Das Projekt "Der Einfluss von Umweltveraenderungen auf den Wurzelbereich von Waldbaeumen: der Zustand der Mycorrhizae" wird vom Umweltbundesamt gefördert und von Eidgenössische Forschungsanstalt für Wald, Schnee und Landschaft durchgeführt. To investigate the structural and physiological characteristics of selected mycorrhizal species in relation to nitrogen availability. To test whether the Hartig-net of mycorrhizae is affected by nitrogen. To examine the biochemical responses of mycorrhizae to nitrogen (particularly enzymes associated with nitrogen metabolism: glutamine-synthetase and glutamate-dehydrogenase). Leading Questions: Can fine-roots and mycorrhizas of forest trees act as indicators for nitrogen and acid inputs into forest stands? What are the biochemical and molecular responses of mycorrhizas to nitrogen and acid inputs (particularly enzymes associated with the nitrogen metabolism and with the plant defense response)? Are there, among selected types of mycorrhiza, differences in the biochemical and molecular responses? Are the structural characteristics of mycorrhizas, i.e. formation of Hartig net, affected by nitrogen and acid inputs?