Effects of H2O2-Containing Acidic Fog on Young Trees

Abstract

The influence of air pollution on forest die-back in Central Europe is not clarified satisfactorily. Both the ‘acidification-theory’ and the ‘ozone-theory’ as well cannot satisfactorily explain the die-back to its full extent. Some researchers try to link damage patterns to occurrence of fog and ground-based clouds, but laboratory experiments have failed to show serious effects of fog water on trees caused by acidic compounds. The role of reactive compounds such as H₂O₂, has been overlooked so far. In this work, the effect of hydrogenperoxide-containing fog on young trees is studied. Young spruces and beeches were exposed for three hours per day to acidic fog with concentrations of 1–5 ppm H₂O₂. After six weeks, serious effects on the internal structure of leaves and needles of H₂O₂ exposed trees were found. The observed symptoms point towards a decreased resistance to drought and a decreased ability to transport assimilates, which in turn may lead to insufficient nourishment of root elements.