Habitat and host associations of Craterellus tubaeformis in northwestern Oregon.

Knowledge of the habitat and host associations of Craterellus tubaeformis (winter chanterelle) is the key to understanding the ecological characteristics needed for its conservation. In this study, a survey of forest types in northwestern Oregon for mycorrhizal associates is performed and the hypotheses that stand age and the volume of well-decayed, coarse, woody debris (CWD) are significant to the standing crop biomass and the probability of C. tubaeformis occurrence are tested. Host associations were identified with polymerase chain reaction (PCR) amplification and restriction fragment-length polymorphism (RFLP) typing. Habitat associations were tested by measurements on 64 plots in the Coast and Cascade Ranges of northwestern Oregon. Data analysis found that stand age and well-decayed, coarse, woody debris were related significantly to the probability of C. tubaeformis occurrence but not to standing crop biomass. Results indicated the volume of well-decayed CWD is particularly important to the probability of C. tubaeformis occurrence in stands less than 100 yr of age. Well-decayed CWD was the substratum for 88% of C. tubaeformis sporocarps across all stands, despite the fact that ground area coverage of CWD ranged only from 3 to 26%. Slope, elevation and aspect were not related to the probability of C. tubaeformis occurrence or standing crop biomass. The occurrence of C. tubaeformis in northwestern Oregon is highly correlated to the presence of western hemlock (Tsuga heterophylla), and their mycorrhizal association was confirmed. Craterellus tubaeformis also can form mycorrhizae with Douglasfir (Pseudotsuga menziesii) and Sitka spruce (Picea sitchensis) but is encountered only rarely in stands without a hemlock component. In northwestern Oregon, the presence of Hydnum spp. in a stand is a good indicator of the presence of C. tubaeformis. Differences in genetic sequences between C. tubaeformis populations in western North America, eastern North America and Europe suggest the likelihood of several distinct species.