Effects of ammonium sulphate on the community structure and biomass of ectomycorrhizal fungi in a Norway spruce stand in southwestern Sweden

<jats:p> Effects of nitrogen and sulphur deposition on the community structure and biomass of ectomycorrhizal fungi in a Norway spruce (Picea abies (L.) Karst.) forest were examined following fertilization with ammonium sulphate. The treated plots had been fertilized three times a year from 1988 with (NH<jats:sub>4</jats:sub>)<jats:sub>2</jats:sub>SO<jats:sub>3</jats:sub> (100 kg N and 114 kg S ∙ ha<jats:sup>−1</jats:sup> ∙ year<jats:sup>−1</jats:sup>). Sampling was carried out in the organic layer of the fertilized and control plots in late autumn in 1992 and 1993. The fungal biomass was estimated in 1992 using ergosterol analysis. The nitrogen treatment reduced the fine-root biomass (to 49% of the control) but did not decrease the mycorrhizal frequency (close to 100%) or concentration of ergosterol in fine roots. To identify mycorrhizas fungal ribosomal DNA was amplified using the polymerase chain reaction and digested with endonucleases. Of the 58 samples analysed, 21 different restriction profiles could be distinguished. Only four of the restriction profiles matched the restriction patterns of the dominant sporocarps on the site. It is suggested that nitrogen deposition will primarily change the community structure of ectomycorrhizal fungi, whereas the number of species may be less affected than has been previously inferred from sporocarp inventories. Key words: air pollution, biomass, diversity, ectomycorrhiza, identification, polymerase chain reaction. </jats:p>