Diversity and host specificity of ectomycorrhizal fungi retrieved from three adjacent forest sites by five host species

Seedlings of Abies grandis (Dougl.) Lindl. (grand fir), Lithocarpus densifl ora (Hook. & Arn.) Rehd. (tanoak), Pinus ponderosa Dougl. ex Laws. (pondero sa pine), Pseudotsuga menziesii (Mirb.) Franco (Douglas-fir), and Arbutus m enziesii Pursh (madrone) were planted in mixture and monoculture in soil co llected from three adjacent forest sites in southwestern Oregon (a clearcut area, a 25-year-old Douglas-fir plantation, and a mature 90- to 160-year-o ld Douglas-fir - pine forest) to determine the effect of host tree diversit y on retrieval of ectomycorrhizal morphotypes. In this greenhouse bioassay, 18 morphotypes of mycorrhizae were recognized overall from all soils with a total of 55 host-fungus combinations: 14 types with ponderosa pine, 14 wi th Douglas-fir, 10 with tanoak, 10 with grand fir, and 7 for madrone. Four genus-specific morphotypes were retrieved (three on ponderosa pine and one on Douglas-fir), even in mixture situations, demonstrating selectivity of s ome fungal propagules by their respective host. Five types were detected on all hosts, but not necessarily in soils from all sites. The remaining nine types were associated with two, three, or four hosts, which indicates a wi de potential for interspecific hyphal linkages between trees. More morphoty pes were retrieved from the monoculture treatments compared with the mixtur e treatments, although the differences were not significant. Several exampl es of acropetal replacement of one fungus by another (interpreted as succes sion) were recorded on all hosts during the course of the experiment. These results illustrate the importance of different host species in maintaining ectomycorrhizal fungus diversity, especially fungi with restricted host ra nge, and the strong potential for fungal linkages between trees in forest e cosystems.