Isotopic and compositional evidence for carbon and nitrogen dynamics during wood decomposition by saprotrophic fungi


Sporocarps of wood decay fungi contain functional information about how different taxa partition carbon and nitrogen resources from wood. We combined carbon and nitrogen concentrations, isotopic ratios (13C:12C, 15N:14N, and 14C:12C, expressed as δ13C, δ15N, and Δ14C values), and compositional patterns in wood, cellulose, and sporocarps to investigate functional and isotopic differences in six taxa of decay fungi during log decomposition. Radiocarbon (Δ14C) measurements separated fungi into heartwood colonizers (Fomitopsis and Hericium, ~30+-year-old carbon) and sapwood colonizers (Mycena, Hypholoma, and Trametes, 1-12-year-old carbon). Decay modes influenced δ13C, with Hericium, a selective white-rot fungus, higher in δ13C than nonselective white-rot fungi because Hericium preferentially assimilated 13C-enriched hemicellulose rather than cellulose. Fungal δ15N was lower in heartwood colonizers than in sapwood colonizers, presumably reflecting greater N turnover and 15N enrichment in sapwood than in heartwood. Sporocarp δ15N correlated with sporocarp %N and with the relative proportion of protein in N-containing pyrolysis products because fungal protein was 4–5‰ higher in δ15N (and 3–4‰ higher in δ13C) than non-protein. From these measurements, we improved the quantitative and conceptual understanding of how sources, composition and metabolic processing determined isotopic composition of fungi.


Soil Biogeochemistry and Microbial Ecology

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Fungal Ecology



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