• fungal diversity;
  • functional groups;
  • nutrient cycling;
  • ectomycorrhizal (ECM) fungi;
  • saprotrophic fungi;
  • stable isotopes


  • •  
    The natural abundance of 13C (δ13C) and 15N (δ15N) of saprotrophic and ectomycorrhizal (ECM) fungi has been investigated on a number of occasions, but the significance of observed differences within and between the two trophic groups remains unclear.
  • •  
    Here, we examine the influence of taxonomy, site, host and time upon isotopic data from 135 fungal species collected at two forest sites in Sweden.
  • •  
    Mean δ13C and δ15N values differed significantly between ECM and saprotrophic fungi, with only a small degree of overlap even at the species level. Among ECM fungi, intraspecific variation in δ15N was low compared with interspecific and intergeneric variation. Significant variation due to site, year and host association was found.
  • •  
    At broad scales a number of factors clearly influence δ13C and δ15N values making interpretation problematic. We suggest that values are essentially site-specific within the two trophic groups, but that species-level patterns exist potentially reflecting ecophysiological attributes of species. The species is therefore highlighted as the taxonomic level at which most information may be obtained from fungal δ13C and δ15N data.