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Date Permissions Signed


Date of Award


Document Type

Masters Thesis

Degree Name

Master of Science (MS)


Environmental Sciences

First Advisor

Bunn, Rebecca

Second Advisor

Helfield, James M.

Third Advisor

Rhoades, Fred M. (Fred Mast)


In September 2011, the removal of two dams on the Elwha River was initiated as part of the largest dam removal project in history. The drainage of Lakes Mills and Aldwell exposed 300 hectares of reservoir bottom. Reestablishment of native vegetation in the lakebeds is critical for the restoration of ecosystem function, but the reservoir sediment composition may inhibit revegetation due to poor water holding capacity. It is known that mycorrhizae can ameliorate the effects of drought stress for host plants but little is known about their availability in the Lake Mills basin. In my project, I first assessed the abundance of arbuscular mycorrhizal fungi (AMF) and ectomycorrhizal fungi (EMF) in the Lake Mills basin. I also conducted a greenhouse bioassay in which I grew willows in potting soil and Elwha silt with different treatments of mycorrhizal inoculum. I then drought stressed the willows in order to replicate the expected summertime conditions in the Lake Mills basin. There are some viable AMF and EMF in Lake Mills, but with higher abundance near the forest and high variability in the soil. There was no effect of mycorrhizal inoculum on growth of willows and no effect of the Elwha silt on formation of AM and EM. My results suggest that willows are not dependent on mycorrhizal fungi and can establish independent of mycorrhizal propagules. Mycorrhizae can then form with willows when propagules are available, boost the mycorrhizal infectivity of the soil and then subsequently facilitate the establishment of other plant species.





Western Washington University

OCLC Number


Subject – LCSH

Restoration ecology--Washington (State)--Elwha River Valley; Lake sediments--Washington (State)--Elwha River Valley; Willows--Effect of drought on--Washington (State)--Elwha River Valley; Willows--Ecology--Washington (State)--Elwha River Valley; Vesicular-arbuscular mycorrhizas--Ecology--Washington (State)--Elwha River Valley; Ectomycorrhizal fungi--Ecology--Washington (State)--Elwha River Valley; Dam retirement--Environmental aspects--Washington (State)--Elwha Dam; Dam retirement--Environmental aspects--Washington (State)--Upper Elwha Dam

Geographic Coverage

Elwha River Valley (Wash.); Elwha Dam (Wash.); Upper Elwha Dam (Wash.)




masters theses




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