MULTIPLE-HOST FUNGI ARE THE MOST FREQUENT AND ABUNDANT ECTOMYCORRHIZAL TYPES IN A MIXED STAND OF DOUGLAS-FIR (PSEUDOTSUGA-MENZIESII) AND BISHOP PINE (PINUS-MURICATA)

The ectomycorrhizal fungal associations of Douglas fir (Pseudotsuga me nziesii D. Don) and bishop pine (Pinus muricata D. Don) were investiga ted in a mixed forest stand. We identified fungi directly from field-c ollected ectomycorrhizal (ECM) root tips using PCR-based methods. Sixt een species of fungi were found, of which twelve associated with both hosts. Rhizopogon parksii Smith was specific to Douglas fir. Three oth er species colonized only one of the hosts, but were too infrequent to draw conclusions about specificity. Seventy-four percent of the bioma ss of ECM root tips sampled in the stand were colonized by members of the Thelephoraceae and Russulaceae. All 12 species of fungi that assoc iated with both tree species did so within a 10 x 40 cm soil volume, s uggesting that individual fungal genotypes linked the putatively compe ting tree hosts.