Churakova (Sidorova) Olga

Key mechanisms of metabolic changes in mountain pine and larch under drought in the Swiss National Park (SNP)
Schlüsselmechanismen metabolischer Veränderungen in Bergföhren und Lärchen unter Trockenheit im Schweizerischen Nationalpark

Project Number: CH-4916
Project Type: Research_Project
Project Duration: 05/01/2013 - 10/31/2015
Funding Source: other ,
Project Leader: PD Dr. Olga Churakova (Sidorova)

e-Mail: olga.sidorova(at)

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Research Areas:

environmental sciences

Dendroclimatology, dendrochronology and plant physiology

In this project we will investigate the mechanisms of metabolic changes in mountain pine and larch trees under drought stress in the Swiss National Park using state-of-the-art methods of classical dendrochronology, tree physiology, stable isotope and compound-specific isotope analyses. Long-term responses of mountain pine and larch trees from a north- and a south-facing site to drought will be inferred from tree-ring width data. Based on climatic data a drought index
will be calculated and reconstructed back in time. New chronologies for 13C/12C and 18O/16O isotope ratios derived from both pine and larch tree-ring cellulose will provide retrospective insight into the long-term whole-plant physiological control of gas exchange derived from estimations of stomatal conductance, photosynthetic rate and intrinsic water use efficiency. Carbon isotope ratios of specific sugar compounds such as sucrose, raffinose, fructose, ribose and pinitol in needle and wood samples will help to evaluate the impact of drought on the carbohydrate balance and carbon allocation. Analyzing the oxygen isotopic compositions of soil water, sap water (water in branches) and precipitation we will determine the role of the different water sources for tree growth under drought conditions. The proposed work will provide a unique opportunity to assess the survival potential of mountain pine and larch trees exposed to drought that will help to estimate risks of recent climatic changes and forest damage.

Leading questions:
In the Swiss National Park (SNP), annual and spring temperatures increased since the 1990s up to 0.5°C and 1.02°C, respectively, compared to the mean values from 1917 to 1989, and average summer temperature increased up to 0.6°C, while annual precipitation decreased by 81 mm (measurements from the Buffalora weather station, which is located closely to the SNP). These climatic trends in combination with the relatively shallow soils in the SNP suggest that detailed
studies of drought effects on the physiological functioning of trees over the last decades are needed.
Mountain pine (Pinus mugo var. uncinata) forests, which predominantly grow on limestone in the SNP, cover ca. 73% of the forests in the SNP and represent the biggest population of mountain pine in Switzerland. Forests with European larch (Larix decidua) and Swiss stone pine (Pinus cembra) cover ca. 11% of the forests in the SNP. Larch is better adapted to cool climate conditions than mountain pine and may reach life spans of more than 500 years, however, mountain pine trees may also live more than 300 years. Such long-living trees allow to reveal physiological responses of trees to climatic and environmental changes over many centuries back into the past and allow to estimate the magnitude and forcing mechanisms of the recent climatic changes. For example, larch trees growing in the Lötschental (Switzerland) already have shown strong responses to drought (Kress et al. 2010) and mortality of different conifer species in subalpine forests of Colorado (USA) has increased due to drought (Bigler et al. 2007). An ongoing research project of the tree-ring laboratory at ETH Zurich allowed to reconstruct mortality of mountain pine in the SNP from the 1920s to 2009 (Christof Bigler, personal communication) and to describe tree-specific patterns of partial cambial mortality (Bigler and Rigling 2013). It is of great interest to investigate and compare the physiological responses of mountain pine and larch to drought and to understand the key physiological mechanisms behind the mortality processes. The research on forest ecology in the SNP has focused so far largely on tree-ring width (Brang 1988; Dobbertin et al. 2001; Bigler and Rigling 2013). However, there are no studies in this region in which the bulk stable isotope analysis or stable isotope analysis of
different compounds such as carbohydrates and/or organic acids has been performed. This gap will be filled in this project to obtain a better understanding of the underlying biochemical and physiological processes.
Stable isotopes have proven to be a highly precise and powerful tool in the field of environmental sciences and their use is well established in tree-ring studies (McCarroll et al. 2004; Sidorova et al. 2008, 2009, 2011, 2012). Climatic parameters like temperature, water availability, air humidity and ambient CO2 influence the photosynthetic CO2 assimilation and water balance, which is reflected in the isotopic C and O ratios of the plant organic matter, yielding a specific isotope pattern in the wood of tree rings. Therefore, analyzing stable isotopes provides specific physiological information on the impact of drought on metabolic changes in trees.

Last update: 12/29/16
Source of data: ProClim- Research InfoSystem (1993-2020)
Update the data of project: CH-4916

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