Total sulphur contents of epiphytic and terricolous lichens in Finland

The sulphur content was studied in the epiphytic lichens Hypogymnia physodes (L.) Nyl. and Pseudevernia furfuracea (L.) Zopf, in the terricolous lichens Cladonia sp. and Peltigera aphthosa (L.) Willd. (incl. some Nephroma arcticum (L.) Torss.), and also in pine and birch bark and in the layer below the birch bark in 31 sites in Finland. Sulphur was determined by the isotope excited X-ray fluorescence method, using a semiconductor detector. The total sulphur content of the lichens appeared to depend closely upon the species and to vary considerably due to several factors. In H. physodes and P. furfuracea it had a highly significant correlation with the wet and dry sulphate deposition. In P. aphthosa (and N. arcticum) the sulphur content also correlated with the sulphate deposition. In Cladonia, however, there was no correlation between the sulphur content and the sulphate deposition, which indicates that the sulphur uptake mechanism is different in this lichen. The sulphur contents of H. physodes and P. furfuracea in different parts of Finland showed statistically significant regional variation. The microclimatic factors were considered, account being taken of the sources and chemical form of the sulphur, and the phorophyte species and their habitats.