Landscape scale environmental DNA sampling for a rare fungal species: Implications for forest management

Surveys for conks on noble fir trees (Abies procera) have suggested that the fungus Bridgeoporus nobilissimus is rare in the Pacific Northwest. As a result, the fungus has been managed for several decades as a rare old-growth forest species on federal lands. We undertook a randomized landscape sampling approach to determine the distribution of B. nobilissimus in an 88,200 ha study area in the northern Oregon Cascade mountains. We used molecular tools to test for the presence of fungal DNA in wood cores from living and dead trees. We sampled 58 plots from a system of permanent forest plots. Of these, 25 (43%) produced positive detections though no plots had visible B. nobilissimus conks. We estimate that B. nobilissimus occurs throughout 41% (+/- 11%) of the northern Oregon Cascade mountains. Bridgeoporus nobilissimus presence was not related with land use status (reserve vs. non-reserve) or stand age. The use of molecular DNA technology with environmental samples changed our perception from a rare species present at a few sites, to a widely distributed species that produces few fruit bodies.

Automated summary

Surveys indicated that the fungus Bridgeoporus nobilissimus is rare in the Pacific Northwest but widely distributed in approximately 41% of the northern Oregon Cascade mountains, regardless of land use status or stand age. The use of molecular DNA technology altered the perception of the species' distribution from rare to widespread, despite producing few fruit bodies.