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Summary• Relative abundances of carbon and nitrogen isotopes in fungal sporocarps are useful in assessing mycorrhizal or saprotrophic status, and might provide insights into the evolutionary history of these traits.• Sporocarps of known mycorrhizal or saprotrophic genera were collected at Woods Creek, OR, USA, and isotopically compared with foliage, litter, soils and wood collected from the same site. Possible trophic strategies were then isotopically assessed in archived specimens of the Pezizales of known molecular phylogeny from the western United States.• At Woods Creek, mycorrhizal fungi were 3.5‰ ± 0.6‰ depleted in δ 13 C and 5.7‰ ± 0.4‰ enriched in δ 15 N compared with saprotrophic fungi. By contrast, fungi from four genera of uncertain mycorrhizal status ( Clavulina , Helvella , Otidia , and Ramaria ) were only 0.4‰ ± 0.4‰ enriched in δ 13 C and 1.2‰ ± 1.1‰ depleted in δ 15 N relative to mycorrhizal fungi.• In archived samples, the δ 13 C measurements appeared to be a better indicator of trophic strategy than δ 15 N measurements. The δ 13 C measurements suggested that mycorrhizal or saprotrophic status was conserved within families of the Pezizales (as determined by molecular phylogeny), with the Helvellaceae and Tuberaceae mycorrhizal and Discinaceae and Morchellaceae being largely saprotrophic.

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Post-fire Pezizales fruit commonly in many forest types after fire. The objectives of this study were to determine which Pezizales appeared as sporocarps after a prescribed fire in the Blue Mountains of eastern Oregon, and whether species of Pezizales formed mycorrhizas on ponderosa pine, whether or not they were detected from sporocarps. Forty-two sporocarp collections in five genera (Anthracobia, Morchella, Peziza, Scutellinia, Tricharina) of post-fire Pezizales produced ten restriction fragment length polymorphism (RFLP) types. We found no root tips colonized by species of post-fire Pezizales fruiting at our site. However, 15% (6/39) of the RFLP types obtained from mycorrhizal roots within 32 soil cores were ascomycetes. Phylogenetic analyses of the 18S nuclear ribosomal DNA gene indicated that four of the six RFLP types clustered with two genera of the Pezizales, Wilcoxina and Geopora. Subsequent analyses indicated that two of these mycobionts were probably Wilcoxina rehmii, one Geopora cooperi, and one Geopora sp. The identities of two types were not successfully determined with PCR-based methods. Results contribute knowledge about the above- and below-ground ascomycete community in a ponderosa pine forest after a low intensity fire.