Introduction

Abstract

Since the mid-1970s damage to firs (Abies alba Mill.) in the form of needle chlorosis and needle loss has been observed in the Federal Republic of Germany. In the early 1980s forest stands with Norway spruce (Picea abies [L.] Karst.) showed the same symptoms on a large geographic scale. These findings gave rise to grave concern. Since the symptoms could not be explained on the basis of the knowledge at that time, both the Federal and the State governments initiated extensive research programmes to uncover the causes of the observed damage (Bayerische Staatsforstverwaltung 1982–1987; Ulrich 1983; Forschungsbeirat Waldschäden 1984, 1986; Projekt Europäisches Forschungszentrum für Maßnahmen zur Luftreinhaltung (PEF) 1985; Projektgruppe Bayern zur Erforschung der Wirkung von Umweltschadstoffen 1985a,b; Deutsche Forschungs- und Versuchsanstalt für Luft- und Raumfahrt (DFVLR) 1987; Stüttgen 1987; Minister für Umwelt, Raumordnung und Landwirtschaft des Landes NRW 1988 ff; Schulze et al. 1989). Slightly damaged trees may occur due to natural causes, for instance, due to climatic influences or epidemics, but more severe damage or even the death of trees was soon attributed to anthropogenic causes such as direct effects of air pollutants on plant organs, acid deposition, soil acidification and impairment of the mineral budget. Research priorities were created which focused on certain investigation sites and which led to manifold interdisciplinary cooperations.