The effects of open-air fumigation with sulphur dioxide on the decomposition of sycamore (Acer pseudoplatanus L.) leaf litters from polluted and unpolluted woodlands

Sycamore (Acer pseudoplatanus L.) leaf litters from 15 woodlands exposed to a broad range of ambient sulphur dioxide (SO2) concentrations were fumigated with environmentally realistic concentrations (ll-20nmol mol−1) of SO2, for 166 d in an open-air fumigation experiment. Fumigation of the sycamore litters significantly increased sulphate-S and proton leaching, and decreased calcium, magnesium and potassium concentrations in leachates and leaf tissues. Leaf litters from relatively unpolluted woodlands showed a tendency to lose higher amounts of sulphate-S, calcium, magnesium and nitrate-N in leachates than litters from polluted sites when exposed to elevated levels of SO2 in treatment plots. Fumigation inhibited the decomposition rates (CO2 evolution) of the leaf litters. Marked changes in the composition of the saprotrophic fungal communities in SO2-fumigated leaf litters were also recorded, but fungal communities and responses to SO2, were similar between woodlands. There was no evidence from our data to suggest that resistance to SO2, was developed in decomposer mycofloras in woodlands more frequently polluted by the gas.