Environmental Sciences Europe volume 24 , Article number: 19 Cite this article. Metrics details. In the years , , , , and , lichen mapping in the towns of Wetzlar and Giessen in Hesse was performed.
The aim was to show the effects of immission load. Despite the application of modified test methods during the study period, the results can still be compared directly because they could be adapted to the requirements of the guidelines of the Association of German Engineers.
Even the earlier study results could be interpreted partly within the scope of the guidelines. Parallel to the lichen mapping, comparative examinations of pH on tree bark were carried out. In both towns, the pH of the tree bark has been increasing continuously, presently almost reaching pre-industrial values. The increase was stronger in Wetzlar than in Giessen. In , the lichen vegetation showed a complete depletion.
Since then the number of species has risen significantly. This development happened faster and more intensely in Wetzlar.
The comparison of the lichen vegetation between and also shows an increased existence of species that are favored by hypertrophic air contaminants.
