NUTRIENT DYNAMICS IN SOME DECOMPOSING LEAF AND NEEDLE LITTER TYPES INA PINUS-SYLVESTRIS FOREST

We investigated the long-term net dynamics of N, P, S, K, Ca, Mg and M n in decomposing litter. Green and brown needles of Scots pine (P. syl vestris L.) lodgepole pine (Pinus contorta), as well as green and brow n leaves of white birch (Betula pubescens) and leaves of grey alder (A lnus incana) were incubated for up to 4 years in a 130-year-old Scots pine forest. The concentrations of N and S increased linearly with acc umulated mass loss, also P concentrations increased linearly after an initial leaching. Moreover, the rate of increase in N concentrations a ppeared to be proportional to the initial concentration. After the inc rease, N and P concentrations reached a phase in which they remained c onstant or declined slightly. Concentrations of Mg and K decreased wit h accumulated mass loss, especially in litter types with high initial concentrations of these elements. For Mn the pattern was similar but l ess pronounced. The relationship between Ca concentrations and accumul ated mass loss was largely negative, resembling a negative X(2) functi on. Absolute amounts of nutrients decreased linearly with litter mass loss once a net release had started. This applied to all litter types and nutrients with the exception of Mn release from grey alder leaves.