Occurrence of ectomycorrhizas on ericaceous and coniferous seedlings grown in soils from the Oregon Coast Range.

Seedlings of Gaultheria shallon, Pseudotsuga menziesii, Rhododendron macrophyllum, and Tsuga heterophylla were grown together in the greenhouse in soils from three young managed Douglas fir forests in the Oregon Coast Range. The objective of the study was to evaluate the ability of ericaceous plants and overstory conifers to share compatible mycorrhizal fungi in order to assess potential mycorrhizal linkages. Ericoid mycorrhizal fungi were examined in Gaultheria and Rhododendron to assess their assumed presence in soils of the Pacific Northwestern region of the United States. Nine ectomycorrhizal types were recognized on the conifers and two on the Ericaceae. All nine ectomycorrhizal types occurred on both conifer species, and the two ectomycorrhizal types on the ericaceous hosts resembled types associated with the conifer hosts. Ectomycorrhizal fungi occurred on all the conifer seedlings and in trace amounts on 26% of the ericaceous seedlings in the study. Ericoid mycorrhiza developed on all the ericaceous seedlings.