Honors Theses (Environmental Science)

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Open Access
Variation in Bumble Bee Foraging Networks Across A Gradient of Forest Canopy
(University of Oregon, 2024-06) Metzger, Sam
Land use change, invasion of non-native species, and other modes of habitat loss contribute to native bee population declines. A key contribution to population decline may be a loss of nutritional resources, which can occur when landscapes have reduced floral diversity and abundance. Increasing floral resources may mitigate future declines and forest ecosystems may offer necessary food and nesting opportunities for native bees. However, it is unclear whether and how forest management practices influence the capacity of forests to fulfill these roles. Our research advances the field's understanding of bumble bee nutrition as a function of plant community structure by examining it within a forest ecosystem. To do this, we focused on foraging patterns of bumble bees across a gradient of canopy openness in the Oregon Coast Range. With the understanding that bumble bees prefer warm, sunny, fair-weathered spaces with abundant floral resources, we hypothesized (1) there would be a positive relationship between floral diet breadth and canopy openness. We further predicted (2) increased canopy cover would result in less floral richness, and greater niche overlap among bumble bee species. Our results support the first hypothesis for two of our most abundant species but not the third. Moreover, floral richness was indeed lower with greater canopy cover, but responses in niche overlap varied across our three most abundant species. This demonstrates that different bumble bees have varying responses in foraging behavior to forest canopy structure. This research provides information that could assist in conifer forest management practices to better provide for wild bumble bee community restoration and conservation.
Open Access
Navigating the Climate Crisis - The Interconnection of Extreme Weather Events and Life Decisions
(University of Oregon, 2024-05) Rosa-O'Hayer, Lyric
The climate crisis is no secret, and extreme weather events - a clear, visual manifestation of the climate crisis - are known to bring destruction in their wake. However, it is unclear how extensive of an impact they have on people. This research aims to answer the questions; how has the presence or experience of extreme weather events influenced college student's mental health and life decisions? Does this experience have a bigger impact than their knowledge of climate change? To answer this, a series of surveys (45 responses) and in-depth interviews (11) with environmental studies college students in Oregon was conducted, asking about their knowledge of climate change, experience with extreme weather events, feelings of climate anxiety, and how these impact their life decisions. Life decisions include but are not limited to whether to have kids, where to live, what to study, and career choice. Overall respondents expressed their belief in climate change and its impact on the severity of extreme weather events, and this knowledge impacted their politics, where to live, and what to study. This also led to the finding that experiencing exti·eme weather events can impact life decisions and mental health, but there are vaiying degrees of impact depending on the severity of the event, dictated by class status and knowledge of climate change. With this knowledge, there is the opportunity to advocate for better policies and initiatives ai·ound resources for post-exti·eme weather event care, as well as increased attention to preventative methods.
Embargo
Seeds, Soil, and Shifting Climates: Climate Change's Impact on Food Security in the Willamette Valley
(University of Oregon, 2024) McCowan, Camille; Cutting-Jones, Hannah
Climate change poses a significant threat to global agricultural systems - raising global temperature, disrupting hydrological cycles, and impacting water patterns, soil health, and plant development. This threat is exemplified by the Willamette Valley, a region renowned for its agricultural diversity and fertile lands. This paper explores the relationship between global climate change, regional agricultural production, and local food security in the Willamette Valley. Through an analysis of the primary impacts of climate change on the agricultural sector, disruptions to ecological patterns, and potential secondary vulnerabilities, it seeks to understand the implications for local food production and security. Additionally, using the Willamette Valley as a model of an affected productive region, it examines the region’s current local food system and proposes strategies for local food production systems to mitigate the impacts of climate change.
Open Access
CULTIVATING CHANGE: ANALYZING THE GEOSPATIAL DYNAMICS OF URBAN AGRICULTURE AND THE CORRESPONDING DEIJ IMPLICATIONS IN PORTLAND, OREGON
(University of Oregon, 2024) Bowen, Karenna; Mhuireach, Gwynne
The discourse within the field of environmental science has been heavily dominated by discussions of mounting global crises stemming from growing urbanization. Downstream ramifications include food insecurity, the depletion of natural resources, and environmental concerns. As urbanization increases and access to rural land decreases, new solutions to ameliorate these issues become increasingly urgent. In response to these formidable concerns, urban agriculture (UA) is one potential solution that has grown in popularity. This thesis explores the premise of UA through a literature review that summarizes current research on the relevance, global trends, and its connection to the three pillars of sustainability—social, economic, and environmental. Building on this research, this study identifies a gap in knowledge associated with UA and diversity, equity, inclusion, and justice (DEIJ) implications. To address this, a case study is conducted in the neighborhoods of Portland, Oregon using ArcGIS Pro to assess UA’s impact on DEIJ from a racial, economic, accessibility, and environmental perspective. The results indicate that from a racial and ethnic standpoint, UA in Portland is located in primarily ethnically diverse neighborhoods. Relying on data exposing the median household income in Portland neighborhoods, UA is also determined through an economic outlook to be most prevalent in less affluent regions. To evaluate inclusion, it is found that UA plots are primarily accessible to the general public. Finally, from an environmental outlook, the distribution of UA is located typically in neighborhoods experiencing higher risk factors displayed by both the environmental hazard index and the urban heat island (UHI) index. Based on the findings from the literature review coupled with the data from the case study, it is concluded that Portland upholds many of the DEIJ principles through the implementation of UA. However, many of these issues have complexities that require future research regarding the long-term impacts between UA and DEIJ.
Open Access
Analyzing Lake Variability In A Highly Dynamic Area Of The Yukon Flats, Alaska Using Remote Sensing
(University of Oregon, 2024) Fleming, Catharine; Cooley, Sarah
Sentinel-2 optical imagery was used to track changes in lake area in a highly dynamic area of the Yukon Flats, Alaska over 2019-2023. Specific questions this research addresses include: how spatially consistent is the variability in water area? Why are certain lakes far less seasonally variable than others? How consistent is the temporal and spatial variability in the water area from year to year? Seasonal lake area fluctuations follow a similar progression from year to year. The seasonal maxima in lake extent are very pronounced for smaller water bodies in 2021 (20% higher average maximum lake area, 40% lower average minimum lake area) than larger water bodies. On average 2019 had the highest mean lateral change along lake shorelines while 2023 had the lowest.
Open Access
In the Neighborhood: Phenology, Species Interactions, and Community Engagement in Ecological Research
(University of Oregon, 2024) Callie, Bryn; Diez, Jeff
Phenology, the timing of biological life cycles, is a key indicator of global climatic change and a powerful tool for generating public awareness surrounding environmental issues. Multiple studies have shown that species are shifting their phenology in response to climate change, causing spring events such as leaf-out and flowering onset to arrive earlier and altering the way humans relate to the natural environment. Furthermore, although many studies have suggested that phenological differences influence the way that species within ecological communities interact, there has been minimal empirical consensus surrounding the impact of phenology on species interactions and even more limited research surrounding the reciprocal relationship — how species interactions impact phenology. This presents a significant knowledge gap as unprecedented rates of climate change and land-use change are altering plant community composition, diversity, and dynamics globally. As such, we studied the reciprocal relationship between flowering phenology, fitness, and competitive neighborhoods among annual plant species. We chose to utilize prairie species native to the Willamette Valley, reintroducing them to areas around the city of Eugene, OR and aiming to advance future restoration efforts by contributing to our understanding of their survival and persistence. Recognizing that public awareness and interest are key to the success of restoration and conservation initiatives, we embedded our experiments within urban natural areas and aimed to generate direct engagement with our research by encouraging community participation in phenological data collection. We found that increased competitor species richness was correlated with the advancement and shortening of flowering periods. We also found that plant fecundity was negatively correlated with competitor density but was unrelated to changes to competitor identity or species richness. Lastly, we observed that the strength of competition tended to vary by competitor identity, but that this variation did not seem to be related to the phenological differences present between species. Our research offers unique evidence that species interactions may impact plant phenology and fitness in complex ways and consequently species’ persistence and coexistence conditions in our changing global environment. Reflecting on the public engagement we witnessed, our project also demonstrates how ecological experiments can be used as an implement for both restoration and education.
Open Access
Invasive annuals increase with fire frequency in the Northern Great Basin
(University of Oregon, 2023) Bailey, Zoey; Hallett, Lauren; Aoyama, Lina; Moffitt, Michael
Wildfire, although a natural part of the sagebrush-steppe ecology in the Great Basin, is poised to occur at more frequent intervals due to the combined influence of rampant annual grass invasion and increasingly long dry seasons. Deviations from the historic fire return interval of 25-75 years to a mere 3-5-year cycle disrupt the establishment of later-seral species, such as the keystone shrub, sagebrush (Artemesia tridentata). More frequent fire can further alter the structure of plant communities by favoring early colonizing annual grass and forbs. As fire frequency increases, the resilience of native species is diminished, and the site becomes more vulnerable to vegetation compositional conversions. The conversion of mixed sagebrush and perennial grass-dominated sites to monocultures of invasive annual species jeopardizes human and wildlife needs on the landscape. To better understand the effects of increased fire frequency on annual species invasion, I surveyed vegetation cover in sites with variable burn history at the North Great Basin Experimental Range in July of 2022. The relative abundance of plant functional groups, as well as two critical invasive annual species, cheatgrass (Bromus tectorum) and desert alyssum (Alyssum desertorum), were recorded in plots burned in 5, 10, and 20 year intervals since 2002. The relationship between forb cover and fire frequency was the only statistically significant difference identified (p=0.02). General trends in the data supported the hypotheses that the mean percent cover of Bromus tectorum and Alyssum desertorum would be higher in sites burned more frequently. These preliminary findings indicate the relationship between fire frequency and invasive annual species warrants greater attention with future larger-scale vegetation surveys. A better understanding of fire frequency effects on vegetation conversion may help restoration practitioners effectively prioritize areas for post-fire restoration to limit loss of native species.

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