Secondary effects of SO2 pollution on leachate chemistry and decay of scots pine and mixed angiospermous leaf litters

Abstract

The secondary effects of SO2 fumigation on CO4 evolution from leaf litter of Scots pine (Pinus sylvestris L.) and mixed broad-leaved species [Quercus petraca mattuschka (Liebl.), Fraxinus excelsior L., Betula pubescens Ehrh., Betula pendula Roth., Acer pseudoplatanus L. and Corylus avellana L.] were investigated. Respiration of Phoma exigua Desm. inoculated onto both types of previously fumigated (48 nl l-1), sterile litter was higher than controls (< 10 nl l-1). Much higher rates of CO4 evolution were measured from control litters than from fumigated litters after 2 weeks; the differences decreased but continued until the end of the 12-wk incubation period. Sulphate concentrations in the leachate solution from fumigated litters remained significantly higher until the end of experiment. In addition, the pH of the leachate solution was lowered by SO2 fumigation. At the start of the experiment, the NH4/+ concentration from pre-fumigated and control litters was similar, but release from the control litter was slightly greater than from pre-fumigated litter, according with measurements of CO2 evolution from the litters. The experiments indicated that environmentally-realistic concentrations of SO2 over a long period could affect leachate chemistry and this might affect the decomposition rate of leaf litters. The Scot pine litter was more affected than mixed angiospermous litter.