SOIL FUNGAL HYPHAL DYNAMICS AND SEASONAL HYPOGEOUS SPOROCARP PRODUCTION IN WESTERN OREGON DOUGLAS-FIR FORESTS (MYCORRHIZAE, ECOSYSTEM, MYCOPHAGY, SPORE DISPERSAL, BIOMASS)

Total length and biomass of fungal mycelium in the soil of a young Douglas-fir stand in the central Oregon Coast Range were estimated over 27 months with the agar-film technique. In a second study, phenology and taxonomy of hypogenous (belowground) sporocarps were studied over 32 months in a nearby, young Douglas-fir stand. Mycelial mass was at maximum in fall and spring and significantly lower in summer. Melanized hyphae dominated those with other colors, averaging 66 percent of monthly litter and 73.7 percent of soil hyphal weight. The mycorrhizal fungus Cenococcum geophilum Fr. has significantly larger average diameter than other hyphae and contributed from 1.2 to 64.8 percent of monthly hyphal volume. Multiple regression analyses with temperature, moisture, and litterfall produced no adequate predictive equations for monthly fungal biomass.; Nine ascomycete and 21 basidiomycete species were collected during the sporocarp phenology study. Production was dominated by a small number of species; taxa accounting for 5 percent or more of total annual dry weight were Gautieria monticola, Hysterangium crassum, H. separabile, and Melanogaster ambiguus. Annual productivity estimates ranged from 5,815 to 6,648 sporocarps ha('-1) and 2.0 to 3.2 kg dry weight ha('-1). Peaks in production generally resulted from a large contribution by one or two species. Pronounced seasonal trends in production were not evident, but sporocarp number and biomass were greater in spring than fall. Annual fruiting period for individual species ranged from only three months for some species to as much as 11 months for others.; Fungi produce the greatest biomass of all soil organisms in temperate coniferous forests. Mycelium and sporocarps are nutrient and energy sources for decomposers and consumers. In addition, they are essential as mycorrhizal symbionts to the growth of most forest-dwelling vascular plants. Consequently, ecosystem studies dealing with nutrient allocation, turnover rates, or mycophagy by soil fauna or vertebrate populations need to account for the contributions of fungal hyphae, sporocarps, and/or mycorrhizae. Because fungal biomass typically fluctuates widely over short periods, frequent sampling and long term study are needed to assess the importance of fungi in ecosystems.