Das Projekt "ForClimSense: Alpine Waldoekosysteme in einem sich aendernden Klima - Palaeoklimatische Modellvalidierung und Empfindlichkeitsanalyse" wird vom Umweltbundesamt gefördert und von Eidgenössische Technische Hochschule Zürich (ETHZ), Institut für Terrestrische Ökologie ITOE durchgeführt. Forests are globally as well as locally important ecosystems and are mounded by climate. Because of the longevity of trees forests can rarely be studied directly, which renders mathematical models indispensable tools to study forest dynamics. We use the ecosystem model ForClim, which had first to be validated by applying it during the end of the last ice age. We simulated species compositions and compared them with pollen records (data from 1.18., 1.19., 1.20.), which we were able to reproduce. By using climate scenarios down-scaled from GCMs by Gyalistras (1.5.) we assessed the sensitivity of mountain forests to impacts of global climatic changes. We found no uniform response: Some forests suffered from temporary die-backs due to strong changes in species compositions or vanished completely due to drought stress, some profited due to increased productivity, and some were hardly affected at all. In general, climatic change affects sensitive forests as found in the mountains immediately, yet to adjust to a new climate a forest requires as long as 600-800 years.