First Advisor

Michael T. Murphy

Term of Graduation

Summer 2004

Date of Publication

8-30-2004

Document Type

Thesis

Degree Name

Master of Science (M.S.) in Biology

Department

Biology

Language

English

Subjects

Cities and towns -- Study and teaching -- Oregon -- Portland Metropolitan Area, Conservation of natural resources -- Oregon -- Portland Metropolitan Area, Fragmented landscapes -- Oregon -- Portland Metropolitan Area, Amphibians -- Geographical distribution

Physical Description

1 online resource (v, 85 pages)

Abstract

Loss of biodiversity due to habitat fragmentation is worldwide problem. With growing human populations and increasing urbanization, it is a necessity to conduct studies on wildlife occurring in urban areas. Currently there is a deficit of research investigating woodland amphibians in urban environments. My objectives were to describe amphibian species richness and abundance in the Portland, Oregon, Metropolitan region, and relate patterns of variation to variables at three increasingly large spatial scales: 1) local microenvironmental (i.e. amphibian/substrate interaction), (2) macrohabitat/patch (i.e. park or greenspace), and 3) landscape (surrounding parks and greenspaces). Environmental variables occurring within the three spatial scales were tested against amphibian species richness and abundance measures using hierarchical partial regression. Ten species were detected in 17 parks and greenspaces. Amphibian distribution was highly nested with the fragmentation resistant species, Ensatina eschscholtzi, being most common. The relationships of urban amphibian species richness and relative abundance with environmental variables did not differ greatly from studies conducted in non-urban areas, although overall capture rate appeared to be much lower. Amphibian species richness was most influenced by macrohabitat/patch scale variables, and was highest at sites that were large, with a high density of high shrubs, low density of low shrubs, and where deciduous trees were dominant. Amphibian abundance varied with a different set of variables and responded most strongly to variation in the forest floor microenvironment. Abundance was highest at sites with cooler, moister soils, where bare soil was common, and cover of fine woody debris was low. Although, found to be insignificant in this study, landscape scale variables, with continuing research, may prove to play a critical role in local population persistence as it relates to a species ability to recolonize fragments and migrate to aquatic breeding sites. To maintain, or possibly increase, species richness and abundance in this area, efforts must be made to promote conditions within the macrohabitat/patch scale that support amphibians. These include preserving the current size of larger parks and greenspaces, increasing the complexity of the tall shrub understory, increasing species richness of the tree community, and maintaining the existing forest patches surrounding parks and greenspaces.

Rights

In Copyright. URI: http://rightsstatements.org/vocab/InC/1.0/

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Persistent Identifier

https://archives.pdx.edu/ds/psu/44641

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