In the late 1970s and beginning 1980s forest die back evolved to a wide spread phenomenon in the world. Atmospheric acid deposition was considered as one of the most important agents causing forest decline. Acid rain produced soil acidification, the leaching of cationic nutrients and heavy metals with seepage water, root damages due to aluminum toxicity, and magnesium deficiency.
In West Germany Prof. Bernhard Ulrich was the main protagonist both in research as well as in the public and political debate on forest decline. His scientific concepts which were mainly based on findings from the Solling Research Area are critically recognized in the presentation. The achievements of abatement policy with respect to air pollution are demonstrated using recent monitoring data from Solling.
With the reduction of sulfur dioxide emissions sulfate concentration in soil solution decreased and lead to a significant reduction of aluminum concentration. However, due to a concomitant decline of base cations, the toxicity of soil solution changed only slightly. While in the 1980s sulfate was partly retained in the soils causing an equivalent buffering of acidity, this process was later reversed causing a remobilization of the previously adsorbed sulfate with an equivalent release of acidity.
A possible recovery of the soils from acidification is delayed by this still ongoing process.