The Invasion Ecology of Ivy (Hedera spp.) in Portland's Forest Park

Invasive ivy (Hedera spp.) has extensive impacts on Pacific Northwest urban forests, many of which are not yet fully understood. In this study of Forest Park, Portland, Oregon, I evaluated several environmental variables obtained or derived from monitoring datasets at three spatial scales to determi...

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Main Author: Butler, Eric Paul
Format: Others
Published: PDXScholar 2019
Subjects:
Online Access:https://pdxscholar.library.pdx.edu/open_access_etds/5265
https://pdxscholar.library.pdx.edu/cgi/viewcontent.cgi?article=6337&context=open_access_etds
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spelling ndltd-pdx.edu-oai-pdxscholar.library.pdx.edu-open_access_etds-63372019-12-05T04:30:55Z The Invasion Ecology of Ivy (Hedera spp.) in Portland's Forest Park Butler, Eric Paul Invasive ivy (Hedera spp.) has extensive impacts on Pacific Northwest urban forests, many of which are not yet fully understood. In this study of Forest Park, Portland, Oregon, I evaluated several environmental variables obtained or derived from monitoring datasets at three spatial scales to determine the following: how ivy is spatially distributed; what factors are most correlated with ivy abundance; and how ivy abundance influences shrub community composition. I found that ivy is significantly clustered at all scales with multiple apparent epicenters along the park's urban periphery. Using NMDS ordination, I determined that ivy is a significant factor in the ecosystem in general and the shrub community in particular at all scales. Random Forest regression found different sets of important environmental predictors and shrub associations at each scale, but spatial relatedness and the abundance of Mahonia nervosa consistently emerged from predictor and shrub models, respectively. All this suggests that while ivy has complicated and often site- and scale-specific interactions with its environment, its clustered dispersal pattern may be at least as important as conditions in the ecosystems it invades. However, each of the monitoring datasets had significant limitations. Future research with refined data methods could be used to infer causal relationships, measure changes over time, and model ivy's ability to spread through the Forest Park landscape. 2019-08-26T07:00:00Z text application/pdf https://pdxscholar.library.pdx.edu/open_access_etds/5265 https://pdxscholar.library.pdx.edu/cgi/viewcontent.cgi?article=6337&context=open_access_etds Dissertations and Theses PDXScholar Environmental Sciences Environmental Studies
collection NDLTD
format Others
sources NDLTD
topic Environmental Sciences
Environmental Studies
spellingShingle Environmental Sciences
Environmental Studies
Butler, Eric Paul
The Invasion Ecology of Ivy (Hedera spp.) in Portland's Forest Park
description Invasive ivy (Hedera spp.) has extensive impacts on Pacific Northwest urban forests, many of which are not yet fully understood. In this study of Forest Park, Portland, Oregon, I evaluated several environmental variables obtained or derived from monitoring datasets at three spatial scales to determine the following: how ivy is spatially distributed; what factors are most correlated with ivy abundance; and how ivy abundance influences shrub community composition. I found that ivy is significantly clustered at all scales with multiple apparent epicenters along the park's urban periphery. Using NMDS ordination, I determined that ivy is a significant factor in the ecosystem in general and the shrub community in particular at all scales. Random Forest regression found different sets of important environmental predictors and shrub associations at each scale, but spatial relatedness and the abundance of Mahonia nervosa consistently emerged from predictor and shrub models, respectively. All this suggests that while ivy has complicated and often site- and scale-specific interactions with its environment, its clustered dispersal pattern may be at least as important as conditions in the ecosystems it invades. However, each of the monitoring datasets had significant limitations. Future research with refined data methods could be used to infer causal relationships, measure changes over time, and model ivy's ability to spread through the Forest Park landscape.
author Butler, Eric Paul
author_facet Butler, Eric Paul
author_sort Butler, Eric Paul
title The Invasion Ecology of Ivy (Hedera spp.) in Portland's Forest Park
title_short The Invasion Ecology of Ivy (Hedera spp.) in Portland's Forest Park
title_full The Invasion Ecology of Ivy (Hedera spp.) in Portland's Forest Park
title_fullStr The Invasion Ecology of Ivy (Hedera spp.) in Portland's Forest Park
title_full_unstemmed The Invasion Ecology of Ivy (Hedera spp.) in Portland's Forest Park
title_sort invasion ecology of ivy (hedera spp.) in portland's forest park
publisher PDXScholar
publishDate 2019
url https://pdxscholar.library.pdx.edu/open_access_etds/5265
https://pdxscholar.library.pdx.edu/cgi/viewcontent.cgi?article=6337&context=open_access_etds
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