Das Projekt "Quantifizierung der Auswirkungen von saurem Regen auf Waldbestaende" wird vom Umweltbundesamt gefördert und von Technische Universität München, Forstwissenschaftliche Fakultät, Lehrstuhl für Bodenkunde und Standortlehre, Lehreinheit Vegetationskunde durchgeführt. The Research Work is Based on the Assumption that Enhanced Proton Inputs from the Atmosphere are Causing Essential Changes in Forest Ecosystems, being Responsible to a High Degree for the Extensive Forest Decline of Recent Years. The Research Work is Subdivided into Two Projects of Investigations: A. The Field Experiments 'Hoeglwald'. In Two Pure Spruce Stands of Different Ages, Experiments with Artificial Rain and with Compensative Limings are Installed. In Old Spruce Stands (76Years Old) a Soil Irrigation of 200 mm per Year with PH 2.7 and PH 5 is Performed, in the Young Stand (12 Years Old) an Above-Canopy Irrigation with the Same Features is Applied. The Liming Comprises 4000 KG per HA 1 CA-MG-Carbonate. B. Site Investigations without Experimental Treatments. Investigations with the Same Aim as Mentioned above but without the Extensive Experimental Treatments as under Point A. Should be Performed in About 50 Stands of Different Species, Sites and Immission Charges.