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Date Permissions Signed
Date of Award
Master of Science (MS)
Helfield, James M.
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
Elwha River Valley (Wash.); Elwha Dam (Wash.); Upper Elwha Dam (Wash.)
Copying of this thesis in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this thesis for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.
Cortese, Andrew, "Mycorrhizal availability in the basin of Lake Mills and influence on colonization and growth of Salix scouleriana under drought stress" (2014). WWU Graduate School Collection. 340.