IRON CONTENT AND ITS RELATIONS TO THE SULFUR AND TITANIUM CONTENTS OFEPIPHYTIC AND TERRICOLOUS LICHENS AND PINE BARK IN FINLAND

The iron content was studied in the epiphytic lichens Hypogymnia physo des (L.) Nyl. and Pseudevernia furfuracea (L.) Zopf in the terricolous lichens Cladina sp. and Peltigera aphthosa (L.) Willd., and in pine b ark collected from 31 sites in Finland. There appeared to be differenc es between lichen species, epiphytes having generally higher concentra tions. The iron content of H. physodes was highly significantly correl ated (p < 0.001) with its sulphur content, reflecting the relations of these elements in precipitation. The highly significant correlations between the iron and titanium contents indicated differences of the ph orophytes. The iron/sulphur ratio of H. physodes on pine was 1.3 and o n birch 1.4 and iron/titanium titanium ratios were 10.4 and 11.3 respe ctively. The iron content of Cladina sp. showed highly significant par allel correlations (p < 0.001) with its sulphur and titanium contents. The iron/titanium ratio decreased from 9.6 to 8.2 when the iron conte nt increased by 95%, the sulphur content being equal. The iron/titaniu m ratio of Cladina sp. was nearly identical to that of P. furfuracea. The relation between iron and sulphur, and the fraction of soluble and insoluble iron in precipitation versus lichens and pine bark were con sidered. Special attention was paid in the discussion to differences i n substrate: pine and birch bark for H. physodes, and soil for Cladina sp.