Description and evaluation of pollution impacts on forest ecosystems: Results of long-term Austrian field experiments - Introduction.

For more than 20 years European research groups have examined the causes of novel forest decline. Monitoring networks have been established in order to survey the condition of trees and their long-term change. Interdisciplinary field projects and chamber experiments were started to improve the knowledge of cause effect relations. The Federal Forest Research Centre (FBVA) is responsible for the Austrian networks (Austrian Forest Inventory, Forest Damage Monitoring System, Bio-Indicator Grid). At the same time, the FBVA concentrates mainly on interdisciplinary research activities in the alpine area ("Zillertal Altitude Profile", "Achenkirch Altitude Profiles"). These projects are aimed at improving the knowledge of the "environmental situation" of the Alps and at describing regional and time-related variations of potential natural and anthropogenic stress factors to forest ecosystems. In cooperation with numerous university institutes and research centres, causal relationships between stressors and their effects on trees are described. The majority of the investigations refer to spruce as the principal Austrian tree species and the main investigation areas represent differently stressed Austrian forest areas. The contributions presented in this series of publications comprise mainly results from the project "Achenkirch Altitude Profiles" and refer to pollutants. The latter are described and assessed with respect to their impacts on forest ecosystems