Honors Theses (Environmental Studies Program)

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Open Access
EARLY TRADE-OFFS OF ROOT TRAITS ON A MYCORRHIZAL COLLABORATION GRADIENT
(University of Oregon, 2023-06) Villano, Lindsay; Diez, Jeff
Aboveground plant traits exist on a spectrum defined by trade-offs between conservative and acquisitive resource uptake. However, belowground traits do not fit this axis because the uptake of soil nutrients can be outsourced to mycorrhizal mutualists. Thus, adding another axis in the root economic space that represents collaboration with arbuscular mycorrhizal (AM) fungi increases our understanding of fundamental variation in root traits. Mature roots exhibit trade-offs between investing in longer root structures that travel farther, or thicker roots that can better support mycorrhizae. Here, I explore whether young roots display trade-offs in collaboration intensity and if so, how long after germination species will begin to reflect niches on this axis. I hypothesize a negative correlation between root growth rate and colonization rate of AM fungi and that the relationship between these variables increases over time as plants refine their resource uptake strategy. I grew five native forb species for twenty-five days and sampled plants at eight time points after germination. Upon sampling, I recorded root length by analyzing the root's structure and then quantified percent colonization by AM fungi. I found that despite variation in species ' root length and colonization rates, they did not fo1m a negative relationship. The con elation of length and percent colonization did increase over time with intraspecific variation in the degree and direction of this correlation. The results of this study provide further insight on young root trait variation and benefit our understanding of species interactions in the rhizosphere that contribute to community dynamics.
Open Access
Impact of Rhizobia Presence and Nitrogen Abundance on Competition Between Legumes and Non-Legumes
(University of Oregon, 2023-06) Patel, Macy; Diez, Jeff
The mutualism between legume species and rhizobia has long been acknowledged as a vital part of plant community dynamics in both natural and agricultural systems. Increasing anthropogenic nitrogen inputs can alter this mutualism and in tum plant commm1ity dynamics. Still, few studies have explored the dependencies of these resource-based mutualistic microbes, rhizobia, on ambient nitrogen levels, and how this may affect competition between hosts and neighboring plants. To test the potential nitrogen-dependent role of rhizobia in mediating coexistence between legumes and non-legumes, we conducted a competition experiment in the greenhouse replicated across rhizobial inoculation and nitrogen fe1tilization treatments. Here, we employ contempora1y ecological theo1y to assess how rhizobia and nitrogen fertilization influence niche differences and fitness inequalities determining competitive outcomes. We measured the fecundity of plants across a competition gradient to parameterize annual plant population models and to use these parameter estimates to predict the outcomes of competition between our plant species. We found that both nitrogen and rhizobia shift the probability of coexistence, and further that the effect of rhizobia was dependent on nitrogen concentration. We also found that these results differed when legumes were competing with either other legumes or non-legumes. These results suggest that these context-dependent mutualisms are impo1tant in dete1mining competitive outcomes. Further, this study sheds light on the ways anthropogenic nitrogen inputs are likely to shift community composition and diversity of native plants and microbial communities alike.
Open Access
OUT ON A LIMB: DO HAZELNUT ORCHARDS PROVIDE HABITAT FOR CAVITY NESTING BIRDS?
(University of Oregon, 2023-06) Clayton, Adam; Hallet, Lauren
Cavity nesting birds are a group of high conseivation concern in the U.S. They depend on areas with mature decaying trees in which cavities can be excavated, but few studies have examined the role of managed landscapes such as orchards in providing nesting habitat. This study assesses the suitability of hazelnut orchards for cavity nesting bird species in the Willamette Valley, where hazelnut farming is a major industry. Using field sUIVeys, I measured the density of suitable tree cavities and size of tree limbs in four commercial hazelnut orchards, three experiencing heavy fungal decay, and one with limited decay. I used observations of birds in the same orchards to determine the abundance of all cavity nesting species. When comparing between orchards, cavity density increased with average tree diameter, but was much lower in the orchard with low levels of fungal decay. Black-capped chickadees were the most abundant cavity nesting birds observed, a smaller species dependent on nest sites with soft wood. These results suggest that orchards with mature trees experiencing fungal decay may be the most valuable for cavity nesting birds, but these qualities also make orchards vulnerable to diseases that reduce crop yield. To control key diseases, many older orchards are being replaced with new blight resistant trees, altering habitat connectivity for Willamette Valley birds. A regional management strategy where some mature, decaying orchard are instead retained could benefit declining bird populations.
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
Exploring Barriers and Solutions to Active Travel to School: A Case Study of River Road/El Camino del Río Elementary Students in Eugene, OR
(University of Oregon, 2024) Staben, Alex; Brown, Anne
Active travel, or transportation modes requiring physical movement, builds physical activity into daily life, and for young children, much of their travel is to and from school. Active travel to school (ATS) improves physical, mental, and social health, as well as classroom behavior and attendance rates. However, since the 1970s, ATS has rapidly declined as more students ride to school in a vehicle. Transportation is inherently place-based; hence, this study focuses on Spanish-English dual immersion elementary school River Road/El Camino del Río (RRECDR) in the Eugene (OR) 4J school district. Like schools across the nation, very few RRECDR students use ATS. To understand why, I distributed a survey and completed follow-up interviews with parents of RRECDR students assessing 1) the barriers that factor into transportation choices and 2) what needs to change for ATS to increase among RRECDR students. Results indicate the need for a diverse multi-sector sustainable leadership team focused on ATS, increased ATS encouragement through group activities such as walking school buses (WSBs), and infrastructural improvements including crosswalk enhancements and advisory bike lanes in specific locations. Findings also suggest further research into the complex relationship between ATS and accessibility of heritage language immersion education and ATS (and active travel more generally) and the housing crisis.
Open Access
Litter decomposition in Oregon prairies depends on fire
(University of Oregon, 2024) Ralston, Ellen; Roy, Bitty
Prairies in the PNW were historically maintained by Indigenous burning practices, which favored some of their food plants and kept the prairies from becoming forested. Current prairie restoration practices are returning to the use of fire, but the consequences of fire for decomposition are unknown in these prairies. To examine decomposition, litter from both burned and unburned prairies was put in decomposition bags, and the bags were removed and weighed at three, six, and nine months. Half of all litter samples were also sterilized to remove their native fungal endophytes to determine whether that reduced decomposition. In general, litter from burned prairies had greater decomposition than litter from unburned prairies. Sterilized litter also had greater decomposition than unsterilized. This information can aid prairie managers as they continue to use fire to manage Oregon prairies.
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
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
Drought Response of Plant Coexistence are Mediated by Arbuscular Mycorrhizal Fungi
(University of Oregon, 2024-06) Tavernier, Austyn
Climate change is predicted to alter interannual precipitation patterns and increase drought severity and frequency. Although plant ecologists are actively investigating the impacts of climate change, we still lack robust and generalizable predictions of future plant community dynamics in light of novel precipitation regimes. One of the most pressing obstacles for making these predictions is understanding how the many species in these communities, as well as the interactions between them, respond to drought. Among the more important biotic players in structuring herbaceous plant communities are arbuscular mycorrhizal fungi (AMF) which have been shown to contribute to plant responses to drought at both an individual and community level. However, the mechanisms of drought-dependent mycorrhizal effects on plant competition have yet to be empirically assessed. To explore how AMF may modify the effect of drought on plant competitive dynamics, we conducted a greenhouse competition experiment within a two-by-two factorial manipulation of soil moisture and AMF presence. We used the data from this experiment to parameterize population dynamic models for each species (Clarkia amoena, Collinsia grandiflora, and Plectritis congesta) within each treatment combination. We used posterior distributions of our parameter estimates to explore how mycorrhizae and drought singularly and interactively influenced species vital rates, interaction coefficients, and the niche and fitness differences underlying pairwise species coexistence. We found that intrinsic growth rates of species generally decreased with drought and increased with AMF inoculation. The effects of drought and AMF were highly variable between species pairs. Overall, we found evidence of a three-way interaction between drought, mycorrhizae, and species pair on niche and fitness differences and the probability of coexistence. Most species pairs exhibited the highest probability of coexistence when both inoculated with AMF and exposed to drought conditions. The results of this study suggest that drought and AMF singularly and/or interactively influence the demographic parameters and interaction coefficients underlying plant community dynamics. Differences in coexistence probability between our treatments may implicate AMF as a key factor in whether species are able to coexist during projected increases in drought frequency. Thus, AMF could prove to be a potentially useful tool for managing plant community resilience to climate change. However, variable species responses to both drought and mycorrhizae suggest that under these conditions competitive outcomes might be affected by the strength of species-specific mycorrhizal mutualisms. Future studies on the interactive effects of mycorrhizae and droughts on plant competition should focus on identifying axes for plant species variation which may underlie the complex, species-specific interactions between mycorrhizal mutualisms and water availability.
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.
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
SHAPING OUR FATE: ANALYZING CIRCULAR ECONOMY PRINCIPLES IN CORPORATE SUSTAINABILITY STRATEGY AS A CRITICAL CLIMATE SOLUTION FOR THE APPAREL INDUSTRY
(University of Oregon, 2023) Stathis, Magdeline; Skov, Joshua; McWhorter, Brian
Apparel is one of the most polluting industries in the consumer goods sector. From microplastic pollution in waterways, to greenhouse gas emissions, and even the release of toxic chemicals into the habitats of biodiverse life, the production and consumption of garments is an extremely hazardous process in its current form. The circular economy is a transformational concept that reimagines how we consume clothing; it proposes alternative business models whereby companies can generate revenue without relying on the extraction of raw materials or the use of nonrenewable resources. However beneficial they may be, circular practices are contradictory to the way most apparel companies currently operate, making it a difficult scheme to implement. Not to mention, the textile value chain is a complexity in and of itself that challenges the prospect for change. This thesis will investigate the current efforts that resemble circularity strategy made by apparel companies and assess the current state of implementation of the economic model. Materials selection, resale, and recovery are highlighted as a few of several practices that exist in an entire toolkit for integrating circularity and addressing shortcomings of current linear business operations in apparel. Specifically, this study will examine the strategies mused to address material selection, resale, and recovery of goods by Patagonia, REI Co-Op, and Cotopaxi. In this piece, I suggest that circularity should be a common goal of all stakeholders in apparel to target the pollution caused by the industry globally. Though it remains unclear if 100% circularity is even possible to achieve – largely due to current consumption patterns and the complications of processing technical materials – it is still something that the industry should collectively work towards to reduce the environmental footprint of apparel.
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.
Open Access
IMPROVING SOIL MOISTURE RETENTION IN HAZELNUT ORCHARDS THROUGH THE USE OF NATIVE COVER CROPS AND CONVENTIONAL MECHANICAL TREATMENTS
(University of Oregon, 2020-12) MARISSA, LANE-MASSEE
The purpose of this study is to understand how hazelnut orchards in the Willamette Valley, Oregon retain soil moisture throughout the spring and summer months, and how orchard floor treatments can be used to improve soil moisture retention in vruious ages of hazelnut orchards. The two orchru·d floor treatments studied looked at how the conventional mechanical processes of flailing and scraping impact soil moisture retention, and how the use of native cover crops can be used as a way to increase soil moisture retention. The mechanical methods of treatment include inigation, flailing, scraping, and many hruvesting processes, and the vegetation treatment methods includes seeding mixes of native and agricultural cover crops. The methods of data collection in the study consist of soil moisture monitoring and vegetation community analysis. The results dete1mined in this study conclude that both mechanical and vegetative treatments have a wide vru·iety of impact on soil moisture retention in hazelnut orchards in the Willamette Valley. Results vruy dependant on orchru·d canopy cover, orchru·d age, and vegetative community composition. Canopy cover had the lru·gest impact on soil moisture retention and flower development in vegetative communities. Orchards with less canopy cover saw a greater po1t ion of native cover smvive to matmity and/or produce seeds, but retained less soil moisture than orchru·ds with more canopy cover. These orchards saw a greater smvival rate of all native seed mixes, especially the growth and flowe1ing of the annual communities. Orchards with more canopy cover did not see lru·ge po1tions of smviving vegetation, but retained soil moisture more than orchards with canopy openings. In these orchards, most annuals did not smvive, but the perennial communities saw successful rates of smvivorship from sunlight competition and repeated mechanical disturbance. Overall, the vegetative communities that were composed of native plants, combined with less invasive mechanical treatments, retained the highest amount of soil moisture throughout the study pe1iod. The moisture retention rate in these plots averaged a 3-5% increase compru·ed to those plots in which vegetation was non-native or non-seeded, or the scraping mechanical treatment. This study has the great possibility to impact how many hazelnut frumers prepare their orchard floors for hruvest, how agricultural systems in the Willamette Valley can reintroduce impo1tant ecosystem se1vices like biodiversity, wildlife habitat, and soil moisture retention, and increase the potential to alleviate the impacts of anthropogenic climate change on agricultural crops like hazelnuts.
Open Access
NITROGEN FIXING SYMBIONTS: LEGUME SURVIVAL AND COEXISTENCE UNDER DROUGHT IN CALIFORNIA GRASSLANDS
(University of Oregon, 2022-05) Kataoka, Natalie Catherine
For the past 200 years, non-native species have been anthropogenically introduced in California grasslands, reducing native species abundance and diversity. Trifolium hirtum is a non-native legume commonly used for cattle fodder and cover cropping because of its ability to fix nitrogen via bacterial symbionts. T. hirtum currently coexists with California native legume Trifolium willdenovii in established communities, however, T. hirtum has the potential to outcompete T. willdenovii under increased environmental stress, such as that caused by climate change. Considering how symbiotic rhizobia contribute to these Trifolium species’ ability to coexist or compete with other species, as well as how climate change alters these interactions, is essential for understanding potential impacts on native biodiversity and the response of important forage species to changing climate conditions. I tested 1) how rhizobial symbionts contributed to the survival and growth of a native and non-native legume species. 2) How drought influences the competitive relationships of the two legumes. And 3) how each species responded under interspecific and intraspecific competition. For both non-native T. hirtum and native T. willdenovii, I measured rhizobia nodule mass, seeded background count, weed species counts, and weighed the aboveground biomass of individuals grown under drought and ambient precipitation treatments. On average, there were no differences in the mass of nodules by species, however there was an observed a negative correlation between the biomass and nodule mass of uninoculated background T. willdenovii. Drought positively impacted the biomass of background T. hirtum individuals, however drought treatments negatively affected focal T. hirtum biomass compared to ambient precipitation. Drought had no significant effect on focal T. willdenovii biomass.
Open Access
Does the nutritional state of jellyfish vary with season along the Pacific Northwest Coast?
(University of Oregon, 2021-06) Li, Ya Lin
Cnidarian jellyfish are ubiquitous predators of pelagic communities, but little is known about their phenology and how food availability affects their nutritional status. Starved medusae tend to decrease somatic growth to allocate resources towards gonad development, thus a ratio of gonad to bell size might help determine the nutritional state of hydromedusae. We hypothesized that when food is scarce, C. gregaria and E. indicans will have larger gonads relative to their body size. I conducted starvation experiments to directly test how bell diameter and gonad area vary with food availability. The same two species of hydromedusae were also collected in a period of low primary productivity (winter) and high primary productivity (summer) along the North California Current System. ImageJ was used to analyze photos of the formalin-preserved specimens to obtain morphological measurements and create a gonadal index (gonad area/bell area). As the preservation method caused a loss in biomass of the collected medusae, we made a correction factor to convert the measurements of the preserved organisms to live ones. The medusae showcased slightly higher gonadal index in the medusae during winter than summer indicating an increased effort towards reproduction when resources are depleted. Understanding the links between oceanographic conditions and population dynamics of gelatinous predators will allow us to better predict their effects on zooplankton community dynamics.
Open Access
BAYESIAN BIOGEOGRAPHIC ANALYSIS OF SQUIRREL EVOLUTION SUGGESTS AN ASIAN ORIGIN
(University of Oregon, 2021-06) Banks, Anna
Squirrels have an incredibly diverse lineage with a global distribution and have dispersed over millions of years from a common ancestor approximately 40-50 MYA. The assumption since the 1980’s has been that squirrels originated in North America and evolved from North American tree squirrels about 34-39 MYA, but in a more recent study, the oldest giant flying squirrel fossil was found in Oregon suggesting a possible eastward migration from Asia. This study made me question the previously accepted hypothesis that squirrels originated in North America and led to an exploration of squirrel evolution and origins. We used an R package called BiogeoBEARS with Bayesian biogeographic analysis and a DEC+J model to get a better picture of where squirrels were located at different points in their evolution. To run this analysis, we input a phylogenetic tree file, representing 225 modern Sciuridae species, and a biogeography file with each of their locations sorted into eight regions. My analysis resulted in a few noteworthy findings regarding major biogeography changes and their timing: (1) we believe that squirrels originated in Asia, (2) North American and Southern African squirrels came from Asia, and (3) we found one long South American branch, genetically distant from all other South American Sciuridae species and stemming from near the oldest common squirrel ancestor, leading to just one species, Sciurillus pusillus, a modern species that has resided in South America for about 37 Ma.
Open Access
Social Representations in the Meat Industry and Influence on Diet
(University of Oregon, 2021-06) Leonard, Francesca Anne
Meat has been ingrained into American culture since the birth of the nation—holidays that center around traditional meat dishes, experiences that almost always pair with some form of meat consumption, and the presence of meat as the dominant center of meals. Meat has been advertised in a way that positively enforces cultural social norms and drives consumption upward for a product known to be one of the most significant pollution sources on the planet. The industry’s power and affluence has made it a prominent actor in the political realm, with the ability to alter policies and regulations. The harmful repercussions of this industry have not gone unnoticed, and the incentive to create a new type of protein, “meatless-meat,” has become an explosive industry with companies like Beyond Beef at the forefront. Despite these emerging companies, the demand for meat in the US has not shrunk significantly. The reasoning behind this is less about ethical obligations to not kill animals for consumption, or to protect the environment, but from deeper socio-cultural norms that are reinforced by media to promote animal-based dieting and forgo plant-based alternatives.
Open Access
INTRASPECIFIC VARIATION IN SANDBERG BLUEGRASS (POA SECUNDA)’S RESISTANCE TO ANNUAL GRASS INVASION
(University of Oregon, 2021-06) Cook, Emily
Exotic species pose a threat to many ecosystems within the western U.S. The annual grass species known as cheatgrass (Bromus tectorum) is a prevailing invader in the Great Basin. Cheatgrass invasion in combination with a change in fire regime and climate exacerbate large fires in the region, contributing to loss of native plant species. Seeding of native perennial grass species has been adopted as a management strategy for post-fire rehabilitation. Native grass species are known to have high variability in traits across climate and space. Knowing this, some populations may be better at resisting invasion to cheatgrass than others. This study explores how water availability and intraspecific variation in traits affects the native Sandburg bluegrass’ (Poa secunda) capacity to resist invasion by cheatgrass. I hypothesize that (1) P. secunda’s resistance to cheatgrass will decline with reduced water availability, but P. secunda populations from warm and arid source environments will have a smaller decline than those from cooler and wetter environment, (2) that the P. secunda populations from warmer, drier areas will be shorter in height, have lower SLA, and higher LDMC and (3) that P. secunda populations with greater trait plasticity will better resist invasion to cheatgrass. Seeds from five populations of P. secunda within the Great Basin were collected and sown in monocultures and in competition with cheatgrass in a greenhouse. I evaluated relationships between several leaf and plant traits with a wet and dry treatment. Significant trait variation was found among populations and between wet and dry treatments. These findings suggest that using seeds that are locally adapted to a restoration area can be beneficial to plant fitness and resistance to invasion. Considering traits connected with disturbance and invasion is valuable to restoration work in the region.

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