strong influence over large parts of the intra-annual tree-ring cellulose δ18O variations, potentially masking signals coming from needle-level processes.

Item ID:	80585
Item Type:	Article (Research - C1)
ISSN:	1469-8137
Copyright Information:	© 2023 The Authors. New Phytologist © 2023 New Phytologist Foundation. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
Date Deposited:	02 Oct 2023 23:12
FoR Codes:	31 BIOLOGICAL SCIENCES > 3108 Plant biology > 310806 Plant physiology @ 100%
SEO Codes:	28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280102 Expanding knowledge in the biological sciences @ 100%
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