DECOMPOSITION AND NUTRIENT DYNAMICS OF LITTER IN LONG-TERM OPTIMUM NUTRITION EXPERIMENTS .2. NUTRIENT CONCENTRATIONS IN DECOMPOSING PICEA-ABIES NEEDLE LITTER

Temporal patterns of changes in nutrient dynamics were followed in decomposing Picea abies needle litter in a long-term optimum nutrition field experiment using N and P fertilizer. Nutrient-poor brown and nutrient-rich green needle litter were incubated in both control plots and fertilized ones. As decomposition proceeded, we could distinguish two groups of nutrients, one for which a clear effect of fertilizer was seen (N, P, Mg) and one for which no clear effect or any clear pattern caused by the fertilizer was seen (K, Ca, Mn). Concentrations of N and P increased and were linearly related to the accumulated mass loss and their dynamics was clearly affected by the fertilizer, viz. the concentrations increased faster in the fertilized plot. Concentrations of Mg decreased linearly in relation to the accumulated mass loss and for the nutrient-poor brown litter the decrease rate in concentration was lower in the fertilized plot. No effect was seen of the green needle litter. For Ca the concentration increased initially in all four cases but then decreased. Concentrations of K decreased initially in all four cases and then remained largely constant. The concentration of Mn increased in all four cases but no significant difference could be seen either between control plot and fertilized plot, or between litter types.