Community Partner

City of Gresham Oregon

Date of Award

2016

Document Type

Project

Degree Name

Master of Environmental Management (MEM)

Department

Environmental Science and Management

Language

English

Subjects

Western painted turtle -- Conservation -- Oregon -- Gresham, Western painted turtle -- Habitat -- Oregon -- Gresham, Western painted turtle -- Ecology -- Oregon -- Gresham, Wetland management

DOI

10.15760/mem.52

Abstract

Western painted turtles (Chrysemys picta belli) are found occupying Fairview Creek Headwaters (FCH) in Gresham, Oregon. This urban stream contains a large wetland with an adjacent butte, all managed by the City of Gresham. This management plan addresses the preferred habitat and population of turtles at the site. A habitat delineation of the site revealed specific locations where habitat improvements could take place as well as areas of already beneficial habitat. Two site plans were prepared showing areas of the site that could be enhanced with nesting habitat as well as additional aquatic habitat and basking habitat. A habitat study was conducted comparing the terrestrial and aquatic habitat in the northern part of the site and the southern portion of the site. The northern portion of the site, where the most turtles are seen, was found to have more bare ground, with a rush species and emergent vegetation as indicator species. The southern portion of the wetland was dominated by reed canary grass and birdsfoot trefoil. This area had high plant density with very little bare ground. The aquatic habitat in the southern portion of the wetland had less emergent vegetation and more floating vegetation.

Two management plans were created for Fairview Creek Headwaters northern section of the site. The first plan is a low impact plan, focusing on nesting habitat creation along the west edge of the north wetland. Amending the soil as well as maintaining low plant density and adequate bare ground should be the focus of habitat restoration with this plan. Plan 2 is a more comprehensive plan which includes improving aquatic habitat and basking habitat. It is recommended that additional wetland be created in the north end of FCH at the Gantenbein Dairy. There should be a variety of habitat to support all age classes of turtles. Reed canary grass and other non-native species should be managed throughout the site.

Seven years of mark-recapture data collected on the turtle was used to summarize findings on the turtle population. Two methods were used to estimate the population size, Lincoln Petersen and Schnabel methods. The Lincoln Peterson method estimated 119 individuals while the Schnabel estimate was 94 individuals. The sex ratio of the population was close to 1:1 with most years having slightly more females caught. A theoretical model of the population growth rate was built to detect which age class (hatchling, juvenile, small adult or large adult) is most important to the conservation of the species. Small and large adults were found to have the largest value for contributions to future generations. Furthermore, maintaining a high survivorship rate for these two age classes is essential for maintaining a positive population growth rate. Thus management should focus on habitat that benefits adult populations.

This study and its resultant management plan focuses on managing the population of painted turtles. It should be considered with other recommendations when making a comprehensive site plan.

Rights

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Comments

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

Persistent Identifier

https://archives.pdx.edu/ds/psu/27663

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