Peatbog resilience to pollution and climate change over the past 2700 years in the Harz Mountains, Germany

Gałka M, Szal M, Broder T, Loisel J, Knorr K-H

Abstract

High-resolution plant macrofossil records were examined alongside geochemical analysis (non-destructive X-Ray fluorescence and carbon stable isotopes), pollen, and micro-charcoal data of an ombrotrophic mountain peatland located in the Harz Mountains, central Germany, Europe. We hypothesize that increased deposition of dust and pollutants across the bog surface causes changes in habitat conditions, which in turn lead to shifts in moss-dominated communities. We observe that increases in the abundance of Sphagnum magellanicum macrofossils – a species with a wider ecological range that occurs even in weakly minerotrophic habitats - coincide with increases of pollutant concentrations in the peat; conversely, increases of Sphagnum rubellum and Sphagnum capillifolium populations – indicators of oligotrophic conditions – coincide with decreases of pollutant concentrations. Pristine Sphagnum populations in the studied ombrotrophic bog have thus repeatedly returned to their original oligotrophic state (an autogenic process) following declines in pollutant input. Modern levels of pollutants should be taken into account in peatland restoration efforts, as they exert a strong control on the composition of present day Sphagnum communities. Moreover, Sphagnum angustifolium in paleoecological studies might be considered as an indicator of water level rise. In this study, the presence of S. angustifolium apparently correlates with wetter moisture conditions.