Epiphytic lichen distribution on trunks of Norway spruce (Picea abies) and its dependency on chemical site factors were investigated. The study was carried out in montane woodlands of the Harz Mountains in Northern Germany. For investigating the influence of forest dieback on epiphytic lichen vegetation and on chemical site conditions, two boggy stands were selected. Within both stands tree vitality ranged from healthy to dead. Differences in tree vitality are assumed to be due to small-scale differences of ground-water levels, as Norway spruce is more susceptible to pollution-caused forest dieback when water logging occurs. Summarizing, there is strong evidence that forest-dieback promotes epiphytic lichen abundance due to reduced concentrations of atmospheric pollutants in stem flow. This applies to SO42- in particular. Furthermore, the importance of the factor soil is highlighted. Differences in epiphytic lichen vegetation between both stands are probably a result of between-stand differences in the concentrations of extractable Mn in the soil.
