Throwing shade: Performance of native Pacific Northwest shrubs in shading out invasive reed canarygrass (Phalaris arundinacea)

Author: 
Date created: 
2021-04-19
Identifier: 
etd21360
Keywords: 
Reed canarygrass
Phalaris arundinacea
Spiraea douglasii
Invasive species management
Live staking
Planting density
Abstract: 

Reed canarygrass (Phalaris arundinacea) is an invasive grass common in wetlands and riparian areas throughout the Pacific Northwest. It is highly adaptable and resistant to many control methods, but is vulnerable to shading. We sought to control reed canarygrass by establishing desirable native shrubs to overtop and shade it. Plots were rototilled, mulched, live-staked, and monitored for 2-6 growing seasons. We tested 1) effective planting densities by live-staking hardhack (Spiraea douglasii) at 50, 30, and 15 cm spacing, 2) relative species performance by planting hardhack, red-osier dogwood (Cornus sericea), and thimbleberry (Rubus parviflorus), all at 30 cm densities, and 3) alternative site preparation methods by using cardboard mulch or excavating the top 20 cm of topsoil. Higher planting density significantly reduced reed canarygrass cover and biomass. Both hardhack and red-osier dogwood successfully suppressed reed canarygrass, though thimbleberry did not. No significant differences between site preparation methods were observed.

Document type: 
Graduating extended essay / Research project
Rights: 
This thesis may be printed or downloaded for non-commercial research and scholarly purposes. Copyright remains with the author.
File(s): 
Supervisor(s): 
Hélène Marcoux
Department: 
Environment: Ecological Restoration
Thesis type: 
(Project) M.Sc.
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