The natural abundance of C-13 and N-15 was measured in basidiocarps of at least 115 species in 88 genera of ectomycorrhizal, wood-decomposing and litter-decomposing fungi from Japan and Malaysia. The natural abundance of C-13 and N-15 was also measured in leaves, litter, soil and wood from three different sites. N-15 and C-13 were enriched in ectomycorrhizal and wood-decomposing fungi, respectively, relative to their substrates. Ectomycorrhizal and wood-decomposing fungi could be distinguished on the basis of their delta(13)C and delta(15)N signatures. Although there was high variability in the isotopic composition of fungi, the following isotope-enrichment factors (epsilon, mean +/- SD) of the fungi relative to substrates were observed:
epsilon(ectomycorrhizal fungi/litter) = 6.1 +/- 0.4 parts per thousand N-15
epsilon(ectomycorrhizal fungi/wood) = 1.4 +/- 0.8 parts per thousand C-13
epsilon(wood decomposing fung/wood) = -0.6 +/- 0.7 parts per thousand N-15
epsilon(wood decomposing fungi/wood) = 3.5 +/- 0.9 parts per thousand, C-13
The basis of isotope fractionation in C metabolism from mood to wood-decomposing fungus is discussed.