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Inner-shelf circulation off the central Oregon Coast
Get PDFInner-shelf circulation and mechanisms of across-shelf transport of water masses were examined using seven years of observations collected by the Partnership for Interdisciplinary Studies of Coastal Oceans (PISCO) program, a long-term monitoring effort along the central Oregon coast. Since 1998, moored velocity and hydrographic measurements have been obtained during the summer upwelling season in water depths of 30, 15, or 8 m at 3-5 stations along a 75 km stretch of the Oregon shelf. These observations enabled a description of along-shelf variations and upwelling dynamics in an area of intermittent wind forcing but little buoyancy influences. While wind forcing and bathymetry were nearly spatially uniform in the inner-shelf, circulation was spatially variable due to an offshore submarine bank. Classic two-dimensional upwelling existed north of the bank, with bottom stress and acceleration balancing the wind stress in the depth-averaged along-shelf momentum equation. This balance failed onshore of the bank where the pressure gradient and nonlinear advection were needed to close the momentum balance. Driven by along-shelf wind forcing, across-shelf surface transport was 25% of the theoretical Ekman transport at 15 m water depth, 1-2 km offshore, and reached full Ekman transport 5-6 km offshore in 50 m of water. This result, based on season-long comparisons of measured across-shelf transport and theoretical Ekman transport, defines the across-shelf scale of coastal upwelling on the Oregon shelf. However, observations of across-shelf circulation also highlight the rapid movement of water masses and variable residence times in the inner shelf. To quantify the time variability of across-shelf exchange, a numerical model was adapted to estimate vertical eddy viscosity using the velocity measurements. Resulting depth-averaged eddy viscosities ranged from 0.8x10[superscript −3] m [superscript 2] s[superscript −1] during upwelling winds to 2.1x8x10[superscript −3] m [superscript 2] s[superscript −1] during downwelling winds, consistent with previous numerical model results. The difference in eddy viscosities between upwelling and downwelling led to varying across-shelf exchange efficiencies and increased net upwelling over time. These results quantify the structure and variability of circulation in the inner-shelf and have significant implications for ecological processes (e.g., larval recruitment, nutrient availability) in the region.Keywords: eddy viscosity, Ekman transport, coastal upwelling, Oregon, inner shelf dynamics, inner shelf circulation, momentum balances, across shelf exchang
How Does Climate Change Adaptation and Carbon Price Policy Affect Forested Landscapes? An Empirical Analysis of Forest Management under Climate Change on the U.S. West Coast
No full textPrivate forest landowners can adapt to climate change by altering their timing and intensity of harvests, by changing thinning or fertilizing activities, and by altering the tree species growing on their land. The well-being of humans is closely tied to the ecosystem services that forests provide as both market and non-market goods and services, including timber, recreation and tourism, carbon sequestration, wildlife species habitat, erosion control, and water purification. Adaptation by forest landowners to climate change can result in changes in a number of ecosystem service provisions. For example, a change in tree species composition and age class structure of forests could lead to degradation and loss of habitat for existing wildlife species; switching to different tree species could change the carbon sequestration rates; and market timber prices could adjust as a dominant tree species is replaced by other species and its market supply declines.There are many who advocate for a policy intervention in forestry in response to climate change, as forests mitigate greenhouse gas emissions as a major carbon sink. The climate mitigation policy of carbon pricing uses a forest’s capacity as a carbon sink to help internalize the negative externalities resulting from climate change. Since different tree species sequester different amounts of carbon at different rates, carbon prices alter incentives for private forest management, potentially resulting in either accelerating adaptation or pushing back. Despite the potential consequences of adaptation behaviors on ecosystem services, there has been little empirical analysis on how climate change and mitigation policy can affect adaptation behavior. Examining how mitigation policies affect adaptation behavior has important policy implications when the mitigation policy has the potential to create other externalities such as endangering existing wildlife species whose habitat may be altered by changes in forest management resulting from both climate change and mitigation policy.My dissertation conducts an empirical micro-econometric analysis of private landowners’ forest management decisions under climate change in California, Oregon, and Washington. The study area consists of diverse climate conditions and some of the most productive forests in the world. I address the following primary research questions: (1) How will the forested landscape evolve over time as humans adapt to a changing climate?; (2) How will climate mitigation policy affect adaptation behaviors?; (3) What is the impact of adaptation on existing wildlife species habitat?; and (4) What is the impact of adaptation on natural disturbances such as fire? Chapter 2 provides the conceptual framework for my approach with an emphasis on commonly used forest management practices, followed by an empirical econometric approach grounded in natural resource economic theory regarding forest management. In Chapter 3, I estimate a nested-logit econometric model for forest management practices while accounting for the simultaneous nature of harvest and replanting decisions, as well as the impact of natural disturbance occurrence on management decisions. In Chapter 4, the estimated discrete-choice econometric model is used as the basis for a dynamic simulation of the time-path of landscape change under both climate change and carbon price scenarios. In the western portion of the Pacific Northwest, I find that landowners shift out of their current dominant tree species choice of Douglas-fir to other tree species more suitable for the future climate, notably hardwood and ponderosa pine. For example, climate change discourages a harvested plot being replanted with Douglas-fir in western Oregon and Washington by 20-65 percentage points relative to a no-climate-change baseline, resulting in the landscape shifting away from the current Douglas-fir forests towards other forest types. My results also indicate that the discrete effect of climate change on the probability of that the stock of forest types changes is 6 percentage points for current Douglas-fir forests in western Oregon, which indicates that the climate path in the next 90 years will add 6 percentage points to the probability of the current Douglas-fir forests switching to different forest types. The discrete effect on the current stock of hardwood forestland is to reduce the probability of switching out of hardwoods by 13 percentage points.The results also imply that a carbon price policy would further accelerate such adaptation behaviors, where carbon pricing has a larger effect on the adaptation away from Douglas-fir than the effects of climate change. For example, the discrete effect of carbon pricing on the probability of switching the current Douglas-fir forest to other forest types is an additional 10 percentage points. The effect of a carbon price on landscape change could necessitate an additional policy intervention to counteract the impact on wildlife species from the landscape’s more rapidly changing habitat. Chapter 6 discusses the impact on wildlife species that have been listed as concerned species by state agencies, with a particular focus on seven “habitat specialists” who have narrow habitat preferences associated with particular forest types. I present changes in their habitat across ecoregions, as well as across the entire habitat range and by states. The direction and magnitude of change vary considerably across regions. The effect of climate change shows that some species gain from climate change (e.g., ringtail), while many others lose. The direction and degree of impact of climate change also vary considerably across regions. The carbon price intensifies the change by inducing additional habitat change through forest management. In Chapter 7, I focus on the effects of climate adaptation on natural disturbance with a distinction between the impact of climate change and the impact of the carbon price scheme. My finding illustrates the mechanism as to why natural disturbance increases in some regions while decreasing in others. I also discuss how the burn severity of wildfires can increase under climate change.My empirical approach combines fine-scale econometric and simulation methods that use recently observed forest management behaviors to estimate a model that serves as the basis for projecting changes in forest management. My framework is developed to reflect forest landowners’ decision-making as observed in recent years. The econometric estimation accounts for the simultaneous nature of various forest management choices and different channels with which climate affects the forest landscape both directly through changes in growing conditions and indirectly through deliberate modifications of forests. The simulation framework treats natural disturbance events as endogenous as landowners’ harvest and replanting decisions affect disturbance outcomes, and the possibility of natural disturbance affects management. The simulation tracks forest attributes such as stand volume and incremental growth, depending on the landowners’ decisions as to the timing and intensity of harvest, as well as replanting choice.The simulated growth of the forest stock is a key determinant that affects the landowner’s decision as the simulation progresses through time. Another novel feature of the simulation is that it allows me to model different policy scenarios because management decisions are explicit functions of forest rents. This allows me to differentiate landscape outcomes into separate components, such as the impact of climate change and the impact from carbon price policy. Private forestland today is formed by deliberate landowners’ decisions in addition to natural processes that affect tree species. Management decisions are affected by site conditions, climate, market conditions, and policy factors. My simulation approach contributes by incorporating interactions between these intertwining factors in a manner that enhances understanding about the impact of climate change on forested landscapes. By providing the time paths of landscape change with a focus on the policy of carbon pricing (Chapter 5), wildlife species conservation (Chapter 6), or natural disturbance occurrence (Chapter 7), my dissertation will offer foundational information to policy makers and natural resource managers about the state of forest landscape change under climate change and climate mitigation policy.In a broad sense, this dissertation uses empirically-driven models to highlight the interplay between climate change, landowner adaptation, carbon prices, natural disturbance, and the spatially heterogeneous biophysical climate conditions in the study area. Although previous studies have examined each component separately, the role of adaptation behavior as the intermediate link that connects climate change and landscape change needs more attention in the literature. The methodology developed in this dissertation could also apply to other economic analyses of policy outcomes at the intersection of land use, land-use change, ecosystem services, climate change, and human well-being to help us better understand the feedback between human behavior, the environment, and long-term sustainability of natural resources. This dissertation research contributes by improving our understanding of the consequences of climate change and climate policies on adaptation behavior in a manner that provides a foundation for improved policy design that balances the needs of people and environmental values.Keywords: Climate Change, Adaptation, Ecosystem Services, Biodiversity, Land-use Modelin
Three essays on food security, food assistance, and migration
Get PDFThis dissertation's three essays explore the determinants of food insecurity for rural farm households, the influence of rainfall variability and long-run changes in rainfall levels on the migration decisions of working-age household heads, and the distributional impacts in core and periphery regions of food assistance to households in the hinterland.
The first essay examines how socio-economic characteristics of households, local conditions, and public programs are associated with the probability that a farm household in rural Malawi is food insecure. The statistical analysis uses nationally representative data for 7,965 randomly-selected households interviewed during 2004/05 for the second Malawi Integrated Household Survey (IHS-2). Regressions are estimated separately for households in the north, center, and south of Malawi to account for spatial heterogeneity. Results of a Probit regression model reveal that households are less likely to be food insecure if they have more cultivated land per capita, receive agricultural field assistance, reside in a community with an irrigation scheme, and are headed by an individual with a high school degree. Factors that positively correlate with a household's food insecurity are number of household members and distance to markets.
The second essay uses nationally representative data from Malawi's 2004/05 Integrated Household Survey (IHS-2) to examine whether rainfall conditions influence a rural worker’s decision to make a long-term move to an urban or another rural area. Results of a Full Information Maximum Likelihood regression model reveal that (1) rainfall shocks constrain migration, most likely by making it difficult for prospective migrants to cover costs of migration, (2) migrants choose to move to communities where rainfall variability is lower, and (3) rainfall shocks have larger negative effects on the earnings of recent migrants than on long-time residents’ earnings.
The third essay examines how benefits from food assistance programs to needy households spillover between areas and among household income groups in the United States. We study the effect of the Supplemental Nutrition Assistance Program (SNAP) in the Portland Oregon metro Core and its Periphery trade area, using a Multiregional Input- Output (MRIO) model based on a Social Accounting Matrix (SAM). The analysis captures direct, indirect and induced effects of SNAP on each region and spillover effects on the other region. SNAP benefits to the lower income household classes in each region are traced to their effects on the local economy in each region, and to the effects on household income by income class. The analysis finds that (1) the economic impact on the Portland Core from a given level of SNAP benefits to households in the Periphery is greater than the economic impact in the Periphery from the same level of SNAP benefits to households in the Core; (2) high-income households benefit more than low-income households from the indirect and induced economic impact of SNAP.Keywords: Food Security, Migration, SNAP, Climate Change, Multiregional Input-output SAM Model, Africa, Assistant Programs, Food Stamp, Malaw
The Use of Nisin and Nisin Resistant Strains of Leuconostoc oenos to Control Malolactic Fermentation and to Prevent the Growth of Spoilage Bacteria in Oregon Wines [1991-1992]
Get PDFNisin, a bactericidal polypeptide, has the potential to inhibit spoilage bacteria and control rnatolactic fermentation in wines. Nisin activity has previously been observed to remain stable in white wines but to decrease in red wines. This decrease is believed to be directly proportional to the concentration of polyphenolic compounds in the wines. Six polyphenolic components of grapes and wine ( gallic acid, catechin, myricetin, quercetin, malvidin 3,5-diglucoside, and crude grape tannin) were tested individually in a model wine system. Tannin resulted in the largest decrease in nisin activity. Grape tannin was further evaluated using a series of red wines ages for two, four, and six months before the addition of nisin. These studies showed a greater loss of nisin activity in the wine aged for six months that in the younger wines. Identical sets of wine, aged for two, four, and six months at either 4'C or 23'C before nisin was added, showed in each case that increased temperature resulted in an increased loss of nisin activity. This information may be valuable for winemakers who are considering the addition of fiisin to their wines to inhibit (or control) malolactic fermentation and the growth of spoilage lactic acid bacteria
OSU Wine and Grape Research and Extension Newsletter : May 2010
Get PDFAs the season progresses and all anticipate bloom, we hope you take the opportunity to read this issue. It is full of useful information on some pests of concern—both old and new—in the vineyard and winery: powdery mildew, grape rust mites, Spotted Wing Drosophila and Brettanomyces.
We include other useful information and resources in this issue including a list of new research publications from the researchers in our Viticulture & Enology Team at OSU and USDA-ARS, and new online diagnostic and learning modules with information on grapevine nutrition and herbicide drift. Finally, you can learn more about the OSU Viticulture & Enology degree program from the OSU Alumni Spotlight article
Nonlinear terahertz spectroscopy of carbon nanomaterials and semiconductor nanostructures
Get PDFThis thesis will cover my work relating to the developing field of terahertz (THz) science and technology. It will present experimental and theoretical studies investigating the optical and electrical properties of various material systems using novel THz imaging and spectroscopy techniques. Due to its low photon energy, THz imaging and spectroscopy are useful tools for non-contact, non-destructive probing of materials. Broadband, single-cycle THz pulses are prepared using modern THz generation technology. Using the THz detection techniques of THz raster imaging and THz time-domain spectroscopy (THz-TDS), the local carrier dynamics of nanomaterials such as graphene and carbon nanotubes were determined. THz measurements on single-layer graphene grown with different recipes and on various substrates exhibit sub-millimeter spatial inhomogeneity of sheet conductivity. THz transmission data reveals that a thin plastic, polymethyl methacrylate (PMMA), layer in contact with single-layer graphene induces a small yet noticeable reduction in conductivity. Ulterior THz measurements performed on vertically-aligned multi-walled carbon nanotubes (V-MWCNT) employ time-resolved THz transmission ellipsometry. The angle- and polarization-resolved transmission measurements reveal anisotropic characteristics of the THz electrodynamics in V-MWCNT. The anisotropy is, however, unexpectedly weak: the ratio of the tube-axis conductivity to the transverse conductivity, σ_z / σ_ xy ≅ 2.3, is nearly constant over the broad spectral range of 0.4-1.6 THz. The relatively weak anisotropy and the strong transverse electrical conduction indicate that THz fields readily induce electron
transport between adjacent shells within the multi-walled carbon nanotubes.
In-depth coverage of the development of a high-field THz generation system based on a lithium niobate prism will be presented. The evolution of techniques in the realm of high power THz generation is ongoing. The resolved issues throughout implementation include: magnesium doping, phase matching, and wave front distortion. The high power, broadband THz emitter (maximum THz field, E_max > 1 MV/cm) allows for nonlinear THz spectroscopy of various material systems including single-layer graphene and high-resistivity, bulk GaAs. THz-induced transparency is observed in two types of single-layer graphene samples: (i) suspended graphene-PMMA layer and (ii) graphene embedded in dielectrics. THz-induced transparency is shown to be significantly higher in suspended graphene than in graphene on a Si substrate. The experimental observation leads to a universal nonlinear THz property of graphene that the sheet conductivity undergoes two-fold reduction when THz fields reach 0.8 MV/cm. We confirm the generality of this result by measuring different grapheme samples on different substrates. Time-resolved THz transmission measurements show that the THz-induced transparency in graphene is dynamic; the transient conductivity gradually decreases throughout the pulse duration. The large THz fields induce sub-picosecond electron thermalization and subsequent carrier-carrier scattering, transiently modulating the
electrical and optical properties, in effect reducing the electrical conductivity of graphene by an order of magnitude. Nonlinear THz spectroscopy methods are also applied to the investigation of a nano-antenna patterned, high-resistivity, intrinsic GaAs wafer. The antenna near-field reaches 20 MV/cm due to a huge field enhancement in the plasmonic nanostructure. Thus, the nonlinear THz interactions take place in the confined nanometer-scale region adjacent to the antenna. As a result of the huge THz fields, nano-antenna patterned GaAs demonstrates remarkably strong nonlinear THz effects. The fields are strong enough to generate high density free carriers (N_e > 10¹⁷ cm⁻³) via high-energy interband excitations associated with a series of impact ionizations (n_I ≈ 33-37); thus inducing large absorption of THz radiation (> 35%).Keywords: Carbon Nanotubes, CNT, High Field, Lithium Niobate, Nano Antenna, GaAs, Terahertz, Graphene, Nonlinear, High Power, Gallium Arsenid
Science inquiry as knowledge transformation : investigating metacognitive and self-regulation strategies to assist students in writing about scientific inquiry tasks
Get PDFScience inquiry is central to the science education reform efforts that began in the early 1990's. It is both a topic of instruction and a process to be experienced. Student engagement in the process of scientific inquiry was the focus of this study. The process of scientific inquiry can be conceived as a two-part task. In the initial part of the task, students identify a question or problem to study and then carry out an investigation to address the issue. In the second part of the task, students analyze their data to propose explanations and then report their findings. Knowing that students struggle with science inquiry tasks, this study sought to investigate ways to help students become more successful with the communication demands of science inquiry tasks.
The study took place in a high school chemistry class. Students in this study completed a total of three inquiry tasks over the course of one school year. Students were split into four experimental groups in order to determine the effect of goal setting, metacognitive prompts, and sentence stems on student inquiry tasks. The quality of the student written work was assessed using a scoring rubric familiar to the students. In addition, students were asked at four different times in the school year to respond to a self-efficacy survey that measured student self-efficacy for chemistry content and science inquiry processes.
Student self-efficacy for the process of scientific inquiry was positive and did not change over the course of the study while student scores on the science inquiry tasks rose significantly. The metacognitive prompts and instruction in goal setting did not have any effect on student inquiry scores. Results related to the effect of the sentence stems were mixed. An analysis of student work indicated that students who received high marks on their initial inquiry task in this study were the ones that adopted the use of the sentence stems. Students who received low marks on their initial inquiry task did not tend to use the sentence stems. An analysis of word counts that compared the number of words used in the Framing section to the number of words used in the Analysis section indicated that students may have been using insufficient writing strategies. This study concludes with implications for classroom practice and recommendations for future research around student writing in the science classroom.Keywords: Inquiry, Writing, Science Education, Self-regulation, Metacognitio
Bovine Kappa-Casein Glycomacropeptide: Its Effects on the Microbiome, Inflammation and the Potential in Irritable Bowel Syndrome Management
Get PDFIrritable bowel syndrome (IBS) is a prevalent gastrointestinal disorder experienced by 10–15% of the global population, manifesting as chronic abdominal pain, bloating and inconsistent bowel habits. The search for effective treatments remains ongoing. One promising contender in this realm is kappa-casein glycomacropeptide (GMP), a milk-derived peptide. Its potential benefits stem from its multifaceted abilities: modulating the gut microbiome, influencing immune responses, impacting gut motility and barrier functions, and binding toxins. These attributes intriguingly align with IBS's pathophysiology, which encompass gut microbiota imbalances, immune system dysregulation and compromised gut barrier functions.
The review offers a comprehensive examination of GMP's role in modulating the gut microbiome, focusing on its impact on various bacterial populations, both beneficial and pathogenic. The analysis also addresses the microbial imbalances identified in IBS patients, suggesting that GMP could play a crucial role in restoring a balanced microbial environment and improving overall gut health. Furthermore, the review evaluates GMP's anti-inflammatory capabilities, exploring its impact on specific inflammatory markers and its potential to alleviate the persistent low-grade inflammation associated with IBS. Additionally, it examines recent findings on GMP’s effects on gut motility and barrier health, comparing these insights to the alterations noted in individuals with IBS.
Complementing this review, the pilot study assessed the effects of administering a 30 g daily GMP supplement for three weeks to a group of five IBS patients. The study focused on changes in gut microbiota, fecal and blood inflammatory markers and overall gut symptoms. Although the review highlighted promising aspects of GMP, the pilot data revealed a subdued outcome: there was no significant change in fecal microbiota, immune markers exhibited minimal variations, and gut symptoms remained consistent post-GMP supplementation.
This dissertation accentuates the potential of GMP as a therapeutic agent for IBS, emphasizing the need for continued investigations to decipher optimal supplementation protocols and to unearth the intricacies of GMP's interactions with gut health