Interactions between fire, fungi, bark beetles and lodgepole pines growing on the pumice plateau of central Oregon are described. Mountain pine beetle (Dendroctonus ponderosae) outbreaks occur mainly in forests that are 80-150 years old with a mean diameter of about 25 cm and weakened by a fungus, Phaeolus schweinitzii. The outbreak subsides after most of the large diameter trees are killed. The dead trees fuel subsequent fires which return nutrients to the soil, and a new age class begins. The surviving fire scarred trees are prone to infection by the slow fungal disease and about 100 years later these trees are then susceptible to bark beetle attack.

Decomposition rates of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) and red alder (Alnusrubra Bong.) wood (simulating logging residues) were determined in clear-cuttings at the Charles Lathrop Pack Experimental Forest of the University of Washington, which is located approximately 120 km south of Seattle, WA. The influence of diameter (1–2, 4–6, and 8–12 cm), vertical location (buried, on the soil surface, and elevated), season of logging (summer and winter), aspect (north and south), and wood temperature, moisture, and chemistry on wood decomposition rates were determined. Red alder wood decomposed faster (k = 0.035–0.517 year−1) than Douglas-fir wood (k = 0.006–0.205 year−1). In general, buried wood decomposed faster than surface wood, which decomposed faster than elevated wood. Small diameter wood generally decomposed faster than larger diameter wood. Aspect and season of logging had little influence on decomposition rates. Moisture and temperature were the dominant factors related to Douglas-fir wood decomposition, with initial chemistry playing a minor role. Initial wood chemistry, particularly soda solubility, was the dominant factor related to red alder wood decomposition.

Heterobasidion annosum produces conidia abundantly in culture; however, since conidiophores are rare in nature, conidia are usually considered to have little or no role in dispersal. Heterokaryotic mycelia of H. annosum produce both heterokaryotic and homokaryotic conidia, whereas basidiospores are homokaryotic. This difference was exploited to assess the relative prevalence of these spore types in western hemlock forests of western Washington state. Two out of 10 spores trapped on selective media were found to give rise to heterokaryotic mycelia identified by the presence of clamp connections. However, homokaryotic conidia could not be distinguished from basidiospores by this method, so two approaches were taken in the laboratory: examining conidia for number of nuclei and determining frequency of clamp connections in conidial cultures. Both methods indicated that from a single heterokaryotic mycelium, half of the conidial progeny were homokaryotic and the other half heterokaryotic. Thus the presence of two heterokaryotic conidia in 10 spores implied that conidia may make up a third to a half of the aerial spore load of H. annosum in western hemlock forests of western Washington state.

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