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Interactive effects of CO2 and light conditions on drought resistance of conifer species during early growth

English title Interactive effects of CO2 and light conditions on drought resistance of conifer species during early growth
Applicant Wohlgemuth Thomas Michael
Number 140966
Funding scheme Project funding (Div. I-III)
Research institution Swiss Federal Research Inst. WSL Direktion
Institution of higher education Swiss Federal Institute for Forest, Snow and Landscape Research - WSL
Main discipline Ecology
Start/End 01.01.2013 - 31.12.2015
Approved amount 281'715.00
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All Disciplines (3)

Discipline
Ecology
Pedology
Other disciplines of Environmental Sciences

Keywords (7)

assisted migration; summer drought; light conditions; common garden experiment; maternal lineage; CO2 enrichment; provenance

Lay Summary (German)

Lead
Wir testen, unter welchen Umweltbedingungen (erhöhter CO2-Gehalt, Beschattung) junge autochthone Walliser Waldföhren (Pinus sylvestris) längere Trockenheit ertragen, und wie gut sie im Vergleich zu mediterranen Föhrenarten (P. nigra, P. halepensis) bzw. der Douglastanne (Pseudotsuga menziesii) an ein zukünftiges Klima im Wallis angepasst sind. Dazu wird die Wuchsreaktion von Keimlingen in einem Gartenexperiment mit mobilen Regendächern und Freiluft-CO2-Begasung während dreier Jahre gemessen.
Lay summary

Statische und dynamische Vegetationsmodelle rechnen vor, dass unsere heimischen Baumarten an ihren angestammten Standorten einer wärmeren und trockeneren Zukunft nicht standhalten werden. In Tieflagen von trockenen Gebieten stellt sich deshalb die Frage, ob trockenresistentere Baumarten z.B. aus dem Mittelmeerraum in Zukunft geeigneter wären. Da erwartet wird, dass Mediterrane Arten von alleine nicht rasch genug einwandern können, ist letztlich die Waldkontinuität in den besagten Gebieten gefährdet. Andererseits wird diskutiert, in welchem Ausmass der ungebremste Anstieg des CO2-Gehalts in der Luft dem Trockenstress der Bäume durch Reduktion der Transpiration entgegenwirken kann.

Im vorliegenden Projekt befassen wir uns mit der Verjüngsphase der Waldföhre (Pinus sylvestris), die in den Tieflagen des Wallis ausgedehnte Bestände bildet. Um zu testen, in welcher Weise autochthone Föhrenkeimlinge von Leuk, VS (600 mm jährliche Niederschlagssumme, 9 °C Jahresmittel),sowie von Herkünften aus dem Mittelmeerraum einem zukünftigen Zentralalpenklima standhalten können, werden in einem Gartenexperiment mit mobilen Regendächern Sämlinge gezogen und über drei Jahre verschiedenen Kombinationen von extremer Dürre, erhöhtem CO2 und variablem Schatten ausgesetzt. Während der Vegetationszeit von März bis September werden folgende Umweltbedingungen simuliert: CO2 normal (390 ppm) oder erhöht (570 ppm), Niederschlag entsprechend einem trockenen (80% des langjährigen Mittels in Sion, VS) oder einem nassen Jahr (150% des Mittels),, 20% oder 40% Beschattung. An den jungen Bäumchen werden sowohl Wachstumswerte als auch stomatäre Leitfähigkeit, WUE (water use efficiency; δ13C und δ18O Verhältnisse), NSC (non-structural carbohydrates; Zucker- und Stärkegehalt) und Frosthärte gemessen. Dabei werden die autochthonen Waldföhren aus den Walliser Tieflagen mit solchen aus Hochlagen (Visperterminen) sowie aus, Spanien und Griechenland verglichen. Weiter werden Provenienzen von Schwarzföhre (P. nigra; Spanien, Österreich, Bulgarien, Griechenland), Aleppo-Föhre (Pinus halepensis; Spanien, Griechenland) und Douglastanne (Pseudotsuga menziesii; in der Schweiz und in Deutschland akklimatisierte Provenienzen aus NW-USA) getestet. Die Resultate werden zeigen, bei welchen Behandlungkombinationen die Testbäumchen einer zukünftigen Trockenheit am besten widerstehen und bis zu welchem Grad die autochthone Waldföhre im Vergleich mit anderen Baumarten und -provenienzen an Extrembedingungen angepasst ist. Die Studie leistet damit eine Beitrag zur Frage, ob die Waldkontinuität in der Schweiz in den trockensten Lagen gefährdet ist, und ob die Beimischung von fremdländischen Provenienzen (Exoten) eine erfolgsversprechende Bewirtschaftungsmassnahme sein könnte.

 

Direct link to Lay Summary Last update: 20.02.2013

Lay Summary (English)

Lead
We test the potential of young autochthonous Scots Pine (Pinus sylvestris) in the Valais, Switzerland to withstand aggravated drought under different environmental conditions (raised CO2, two shade grades) by exposing them to various conditions in a common garden with mobile rainout shelters and free-air CO2 enrichment (FACE). P. sylvestris individuals are compared with such of P. nigra, P. halepensis and Pseudotsuga menziesii of totally 14 provenances from Spain, Bulgary or Greece.
Lay summary

Projections of increased temperatures and more frequent drought events question the persistence of extant tree species in their current distributions because these long-lived but slowly regenerating species might not be able to keep pace with rapidly changing climatic conditions, neither by adapting to new conditions nor by migrating fast enough to colonise new suitable habitats. Effects of climate change make the continuation of forest uncertain in zones where trees are currently at the edge to steppe. On the other hand, the simultaneous unbroken CO2-increase is considered to mitigate water stress during the growing season to some extent, a fact that complicates predictions of vegetation change.

In this project, we focus on the regeneration stage of Pinus sylvestris, which forms extensive forest stands at low elevations of the Central Alpine valleys. To test the potential of autochthonous P. sylvestris (Leuk, Valais, Switzerland: 600 mm, 9 °C) to withstand aggravated drought under different environmental conditions (elevated CO2, light conditions), seedlings will be grown from seeds in a common garden with mobile rainshelters and free-air CO2 enrichment (FACE). During the growing season (Mar–Sep), seedlings will be exposed to ambient (390 ppm) and future (570 ppm) CO2 concentrations and two precipitation regimes that correspond to a wet Central Alpine vegetation season (150% of the long-term average in the Rhone Valley) and a dry Central Alpine vegetation season (80% of the long-term average). Over three years of seedling development, we will measure growth metrics, stomatal conductance, water use efficiency (δ13C and δ18O ratios), non-structural carbohydrates and frost hardiness of autochthonous, low elevation P. sylvestris in comparison to other P. sylvestris provenances (Grisons, Valais high, Spain, Greece), provenances of more drought-resistant P. nigra (Spain, Austria, Bulgaria, Greece) and minimally frost-resistant but most drought-resistant P. halepensis (Spain, Bulgaria, Greece). The experiment also includes acclimated provenances of North-American Pseudotsuga menziesii (Switzerland, Germany), which has been planted in Europe for more than 100 years. Results will show whether interactive effects of light conditions and increased CO2 will compensate for transiently or continuously aggravated drought during early stages of tree growth, to what degree autochthonous P. sylvestris can adapt to future conditions in comparison with other provenances and species, and whether forest continuation in general will be at risk or can be assured by adding more drought resistant species or/and provenances to autochthonous forests.

Direct link to Lay Summary Last update: 20.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Safety margins against spring frost damage allow for the assisted migration of Mediterranean pines to regions with intermittent frost
Bachofen Christoph, Wohlgemuth Thomas, Ghazoul Jaboury, Moser Barbara (2015), Safety margins against spring frost damage allow for the assisted migration of Mediterranean pines to regions with intermittent frost, in Functional Ecology, Published online Nov 03, 2015, 1-10.

Collaboration

Group / person Country
Types of collaboration
Prof. Dr. Christian Körner Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Jahrestagung GFÖ Talk given at a conference Spring growth compensates preceding drought induced sink limitation in Pinus nigra but not in Pinus sylvestris 31.08.2015 Göttingen, Germany Wohlgemuth Thomas Michael;
99th annual ESA congress Talk given at a conference Elevated atmospheric CO2 mitigates water shortage in Pinus only under severe drought stress 10.08.2015 Sacramento, CA, United States of America Wohlgemuth Thomas Michael; Ghazoul Jaboury;
ClimTree 2013, Zürich 2013 Talk given at a conference Frost sensitivity limits assisted migratino of Pinus halepensis but not Pinus nigra into regions with spring frost 02.09.2013 Zürich, Switzerland Ghazoul Jaboury; Wohlgemuth Thomas Michael;


Associated projects

Number Title Start Funding scheme
118002 Germination and early seedling growth of Pinus and Quercus at the forest-steppe ecotone: effects of environmental stress and facilitation 01.01.2008 Project funding (Div. I-III)

Abstract

Projections of increased temperatures and more frequent drought events question the persistence of extant tree species in their current distributions because these long-lived but slowly regenerating species might not be able to keep pace with rapidly changing climatic conditions, neither by adapting to new conditions nor by migrating fast enough to colonise new suitable habitats. Effects of climate change make the continuation of forest uncertain in zones where trees are currently at the edge to steppe. On the other hand, the simultaneous unbroken CO2-increase is considered to mitigate water stress during the growing season to some extent, a fact that complicates predictions of vegetation change. In this project, we focus on the regeneration stage of Pinus sylvestris, which forms extensive forest stands at low elevations of the Central Alpine valleys. To test the potential of autochthonous P. sylvestris (Leuk, Valais, Switzerland: 600 mm, 9 °C) to withstand aggravated drought under different environmental conditions (elevated CO2, light conditions), seedlings will be grown from seeds in a common garden with mobile rainshelters and free-air CO2 enrichment (FACE). During the growing season (Mar-Sep), seedlings will be exposed to ambient (390 ppm) and future (570 ppm) CO2 concentrations and two precipitation regimes that correspond to a wet Central Alpine scenario (150% of the long-term average in the Rhone Valley) and a dry Central Alpine scenario (80% of the long-term average). Over three years of seedling development, we will measure growth metrics, stomatal conductance, water use efficiency (d13C and d18O ratios), non-structural carbohydrates and frost hardiness of autochthonous, low elevation P. sylvestris in comparison to P. sylvestris provenances from Switzerland (high altitude), Spain, Bulgaria, Germany and Estonia, provenances of more drought-resistant P. nigra (Spain, Austria, Bulgaria, Greece) and minimally frost-resistant but most drought-resistant P. halepensis. Moreover, the experiment will include acclimated provenances of North-American Pseudotsuga menziesii (Bözinger Berg BE, St. German VS), which has been planted in Switzerland for more than 100 years. Results will show whether interactive effects of light conditions and increased CO2 will compensate for transiently or continuously aggravated drought during early stages of tree growth, to what degree autochthonous P. sylvestris can adapt to future conditions in comparison with other provenances and species, and whether forest continuation in general will be at risk or can be assured by facilitating the migration of more drought resistant provenances from southern Europe or other suitable climate regions.
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