First Advisor

Mark Sytsma

Date of Publication

2009

Document Type

Thesis

Degree Name

Master of Science (M.S.) in Environmental Science and Resources

Department

Environmental Science and Management

Language

English

Subjects

Purple loosestrife -- Biological control -- Columbia River Estuary (Or. and Wash.), Galerucella -- Columbia River Estuary (Or. and Wash.)

DOI

10.15760/etd.5464

Physical Description

1 online resource (72 p.)

Abstract

Galerucella pusilla and G. calmariensis have provided successful biological control of purple loosestrife (Lythrum salicaria L.) in non-tidal areas but only marginal control in areas of tidal influence. While a previous study identified mechanical scour by tidal waters as the main cause of establishment failure, purple loosestrife stem density explained more than 80% of the variability in presence and absence of Galerucella at my study sites in the Columbia River Estuary. A logistic regression model using purple loosestrife stem density, elevation, and their interaction as predictors accurately predicted 92.5% of Galerucella presence or absence observations of a test data set (n= 201). Field data also identified a critical threshold of approximately 32 purple loosestrife stems/m2 , above which Galerucella were present 100% of the time at the release sites.

Rights

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Comments

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Persistent Identifier

http://archives.pdx.edu/ds/psu/20309

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