First Advisor

Leslie Hammer

Term of Graduation

Summer 2021

Date of Publication


Document Type


Degree Name

Doctor of Philosophy (Ph.D.) in Applied Psychology







Physical Description

1 online resource (xii, 164 pages)


Plant-microbe associations and interactions provide critical context to studies in both community and ecosystem ecology, especially in systems that are relatively new and still undergoing early successional processes. Microbes can colonize the surfaces and interiors of all plant tissues, and these assemblages vary in composition both spatially and temporally, even within the same plant. Endophytes are bacteria or fungi that spend most of their lifecycles living within plant tissues asymptomatically--typically, "endophyte" refers specifically to aboveground tissues such as leaves and stems, and therefore may have direct influences on defenses against herbivory, pathogen or pest tolerance, and even afterlife effects on litter decomposition. Similarly, root-associated symbionts such as mycorrhizae, Frankia, and Rhizobia are especially crucial to host plants' abilities to survive in nutrient-poor environments, such as those found during primary succession. Within these new, harsh systems, advantageous microbial symbioses can be critical for plant establishment and survival, as is the case for pioneer plants with nitrogen-fixing symbionts--e.g. alder, an important native tree species in the Pacific Northwest that is nodulated by Frankia bacteria. Here, we chose red and Sitka alder (Alnus rubra and A. viridis ssp. sinuata, respectively) as plant systems to model multi-scale interactions and associations in the primary successional environment of the Pumice Plain of Mount St. Helens. In Chapter 2, we first surveyed culturable fungal endophytes within red alder to gain a baseline understanding of the structure and composition of endophytes in a closely related species within more established habitats. We found significant differences in community composition among sample sites that may have been driven by differences in air quality, and also verified taxa common to red alder. We were able to use these results as a comparison for Chapter 3, where we surveyed culturable fungal endophytes of six woody species on the Pumice Plain of Mount St. Helens. We found much lower frequencies of isolation (


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