PERSISTENCE OF BASIDIOSPORES AND SCLEROTIA OF ECTOMYCORRHIZAL FUNGI AND MORCHELLA IN SOIL

Locations of epigeous basidiocarps of five common ectomycorrhizal fungi with substantial spore deposits beneath them and of two hypogeous species were marked in the fall. Subsamples of the litter and mineral soil at 0- to 3- and 3- to 6-cm depths were subsequently taken with a soil corer from locations marked for epigeous basidiocarps, and extracted in the fall and again following snowmelt with a procedure developed to enumerate propagules of ectomycorrhizal fungi from the soil. Spores of most epigeous species were plentiful in the litter layer in the fall but were much less abundant in the spring. Spores of Suillus brevipes, Suillus tomentosus and Lactarius scrobiculatus were still present at the 0- to 3-cm depth in the spring. No spores of any of the epigeous fungi were found at the 3- to 6-cm depth in the spring. Subsamples of mineral soil were also taken in the spring at locations marked for the hypogeous fungi. Spores of both Rhizopogon subcaerulescens and Rhizopogon rubescens were present in high numbers in the lowermost soil fractions after snowmelt. In a second study sclerotia of two species of fungi were extracted from soil in a burned area and a nearby unburned forest for 2 years following fire. Sclerotia of Cenococcum geophilum and a species of Morchella were more numerous in the burn than in the unburned forest in both years. Both basidiospores and sclerotia persisted in the soil for at least 2 years. Basidiospores of hypogeous fungi appear to persist in the soil for longer periods than those of epigeous fungi due to in situ dispersion deeper into the soil profile. Although maximum longevity of spores in the soil has not been determined, observed differential persistence of spores from epigeous and hypogeous ectomycorrhizal fungi could play a role in soil mycorrhiza-forming potential and population dynamics of ectomycorrhizal fungi.