THE DYNAMICS OF CHEMICAL-ELEMENTS IN FOREST LITTER

Litter bags with natural mixed litter were incubated until approximate to 60-70% mass loss in two oak-hornbeam and two pine-beech forest stands in southern Poland. At the same stands the input of chemical elements with throughfall was followed. Decomposition constants k for the oak-hornbeam litters were -0.57 and -0.55, and for the pine-beech litters -0.30 and -0.27. Chemical elements (except for Cu and Mn) revealed similar relative mobility in the four litters. On average the elements could be ordered by decreasing mobility as follows: K > Mg > Ca > S > Cu > Na > Mn = N > Cd > Pb = Zn > Fe. Instead of the two presupposed factors controlling litter decomposition, biological and chemical, three factors were specified: (1) biological, dominating the decay of organic matter and the dynamics of N, Ca, Mg, Mn, and S; (2) physical, dominated by leaching and atmospheric deposition, and controlling the dynamics of organic matter, K, Na, Pb, Cd, and Zn; and (3) chemical, determining the dynamics of Fe, Zn, Pb, and Cd through the fixation of metal ions to humic substances. Potassium was the only element that decreased in concentration in all litters, while the concentrations of N, Na, Fe, Zn, Pb, and Cd increased in all litters. S, Ca, Mg, and Mn concentrations revealed different patterns in different litters, presumably due to the differences in initial concentrations and soil acidity. No clear trend was found for Cu. In all litter types, Fe, Zn, Pb, and Cd significantly increased in absolute amounts at the end of litter-bag incubation. In all four stands the input with throughfall was high enough to explain the increases in amount of elements, with the exception of Fe in the oak-hornbeam litters.