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Effect of experimentally applied drought and warming stress on three oak species and provenances using C and O stable isotopes in leaves, shoots, stem and roots

English title Effect of experimentally applied drought and warming stress on three oak species and provenances using C and O stable isotopes in leaves, shoots, stem and roots
Applicant Arend Matthias
Number 130782
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 Agricultural and Forestry Sciences
Start/End 01.12.2010 - 30.11.2013
Approved amount 193'801.00
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Keywords (9)

drought; warming; experiment; stable isotopes; 13C labelling; oak species; provenances; carbon; oxygen

Lay Summary (English)

Lead
Lay summary
The predicted climate change will have a profound effect on ecosystems in Switzerland, including forests. Tree species, for example oaks, which are more adapted to warmer and dryer conditions are expected to profit from the changing climate. Models predict a large increase in the distribution of oaks that are currently covering only 2% of Swiss forests. Unfortunately, no long-term trials exist in Switzerland that could be used to test for climate sensitivity of the various oak species.At the Swiss Federal Institute WSL, therefore, an experiment in 16 open-top chambers was carried out to test how the three native oak species react to drought and warming. Regarding drought tolerance and temperature preference, the natural distribution suggests that Q. pubescens is the most drought-tolerant, followed by Q. petraea and Q. robur.The warming treatment is achieved by selecting two opening angles of the chamber window. Under less opened windows air and soil surface temperatures increases by 1 to 3°C. Automatically closing roofs exclude rain. An artificial drought treatment is achieved by reducing the mean local precipitation from April to October (600 mm) to less than half. While the control and warming treatment, receive water in regular intervals, the drought treatment and the warming and drought combination are only periodically watered. To prevent irreversible damage under drought stress trees usually close the stomata to minimize water loss via transpiration. This, however, reduces the net photosynthesis and thus the carbon fixation. The potential to optimize between water loss and carbon fixation is a key in understanding tree responses to climatic change. Besides stomata closure, photosynthesis is determined by other factors, including temperature. Both, stomata closure and photosynthetic capacity affect the fractionation of the stable carbon and oxygen isotopes. Therefore, the determination of the isotope ratios ?13C and ?18O in plant tissue allows to draw conclusion on how drought and warming affect the trees. The following samples are collected and are intended to be analyzed: a) fresh leaves, b) wood section from shoots, c) stemwood and d) root samples. The proposed study with the stable C and O isotopes will be an ideal complement to the other measurements, such as shoot elongation, biomass change, gas exchange, root growth and leaf size and nutrient content. Based on these results, potentially useful oak species and provenances for future seeding or planting can be identified and recommendations for the forest practice can be made. In addition, the derived isotope ratios would allow the identification of drought stressed trees.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Name Institute

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
ClimTree Talk given at a conference Physiological characterisation of Swiss native oak species using the dual isotope approach 05.09.2013 Zürich, Switzerland Siegwolf Rolf Theodor Walter; Arend Matthias; Goerg-Günthardt Madeleine; Schuch Ellen;
IAS-PhD Symposium Poster Effect of experimental applied drought and warming on three oak species and proveniences using d13C and d18O in several tissues 07.10.2011 Rüschlikon, Switzerland Schuch Ellen;
Querco-Meeting Talk given at a conference Effect of experimental applied drought and warming on three oak species and proveniences using 13C and 18O in several tissues 23.03.2011 Birmensdorf, Switzerland Arend Matthias; Schuch Ellen; Goerg-Günthardt Madeleine;


Associated projects

Number Title Start Funding scheme
136295 iTREE-Long-term variability of tree growth in a changing environment - identifying physiological mechanisms using stable C and O isotopes in tree rings. 01.04.2012 Sinergia
145227 Path flow of oxygen isotopes in water from branch to needle 01.09.2012 International short research visits
153428 Tracing rapid plant responses to environmental changes 01.09.2014 Project funding (Div. I-III)

Abstract

The predicted climate change will have a profound effect on ecosystems in Switzerland including forest ecosystems. Tree species, which are more adapted to warmer and dryer conditions are expected to profit from the changing climate. Models predict in particular, an increase in the distribution of oak species currently covering only 2% of Swiss forests. Unfortunately, no long-term provenance trials exist in Switzerland for oak species that could be used to test for drought and warming sensitivity of the various species and provenances. Therefore, a combined drought/warming model ecosystem experiment (Querco) for the three native oak species (Quercus robur L., Qu. petrea Liebl. and Qu. pubescens Willd.) was designed at the Swiss Federal Institute of Forest, Snow and Landscape Research using four Swiss provenances from each species. Regarding drought tolerance and temperature preference, the natural distribution suggests that Q. pubescens is the most drought-tolerant, followed by Q. petraea and Q. robur.To prevent irreversible damage under drought stress, such as xylem cavitation, trees usually reduce stomatal conductance (gs) to minimize water loss via transpiration. This, however, reduces the net photosynthesis rate and thus the carbon acquisition. The potential to optimize between water loss and carbon acquisition is a key in understanding tree responses to climatic change. Besides stomatal conductance, photosynthesis is determined by biochemical factors, which are driven by irradiance and modulated by temperature, CO2 and nutrient availability. The interaction between stomatal conductance and photosynthetic capacity (Amax) under different environmental conditions is therefore of great ecological interest. Both processes affect the fractionation of the stable C and O isotopes. Therefore, in addition to direct measurements of gas exchange and stomatal conductance, the determination of the d13C and d18O values in plant tissue allows to draw conclusion on long-term stomatal conductance and photosynthetic capacity as a temporal integration.In the Querco experiment, sixteen open-top chambers arranged in a 4x4 Latin square design allowed to apply drought and warming treatments in a 2 x 2 factorial design with four replications. Two identically designed ambient plots were used to test for chamber effects. Two different soil types (acidic and calcareous) were filled into each separated half of the chambers in a split-plot design. Within each quarter chamber the tree seedlings were randomly allocated to 12 positions of equal space and mirror imaged onto the adjacent quarters. The warming treatment was achieved by selecting two opening angles of the side window of the chambers. Under less opened windows air and soil surface temperatures increases (air on average by 1 °C, but more during day time). An artificial drought treatment was achieved by reducing the mean precipitation during the vegetation period (April-October) at the site Birmensdorf (600 mm) to less than half. While the control (CO) and warming treatment (AW), received water in regular intervals, the drought treatment (D) and the warming and drought combination (AWD)) were only periodically watered. Water ion concentrations were kept identically to the mean concentration found in rainfall in Birmensdorf over the last 30 years. Soil water potential and water content in the drought plots is continuously monitored to follow the effect of the treatments. Within the existing project, shoot elongation, biomass change, gas exchange, isoprene emissions, chlorophyll fluorescence, leaf water potential is measured and selected biochemical and microscopic analyses are undertaken. The proposed study with the stable C and O isotopes in the controlled Querco experiment will be an ideal complement to these existing measurements. The simultaneous estimation of d13C and d18O isotope values in organic material allows separating the effects of changes in stomatal conductance and photosynthetic capacity. As this concept has proven to be a very specific and useful method especially for the evaluation of the water use efficiencies, we will apply this conceptual model to evaluate the isotope data resulting form the four different treatments on two different soil types. Thus we can compare the response pattern of the trees to warming and drought stress, for the different proveniences. In the proposed project we intend to analyze all compartments for d13C and d18O selecting three species/provenance and provenances with assumed very different drough stress tolerance. A drought stress tolerance increased was hypothesized from Qu. robur (Loaction Tägerwilen) to Qu. petrea (location Corcelles), to Qu. pubescens (location Leuk). Following sampled have already been collected ard are intended to be analyzed: a) fresh leaves from various annual flushes collected in 2008 and 2009, b) wood section from various shoots collected in 2009, c) wood of stems for all trees rings formed in the various years collected in 2009, and d) root samples for roots from three size classes (< 2 mm, 2-5 mm, > 5 mm) have been taken in Fall 2009.The results of the proposed study will a) give us new insight about the drought-warming interactions of oaks, b) allow the adaptation of the dual isotope concept as stress indicator to be used under field conditions and c) help to identify oak species and provenances that are more or less drought and heat tolerant. Based on these results, potentially useful provenances for future seeding or planting can be identified and recommendations for the forest practice can be made. In addition, the derived indicators would allow the identification of potentially stressed trees where current species are growing close to their limits of survival due to scarce water availability.
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