Pacific Southwest

Title: Oaks belowground: mycorrhizas, truffles, and small mammals

Author: Frank, Jonathan; Barry, Seth; Madden, Joseph; Southworth, Darlene

Date: 2008

Source: In: Merenlender, Adina; McCreary, Douglas; Purcell, Kathryn L., tech. eds. 2008. Proceedings of the sixth California oak symposium: today's challenges, tomorrow's opportunities. Gen. Tech. Rep. PSW-GTR-217. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: p. 131-138

Station ID: GTR-PSW-217

Description: Oaks depend on hidden diversity belowground. Oregon white oaks (Quercus garryana) form ectomycorrhizas with more than 40 species of fungi at a 25-ha site. Several of the most common oak mycorrhizal fungi form hypogeous fruiting bodies or truffles in the upper layer of mineral soil. We collected 18 species of truffles associated with Oregon white oak. Truffles do not release spores directly into the air, but remain closed belowground. In conifer ecosystems, animals eat truffles and disperse the spores, providing mycorrhizal inoculum for new roots. We did a survey to determine the extent that small mammals eat hypogeous fungi and defecate the spores, thus dispersing mycorrhizal inoculum. We trapped small mammals near Oregon white oaks and examined fecal pellets for hypogeous fungal spores. Three species of rodents, California voles (Microtus californicus), deer mice (Peromyscus maniculatus), and harvest mice (Reithrodontomys megalotis), had 12 species of fungal spores in their fecal pellets. The most common spores in fecal pellets were those of Tuber candidum/T. quercicola, Hydnotryopsis setchellii, and Cazia flexiascus, all Ascomycota. Seedlings growing in the root zone of mature oaks have access to the mycorrhizal network of parent trees, but seedlings germinating outside the root zone may lack mycorrhizal sources. If the mycorrhizal community on saplings located away from mature oaks includes hypogeous fungi, then small mammals may be dispersing fungal spores into shrublands where saplings are located. We examined roots of oak saplings at distances up to 72 m from mature oaks and found mycorrhizas of Tuber candidum and Peziza infossa, both hypogeous species, suggesting that small mammals disperse spores for mycorrhizal inoculum. We propose a model that identifies the major players in oak ecosystems and hypothesize that regeneration of oak woodlands depends on the dispersal of mycorrhizal fungal spores by small mammals.

Keywords: hypogeous fungi, mycophagy saplings, mycorrhizal inoculum, Oregon white oak, Quercus garryana

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Citation

Frank, Jonathan; Barry, Seth; Madden, Joseph; Southworth, Darlene  2008.  Oaks belowground: mycorrhizas, truffles, and small mammals.   In: Merenlender, Adina; McCreary, Douglas; Purcell, Kathryn L., tech. eds. 2008. Proceedings of the sixth California oak symposium: today's challenges, tomorrow's opportunities. Gen. Tech. Rep. PSW-GTR-217. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: p. 131-138.