ACCUMULATION PATTERNS OF HEAVY-METALS IN SOIL PROFILES AS AFFECTED BYFOREST CLEAR-CUTTING

Vertical distribution of Zn, Pb, Cu and Cd was studied in podzol soil profiles of adjacent forested and clear-cut areas in a region contamin ated with Zn, Pb and Cd from long-range atmospheric transport. This wa s in order to investigate possible effects of deforestation on accumul ation and distribution patterns of these metals in surface soil profil es. Lower Zn and Cd contents were observed in the H horizon of clear-c ut area soils than in forest area soils. However, this was not suffici ent to entail a significantly lower total Zn and Cd pool in the humus layer of clear-cut area soils compared to forest area soils. The total content of Pb in the L + F + H horizons was significantly lower in cl ear-cut than in forested areas, attributable to distinctly lower Pb co ntents in the H horizon of clear-cut area soils. This fact combined wi th significantly thinner humus layers in clear-cut areas compared to f orested areas, presents evidence for increased losses of Pb from the h umus layer after clear-cutting. Higher Pb contents in the Ae and B hor izons of clear-cut area soils than in forest area soils, show that at least parts of the Pb lost from the H horizon in clear-cut areas were re-adsorbed or re-precipitated in the Ae and B horizon. As in the case of Pb, Cu concentrations were higher in the Ae and B horizons of clea r-cut area soils compared to forest area soils. In the case of Cu, how ever, this cannot be explained by increased inputs from the humus laye r following forest clear-cutting, but rather by increased weathering i n the Ae and B horizons. The high retention of Zn, Cu and Cd in the hu mus layer of clear-cut areas, compared to that of Pb, is most probably due to a stronger accumulation of these metals in ectomycorrhizal bio mass.