Natural 13C abundance reveals trophic status of fungi and host-origin of carbon in mycorrhizal fungi in mixed forests

Fungi play crucial roles in the biogeochemistry of terrestrial ecosystems, most notably as saprophytes decomposing organic matter and as mycorrhizal fungi enhancing plant nutrient uptake. However, a recurrent problem in fungal ecology is to establish the trophic status of species in the field. Our i...

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Published inProceedings of the National Academy of Sciences - PNAS Vol. 96; no. 15; pp. 8534 - 8539
Main Authors Hogberg, P, Plamboeck, A.H, Taylor, A.F.S, Fransson, P.M.A
Format Journal Article
LanguageEnglish
Published Washington National Academy of Sciences of the United States of America 20.07.1999
National Acad Sciences
National Academy of Sciences
The National Academy of Sciences
Subjects
Agaricales
biochemical pathways
Biological Sciences
Carbon
chemical composition
Conifers
Ecology
ectomycorrhizae
forest trees
fruit bodies
fungal anatomy
Fungi
Isotopes
Karsts
mixed forests
Mycology
Mycorrhizal fungi
Overstory
Plants
saprophytes
soil fungi
stable isotopes
Symbiosis
Trees
Understory
Sweden
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Summary:Fungi play crucial roles in the biogeochemistry of terrestrial ecosystems, most notably as saprophytes decomposing organic matter and as mycorrhizal fungi enhancing plant nutrient uptake. However, a recurrent problem in fungal ecology is to establish the trophic status of species in the field. Our interpretations and conclusions are too often based on extrapolations from laboratory microcosm experiments or on anecdotal field evidence. Here, we used natural variations in stable carbon isotope ratios (delta13C) as an approach to distinguish between fungal decomposers and symbiotic mycorrhizal fungal species in the rich sporocarp flora (our sample contains 135 species) of temperate forests. We also demonstrated that host-specific mycorrhizal fungi that receive C from overstorey or understorey tree species differ in their delta13C. The many promiscuous mycorrhizal fungi, associated with and connecting several tree hosts, were calculated to receive 57-100% of their C from overstorey trees. Thus, overstorey trees also support, partly or wholly, the nutrient-absorbing mycelia of their alleged competitors, the understorey trees.
Bibliography:To whom reprint requests should be addressed. e-mail: Peter.Hogberg@sek.slu.se.
Communicated by Harold Alfred Mooney, Stanford University, Stanford, CA
ISSN:0027-8424
1091-6490