[Mapping of lichen frequencies as a tool in evaluating intensity of pollution]

With the hitherto existing methods of mapping lichen distribution usually only a qualitative record of only relatively great differences in the intensity of pollution is possible. By the following method of evaluating the frequency of the lichen species on individual trunks even very small differences in intensity of pollution can be detected, and quantitative gradation is possible. The lichens growing on the trunks of isolated trees in the surroundings of factories or other pollutants have been investigated. A "ladder" enclosing ten panels is used to determine the frequency: the calculation is made electronically and permits statistical statements about the quantity of the lichens to be made. The numerical material evaluated consists of reproduceable data obtained by a standardized method that appears to be suitable for routine use.As an example the occurrence of some lichen species in the surroundings of a potassium chloride mine is shown. Zones can be recognized by changes in frequency of the variously sensitive species. The following species show increasing sensitivity to the pollution under consideration: Parmelia sulcata, Parmelia dubia, Hypogymnia physodes, Evernia prunastri, Pseudevernia furfuracea.