Effects of simulated nitrogen deposition to the forest floor on the macrofungal flora of a beech forest

The effects of an increased nitrogen deposition to the forest floor on fruit body production and species richness of the macrofungal flora of a Swedish beech forest were simulated by applying small amounts of ammonium nitrate (12 and 36 kg N per ha) on 22 occasions over a period of 4 years. Within 3-4 years all mycorrhizal species practically ceased producing fruit bodies even at the lower treatment rate, which corresponded to about 3 times the ambient deposition rate at this site situated in an area with no major sources of pollution. Several decomposer taxa, on the contrary, increased their sporophore production in the treated plots, e.g. Mycena pura, M. pelianthina, Clitocybe dicolor, C. gibba, C. phyllophila, Lepista inversa, Agaricus spp. and Lycoperdon spp. Most wood decomposers showed no obvious reaction to treatment.