EFFECTS OF AMMONIUM-SULFATE ON THE COMMUNITY STRUCTURE AND BIOMASS OFECTOMYCORRHIZAL FUNGI IN A NORWAY SPRUCE STAND IN SOUTHWESTERN SWEDEN

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 fr om 1988 with (NH4)(2)SO3 (100 kg N and 114 kg S ha(-1) year(-1)). Samp ling was carried out in the organic layer of the fertilized and contro l plots in late autumn in 1992 and 1993. The fungal biomass was estima ted 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 amplif ied using the polymerase chain reaction and digested with endonuclease s. Of the 58 samples analysed, 21 different restriction profiles could be distinguished. Only four of the restriction profiles matched the r estriction patterns of the dominant sporocarps on the site. It is sugg ested that nitrogen deposition will primarily change the community str ucture of ectomycorrhizal fungi, whereas the number of species may be less affected than has been previously inferred from sporocarp invento ries.