Life Sciences Commons^™

Post-Fire Tree Mortality And Regeneration Patterns As Proxies Of Conifer Forest Resilience, Sebastian Upton Busby

Dissertations and Theses

Shifting wildfire patterns and climate conditions, magnified by anthropogenic climate change, are threatening the resilience of conifer forests in North America and more specifically, the western US. If native conifer species are functionally maladapted to novel fire patterns and post-fire climate conditions, large-scale shifts in conifer forest structure, composition, and extent may occur as warming intensifies. Forest resilience in the context of fire and climate can be understood and quantified by the survival of trees through fire events and success of trees to regenerate post-fire and maintain population levels. In this dissertation, I use field observations and remote sensing to …

Mitonuclear Mismatch Is Associated With Increased Male Frequency, Outcrossing, And Male Sperm Size In Experimentally-Evolved C. Elegans, Brent William Bever

Dissertations and Theses

We provide the first controlled study of how male frequencies and rates of outcrossing evolve in response to mitonuclear mismatch by allowing replicate lineages of C. elegans nematodes containing either mitochondrial or nuclear mutations of electron transport chain (ETC) genes to evolve under three sexual systems: facultatively outcrossing (wildtype), obligately selfing, and obligately outcrossing. In partial support of a tenet of the mitonuclear sex hypothesis, which predicts that outcrossing will be favored in cases of mitonuclear mismatch, we found evolution of increased male frequency in at least one replicate line of all four ETC mutant backgrounds tested--nuclear isp-1, mitochondrial …

Microbes On The Mountain: Plant-Microbe Associations And Interactions On Mount St. Helens, Emily Rose Wolfe

Dissertations and Theses

Plant-microbe associations and interactions provide critical context to studies in both community and ecosystem ecology, especially in systems that are relatively new and still undergoing early successional processes. Microbes can colonize the surfaces and interiors of all plant tissues, and these assemblages vary in composition both spatially and temporally, even within the same plant. Endophytes are bacteria or fungi that spend most of their lifecycles living within plant tissues asymptomatically--typically, "endophyte" refers specifically to aboveground tissues such as leaves and stems, and therefore may have direct influences on defenses against herbivory, pathogen or pest tolerance, and even afterlife effects on …

Exploring Linkages Between Landscape Patterns And Freshwater And Estuarine Bivalves In The Coast Range Of Oregon, Kaegan Michael Scully-Engelmeyer

Dissertations and Theses

Spatial configurations of landscape variables (biotic, abiotic, and socio-ecological) affect and are affected by ecological processes and species in watersheds. This dissertation explores relationships among landscape patterns, ecosystem processes and bivalve species dynamics in coastal watersheds in Oregon, USA. I approached this broad topic through two primary avenues of research: investigating cross-ecosystem threats from pesticide use in forestland management to downstream aquatic environments, and the landscape ecology of an at-risk freshwater mussel species.

Terrestrial land use activities present cross-ecosystem threats to riverine and marine species and processes. Specifically, pesticide runoff can disrupt hormonal, reproductive, and developmental processes in aquatic organisms, …

Beaver Reintroduction And Its Potential As An Ecological Conservation Measure For At-Risk Amphibian Species In The Pacific Northwest, Danielle Schwantes

University Honors Theses

Amphibian decline is a major concern in the Pacific Northwest (PNW), with many amphibian species listed as sensitive, threatened or endangered throughout the region. Some of the predicted main causes of amphibian decline are climate change and loss of habitat. The reintroduction of beavers into ecoregions of the PNW could be an important step in the conservation of this region’s amphibians, due to the beaver’s ability to engineer and structurally manipulate forest ecosystems. Beavers are able to restore wetland quality, productivity and biodiversity, creating vital amphibian habitat. This work explored the linkage between beaver presence and wetland hydrology, geomorphology, landscape …

Human Impact On Pacific Harbor Seals In Urban Southern Puget Sound, Washington, Vicky Gomez

University Honors Theses

This research proposal aims to highlight the quantitative and qualitative impact of human disturbances Pacific Harbor Seals (Phocca vitulina) are experiencing in urban southern Puget Sound, Washington and how the data collected can educate the community to protect and conserve a healthy population of Harbor Seals. Urbanization and areas utilized by harbor seals within urban settings prompted data collection from four nearby sites: site A, Carylon Beach, includes pedestrian and boat disturbances, site B, Tacoma Tidal Flats, only experience boat disturbances, site C, West Bay Marina, experiences motorized and non-motorized boat disturbances and site D, Gertrude Island, is …

Our Peer The Pigeon: Impacts Of The Covid-19 "Anthropause" On Psu Campus Urban Foragers, Audrey Douglass

University Honors Theses

The 2020 COVID Pandemic presented a paradigm shift dubbed, by some scholars, the 'Anthropause', an ecological epoch in which humans faded from the public sphere. As was the case for many urban species that depend on the foraging of food waste, this meant a fundamental disruption to their food systems and to the entire urban eco-web. The PSU Campus Park Blocks presents a unique opportunity to observe animal behavior, while also a succinct microcosm to study food waste flow changes, and compare species layout to other urban parks in the METRO area. Decreased food waste output from proximal …

Density Of Free-Roaming Cats Related To Feeding Stations On Hayden Island, Oregon, Olivia Helback, Joe Liebezeit

University Honors Theses

Free-roaming cats have a devastating impact on wildlife populations with stray/feral cats being the most problematic. In some areas, community members provide these cats with food, water, and shelter often in conjunction with a trap, neuter, return (TNR) program. Hayden Island located north of Portland, Oregon is home to a managed colony of feral and stray cats. Some island residents provide feeding stations for the cats and actively participate in population management. To determine how feeding stations might affect cat spatial distribution, camera traps were placed at 19 different stations in urban and natural areas on Hayden island. Additional annual …