Evaluation of pollution-related stress factors for forest ecosystems in central Europe

Since the early eighties air pollution by SO2 and Pb and, to a lesser degre e by NOx and NH3, have been significantly reduced in Europe. This was done in part for the protection of forest ecosystems. The reductions are reflect ed in the pollutant impacts and inputs and have been verified through the b ioindicator Norway spruce. In contrast, ozone concentrations increased at m ost of the evaluated measuring locations and trends were calculated based o n the results of about 100 stations in Austria and Germany. Despite reduced emissions, large parts of the forest ecosystems are still a ffected by air-pollution impacts. Negative effects can be assessed using di fferent legal standards and Critical Levels and Critical Loads, respectivel y: The legal standard for the evaluation of SO2 impact, as used in Austria, is well suited. The provisional European Critical Level for ozone, the AOT 40 must, in order to be a meaningful criterion for field applications, be f urther refined. Continuing the Critical Load concept, the spatial risk of a cid depositions in areas of high geomorphic variability were evaluated usin g the new parameter of 'critical soil depth'. With the help of the newly de fined 'lead accumulation index', the accumulation of Pb from air pollution could be evaluated. Air-pollution inputs and the spatial acidification risk is directly related to altitude. Up to altitudes of 1000 m and 1100 m, SO2 impact and acid dep ositions, respectively were indicated and elevated ozone doses and Pb input s were observed in the sensitive sub-alpine areas. These results underline the necessity for increased protection of mountain forest ecosystems, among others through a further reduction of emissions or forest-related strategi es.