Community Partner

East Columbia Neighborhood Association

Date of Award

4-2015

Document Type

Thesis

Degree Name

Master of Environmental Management (MEM)

Department

Environmental Science and Management

Physical Description

1 online resource (76 pages)

Subjects

Ludwigia -- Control, Wetlands -- Oregon -- Portland, Blue Heron Wetland Restoration Project, Introduced organisms -- Control, Great blue heron -- Ecology -- Oregon

DOI

10.15760/mem.46

Abstract

The Blue Heron Wetland Restoration Project (BHWRP) is an ongoing community driven effort to eradicate Ludwigia peploides ssp. montevidensis from a 3.5 acre ephemeral wetland in Portland, OR. Established in summer 2011 by the East Columbia Neighborhood Association (ECNA), the BHWRP consisted of an herbicide efficacy pilot study, widespread eradication effort, and establishment of a stewardship program. Ludwigia peploides ssp. montevidensis is an emerging threat to northwestern Oregon and the infestation within the Blue Heron Wetlands (BHW) represented one of the first known infestations of L. peploides ssp. montevidensis within the State of Oregon.

First observed within the BHW in 2004, L. peploides ssp. montevidensis rapidly colonized 2.4 acres of wetland habitat, reduced native floral diversity and minimized resources for wildlife. In fear of continued impact to wildlife and increased likelihood of wetland flooding, an integrated pest management strategy involving chemical and manual removal was implemented to eradicate L. peploides ssp. montevidensis from the BHW. The initial pilot study of 2011 tested glyphosate and triclopyr at relatively low concentrations within the wetlands. The herbicide mixes of 1% triclopyr and 0.75% glyphosate did not significantly reduce percent cover of L. peploides ssp. montevidensis. To improve results of L. peploides spp. motevidensis control, an increased concentration of 3% glyphosate was applied to the infestation on September 26, 2012 and August 8, 2013. The entire population was then hand pulled in 2013 and 2014.

Application of 3% glyphosate provided adequate control to populations of L. peploides ssp. montevidensis that were flowering at time of herbicide application. The fall application of 2012 reduced the density of L. peploides ssp. montevidensiswithin the central region of the wetlands where flowering occurred later in the season due to perennially saturated soils. Populations along the wetland perimeter that flowered and went dormant early in the season in response to drying soils returned at high densities in the coming year. The early August 2013 application and following hand removal events greatly reduced the range of L. peploides ssp. montevidensis within the BHW by a total of 76%. Within the BHW 3% glyphosate application was most effective as a systematic herbicide when applied as close to the time of flowering as possible and prevented further additions to the local seedbank. Hand removal insured surviving individuals were quickly removed and prevented plants from quickly increasing in biomass.

Outreach and education carried out by the BHWRP successfully identified and trained a core group of East Columbia residents to carryout long-term management of the L. peploides ssp. montevidensis infestation. The community led effort generated over $43,300.00 in volunteer labor and in-kind donations since project establishment. Average costs for chemical application, hand removal and wetland seeding was $3,906.59 per acre from 2012 to 2014. For financial support, the ECNA has secured funding for further hand removal events into 2016, in attempts to reach the initial goal of complete L. peploides spp. montevidensis eradication.

Description

A report submitted in partial fulfillment of the requirements for the degree of Master of Environmental Management

Persistent Identifier

https://archives.pdx.edu/ds/psu/27654

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