Decomposition of pine-litter organic matter and chemical properties of upper soil layers: transect studies

The relationship between Scots pine litter decomposition rate and some chemical properties of the upper soil layers and litter (contents of iron, manganese, zinc, copper, lead, mercury, nickel and chromium) was determined. For the metal content in the organic-mineral horizon of soils, the strongest correlation was between needle decomposition and copper (r=0.90), zinc (r=0.90), iron (r=0.83), and nickel (r=0.85) concentrations. For the metal content of litter, the strongest correlations were between needle decomposition and nickel (r=0.89), iron (r=0.83), zinc (r=0.80), and lead (r=0.82) concentrations. For mixed-litter decomposition and litter heavy metal concentrations, the highest correlations were with nickel (r=0.72), iron (r=0.71), zinc (r=0.66), and lead (r=0.68). There were no significant correlations between the rate of decomposition of wood or cones and the litter concentration of metals other than chromium. In some cases, the correlations between decomposition rate and metal concentration were positive. Two out of six significant correlations between needle decomposition and the concentration of metals in litter were positive. For mixed litter decomposition, the five significant correlations included two that were positive. In both cases, decomposition responded positively to the presence of iron and lead. Comparing decomposition rates with the level of soil metal content, all five significant correlations with needle decomposition were positive; for mixed-litter decomposition, only one significant correlation was positive.