• Outpatient care in Fairbanks: supporting people with schizophrenia

      Wiley, Alex; Renes, Susan; Gifford, Valerie; Harrison, Lynn (2015)
      With the current lack of residential treatment facilities, long-term hospitalization, and mental health agencies that can fully support people with schizophrenia in Fairbanks, Alaska, there are many ethical concerns that must be addressed to best support clients with schizophrenia. The ethical considerations present in the success of outpatient care include: a) promoting the welfare of clients, b) utilizing plans that offer reasonable promise of success, c) understanding the limits imposed on the support networks of these clients, and d) the limitations of employment opportunities for these clients in an outpatient setting. Reviewing literature on the experiences of people with schizophrenia revealed three stages of treatment normally experienced: a) acute care, b) transition care, and c) chronic care. Areas most impacted for people with schizophrenia are socialization and work, memory and intelligence, suicide risk and other disorders, and interactions with family, friends and the community. In Fairbanks, Alaska where weather hinders socializing and available services are limited, building many strong support resources is incredibly important to give people with schizophrenia the best chance of recovery and a stable quality of life.
    • Overcoming CubeSat downlink limits with VITAMIN: a new variable coded modulation protocol

      Sielicki, Thomas; Thorsen, Denise; Hamkin, Jon; Hawkins, Joseph; Mayer, Charles (2013-12)
      Many space missions, including low earth orbit CubeSats, communicate in a highly dynamic environment because of variations in geometry, weather, and interference. At the same time, most missions communicate using fixed channel codes, modulations, and symbol rates, resulting in a constant data rate that does not adapt to the dynamic conditions. When conditions are good, the fixed date rate can be far below the theoretical maximum, called the Shannon limit; when conditions are bad, the fixed data rate may not work at all. To move beyond these fixed communications and achieve higher total data volume from emerging high-tech instruments, this thesis investigates the use of error correcting codes and different modulations. Variable coded modulation (VCM) takes advantage of the dynamic link by transmitting more information when the signal-to-noise ratio (SNR) is high. Likewise, VCM can throttle down the information rate when SNR is low without having to stop all communications. VCM outperforms fixed communications which can only operate at a fixed information rate as long as a certain signal threshold is met. This thesis presents a new VCM protocol and tests its performance in both software and hardware simulations. The protocol is geared towards CubeSat downlinks as complexity is focused in the receiver, while the transmission operations are kept simple. This thesis explores bin-packing as a way to optimize the selection of VCM modes based on expected SNR levels over time. Working end-to-end simulations were created using MATLAB and LabVIEW, while the hardware simulations were done with software defined radios. Results show that a CubeSat using VCM communications will deliver twice the data throughput of a fixed communications system.
    • An overview on the author's graduate recital program

      Koukakis, Dimitrios Paganos; Zilberkant, Eduard; Post, William; Celaire, Jaunelle (2016-05)
      The following project paper consists of three chapters, examining the works in my Graduate Recital Program. The first chapter analyzes the form, structure and particular interesting elements that Aram Khachaturian uses in his Sonata for Piano. The second chapter gives a brief historical information of the term Fantasy and examines two examples of the genre, Chopin's Fantasy in F minor op. 49 and Carl Vine's Sonata no. 3 "Fantasia". The third chapter covers some biographical information of Elliott Carter and examines the form and structure of his work for solo piano, 90+.
    • Overwintering Physiology Of Arctic And Subarctic Insects From Interior Alaska

      Sformo, Todd L.; Barnes, Brian; Duman, John; Boyer, Berty; Martinson, Tracey (2009)
      This dissertation focuses on the overwintering of three insects from Interior Alaska: a hemipteran, Elasmostethus interstinctus, and a coleopteran, Cucujus clavipes puniceus, that are freeze avoiding in the strict sense of the phrase, and a dipteran, Exechia nugatoria, that is simultaneously partially freeze avoiding and freeze tolerant. The variability within the freeze avoidance strategy itself is a key theme throughout this dissertation. Two significant contributions to comparative physiology are the confirmation of insect vitrification (glass formation) with its attendant extension of freeze avoidance and survival into a new, extreme low temperature record of -100�C and the simultaneous coupling of freeze avoidance and tolerance within an individual, which may more properly be described as a new overwintering strategy. Vitrification is the process by which ice crystallization is circumvented, resulting in a supercooled amorphous solid. Through a combination of antifreeze proteins that inhibit ice nucleation, dehydration tolerance, presence of high glycerol concentration, and low temperatures, the mobility of the remaining liquid water molecules is reduced, effectively by-passing the crystalline state. The second contribution is the discovery of a new overwintering strategy that combines freeze avoidance and freeze tolerance within an individual. In this case, the abdomen freezes (and the insect survives), while the contiguous head/thorax remains supercooled. These findings lead to the following evolutionary and trans-disciplinary questions. Is vitrification an adaptation? What is the selective advantage of compartmentalizing ice between body sections of an individual insect? Is this new overwintering strategy an example of a species transitioning between either becoming exclusively freeze avoiding or free tolerant? Applying new understanding of mechanisms of insect vitrification and avoidance of devitrification to cryomedicine may extend preservation of human tissues and organs. Similarly, for physical and material scientists, by understanding the patterns of ice formation within insects that tolerate, inhibit, and/or impede ice formation below the homogeneous ice nucleation temperature of water (-40�C), new biomimetic possibilities can be envisioned.
    • Oxidative stress is transient and tissue-specific during cold acclimation of threespine sticklebacks

      Kammer, Aaron R. (2010-08)
      We sought to determine if oxidative stress occurs in liver, oxidative muscle or glycolytic muscle of threespine sticklebacks during cold acclimation. Fishes were held at 20°C for 12 wks and then acclimated to 8°C for 9 wks or held at 20°C for an additional 9 wks. Animals were harvested during the first four days of cold acclimation, and at wk 1, 4 and 9. Protein carbonyls were quantified as an indirect measure of the production of reactive oxygen species (ROS). The activity of superoxide dismutase (SOD), levels of SOD mRNA, and glutathione levels were quantified as indices of protection against ROS. All measurements were made in liver, glycolytic muscle and oxidative muscle. Protein carbonyl levels increased in livers of fishes after 1 wk at 8°C and decreased after wk 4. Total glutathione levels increased in livers on day 3 of cold acclimation and then decreased by wk 4. Measured at a common temperature, SOD activity increased early in all tissues and remained elevated throughout cold acclimation. Measured at the acclimation temperature, SOD activity increased only in oxidative muscle after 9 wks of cold acclimation. Together, these results indicate that oxidative stress is transient and tissue-specific during cold acclimation of fishes.
    • Oxytetracycline tags in pink salmon fry applied by immersion and detected by fluorescence spectrometry

      Page, Timothy Kent (1989-05)
      I investigated the feasibility of using spectrophotofluorescence as a quantitative method of analyzing pink salmon fry otoliths for the presence of oxytetracycline (antibiotic). I exposed twenty-four groups of pink salmon fry (approximately 250 individuals each) to solutions of oxytetracycline ranging in concentration from unexposed to 2000 ppm, and in duration of exposure from one to twelve hours. Otoliths from unexposed fry had the lowest mean fluorescence (log e [mean flu. units] = -1.77). Otoliths from fry exposed to 500 ppm for twelve hours had the highest fluorescence (log e [mean flu. units] = 0.899). Fluorescence increased nonlinearly with duration of exposure. There is a linear increase of fluorescence with exposure up to 500 ppm; above which fluorescence decreases. Pink salmon fry exposed to OTC in solution absorb detectable amounts of OTC in their otoliths. These amounts of OTC can be quantitatively measured by spectrofluorometry.
    • Ozone depletion and biologically relevant ultraviolet radiation

      Zeng, Jun; Stamnes, Knut; Benner, Richard; Bowling, Sue Ann; Eslinger, David; Kawasaki, Koji; Watkins, Brenton (1995)
      An atmospheric radiative transfer model is used to calculate surface spectral ultraviolet irradiance under cloud-free conditions, and compared with measurements made at Lauder, New Zealand (45$\sp\circ{S}$, 170$\sp\circ{E})$ before and after the eruption of Mt. Pinatubo, and including a snow-covered surface. The ratios of diffuse to direct irradiance depend critically on solar elevation, surface albedo, and aerosol extinction. Ozone changes have pronounced effects on the global UVB irradiance, but have only a minor effect on these ratios. The comparison suggests that the ultraviolet radiation exposure can be computed with confidence for clear sky conditions, if the appropriate atmospheric pressure and temperature profiles, ozonesonde data, surface albedo, and aerosol optical properties are available. The total ozone abundances are derived by using ground-based UV irradiance measurements and compared with TOMS in Antarctica and the Arctic from 1990 to 1994. The comparisons show that they are generally in good agreement. Possible reasons for the discrepancies between the two methods are discussed. The equivalent cloud optical depths are also inferred from these data. Ozone depletion can also increase the penetration of ultraviolet radiation into the aquatic system. A coupled atmosphere-ocean radiative transfer model is used to investigate the effect of ozone depletion on UV penetration through the atmosphere and into the underlying water column. Comparisons between model computations and in situ measurements of irradiances made in Antarctic water show good agreement in the UV spectral range between 300 and 350 nm. The ratio of UVB (280-320 nm) to total (280-700 nm) irradiance also compared well. For a given ozone reduction the largest relative increase of UVB radiation arriving at the surface and penetrating to various depths in the ocean occurs at large solar zenith angles. At high latitudes the most pronounced increase in UVB exposure due to an ozone depletion occurs in the early spring, when ozone depletion is expected to be the most severe. The sensitivities of irradiance reflectance and diffuse attenuation coefficients to solar zenith angle, sky conditions, and chlorophyll concentration are discussed by using a coupled atmosphere-ocean radiative transfer model. The irradiance reflectance is sensitive to solar zenith angle, cloud cover, and chlorophyll concentration; the diffuse attenuation coefficient is sensitive to solar zenith angle and chlorophyll concentration, but less sensitive to sky conditions.
    • Pacific sleeper sharks in the Northeast Pacific Ocean: relative abundance, plausible incidental exploitation rates, trophic ecology, and habitat use

      Courtney, Dean Louis; Adkison, Milo D.; Foy, Robert; Sigler, Mike; Criddle, Keith R.; DiNardo, Gerard (2017-12)
      Pacific sleeper shark relative abundance indices in the eastern Bering Sea and Gulf of Alaska were developed from sablefish longline surveys and the sustainability of a plausible range in Pacific sleeper shark incidental exploitation rates in the Gulf of Alaska was evaluated with a risk analysis using Monte Carlo simulation for use in fisheries management. A significant increase in Pacific sleeper shark relative abundance was identified in the Gulf of Alaska during the years 1989-2003. The aggregate risk of ending in an overfished condition in the Gulf of Alaska increased from 0% under a low exploitation rate scenario to 59% under a high exploitation rate scenario. Baseline information about Pacific sleeper shark trophic ecology and habitat utilization in the eastern Bering Sea and Gulf of Alaska was developed for use in ecosystem-based fishery management. Analysis of stable isotope ratios of nitrogen (δ¹⁵N) and lipid normalized carbon (δ¹³C′) identified significant geographic and ontogenetic variability in the trophic ecology of Pacific sleeper sharks in the eastern Bering Sea and Gulf of Alaska and revealed wider variability in the feeding ecology of Pacific sleeper sharks than previously obtained from diet data based on stomach contents alone. Time series analysis of Pacific sleeper shark electronic tag data from the Gulf of Alaska identified a simple autoregressive relationship governing short-term movements (hours) throughout the time series which included substantial variation in longer time period movement patterns (months) and demonstrated that statistical inference about habitat utilization could be drawn from simultaneous analysis of an entire time series depth profile (six months of data) stored on an electronic archival tag.
    • Pacific walrus use of higher trophic level prey and the relation to sea ice extent, body condition, and trichinellosis

      Seymour, Jill-Marie; Horstmann-Dehn, Lara; Atkinson, Shannon; Barboza, Perry; Rosa, Cheryl; Sheffield, Gay; Wooller, Matthew (2014-05)
      The changing Arctic ecosystem may prompt Pacific walruses (Odobenus rosmarus divergens) to change their usual diet of lower trophic level prey (e.g., benthic invertebrates) by increasing the consumption of higher trophic level prey (HTLP). Prey-switching may have consequences to walrus populations through increased energetic costs, increased stress response, declines in body condition, and exposure to diseases, including the zoonotic parasite Trichinella spp. Trichinella is possibly transmitted to walruses via predation or scavenging on seals. The goal of this study was to quantify reliance on HTLP using stable carbon and nitrogen isotope ratios, and assess potential correlations among consumption of HTLP and sea ice extent, sex, Trichinella infection, body lipid stores, and cortisol concentrations used as an index of the stress response. Walrus diet is comprised of ~1-22% HTLP and reliance on HTLP may be correlated with sea ice extent in a complex way. Trichinella was present in ringed seal (Pusa hispida, 1/57), Arctic fox (Vulpes lagopus, 3-7/32), and polar bear (Ursus maritimus, 1/1), but was not detected in walruses (0/137) regardless of %HTLP in the diet. Walrus blubber and attached skin contained 44.6 ±12.4% lipid wet weight, which was lower than that found for other Arctic marine mammals; however, the inclusion of skin likely decreased our %lipid values. While the absolute value of %lipid from blubber and attached skin was not a suitable substitute for %lipid from blubber only, we were still able to detect the influence of biological factors, with sex-linked variability in walrus lipid stores observed. Cortisol analysis from full-thickness blubber resulted in a wide range of concentrations (2.77 to 34.04 ng/g), but showed that this stress hormone can be extracted from blubber. While neither %lipid nor blubber cortisol was correlated with the proportion of HTLP in walrus diet, they may serve as minimally-invasive methods for health monitoring of walruses. Overall, dietary plasticity of walruses is robust and switching to HTLP is not likely to have immediate adverse effects on the Pacific walrus population.
    • Pairwise comparisons of shrub change across alpine climates show heterogeneous response to temperature in Dall's Sheep range

      Melham, Mark; Valentine, Dave; Panda, Santosh; Brinkman, Todd (2019-12)
      Encroachment of woody vegetation into alpine and high latitude systems complicates resource use for specialist wildlife species. We converted Landsat imagery to maps of percent shrub cover in alpine areas of Dall's sheep (Ovis dalli dalli) range. We then compared percent cover to interpolated climate data to infer drivers of shrub change between the 1980s and 2010s and determine if that change is occurring at different rates in climatically distinct alpine areas. We identified areas spatially interconnected by their mean July temperature intervals and compared their rates of shrub change, finding net rates of shrub growth were higher at temperatures notably above shrub growing season minimums. Along a climatic gradient, high precipitation areas had highest net shrub change, Arctic areas followed, while alpine areas of interior Alaska and the cold Arctic showed the least amount of net shrub change at these higher temperatures. Despite the requirement of higher temperatures for shrub growth, temperature and net shrub change displayed different relationships across the range wide climatic gradient. In areas of rapid climate warming, such as the Arctic and cold Arctic, the linear correlation between shrub change and temperature was highest. In the high precipitation areas where temperatures have been largely above growing season minimums during the study period, precipitation had the strongest linear correlation with shrub change. High latitude studies on shrub change focus primarily on expansion in the Arctic, where increased greening trends are linked to higher rates of warming. We provide the broadest climatic examination of shrub change and its drivers in Alaska and suggest shrub expansion 1) occurs more broadly than just in areas of notable climate warming and 2) is dependent on different environmental factors based on regional climate. The implications for Dall's sheep are complicated and further research is necessary to understand their adaptive capacity in response to this widespread vegetative shift.
    • Paleobiology of ichthyosaurs: using osteohistology to test hypotheses of growth rates and metabolism in a clade of secondarily aquatic marine tetrapods

      Anderson, Katherine L.; Druckenmiller, Patrick; Erickson, Gregory; Horstmann, Lara; Fowell, Sarah (2019-08)
      Ichthyosaurians (Ichthyosauria) are one of the most prominent groups of secondarily aquatic Mesozoic marine reptiles. Over their 160 million years of evolution, the clade evolved a streamlined body plan with paddle-like limbs, convergent with modern cetaceans. Despite the fact that ichthyosaurians have been studied by paleontologists for over a century, very little is known about aspects of their biology, including quantification of their age structure and growth rates. Multiple lines of evidence, including oxygen isotope, swimming modality, and body shape analyses suggest that ichthyosaurians experienced elevated growth rates and likely maintained an elevated body temperature relative to ambient sea water. In this dissertation, I test these hypotheses using osteohistological methods. In the first manuscript, we describe new material of the small-bodied Upper Triassic ichthyosaurian Toretocnemus from the Nehenta Formation and the Hound Island Volcanics (both Norian, Upper Triassic) of Southeast Alaska. During the Upper Triassic, ichthyosaurians experienced their greatest size disparity, with large-bodied species rivaling the size of modern blue whales (Balaenoptera musculus; 20+ m body length) living alongside small-bodied species (1 m body length) like Toretocnemus. Prior to this study, Toretocnemus was known from Carnian deposits of California and possibly Sonora, Mexico. The referred material described here expands its geographic and temporal range. There are very few known ichthyosaurians from the Norian; thus, this material sheds light on the clade's diversity before the end Triassic extinction event. In the second and third manuscripts, we use osteohistological methods to describe the microstructure of various skeletal elements of two species of Stenopterygius from the Posidonia Shale (Lower Jurassic) of Germany. The Posidonia Shale is a Konservat-Lagerstätten that preserves over 3000 ichthyosaurian specimens, approximately 80 percent of which are referable to Stenopterygius. First, we sampled over 40 skeletal elements from one individual specimen referred to Stenopterygius quadriscissus to 1) describe the mineralized tissues across the skeleton, 2) infer relative growth rate, and 3) identify elements with growth marks. Almost all elements described demonstrate fibrolamellar primary bone, indicative of a rapid growth rate. We also identify growth marks in several elements, including the dentary and premaxilla, that will be used in future growth studies. In the third manuscript, we sample a scleral ossicle from Stenopterygius triscissus to describe its microstructure and investigate the use of ossicles for skeletochronology. The use of scleral ossicles for determining age structure has been documented in extant sea turtles as well as dinosaurs. We sectioned one ossicle in three planes and document conspicuous growth banding in the short axis section. Although this method requires further testing, we tentatively determine a minimum age of 7 years at the time of death for this individual. This dissertation lays critical groundwork for future studies of the paleobiology of ichthyosaurians. We are already in the preliminary stages of using these results to 1) quantify age structure and growth rates of an ichthyosaurian (Stenopterygius quadriscissus) for the first time, and 2) test the use of scleral ossicles for skeletochronology of ichthyosaurians. Through addressing these basic aspects of ichthyosaurian biology, we can begin to investigate how ichthyosaurian development and physiology changed over time and space and develop a greater understanding of this clade's 160 million years of evolution.
    • Paleoceanographic shifts in the Gulf of Alaska over the past 2000 years: A Multi-proxy perspective

      Boughan, Molly McCall; Finney, Bruce; Naidu, Sathy; Whitledge, Terry E. (2008-12)
      The Gulf of Alaska (GOA) is a dynamic region influenced by climate variability on time scales ranging from days to millennia. Recent regime shifts suggest interdecadal GOA primary productivity patterns, yet it is unclear whether such fluctuations extend beyond the instrumental record. This thesis examined the nature of prevalent climatic and oceanographic patterns before the twentieth century using several marine sediment core proxies for paleoproductivity and paleoceanography. Sediment cores were from two locations: Bay of Pillars, Kuiu Island, in southeast Alaska (56.63 ̊N, 134.35 ̊W), and a central midshelf location (GAK4) along the Global Ecosystem Dynamics (GLOBEC) Seward Line (59.25 ̊N, 148.82 ̊ W). Proxy data from these cores include: percentages of organic carbon, nitrogen and biogenic opal; organic carbon-to-nitrogen ratios; stable isotope ratios from sediment organic matter (δ13C and δ15N) and foraminifera tests (δ13C and δ18O); and foraminifera faunal analysis. Bay of Pillars proxy data suggest that the onset of the Little Ice Age (LIA) ca. 1200 AD coincides with pulses of decreased salinity and increased productivity. GAK4 proxy data indicate increased productivity and decreased terrestrial input over the past century; as well as fresher surface water was during the latter portion of the LIA (1716 – 1894) and positive Pacific Decadal Oscillation phases.
    • Paleoclimate and paleoenvironment of the Prince Creek and Cantwell formations, Alaska: terrestrial evidence of middle Maastrichtian greenhouse event

      Salazar Jaramillo, Susana; Fowell, Sarah; McCarthy, Paul; Trainor, Tom; Druckenmiller, Patrick (2014-05)
      I studied the paleoclimate and paleoenvironmental conditions of the Prince Creek Formation, North Slope Alaska, and the lower Cantwell Formation in Denali National Park, Alaska. I used data from pollen analysis, clay mineral analysis and stable isotope analysis of clay minerals and organic matter applied to paleosols of the Prince Creek Formation. In the lower Cantwell Formation, I reconstructed the sedimentary environment, produced a terrestrial carbon stable isotope record and obtained a ~ 69.5 Ma radiometric age for the lower Cantwell Formation. Clay analysis in the Prince Creek Formation indicates that the genesis of the paleosols was strongly influenced by the properties of the parent material and that an epiclastic bentonitic source contributed to the development of non-allophanic properties which suggests the presence of Andept-like paleosols. Paleosols formed on the floodplains of the Prince Creek Formation reveal features attributed to wet-dry cycles as a result of seasonal flooding, perhaps due to snow melt in the ancestral Brooks Range. Carbon and oxygen isotope analyses, and the geochemistry of paleosol Bw/Bt horizons indicate mean annual precipitation values between 745.56 and 1426.88 ±221.38 mm/yr and mean annual temperatures of 12 ±4.4 °C. The meteoric water δ¹⁸O value calculated from smectite at a 6.3 °C mean annual temperature is ~-24 ⁰/₀₀. The calculated value is δ¹⁸O-depleted as is expected for high latitudes during the Late Cretaceous. Sedimentary facies analysis suggests that The East Fork measured section of the lower Cantwell Formation was likely deposited in the distal part of an alluvial fan. A new U-Pb age of 69.5 ±0.7 Ma from bentonites and carbon isotope values of bulk sedimentary organic matter and wood fragments indicates that a greenhouse event, known as the mid-Maastrichtian Event (MME), is recorded at the East Fork of the Toklat River Section. A mean annual precipitation value of ~ 517.92 ±134.44 mm/yr was obtained from δ¹⁸O terrestrial organic matter. The coeval nature of the lower Cantwell Formation (~69.5 Ma) and the Prince Creek Formation (~69.2 Ma) suggests that the MME likely affected the Prince Creek Formation as well. In the Prince Creek Formation, the age, precipitation, temperature and meteoric water composition from bentonite smectites are consistent with increased precipitation due to an intensified paleo-arctic hydrological cycle, which may have been the result of increased latent heat transport during the mid-Maastrichtian greenhouse episode.
    • Paleoecology and ecomorphology of the giant short-faced bear in Eastern Beringia

      Matheus, Paul Edward; Guthrie, R. Dale (1997)
      The short-faced bear (Arctodus simus) was a widespread Tremarctine bear indigenous to North America until its extinction around 11,500 BP. Arctodus inhabited Pleistocene ice-free refugia in Eastern Beringia (the northwestern limit of its range) until at least 20,000 BP. Because of its gracile, long-legged build and extremely large size, most paleontologists believe this bear was a high-speed pursuit predator which had preyed on the largest herbivores of Pleistocene North America. Alternatively, energetic arguments have been used to suggest that Arctodus was too large to be carnivorous and evolved its large size within an herbivorous or omnivorous niche. To test these competing hypotheses, I reconstructed aspects of Arctodus' trophic position and paleodiet by analyzing stable isotope ratios ($\delta\ \sp{13}$C and $\delta\ \sp{15}$N) in bone collagen extracted from east Beringian fossils. Other bears and carnivores from Beringia were analyzed to help interpret the results. Isotopes reveal that Arctodus was highly carnivorous, it fed on herbivores which consumed C3 vegetation, and it did not eat salmon. The herbivore/omnivore hypothesis is thus rejected. Predatory hypotheses predict that we should find certain morphological features in a predatory bear which would enhance one or more of the following skills: top running speed, acceleration, or maneuverability at high speeds. I re-analyzed the postcranial morphology of Arctodus and used data on running speed and bone strength in other large mammals to show that a bear the size of Arctodus with long, gracile limbs would not have been able to endure the extreme dynamic forces incurred during predatory activities. Instead, Arctodus' morphology and body size indicate it had evolved to maximize locomotor efficiency using a pacing gait. I suggest that Arctodus evolved as a specialized scavenger adapted to cover an extremely large home range in order to seek out, procure, and defend large-mammal carcasses from other carnivores. By modeling herbivore populations and their mortality, I show that enough carcass biomass was being produced in Pleistocene Beringia to make this scavenging niche energetically feasible. The model helps show that Arctodus' extinction probably is best tied to a reduction of year-round carcasses on the landscape, a condition which arose in the Holocene when the herbivore fauna became less diverse and began to experience more seasonal mortality.
    • Paleoecology of Twin Cays: interpretation of palynological, isotopic, and stomatal proxies in a peat core from Belize

      Morgan, Rebecca Leea (2005-08)
      Reconstructions of Holocene climate from numerous mid- and high-latitude sites have identified millennial-scale cool and arid intervals at 8,200 and 4,200 yrs. B.P. The global nature of these events can only be established by examination of Holocene climate records from low latitude sites. The Central American island of West Twin Cays was chosen as the study location due to its thick peat deposits, which allow for the reconstruction of Holocene vegetation, sea level, and climate for the Belize coastal region. Rhizophora mangle (red mangrove) dominated the island's vegetation since its formation 8,200 cal. yrs. B.P. Alternating periods dominated by dwarf or tall R. mangle reflect changes in phosphorus and nitrogen availability. Heightened Myrsine-type pollen concentrations between 6,300 and 4,200 cal. yrs. B.P. suggests lower sea levels and drier climates. Regional warming accompanied by increased precipitation in the middle to late Holocene is recorded by an increase in exotic Pinus concentrations. These vegetation shifts correlate with regional Central American climate changes and westem Atlantic sea level shifts at 8,200 and 4,200 cal. yrs. B.P. More importantly, these data link Central American changes to worldwide climate events.
    • Paleoenvironmental changes at treeline: a 6,500 year long pollen and stable isotope record

      Rohr, Melanie (2001-05)
      Combined pollen, macrofossil and stable-isotope records from two lakes in the sub-alpine zone of the north-central Alaska Range indicate significant changes in vegetation and lake productivity during the past 6̃750 ¹⁴C yrs BP. These changes are associated with neoglacial cooling and climate variations during the Little Ice-Age (LIA). Highest spruce densities occurred during a period from 5,000 ¹⁴C yrs BP and 2,500 ¹⁴C yrs BP and coincided with the onset of cooler and moister climate. The shifts in climate, which resulted in increased effective moisture levels in Central Alaska, possibly shifted the competitive balance towards spruce and against tundra taxa. Lake productivity declined as climate cooled. A brief episode of climate amelioration between 1,500 ¹⁴C yrs BP and 800 ¹⁴C yrs was followed by cooking events of the LIA which resulted in decreased spruce densities in the sub-alpine forest-tundra zone and a possible lowering in treeline at higher elevation.
    • Paleoethnobotany in Interior Alaska

      Holloway, Caitlin R.; Potter, Ben A.; Bigelow, Nancy H.; Reuther, Joshua D.; Clark, Jamie L. (2016-05)
      Vegetation and plant resources can impact forager mobility and subsistence strategies. However, misconceptions about the preservation of organics in subarctic archaeological contexts and underestimations of the importance of plant resources to foraging societies limit paleoethnobotanical research in high-latitude environments. This research draws upon concepts from human behavioral ecology to address questions relating to site seasonality, plant resource use, land use, and deposition and taphonomy. The model developed in this thesis outlines expectations of seasonal archaeobotanical assemblages for Late Pleistocene and Holocene sites in interior Alaska. I consider these expectations in light of plant macroremains found in anthropogenic features from Components 1 and 3 (approximately 13,300 and 11,500 cal yr BP, respectively) at the Upward Sun River site, located in central Alaska. Site-specific methods include bulk sampling of feature matrix in the field and wet-sieving matrix in the laboratory to collect organic remains. Analytical measures of density, diversity, and ubiquity tie together the model expectations and the results from Upward Sun River. The dominance of common bearberry in the Component 1 archaeobotanical assemblage meets the expectations of a late summer or fall occupation. This suggests that site occupants may have focused on mitigating the risk of starvation in winter months by foraging for seasonally predictable and storable resources. The variability in results from the Component 3 features could relate to longer-term occupations that extended from mid-summer to early fall, in which site occupants foraged for locally available and predictable plant resources such as blueberry or low-bush cranberry species. In this thesis, I argue that large mammal resources were a key component in Late Pleistocene and Holocene subsistence strategies. However, foragers were flexible in their behavior and also targeted small mammals, fish, waterfowl, and plant resources in response to environmental conditions and cultural preferences. The results illustrate the long-standing use of culturally and economically important plant resources in interior Alaska and draw attention to aspects of human behavior that are under-conceptualized in northern archaeology, such as the gender division of labor, domestic behavior, and potential impacts of plant resource exploitation on mobility and land use.
    • Paleohydrology of a catastrophic flood release from Okmok caldera and post-flood eruption history at Okmok Volcano, Umnak Island, Alaska

      Wolfe, Benjamin Alan (2001-08)
      Okmok caldera, located on the northeastern end of Umnak Island, Alaska, contained a 5.8 x 10⁹m³ lake that catastrophically drained as a result of failure of the 2050 yr. B.P. caldera rim between 1560 and 1010 yr. B.P. Flow competence equations, dam-break models, and the Simplified Dam-Break computer model were used to estimate the paleohydrology of the flood. Models indicate that the peak discharge at the breach in the caldera rim was at least 5.8 x 10⁴ m³/s, and the maximum possible discharge was 1.9 x 10⁶ m³/s. A second smaller flood release occurred 190 yr B.P., coinciding with the 1817 A.D. eruption, and destroyed a small Aleut village at Cape Tanak. Stratigraphic analysis reveals that Okmok Volcano has maintained a high level of volcanic activity following the large flood release. Major eruptive events producing air-fall tephra deposits average 1 every 80 years since 1010 yr. B.P.