In Valais, Scots pine (Pinus sylvestris) and pubescent oak (Quercus pubescens) grow at least temporally at the edge of their physiological capabilites. We investigate the (potential) adaptation of these and co-occurring tree species to climate change and search for limits they might reach with increasing temperatures and droughts.
Plants in general and trees in particular respond to climatic changes in a very sensitive way. Factors of tree water relations and carbon balance are continuously measured in the natural environment of this dry valley. These data sets allow us to draw conclusions on the physiological regulation mechanisms (e.g. stomatal regulation) and tree growth.
Systemic models help to interpret the ecophysiological measurments and allow us to gain a more detailed understanding on the underlying mechanisms and adaptation processes of different tree species to the current climate. We search for the limiting factors and thresholds of climatic conditions which might bring the trees to the edge of their physiological capabilities. In the Valais, Scots pine (Pinus sylvestris) and pubescent oak (Quercus pubescens) reached their physiological limits under the extreme conditions as they occurred during the 2003 summer season. Furthermore, first results demonstrate why pubescent oak has an advantage over Scots pine when growing under warmer and drier climate conditions.