Drought in Switzerland is further intensifying. Particularly forest trees in the lowlands (Mittelland) show steadily increasing tree water deficit-induced stem shrinkage (TWD, Baumwasserdefizit). The values are far above the TWDs measured in the past eight years and indicate a very high drought stress.
The network TreeNet detects with point dendrometers how much tree stems shrink during dry periods. This so-called tree water deficit (TWD) indicates how much trees are suffering from dry conditions. The higher the value is the more a tree is thirsty. The figure shows that the situation accentuated in the Swiss lowlands (Mittelland) and also in the Valais (Alp Valais). No further increase of TWDs has been measured in the northern part of the Alps. Analyzed were beech, spruce, pine and oak trees.
See also the earlier reports about the development and interpretation of tree water deficits in trees:
TreeNet Switzerland collects continuous data on stem radius fluctuations measured with point dendrometers from about 250 trees all over Switzerland and estimates drought and growth indicators for Swiss forest ecosystems. We closely collaborate with the Long-term Forest Ecosystem Research Programme (LWF/WSL), the ETHZ and the Institute for Applied Plant Biology (IAP).
For more information about the actual drought in Switzerland refer to drought.ch