Rhizopogon olivaceotinctus increases its inoculum potential in heated soil independent of competitive release from other ectomycorrhizal fungi

ABSTRACT

Rhizopogon olivaceotinctus is a rarely collected ectomycorrhizal fungus that has been found primarily in California and southern Oregon. Prior work has shown that it (i) is common in soil spore banks associated with pine forests from these areas; (ii) is rare or absent on trees in undisturbed forests in these same areas; (iii) exhibits an increased abundance on pine seedlings following fire or experimental soil heating; and (iv) has spores that are more resistant to heat than those of several other ectomycorrhizal species tested to date. Here, we reject the hypothesis that the increased abundance of the species following soil heating is caused only by reduced competition with other ectomycorrnizal fungi and show instead that heating alone significantly increases the inoculum potential of its spores. We argue that this is likely caused by heat stimulation of the spores, a process that has precedent in saprotrophic fungi and plant seeds. This result, in combination with those of previous studies, shows that Rhizopogon olivaceotinctus is well adapted to fire.

KEYWORDS:

• Conservation
• seedling bioassays
• soil heating
• spore longevity

Additional information

Funding

Funding was provided by National Science Foundation (NSF) grant DEB 236096 to T.D.B. for the early collections and long-term storage of R. olivaeotinctus spores, and by Department of Energy grant DE-SC0016365 for current funding on post-fire fungi.