Decomposition and Nutrient Dynamics of Litter in Long-term Optimum Nutrition Experiments I. Organic Matter Decomposition in Picea abies Needle Litter

The chemical composition of the falling litter was investigated over the different fertilization regimes. The nitrogen concentration in the needle litter increased with dosage of nitrogen fertilizer. Nitrogen concentration in needle litter was positively correlated to those of lignin, sulfur and calcium, but negatively to those of zinc, aluminum, and manganese. Phosphorus concentrations were negatively correlated to those of lignin, manganese, zinc, calcium and magnesium. Concentrations of sulfur were negatively correlated to concentrations of zinc, calcium, aluminum, magnesium and boron. The decomposition patterns of Norway spruce needle litter were followed in an optimum nutrition field experiment. Control plots and plots given high dosages of nitrogen and phosphorus fertilizer were used. As decomposition proceeded soluble substances disappeared quickly and the concentration of soluble substances consequently decreased fast. Lignin, being a recalcitrant compound, increased in concentration and the concentrations increased linearly to accumulated mass loss. There was a clear difference in pattern as regards increase in lignin concentrations among needle litters depending on whether they were incubated in a control plot or a highly fertilized one. The concentration of lignin at a given mass-loss value was thus significantly higher for litter incubated in a fertilized plot than in the control plot. In late decomposition stages, mass-loss rates decreased linearly as compared to lignin concentrations among needle litters highly fertilized one. The concentration of lignin at a given mass-loss value was thus significantly higher for litter incubated in a fertilized plot than in the control plot. In late decomposition stages, mass-loss rates decreased linearly as compared to lignin concentrations, up to a certain concentration of lignin, after which some other factor was more rate regulating. No difference was seen between the control plot and the fertilized plot as regards the influence of lignin concentration on mass-loss rate.