Individual mushrooms and cup-fungi produce millions to billions of spores, which serve 

 as mechanisms for long-distance spread and maintenance of genetic diversity in the 

 population. Usually spores are discharged and spread through the air, often for long 

 distances, when temperature and humidity conditions are favorable. Although only a 

 small proportion of spores germinate and colonize suitable substrates, long-distance 

 spread is achieved, and different genetic material is continuously added to the popula- 

 tion. Spores are produced from the hymenal surface of mature mushrooms. The 

 hymenal surfaces are the gills or pores, usually on the underside of these fruiting bod- 

 ies. On cup-fungi, such as morels, the spore-bearing surface lines the pits of the outer 

 surface of the cap, known as the pileus. Timing of spore production differs by species 

 of fungus. Spores are not produced in significant amounts until the mushroom is ma- 

 ture. For the Basidiomycetes, maturity is indicated after the cap expands, separating 

 from the stem (stipe) and exposing the spore-bearing surface. Morels produce spores 

 1 5 to 30 days after the fruiting body is first formed; the spores line the exposed surface 

 of the pits and grooves (Ower 1982, Weber 1995). Truffles produce spores inside the 

 fruiting body itself. Various animals eat the mature truffle and the spores then travel 

 through their digestive tract and are dispersed in the fecal pellets. 



Mushroom fruiting differs among species. Some mushroom species are easily propa- 

 gated and can be grown on farms. Some are more difficult to raise but are cultivated 

 by hobbyists and small-scale entrepreneurs who use intensive and exacting tech- 

 niques. Other species have very exacting requirements, seldom fruit, and are consid- 

 ered rare, although the vegetative fungus (mycelium) may be common. Most fungi 

 usually have fairly exacting requirements of temperature and moisture for the forma- 

 tion of mushrooms. It is widely believed and frequently hypothesized that weather of 

 previous months (that is, abundant moisture and accumulated degree days) will 

 strongly influence fruiting. Most mushrooms have their specific season, usually spring 

 or fall when moist conditions prevail. When conditions are favorable, mushroom pro- 

 duction literally can occur overnight. Site or substrate conditions also are critical for 

 mushroom formation. Some fungi fruit after fires or ground disturbance, others will be 

 produced only on a few species of trees, and others may require undisturbed condi- 

 tions. As sites experience constant change in vegetation as plant succession occurs, 

 mushroom production also will change. 



Morels, and some other fungi, produce sclerotia, which are dormant fungal structures that 

 carry the fungus through periods of poor growing conditions by storing food reserves used 

 when conditions for fruiting occur. Sclerotia require a disturbance such as high heat (fire) 

 for activation and cause the fungus to become active, grow, and fruit. There is a clear re- 

 lation between fire and subsequent abundant fruiting of morels. In some cases, abundant 

 mushroom production is restricted to the following year; in other cases mushrooms are 

 Morels produced for 2 or 3 years. Fruiting is observed in burned harvest units as well as sites 



burned by wildfires. The relation between burn intensity levels and subsequent fruiting is 

 currently being studied in the Blue Mountains.'' 



*Pil2, D.; Weber, N; Carter, C; Parks, C. 1995 Investi- 

 gations of morel mushroom productivity, ecology, taxon- 

 omy, and population genetics follow/ing wildfires and tree 

 mortality in Pacific Northwest forests: a study plan On file 

 with: Catherine Parks. 



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