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 sta nds in southern Poland. At the same stands the input of chemical eleme nts with throughfall was followed. Decomposition constants k for the o ak-hornbeam litters were -0.57 and -0.55, and for the pine-beech litte rs -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, thr ee factors were specified: (1) biological, dominating the decay of org anic matter and the dynamics of N, Ca, Mg, Mn, and S; (2) physical, do minated by leaching and atmospheric deposition, and controlling the dy namics of organic matter, K, Na, Pb, Cd, and Zn; and (3) chemical, det ermining the dynamics of Fe, Zn, Pb, and Cd through the fixation of me tal ions to humic substances. Potassium was the only element that decr eased 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 con centrations revealed different patterns in different litters, presumab ly 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-ba g incubation. In all four stands the input with throughfall was high e nough to explain the increases in amount of elements, with the excepti on of Fe in the oak-hornbeam litters.