DYNAMICS OF SOME MINERAL NUTRIENTS AND HEAVY-METALS IN DECOMPOSING FOREST LITTER

The dynamics of three major mineral nutrients (K, Ca. Mg) and six heav y metals (Fe, Mn, Zn, Cu, Pb and Cd) were studied in decomposing natur al, unpolluted litter in two forest types: Scots pine needle litter in a pure Scots pine forest and oak-hornbeam leaf litter in a mixed oak- hornbeam stand. Of the mineral nutrients, only K in the oak-hornbeam s ystem showed a significant decrease in concentration during the course of litter decomposition. For Ca and Mg in both systems and for K in t he Scots pine system no clear relation between concentration and accum ulated litter-mass loss was observed. On the other hand, for Fe, Zn, P b and Cd at both sites, as well as for Mn in the oak-hornbeam stand an d Cu in the Scots pine stand highly significant positive relations wer e found between heavy metal concentrations and accumulated mass loss. A decrease in concentration was noted only in the case of Mn in the Sc ots pine system. No clear pattern was found for Cu in the oak-hornbeam stand. Concentrations of heavy metals in the decomposing litter reach ed levels at or above those reported to retard decomposition in other studies. At the oak-hornbeam stand increased also the absolute amounts of Fe. Zn, Pb and Cd.