Thesis Defence: Edge influences and effects of fragmentation on ectomycorrhizal fungal communities in and surrounding 27-year-old openings in an Engelmann spruce – Subalpine fir forest

Olivia Rianhard, supervised by Dr. Melanie Jones, will defend their thesis titled “Edge influences and effects of fragmentation on ectomycorrhizal fungal communities in and surrounding 27-year-old openings in an Engelmann spruce – Subalpine fir forest” in partial fulfillment of the requirements for the degree of Master of Science in Biology.

An abstract for Olivia Rianhard’s thesis is included below.

Defences are open to all members of the campus community as well as the general public. Registration is not required for in person defences.

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ABSTRACT

The response of ectomycorrhizal fungi (EMF) to high elevation logging is understudied. Furthermore, studies of EMF communities after logging often focus on openings without examining adjacent uncut forests. This study investigated EMF communities on Engelmann spruce and subalpine fir roots in and surrounding openings in interior British Columbia. Studies conducted at the same site three seasons after logging found a decline in EMF richness and diversity (i) on roots of cut trees as they died; and (ii) on roots of young seedlings planted at > 16 m into the openings as compared to seedlings planted at the forest edge. Additionally, EMF communities in the openings remained different from those in the forest 15 years after logging. I returned to the same site 27 years after logging; I hypothesized that forest influence on EMF richness and community composition would not have progressed further into the openings since last studied due to persisting environmental heterogeneity between the openings and forest. I also investigated the EMF community in the forest for the first time at this site. I conducted Pacific Bioscience (PacBio) sequencing on ectomycorrhizal root tips of spruce and fir collected from the forest and openings and found that the EMF community in the forest was still different than that in the openings. The forest community had 76.35% greater richness and an overall different composition than opening communities. While the forest was characterized by late-seral associated taxa such as Russula spp., opening communities were still characterized by ruderal taxa including Amphinema byssoides and Thelephora terrestris. I also found (i) no change in the extent of forest influence on EMF richness or community composition in the openings; and (ii) no threshold distance into the forest at which EMF richness or community composition changed. These findings indicate that though EMF succession in the openings is slow after logging, the EMF community in the surrounding uncut forest is not strongly affected by fragmentation. Therefore, similar forests may benefit from methods of timber harvest that increase forest influence by maximizing the edge to area ratio of openings or increasing environmental homogeneity between the forest and openings.