Response of saprotrophic fungal communities to declining SO2 pollution in the natural environment.

The composition of saprotrophic fungal communities on sessile oak (Quercus petraea) and sycamore (Acer pseudoplatanus) leaf litters from a woodland at Cefnpennar in South Wales, UK, were analysed in late winter and early spring every three years between 1988 and 2000. Decreases in predicted (assessed by presence of lichen indicator species) and measured concentrations of gaseous SO2 emitted from a nearby phurnacite briquetting plant were recorded at the woodland during this period, together with reductions in concentrations of SO42–-S leached from leaf litters. Changes to the saprotrophic fungal communities on the litters were also observed between 1988 and 2000. Generalised linear models and rank correlation analyses indicated that Aureobasidium pullulans, Fusarium avenaceum, F. lateritium, Verticillium lecanii and Torula herbarum became more abundant on oak and sycamore litters. By contrast, Acremonium persicinum, Cylindrocarpon orthosporum, Phoma macrostoma and Trichoderma spp. became less abundant on both litter types. These changes to the composition of saprotrophic fungal communities broadly corroborate those derived from open-air SO2 fumigation experiments. They infer that fungal community composition is influenced by SO2 in the natural environment and that recovery of communities takes place following chronic exposure to the gas.