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Linking dendrochronology with ecophysiology: The influence of water stress on cambial activity


Sap-flow measurement

Photo: Ch. Hug (WSL)

In a changing environment, the analysis of how forest ecosystems may react under scenarios involving changing climatic conditions is of major importance. An approach to such analyses is the study of how forests have reacted to past climatic events and trends.

Dendrochronological methods, through proxies such as tree rings, enable the reconstruction of past responses of trees to past environmental changes. However, they do not provide details about the plant responses to different environmental factors. Ecophysiological methods, instead, enable a deep understanding of current intra-annual plant responses.

The relationships between plant physiology and cambial activity (expressed as inter- and intra-annual tree-ring growth) are still not understood (e.g. Cherubini et al. 2002 J. Ecol. 90, 839-850).

Project aims

The aim of this project is to evaluate the influence of expected climatic changes (changes in the precepitation and temperature regimes) on trees and the state of our forests. We will provide information about:

  • past responses of tree growth to climatic events and trends
  • current response of cambial activity of five different co-occurring species to climatic variability


  1. Ring-width measurements, using TSAP (Rinntech, Heidelberg, Germany) measurement equipment and software
  2. Sap-flow measurements with Thermal Dissipation Probe (TDP) (ADC, Herts, England), originally proposed by Granier (INRA, Champenoux, France), at one of the Swiss LWF plots (ICP-Level II) (Bettlachstock, Solothurn, Switzerland). This site is drought-sensitive. We measure sap-flow on 36 trees of different species (Abies alba, Picea abies, Fagus sylvatica, Acer preudoplatanus, Fraxinus excelsior).
  3. Measurements of diurnal changes in stem circumference using electronic girth bands.
  4. Measurements of the 18O/16O-ratio (pyrolisis) and of the 13C/12C ratio (combustion), using an elemental-analyser coupled to a mass-spectrometer (PSI, Villigen, Switzerland).


  • Christian Hug (Technical Project leader)
  • Paolo Cherubini (Scientific Project leader)
  • Matthias Saurer (stable isotopes)
  • Martine Rebetez (meteorology)
  • Flurin Sutter (databanks, Oracle))
  • Rudolf Häsler (sap-flow)
  • Matthias Dobbertin (tree growth)
  • Elisabeth Graf Pannatier (soil physics)
  • Peter Plüss (data-logger programming)
  • Gustav Schneiter (data transfer)
  • Marcus Schaub (photosynthesis)
  • Niklaus Zimmermann (modeling)
  • Norbert Kräuchi (coordination LWF programme)


Keywords Sap-flow, TSAP, Thermal Dissipation Probe, Swiss LWF Plot Bettlachstock