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High-resolution stable isotope analysis for tracing environmen-tal changes - HIRES

English title High-resolution stable isotope analysis for tracing environmen-tal changes - HIRES
Applicant Gessler Arthur
Number 189724
Funding scheme R'EQUIP
Research institution Swiss Federal Research Inst. WSL
Institution of higher education Swiss Federal Institute for Forest, Snow and Landscape Research - WSL
Main discipline Other disciplines of Environmental Sciences
Start/End 01.01.2020 - 30.04.2021
Approved amount 275'694.00
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All Disciplines (2)

Other disciplines of Environmental Sciences
Agricultural and Forestry Sciences

Keywords (6)

climate reconstruction; oxygen isotopes; photosynthetic carbon isotope discrimination; tree ring; post-photosynthetic discrimination; carbon isotope discrimination

Lay Summary (German)

Die Zusammensetzung der stabilen Isotope von Kohlenstoff und Sauerstoff in von Pflanzen assimilierter organischer Substanz gibt Hinweise auf die Umweltbedingungen während ihrer Bildung und darauf wie Pflanzen auf diese Bedingungen reagieren. Jahrring-Isotope von Bäumen geben Einblick in deren physiologische Reaktion auf aktuelle Umweltveränderungen und das im vorindustriellen Kontext. Dieses Projekt ermöglicht, die zeitliche Auflösung und damit die Genauigkeit solcher Studien massiv zu erhöhen.
Lay summary

Inhalt und Ziele des Forschungsprojekts

Im Rahmen dieses Projektes wird Forschungsinfrastruktur beschafft, die erlaubt pflanzenphysiologische Prozesse nachzuvollziehen, welche das Isotopenverhältnis der für die Jahrringbildung verwendeten Zucker beeinflussen. Ausserdem kann die intraannuelle Variation der Isotopenzusammensetzung in Jahrringen über lange Zeiträume zurück in die Vergangenheit analysiert werden – und das mit hoher Auflösung und einer grossen Probenanzahl.

Die Infrastruktur besteht aus 2 Messgeräten: 1) Ein Isotopenlaserspektrometer ermöglicht es in hoher zeitlicher Auflösung die Isotopenzusammensetzung im veratmeten COund daraus abgeleitet der Substrate zur Jahrringbildung zu bestimmen. So werden die Einflüsse von Umweltparametern analysiert. 2) Ein Laser-Ablations-Isotopenmassenspektrometer ermöglicht hochaufgelöste Jahrring-Isotopenmessungen und erlaubt die Information von 1) auf lange Zeiträume zu übertragen.


Wissenschaftlicher und gesellschaftlicher Kontext des Forschungsprojekts

Das Projekt befasst sich mit Grundlagenforschung. Das Wissen um die Umweltbedingungen in der Vergangenheit und die Reaktion von Bäumen auf diese Bedingungen helfen besser zu verstehen, wie sich unsere Waldökosysteme in Zukunft in einem sich stark und schnell verändernden Klima verhalten werden.

Direct link to Lay Summary Last update: 18.11.2019

Responsible applicant and co-applicants

Associated projects

Number Title Start Funding scheme
179978 From assimilates towards tree-rings - Triple isotope analysis of carbohydrates (TreeCarbo) 01.05.2019 Ambizione
182092 Development of a diagnostic stable isotope tool to elucidate the drought response of trees 01.05.2019 Project funding (Div. I-III)
189109 Acclimation and environmental memory - how do trees adjust to warmer droughts on different time scales and where are the limits? 01.03.2020 Project funding (Div. I-III)
175888 Disentangling source water and leaf water signals in highly resolved oxygen isotope data from tree rings 01.05.2018 Project funding (Div. I-III)


Stable isotopes in tree rings are being increasingly used to retrospectively assess the effects of environmental drivers on tree physiology as well as to reconstruct past climatic conditions. But still there is a strong lack of understanding how environmental conditions that change rapidly at the diurnal and seasonal scale translate into carbon (d13C) and oxygen (d18O) isotope compo-sition in wood or cellulose of the tree ring. High resolution intra-annual analysis of tree rings provides additional information allowing to identify when stored or recently assimilated carbo-hydrates are used to build up tree ring structural material thus allowing to characterize lagged or direct effects of climatic drivers on the isotopic signal. Further, it is important to consider at high temporal resolution changes in photosynthetic fractionation of 13C, that is dependent on stomatal conductance and assimilation rate, soil water availability and light, and post-photosynthetic 13C discrimination that can alter the isotopic signal on its way from the leaf assimilates to the tree rings. These post-photosynthetic fractionation steps are not yet well un-derstood. Comparably for 18O the evaporative enrichment signal imprinted on the leaf sugars (mainly influenced by VPD and to a lesser extent by transpiration) is additionally influenced by oxygen atom exchange downstream of photosynthesis. In this proposal we apply for infrastructure (isotope laser spectrometer to determine the carbon and oxygen isotopologues of CO2 and laser-ablation isotope-ratio mass-spectrometer (LA-IRMS) for high resolution tree ring isotope analysis) that is on the one hand able to provide the neces-sary information to better understand the linkage between environmental drivers, plant internal processes and tree ring isotope information and on the other hand allows for high-throughput and thus long-term intra-annual assessments of tree ring isotopes for the reconstruction of past climatic and environmental conditions.With the isotope laser spectrometer, we will design lab and field experiments for continuous determination of d13C in CO2. This will enable characterizing the isotopic signal in newly assimi-lated sugars by assessing online photosynthetic 13C discrimination. Together with the continu-ous analysis of d13C in trunk respiration we will obtain information on the drivers of photosyn-thetic and post-photosynthetic isotope discrimination. The information will also be used in mechanistic models to characterize diurnal and seasonal variations in d13C of sugars available for xylem cell formation. In combination with high-resolution high throughput LA-IRMS anal-yses of tree rings, our approach will allow seamlessly tracking the fate of the d13C signal from its generation in the chloroplast on its way into the tree ring and characterizing seasonal xylem cell growth and stem carbon allocation dynamics. Furthermore, we will extract seasonal climat-ic and environmental information from specifically narrow tree rings, small latewood, intra-annual density fluctuations or other wood anatomical features restricted to small parts of the tree ring which currently cannot be manually separated for isotope analysis. This will improve isotope-based reconstructions of the seasonal response of trees to past extreme events, such as drought and heat spells, cold years (e.g. years with volcanic eruptions), or insect outbreaks. In a further step, these analyses will be extended to d18O as well.The new equipment, in combination with the broad and worldwide unique background on iso-topes, physiology, tree-rings, ecology etc. available at WSL, will provide a boost in the high-resolution tree-ring research. The combination of LA-IRMS with isotope laser spectroscopy is important for deciphering the relevant isotope fractionation and mixing processes, which will help in recovering the full information stored in the intra-annual tree-ring isotope signals. In addition, there is a huge potential for highly novel application of the LA-IRMS to materials like biofilms, roots, root-soil interfaces, leaf-petiole-phloem interfaces, hairs, insects, or micro-meter sized organic particles offers new research areas for understanding ecosystem functions.