Effects of dry-deposited sulphur dioxide on fungal decomposition of angiosperm tree leaf litter III. Decomposition rates and fungal respiration.

Ash (Fraxinus excelsior L.), birch (Betula spp.), hazel (Corylus avellana L.), sessile oak [Quercus petraea (Mattuschka) Liebl.] and sycamore (Acer pseudoplatanus L.) leaf litters from a virtually non-polluted and a heavily sulphur dioxide (SO )-polluted woodland were fumigated with environmentally-realistic concentrations (0.010-0.030μl l ) of SO for 16-68 wk in an open-air field-fumigation experiment. Fumigation inhibited the respiration (CO evolution) and decomposition rates of the leaf litters. However, there were few differences in the responses between leaf litters from the two woodlands. In addition, pure cultures of four saprotrophic fungi were grown individually on irradiated hazel litter and exposed to c. 0.030μl l of gaseous SO , for 28 d in the laboratory. The gas inhibited the respiration of Phoma exigua Desm. and Phoma macrostoma Mont, but not the respiration of Cladosporium cladosporioides (Fres.) de Vries or Coniothyrium quercinum Sacc. var. glandicola Grove. These results in part substantiated findings of previous experiments examining the effects of SO on the structures of saprotrophic fungal communities. The effects of SO on fungal decomposition of angiosperm tree leaf litter as possible causes of forest decline are discussed.