Geography Theses and Dissertations

Permanent URI for this collection

https://hdl.handle.net/1794/6282

Browse

Browsing Geography Theses and Dissertations by Issue Date

Filter results by year or month
Now showing 1 - 20 of 158
  • Thumbnail Image
    ItemOpen Access
    Remote Sensing of Lake Ice Dynamics in the Lower Kuskokwim River Basin, AK
    (University of Oregon, 2024-08-07) Pletcher, Addison; Cooley, Sarah
    The formation and breakup of lake ice plays a critical role in the hydrology, ecology, and subsistence activities of Arctic regions. However, little research has examined ice phenology in small water bodies and complex deltaic environments, areas that are particularly responsive to climate changes and could provide early indicators of broader environmental shifts. This study uses Sentinel-2 optical imagery to map the timing of lake ice breakup in the Lower Kuskokwim River Basin in southwest Alaska from 2018 to 2023. We detect ice breakup timing in 145,955 lakes, as small as 0.001 km2, filling a gap in our understanding of finer scale lake ice dynamics. Our results indicate that the average ice breakup date across the study period is May 14, with a standard deviation of 9.6 days. Breakup timing shows significant interannual variability, with the earliest mean breakup occurring on May 6 in 2019 and the latest on May 27 in 2023. The standard deviation in breakup timing also varies, with certain years exhibiting wider variability (e.g., 2019 and 2023) compared to others (e.g., 2018, 2020, 2021, and 2022). Temperature is a primary driver of breakup timing; we identify a statistically significant positive correlation between the date of the 0°C isotherm and breakup timing. Smaller lakes (defined as lakes < 1 km2) tend to break up earlier than larger lakes (6 days earlier on average), demonstrating a faster thermal response to climatic conditions. We find that the lag interval between the 0°C isotherm and breakup date averages 8.4 days, with smaller lakes exhibiting shorter lag intervals compared to larger lakes. Our analysis of 145,955 lakes over six years demonstrates the utility of Sentinel-2 imagery in accurately detecting ice breakup, typically within 2.8 days of observed dates, despite challenges such as cloud cover, sensor resolution, and temporal gaps. The significant interannual variability, along with notable differences in breakup timing between smaller and larger lakes, underscores the responsiveness of small lakes to temperature fluctuations. These findings emphasize the importance of incorporating high-resolution satellite imagery to capture rapid environmental changes, providing a more nuanced understanding of climatic impacts across diverse lake types.
  • Thumbnail Image
    ItemEmbargo
    (De)Constructing Hazard: The Making of Meaning and Value in Oregon’s Firescapes
    (University of Oregon, 2024-08-07) Casey, Alexandra; Walker, Peter
    Amidst the global rise of wildfire disasters and the complex human-environment interactions they (re)produce (Fischer, et al., 2016), Oregon’s Senate Bill 762 stands out as an ambitious policy initiative aiming to improve wildfire adaptation, resilience, and mitigation across scales—from home protection zones to entire firesheds. However, this legislative effort met significant public pushback after the release of a wildfire hazard map that identified high-hazard areas for downstream regulation. The SB 762 hazard map has since been rescinded, and implementation of new fire safety codes were delayed as the state revised its approach under SB 80. This thesis explores the political ecology, critical physical geography, and critical GIS of wildfire hazard mapping in Oregon, focusing on the construction of SB 762 wildfire map and its rearticulation under SB 80. Chapter I presents a broad overview to mixed-methods research and builds on an interdisciplinary body of literature from geography, sociology, science and technology studies, wildfire risk science, and political science to uncover how these maps are dynamic entities shaped by scales of influence and visibility. Chapter II uses geospatial data, interviews, and public meeting transcripts to find how units of measurement such as pixels and tax lots do not just determine the scale of analysis but also influence the extent and outcomes of negotiations within GIS decision-making processes. Through a close examination of these units, I find that the fixed scales of scientific assumptions in the initial SB 762 map affect whose voices are amplified in the shaping of definitions, thresholds, and distribution of power and responsibility in wildfire risk management. In Chapter III, I analyze a large set of appeals and public meetings to understand how individuals work to articulate property’s conditions in ways legible to current and anticipated future hazard metrics. I ultimately find that influence from individuals and representatives of rural agricultural interests shifts the map's meaning of hazard. Overall, this thesis argues that scientific units of analysis and political representation produce the parameters through which rural agricultural stakeholders (re)negotiate the SB 762/80 wildfire map.
  • Thumbnail Image
    ItemEmbargo
    Forecasting Alaskan Boreal Ecosystem Changes: A Landscape Analysis of Permafrost Thaw and Hydrological Trajectories Resulting From Climate-Driven Change in the Fire Regime and Conifer Decline
    (University of Oregon, 2024-08-07) Abreu-Vigil, Gabriel; Lucash, Melissa
    Boreal forests, covering about 30 percent of Earth's forested area, are dominated by coniferous forests and deemed crucial reservoirs of permafrost and belowground carbon. Undergoing rapid ecological changes from a warming rate nearly three times the global average, questions remain about future interactions of increased wildfire, vegetation shifts, permafrost thaw, and soil moisture for tree growth. Utilizing the LANDIS-II landscape forest model, we simulated soil temperature and moisture, forest succession, and disturbance regimes over a century across 380,400 hectares in interior Alaska under historical and future RCP 8.5 climate scenarios. This integrated approach marks a significant advancement in simulating the dynamic and interconnected processes that define boreal forest resilience and response to climate change. [It would be good if there can be statements here about the predictive capacity of the model…calibration and validation studies, for example]. Under future climate change, permafrost at near-surface levels (3 m) is projected to disappear by mid-century with a thaw rate of 26 cm/year and 18 cm/year under extreme and moderate climate forcing respectively. Exacerbated by a changing fire regime and landscape-level shifts from insulative coniferous to less insulative hardwood coverage, these shifts are accompanied by increased soil temperatures and decreased moisture levels. The complex interplay between these dynamics in the face of a changing climate has profound implications for boreal forests and the global system alike.
  • Thumbnail Image
    ItemOpen Access
    Deconstructing Borders, Territories, and Toponyms: Cartographic Designs in the Political Disputed Territory of Sakhalin
    (University of Oregon, 2024-08-07) Sui, Zhaoxu; Fish, Carolyn
    In this research, I aim to deconstruct and quantify the cartographic designs of maps of Sakhalin Island—a politically contested area between Russia, China, and Japan. This will enhance understanding of how the design of borders, background fill colors, and toponyms (place names) are presented and used to advance territorial claims. I conducted a quantitative content analysis of 200 maps in four languages, identifying key cartographic designs such as border dash effects, fill color visual variables, and toponym types. I found that uncertain designs of borders and territorial fill colors are more frequently adopted by Japanese map makers to express the neutrality of the contested region of Southern Sakhalin and question Russian’s legitimate control, and uncertain designs of toponyms (double labeling) appeared more in Chinese and Japanese maps to signify their historical presence and control of the Island. All these are indicative of specific ways that the cartographic design of borders strokes, territorial fill-colors, and toponyms serve to assert and facilitate political stances and claims towards the contested territory of Sakhalin.
  • Thumbnail Image
    ItemEmbargo
    Memory, Whiteness, and Right-Wing Opposition to National Heritage Areas
    (University of Oregon, 2024-08-07) Ford, Sophia; Pulido, Laura
    The political right is most often associated with defending statues and monuments honoring colonizers, confederates, and enslavers. An example is the 2017 'Unite the Right Rally' in Charlottesville, Virginia, where activists violently protested the removal of a confederate monument to Robert E. Lee. Despite this known inclination of the right defending memorials, tensions rise as white, right-wing landowners across the United States vehemently oppose the expansion of National Heritage Areas (NHAs), framing them as a “federal land grab.” Established in 1984 under President Ronald Reagan and overseen by the National Park Service (NPS), NHAs receive federal funding to maintain historic sites, museums, monuments, and other public memorials. This dissertation examines the right’s growing resistance to NHAs, focusing on a case study spanning Kansas, Nebraska, and Missouri. I explore the right’s support of historic commemoration through ethnographic methods, archival analysis, and fieldwork. Central to this study are questions such as: Why do people support or oppose National Heritage Areas, and what discourses do they use? What groups oppose NHAs, how are they funded, and who are their alliances? To what extent does whiteness play a role? What kind of relationship, if any, to the past, do opponents want? Overall, I find an increasing emphasis on local management of commemorative sites, aligning with broader right-wing movements characterized by a sense of white masculinist entitlement to private property. Additionally, prominent right-wing organizations, including the John Birch Society, American Stewards for Liberty, the Heritage Foundation, and Protect the Harvest, leverage these sentiments to advance their interests, particularly within the oil and gas industries. By examining the complexities of resistance to NHAs, this research contributes to a deeper understanding of the intersections between historical commemoration, political ideology, race, gender, and class.
  • Thumbnail Image
    ItemOpen Access
    Snow Depth Distribution Mapping in a Post-fire Landscape from UAS LiDAR
    (University of Oregon, 2024-08-07) rutherford, devlin; Ryan, Jonathan
    1
  • Thumbnail Image
    ItemEmbargo
    Simulating Forest Dynamics, Disturbance, and Management in the Elliott State Research Forest, Oregon: A Comparative Study of Land Sharing, Land Sparing, and Triad Management
    (University of Oregon, 2024-08-07) Mast, Colin; Lucash, Melissa
    Forests serve as critical reservoirs for carbon, provide habitat for a significant proportion of terrestrial species, and provision renewable building materials in the form of timber. However, forests are increasingly at risk due to increased demand for forest products and forested land, necessitating new forest management strategies that lessen the impacts of resource production on carbon storage and biodiversity. The recent management plan for the Elliott State Research Forest (ESRF) outlines the experimental comparison three strategies: land sparing (separates timber production from conservation), land sharing (integrates timber production with conservation), and Triad management (divides forests into intensive, extensive, and reserve areas). However, the long-term results from implementing these strategies will not emerge for decades. Therefore, we used LANDIS-II to simulate the proposed management plan under natural disturbances (i.e. windthrow and wildfire) and climate change. Results indicate that while all management strategies ensured sustainable timber production, land sharing promoted the highest diversity of trees and shrubs, whereas Triad management maximized carbon storage. However, under extreme climate change projections, carbon storage was compromised and there was a further shift towards Douglas-fir. Managers must therefore evaluate tradeoffs and choose the strategy best suited to management objectives. This study represents the first modelled comparison of land sharing, land sparing, and Triad management under climate change and natural disturbance and highlights the potential use of LANDIS-II in adaptive forest management.
  • Thumbnail Image
    ItemOpen Access
    Role of Surface Albedo for Explaining Differences of Modeled Greenland Ice Sheet Melt
    (University of Oregon, 2024-08-07) Shapovalov, Maxim; Ryan, Jonathan
    The Greenland Ice Sheet has been in a state of negative mass balance for the past several decades and is currently responsible for a substantial proportion of global sea-level rise. Accurate projections of ice sheet mass loss are therefore imperative, and a number of regional climate models (RCMs) have been developed for this purpose. However, a recent intercomparison (GrSMBMIP) of surface mass balance (SMB) models demonstrated substantial discrepancies between their individual projections. One likely explanation for model spread is inaccurate simulation of albedo, which determines the amount of shortwave radiation that is absorbed by the ice sheet surface. Here, we force a state-of-the-art surface energy balance model (IceModel v1.0) with four albedo products to investigate the sensitivity of meltwater production to different albedo parameterizations for the 2009-2022 period. The four albedo products include one product from satellite observations (MODIS MCD43A3), which we treat as “ground-truth”, one atmospheric reanalysis (MERRA-2), and two RCMs (MAR v3.12.1 and RACMO2.3p2). We find that, for fifteen of automated weather stations located at the margins of the ice sheet, MAR and MERRA-2, on average, overestimate observed (MODIS) glacier ice albedo by +0.11 and +0.13, respectively, while RACMO underestimates it by -0.07. These biases mean that IceModel underestimates melt -36.3% and -27.1% when forced by albedo derived from MAR and MERRA-2, respectively. In contrast, IceModel overestimates melt by +5.5% when forced by albedo derived from RACMO. We also identify several compensating effects in our analysis. We also highlight the presence of counteractive errors of albedo representations in all models that result in diminished uncertainty. Specifically, RACMO tends to overestimate snow albedo, while generally underestimating glacier ice albedo, which results in an estimate that appears to be more accurate relative to observations. Ultimately, based on the partitioned information that we outline further in this thesis, we offer suggestions for future improvements in modeled albedo parameterizations.
  • Thumbnail Image
    ItemEmbargo
    Cuerpo-Territorio: Embodied Transformative Memory and Cartographies of Healing among GuateMaya Feminist Groups
    (University of Oregon, 2024-03-25) Macal Montenegro, Carla; Pulido, Laura
    My dissertation presented case studies of two GuateMaya feminist groups that are challenging state-dominant narratives of the Guatemalan 36-year- war (1960-1996) and foregrounding counter-memory with art, Maya cosmovision spirituality, and gendered embodied memory production. The groups also denounced contemporary feminicide cases through the cosmo-political praxis of cuerpo-territorio. Cuerpo-territorio declares the body our first territory and advocates for a communal subject agency. I develop this deeply embodied framework to examine how 8 Tijax and GuateMaya Mujeres en Resistencia-Los Angeles (GMR-LA) challenge the state’s hegemonic memory by actively engaging in embodied transformative memory experiences, or what I describe as healing cartographies. I asserted that such healing cartographies at the scale of the intimate contribute to hemispheric decolonial solidarity. These healing cartographies contradict and actively challenge the Guatemalan state’s claims of what can be remembered or erased when the evidence is embodied and reiterated, told through stories, and brought into being by active remembrance. I use a community-based participatory approach and feminist ethnographic methods to examine and support the transnational affective solidarity connecting GuateMaya women throughout the hemisphere. My research is a political project of unearthing the counter-memory, silences, fear, and intergenerational trauma from the oral and embodied testimonios of GuateMaya women survivors of genocide who are currently involved in collective projects to recover Guatemala’s historical memory. While GuateMaya feminist groups are connected across the United States, Mexico, and Canada, my dissertation focused on the relational testimonios of GuateMaya feminist groups in Guatemala and Los Angeles.
  • Thumbnail Image
    ItemEmbargo
    Seeing Beyond Catastrophe: Rethinking Development and Environmental Transformation in the Aral Sea Region of Uzbekistan
    (University of Oregon, 2024-01-10) Shields, Katherine; Johnson, Leigh
    The Aral “catastrophe” has resulted from ongoing diversion of water flowing into the Aral Sea for irrigation, largely cotton, primarily from the 1960s until present. The shrinking of the sea has resulted in loss of livelihoods, local climate change, health impacts, and the creation of the world’s newest desert. This dissertation sees beyond catastrophe to de-exceptionalize the Aral Sea and tell nuanced stories of the human and more-than-human (e.g. trees, fish, insects) residents of the region. It highlights the life, value and beauty of the Aral Sea region while showing how the region has been devalued. Using feminist mixed-methods that treat all data as situated knowledges and embodied (rather than disembodied) visions, this work interweaves the partial perspectives of ethnographic data from nine months of fieldwork, geophysical, and remote sensing data while attending to the politics of these data’s creation. This dissertation contributes to scholarly conversations on the co-production of development and expertise, political ecologies of the state, and feminist methods for human-environment interactions. Using ethnographic data, I first unpack the 2021 designation by the UN General Assembly – initiated at the behest of the Uzbek state – of the Aral Sea region as a “Zone of Ecological Innovations and Technologies.” I problematize the ideology of innovation that lies behind the “Zone” arguing instead for an ethos of repair. Next, I probe state-sponsored and crowed-funded plantation-style afforestation that is framed as mitigation of the consequences, particularly toxic dust, of the dried Aral Seabed. Data come from a visual classification of the seabed using Google Earth Pro and participant observation. I argue afforestation should be understood as a performance of environmental stewardship and mobilization of trees as infrastructure rather than ecosystem restoration. Finally, interweaving remote sensing, geophysical and ethnographic data, I illustrate how flows of water into the Amu Daryo delta have decreased and how surface water in the delta is increasingly variable over time and discontinuous across space. I conclude that the greatest risk for residents is not toxic dust, but ongoing violence of water allocation policies that continue to remake the landscape and affect residents’ ways of life, livelihoods and nutrition.
  • Thumbnail Image
    ItemOpen Access
    Multiscale and Spatiotemporal Dynamics of Socioeconomic and Environmental Effects on Mental Illness Mortality
    (University of Oregon, 2024-01-10) Song, Insang; Luan, Hui
    Mental illness is a pressing global and national public health concern, necessitating the identification of risk factors to develop effective prevention measures. In this dissertation, I attempt to fill two research gaps by revealing the spatial and/or temporal disparity in the impacts of unemployment and greenspace on mental illness mortality with spatiotemporal modeling and a causal analysis across three spatial scales.In Chapter 2, the association between mental illness and substance use mortality and unemployment was examined using Bayesian spatiotemporal hierarchical models. The findings revealed heightened positive effects in rural Appalachian and Midwestern counties. Overall mild effects were observed during the Great Recession period. The patterns could be attributed to local contexts such as the availability of healthcare supply and relative deprivation. Chapter 3 challenges the assumption of a spatially constant effect of greenspace exposure on mental illness mortality, using census tract-level data from Oregon and Washington. Results indicated that the impact of greenspace exposure on mental illness mortality varies across census tracts, with protective effects more likely in areas between Seattle and Portland. Protective effects were more likely observed in areas between Seattle and Portland. The contrast between urban and rural areas was explained through factors such as patient preference and differential availability and accessibility to greenspaces. Chapter 4 shed light on the spatial differences in the causal effects of greenspace exposure on mental illness mortality using data from the State of Washington. Dichotomized treatment settings and propensity score matching methods were leveraged to examine the spatial disparity in causal effects of greenspace exposure to mental illness mortality. The results elucidated that the causal effect differed significantly across regions within Washington state, emphasizing that spatial heterogeneity is a critical element when examining the causal effects of greenspace exposure on mental illness mortality. By highlighting the spatial and/or temporal disparity in socioeconomic and physical environment factors’ effects, this dissertation provides new perspectives to spatiotemporal mental health research and suggests a transition from disease mapping to effect mapping. This transition offers evidence to devise locally-focused measures that consider the spatial disparities of associative and causal effects.
  • Thumbnail Image
    ItemOpen Access
    Pinpointing the Location of Buried Waste across the Greenland Ice Sheet
    (University of Oregon, 2024-01-10) Kuentz, Lily; Ryan, Johnny
    Military sites have historically become major point sources for environmental contamination. With globally changing climate patterns there is even higher potential than before for certain of these waste sites to become destabilized and cause human-ecological harm. During the Cold War, US strategy sought to turn the Arctic into a theater of war, which has resulted in an extensive network of military sites across its now changing land- and ice-scapes. Recent scientific investigations of the abandoned “city under the ice” at Camp Century, Greenland have analyzed the physical dimensions of the debris field, while various other scholars have articulated the historical and geopolitical dimensions that gave rise to this network of sites. We sought to expand existing discussions of pollution in Greenland by conducting an interdisciplinary and comprehensive analysis of military infrastructure in the ice sheet. We applied a mixed-methods approach that joins historical documents review, remote sensing analysis, and ice sheet modeling to expose the larger undiscussed extent of the US’s ice sheet network. With this study, our specific goals are to: 1) determine the positions of all abandoned US military installations across the Greenland Ice Sheet; 2) draw attention to the history and present-day status of these other sites; and 3) introduce these sites within the framing of “waste colonialism” to better understand the threat they pose to ecological resilience.
  • Thumbnail Image
    ItemOpen Access
    Assessing the Relative Accuracy of Planet and Sentinel-2 Derived Water Maps Using Field Data
    (University of Oregon, 2024-01-09) Van Dusen, Ian; Cooley, Sarah
    This study compares the accuracy of surface water maps from Sentinel-2 and Planet satellites with 43 shoreline observations on the Tanana and Willamette Rivers. High-precision GNSS rover provided the most precise results, with ~10cm accuracy. Handheld devices (BadElf: ~1m, eTrex: ~2m) were less accurate but still can be used for ground validation of satellite shorelines. For the Tanana River, Planet NDWI-derived water maps (~5m) were slightly more accurate than Sentinel-2 (~6m), despite smaller differences than their spatial resolutions. On the Willamette River, Planet achieved ~3m accuracy and Sentinel-2 ~4m accuracy using NIR-band thresholding due to minimal reflectance difference. The temporal advantage of Planet data was evident, with more clear sky observations, particularly in regions with low orbital convergence and during non-clear sky months. Despite slightly lower spatial accuracy and temporal resolution, the accessibility and reliability of Sentinel-2 data make the datasets comparable.
  • Thumbnail Image
    ItemOpen Access
    Holocene Vegetation, Drought, and Fire Variability in the Northern Great Basin, Oregon
    (University of Oregon, 2024-01-09) Saban, Chantel; Gavin, Daniel
    The Northern Great Basin of Oregon is an area of diverse ecologies organized along elevational gradients and variable water sources. At the lowest elevations are the remnants of Pleistocene pluvial lakes, now deflated alkaline playas. Sagebrush (Artemisia tridentata) steppe dominates the region, and anywhere there is water at or very near the surface, marshes are present. At higher elevations open dry-forest systems begin appearing, composed primarily of Pinus ponderosa, but also including Pinus contorta and Juniperus occidentalis. Populus tremuloides is also found in greater abundance at these mid-elevation areas. High-elevation sites often host mixed conifer forests, subalpine forests, and some alpine conditions, with white-bark pine (Pinus albicaulis) found at some of the highest peaks. During the Pleistocene atmospheric conditions were cooler than present day, and evapotranspiration was much lower, resulting in the formation of large lakes. There were also glaciers present in some places, as well as locations too cold and dry to form glaciers.Climatic conditions began changing rapidly beginning ca. 12,000 years ago (Mehringer 1987; Wigand 1987). Maximum insolation continued warming the planet and peaked by 11,000 years ago most of the continental ice sheets were rapidly retreating while montane glaciers in the NGB had already retreated (Osborn and Beavis, 2001). By 9000 years ago maximum air temperatures and increased aridity resulted in the Northern Great Basin pluvial lakes desiccating and many vegetation communities shifting upward in elevation. Such climate changes would also cause fire event frequency to also change during this time, resulting in conditions and disturbance timings very different than the current day. Towards the end of the early Holocene the catastrophic eruption of Mount Mazama in ca. 7640 cal yr BP (Egan, 2015) would again alter vegetation communities and fire events to varying degrees depending on locations relative to the main eruption blast zone. Despite periodic droughts climatic conditions in the NGB have generally cooled through the late Holocene, with vegetation communities again responding. (Benson et al., 1997; Minckley et al., 2007; Marsicek et al., 2018). With an emphasis on the Holocene, questions behind this dissertation were driven by asking 1) by how much did vegetation communities change in the Northern Great Basin responding to changes in climate and fire, 2) which taxa changed the least, which the most, and was it climate or fire that drove those changes, 3) by how much is it possible to observe regional or local drought severity, and 4) by how much and when did climatic timing in the Northern Great Basin differ from Central and Southern Great Basin regions, if at all? To address these broad questions three locations were identified as good study sites. These three locations are within 40 km of each other but at different elevations. Differing elevations were sought for the purpose of attempting to determine what the rate of ecological change was for each location. There are few records showing continuous ecological and fire records at different elevations in the NGB from the early Holocene through to today, but of the records that do remain a rich history of variable timing for fire histories and ecological community structures are sharply delineated and preserved (Gruell, 1995; Minckley et al., 2007). Environmental conditions were reconstructed using traditional and novel methods for three sites identified as ideal for contributing ecological perspectives that would overlap in time. To reconstruct ecological settings, pollen was the primary data source for all three sites. Pollen assemblages provide a view of the climatic conditions at a given point in time, but in some cases may not reflect the full context of conditions as other variables such as tephra or charcoal may alter interpretations. Iin the case of coprolite pollen, a false sense of what vegetation is present on the landscape and in what abundances can occur. When available, carbon and nitrogen concentrations show how climate affected lake productivity, and charcoal provides insights on the fire-adapted landscape and how vegetation responded to changing arid conditions and fire events over time. Chapter 2 examines the late Pleistocene through early Holocene environmental conditions at a low-elevation site by contrasting the regional pollen signal preserved in the sediments of Paisley Caves to the more focused and hyper-local pollen found in chronologically contemporaneous coprolites produced by medium to large-sized mammals as they moved across their ancient landscapes. The results show several consistent differences in pollen assemblage composition in the coprolites compared to the sediments, consistent with the coprolite producers favoring certain environments prior to depositing coprolites in a cave. Chapter 3 examines the history of a rare mid-elevation freshwater lake in the NGB. Dog Lake is a landslide-formed lake whose lake level fluctuates annually, but remained very low during the early Holocene, followed by a period of low lake productivity and lower vegetation cover between 8700 and 8200 cal yr BP, then deepened to a point it resembled depths seen today. Using pollen, C and N concentrations, plant macrofossils, and charcoal, we found when lake productivity was low resulting from increased aridity in the early Holocene, there was also fewer fire episodes than expected from climate, likely due to low fuel availability and probably fewer ignition events. Fire frequencies increased with cooling temperatures and increased effective moisture during the middle Holocene. Chapter 4 describes the fire and hydrological history of White Pine Marsh (WPMA), a high-elevation site located in a small cirque valley at the northern terminus of the Warner Mountains. The site is in a mesic, mixed conifer forest with the perennial marsh having formed after the Mazama eruption and subsequent deposition of tephra in the basin. Sediments also show the fire history was also altered by the tephra. Charcoal showed fires were more frequent and increased in intensity during the early Holocene, abruptly changing to lower intensity and longer fire intervals post-Mazama. Pollen showed mixed conifer conditions since 9500 cal yr BP with Pinus ponderosa always dominant with variable presence of Abies. This dissertation includes published and unpublished co-authored material. At the time of writing Chapter 2 is in press at Quaternary Review. Co-authors include Daniel Gavin, Erin Herring, and Dennis Jenkins. Herring processed the coprolites and provided analysis descriptions. Jenkins provided site expertise to this paper. Gavin and Saban conceptualized the study and devised the methodology of analysis. Both Gavin and Saban analyzed the sedimentary lithological components. Saban wrote the original manuscript with Gavin’s help in the analysis and visualization of the data. Gavin also reviewed, edited, and contributed to the final manuscript. In chapter 3 Saban and Gavin conceptualized the study and analyzed sediments. Saban analyzed the pollen and charcoal. Analysis and data visualizations were significantly aided by Gavin while Saban wrote the original manuscript. Gavin further reviewed, edited, and contributed to the final manuscript. In chapter 4 Saban and Gavin conceptualized the study and devised the research methodology as well as analyzed the sediments, while Saban processed and analyzed pollen and charcoal. Saban wrote the original paper, and Gavin reviewed, edited, and contributed to the final manuscript.
  • Thumbnail Image
    ItemOpen Access
    Mapping Soil Carbon in Wildfire-Affected Areas of the McKenzie River Basin, Oregon, USA
    (University of Oregon, 2024-01-09) Katz, Sydney; Silva, Lucas
    Large-scale wildfires are increasing in frequency and are likely to become more severe under future Pacific Northwest climate scenarios. The effects of wildfires on soil organic carbon (SOC) remain difficult to estimate because soil heterogeneity limits generalizations. We sampled a burn severity gradient (unburned, low, high) of the Holiday Farm Fire (McKenzie River, Oregon, 2020) in a detailed scheme to account for intra-site variation. We measured total SOC, mineral-associated organic carbon (MAOC, stable), particulate organic carbon (POC, unstable), and pyrogenic carbon (PyC, fire-derived). Compared to unburned, the low severity site had higher MAOC and significantly lower POC. We found lower PyC in burned sites, indicating combustion of this pool. There was remarkable variation within each site, but the consistent high levels of MAOC in low severity areas support prescribed burning as a technique to mitigate wildfire risk while limiting losses or increasing SOC compared to high severity fires.
  • Thumbnail Image
    ItemEmbargo
    Neurological Role of Cartographic Visual Contrast in Geospatial Cognition
    (University of Oregon, 2023-07-06) Limpisathian, P. William; Lobben, Amy
    Cartographers assert that, as a core tenet of effective design, effective implementation of visual contrast is crucial for map reading. It is theorized that without sufficient contrast, readers are hindered from efficiently accessing the underlying spatial information. Yet this essential task of practically implementing effective visual contrast is left unsettled in modern cartographic literature beyond cursory discussions. Numerous cartographers over the past century have studied and failed to conclusively resolve this cartographic conundrum. Further, cartographic theories on visual contrast are themselves borrowed from dated Gestalt psychological theories dating back to the 1920s. This research reexamined cartographic understanding of visual contrast through the modern lens of exploratory neuroscience. An interdisciplinary review of related cartographic, geospatial and neuropsychological literature highlighted the theoretical and epistemological dissonance across visual contrast research. Building from that review, a traditional cartographic behavioral experiment was conducted in parallel to a more novel-to-cartography fMRI neuroimaging experiment. The behavioral study evaluated the effect of visual contrast on the cognitive task of map rotation. The addition of fMRI neuroimaging methods enabled further insight into how visual contrast mediates the underlying geospatial cognitive brain processes associated with map rotation. Together, this novel dual-pronged approach attempted to resolve the cartographic contrast conundrum as well as pinpoint related perceptual and cognitive processes essential for map reading. The research found that changes to cartographic visual contrast result in corresponding changes to behavioral task performance (response time and accuracy) as well as associated brain activities. The behavioral statistical models showed that there were statistically significant relationships between combinatorial levels of hue and lightness contrast on map reader’s accuracy and response time as indicators of general map cognitive performance. The neuroimaging models also showed that there were statistically significant brain activation differences for high versus low hue and high versus low lightness contrast. Further, this dissertation identified regions of the brain associated with map reading and design-centric information decoding that were previously poorly understood. Thus, this dissertation expands the importance and understanding of cartographic visual contrast within modern cognitive cartography literature.
  • Thumbnail Image
    ItemEmbargo
    Modeling Future Fire, Vegetation, and Carbon Trajectories Under Climate Change in Interior Alaska Boreal Forest
    (University of Oregon, 2023-03-24) Weiss, Shelby; Lucash, Melissa
    Fire activity has increased in interior Alaska in recent decades and these trends are projected to continue under climate change. A greater frequency and severity of wildfires have been found to favor broadleaf-deciduous species across numerous field and modeling studies, impacting the resilience of black spruce forests and potentially impacting the carbon storage capacity in the region. This dissertation explores potential future trends in boreal forest fire regimes, vegetation composition, and carbon storage under climate change through three studies using the spatially explicit landscape simulation model, LANDIS-II. The modeling framework represented wildfire dynamically using the SCRPPLE fire extension and captured belowground carbon, hydrologic, and permafrost dynamics in addition to vegetation growth using the DGS succession extension. All three studies relied on simulations of a 380,400-hectare landscape (4-ha resolution) under both historic and future (RCP 8.5) climate projections. The first study explored impacts of wildfire under different climate change scenarios and found that annual area burned and average fire size were greater under climate change; climate change scenarios also resulted in a greater rate of areas burning multiple times during the simulation period. The second study focused on quantifying and identifying drivers of potential shifts in dominant forest type following different numbers of wildfires. It showed that initially-conifer-dominated areas on the landscape that experienced greater numbers of fires more often shifted to broadleaf-deciduous dominance, and this effect was exacerbated by climate change. Vegetation type transitions away from conifer dominance were most strongly driven by percentage of biomass removed in the most recent wildfire. The third study quantified differences in carbon pools and vegetation productivity under different climate scenarios and found that while carbon and net primary productivity overall increased across the landscape under climate change, the amount of soil carbon available for decomposition also increased and associated increases in heterotrophic respiration led to the landscape being a net source of atmospheric carbon. Altogether these results reflect the importance of accounting for key ecosystem processes when modeling future change in interior Alaska and how climate change and wildfire behavior can interact to drive change in vegetation composition and future carbon storage.
  • Thumbnail Image
    ItemEmbargo
    Contradictions of Capital and Labor: Capital Accumulation and the Racialized Policing of Asian Massage Parlors in Seattle's Chinatown-International District
    (University of Oregon, 2023-03-24) Chen, Kaijing Janice; Fish, Carolyn
    Massage parlors in Seattle’s Chinatown-International District have experienced heightened police surveillance, mobilized by legislation that increasingly regulates massage labor performed by Asian migrant women. This wave of criminalization coincides with contested and renewed investment in the neighborhood, indicating the use of policing to displace workers and create the conditions for a new spatial fix, or the production of space through capital accumulation. Through an analysis of legislative records, police reports, and media accounts, I argue that the policing of Asian massage parlors draws on a sensationalist imaginary of human trafficking that simultaneously evokes longstanding racialized tropes and furthers the racialization of Asian migrant workers. Finally, I investigate how anti-trafficking rhetoric rationalizes greater police surveillance that displaces Asian massage workers and opens new spaces for capital accumulation.
  • Thumbnail Image
    ItemOpen Access
    From Plot to Region: Assessing the Role of Land Use in Tropical Montane Forest Structure and Dynamics
    (University of Oregon, 2022-10-26) Uscanga Castillo, Adriana; de Carvalho Ramos Silva, Lucas
    Forest disturbance and land use are strong drivers of forest structure, composition, and dynamics and yet, their role in shaping tropical montane landscapes is poorly understood. The overarching goal of my dissertation is to broaden our understanding on the role of land use in shaping forest structure and forest dynamics in tropical montane landscapes, with a particular focus on aboveground biomass (AGB). Using the Northern Mountains of Oaxaca (NMO), Mexico, as a study system, I investigate changes in vegetation across space and time, particularly in an ecosystem known as tropical montane cloud forest (TMCF). The NMO has experience forest disturbance by land use for centuries. Deeply influenced by regional and global socioeconomic forces, land use has changed over time, modifying montane landscapes accordingly. Tropical mountains are currently experiencing large rates of forest loss related to the expansion of agricultural commodity production. Land-use and land-cover change, transformations of land tenure regimes, landscape management strategies, the development of policies related to agricultural production and forest protection, and the environmental conditions that define vegetation growth, are all factors that intertwine to define current and future forest dynamics. Thus, in this project I analyze various aspects of land use in shaping forest structure and dynamics, including the local and regional effects of land-use intensity on tropical montane forests, ways to include these effects at regional scales through forest structure models, and current land use dynamics taking place in the NMO. In the first chapter I explain the global relevance of tropical mountains and I introduce the foundational concepts of my dissertation, including forest structure and succession, a brief overview of land use in the study region, and the significance of my research. In the second chapter I analyze the relative roles of land use and environmental factors on AGB spatial patterns, as well as the relationship between forest structure and tree diversity. I conclude that land use has a larger role in shaping AGB spatial patterns, and that the relationship between tree diversity and AGB is positive but weak. In chapter three I use remote sensing data to study recent small-scale disturbance related to land use in TMCF. Seeking for novel methods to incorporate land use effects on forest structure in AGB estimates, I found several remote sensing variables that have the potential to be used as input variables in AGB predictive models. These variables are derived from Landsat time series that track vegetation cover change over time. I conclude with providing some recommendations on the use of these variables. In chapter four I assess trends of forest loss and forest conservation in the NMO over the last two decades. Here, I provide a map of the spatial distribution of forest loss and the ecosystems that have been affected the most. I show that forest loss in the NMO has increased in the last six years. I discuss possible driving causes of forest loss, including its relation to the establishment of cattle ranches and agricultural production, and assess the effects of the forest conservation projects taking place in the region. Finally, in the last chapter I summarize the main results of my dissertation.
  • Thumbnail Image
    ItemOpen Access
    Simulating the Effects of Prescribed Fire on Forested Landscapes in the Siskiyou Mountains, USA
    (University of Oregon, 2022-10-26) Deak, Alison; Silva, Lucas
    Land managers, scientists, and policymakers have increasingly promoted and invested in prescribed fire to reduce wildfire risk and restore fire-adapted ecosystems. We investigate the amount of prescribed fire needed to meet these goals in the Siskiyou Mountains of northwest California and southwest Oregon using a forest-succession model. Specifically, we ask, how much prescribed fire is required to maintain carbon storage and reduce the severity and extent of wildfires under divergent climate change scenarios? A prescribed fire frequency of fifteen years was found adequate for maintaining carbon storage on sites. Prescribed fire lowered the severity of wildfires at a local-scale and was most effective under a warmer and wetter climate. These results suggest targeting treatments in areas with high social-ecological concern and within climactic and topographic gradients most conducive to its effects will provide opportunities to decrease the risk of high-severity fire and contribute to meeting climate mitigation goals.