Sponsor
Portland State University. School of Earth, Environment, and Society
First Advisor
Heejun Chang
Term of Graduation
Summer 2026
Date of Publication
8-18-2026
Document Type
Dissertation
Degree Name
Doctor of Philosophy (Ph.D.) in Earth, Environment, & Society
Department
Earth, Environment, & Society
Language
English
Subjects
Machine learning, Multivariate analysis, Spatial scale, Thermal regime, Water temperature, Wetlands
Physical Description
1 online resource (xi, 190 pages)
Abstract
Water temperature strongly influences aquatic ecosystem processes and the distribution of temperature-sensitive organisms. This dissertation advances understanding of wetland thermal regimes by synthesizing knowledge, investigating controls on wetland water temperature across spatial scales, and developing predictive modeling approaches for wetland temperature dynamics in the Pacific Northwest.
Chapter One reviews published literature examining water temperature controls in freshwater wetlands. The synthesis identifies landscape drivers including topography, geology, and land cover, alongside site-level factors such as wetland size, vegetation structure, hydroperiod, and groundwater inputs. The review evaluates how wetland condition assessments used in monitoring and management conceptualize thermal influences and highlights the need for refined typologies that integrate landscape and site-level controls.
Chapter Two examines how wetlands regulate water temperature magnitude and variability using field measurements from seven palustrine wetlands in Oregon's Cascades. Multivariate analyses reveal that climatic and elevational gradients shape overall temperature magnitude, while vegetation structure and hydrologic conditions influence day-to-day thermal variability. Comparisons with indicators from the Oregon Rapid Wetland Assessment Protocol further assess how well rapid wetland condition assessments capture thermoregulation.
Chapter Three evaluates statistical and machine-learning approaches for predicting daily wetland water temperatures. Model complexity resulted in higher performance, particularly in larger wetlands and when hydrologic measurements were included. Predictor importance highlighted wetland size, elevation, and solar exposure, while locally calibrated models improved predictive accuracy and revealed strong site-specific hydrologic controls.
Together, these findings demonstrate that wetland thermal regimes emerge from interactions among climatic, landscape, and site-level hydrologic controls, the more dynamic of which are not fully captured by existing wetland classifications or condition assessments. Operating across spatiotemporal scales, with broad-scale factors setting a thermal magnitude baseline, and local wetland characteristics influencing thermal variability, sensitivity, and departures from regional patterns.
Rights
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Persistent Identifier
https://archives.pdx.edu/ds/psu/45126
Recommended Citation
Krochta, Michael Benjamin, "Controls, Variability, and Prediction of Water Temperature Dynamics in Freshwater Wetlands" (2026). Dissertations and Theses. Paper 7196.