Document Type

Thesis

Date of Degree Completion

Spring 2023

Degree Name

Master of Science (MS)

Department

Biology

Committee Chair

Jim Johnson

Second Committee Member

Mary Poulson

Third Committee Member

Eric Graham

Abstract

Ectomycorrhizal fungi are integral parts of natural ecological systems that provide access to nutrients that would otherwise be unavailable by forming symbiotic relationships with plants. Relationships with ectomycorrhizal fungi are known to improve plant growth rate, increase plant resistance to pathogens, and improve survival. Current revegetation practices often ignore this relationship between fungi and plants. During the revegetation of the Interstate 90 Keechelus Lake wildlife overcrossing (Easton, WA), soil from forest sites adjacent to the restoration area were collected and used to inoculate a set of experimental plots to determine whether ectomycorrhizal fungi would become established in the plots and if presence of ectomycorrhizal fungi would enhance of survivorship of plants used for revegetation. Each plot was centered on a plant known to have ectomycorrhizal associations. We assessed the establishment of ectomycorrhizal communities by comparing 125 soil DNA samples from the experimental and control plots to the adjacent forested areas using Illumina MiSeq amplicon sequencing of the internal transcribed spacer 1 region. Fungal communities in the overcrossing post-revegetation were compared to a previous study that examined the nurseries and overcrossing soil from before revegetation. We monitored plant survival and soil temperature/moisture within the control and experimental plots over a two-year period after revegetation. Ectomycorrhizal composition found in pre- and post-inoculation sites were notably different, as were those found in the nurseries and post-inoculation soils. Fungal communities in the inoculated and control sites were not found to be different. Despite a higher diversity and abundance of ectomycorrhizal fungi present post-inoculation, we found that plant survival was not significantly impacted by inoculation. 61.5% of plants survived to the end of the study with a 24.8% decrease in survival between June 2nd 2022 and October 23rd 2022. This time period had higher soil temperatures than the previous year and drought conditions.

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