Das Projekt "Wasserverhaeltnisse in einer reifen gemeinen Fichte" wird vom Umweltbundesamt gefördert und von Eidgenössische Forschungsanstalt für Wald, Schnee und Landschaft durchgeführt. Water relations of mature Picea abies tree in the Seehornwald (1640m a.s.l.) near Davos, Switzerland, are under investigation. In the soil, temperature and soil matric water potential are being measured. As micrometeorological parameters we measure solar radiation, air temperature, water vapour pressure deficit, wind speed and evaporation throughout the canopy. Precipitation is measured at the top of the canopy only. To estimate the water relations of lichens in the tree crown, the electrical resistance of lichens growing on the twigs is measured. To estimate tree water relations transpiration of selected twigs is measured using climatized gas exchange chambers, xylem sap flow in the stem and some branches using sap flow meters, and the water potential and the osmotic values of the needle tissue is estimated using the pressure bomb technique and cryoscopy respectively. Leading Questions: How does the quantity of water evaporated from a mature Picea abies tree in a subalpine forest vary with different micro-meteorological conditions?Is drought a problem for a tree in a subalpine forest, and what are the reactions of the tree to this stress? Do different parts of the crown (in the sun and in the shade) react to water stress in the same manner? What drought conditions cause needle fall?