• Vegetation-Climate Interactions Along A Transition From Tundra To Boreal Forest In Alaska

      Thompson, Catharine Copass; McGuire, A. David (2005)
      The climate of the Alaskan Arctic is warming more rapidly than at any time in the last 400 years. Climate changes of the magnitude occurring in high latitudes have the potential to alter both the structure and function of arctic ecosystems. Structural responses reflect changes in community composition, which may also influence ecosystem function. Functional responses change the biogeochemical cycling of carbon and nutrients. We examined the structural and functional interactions between vegetation and climate across a gradient of vegetation types from arctic tundra to boreal forest. Canopy complexity combines vegetation structural properties such as biomass, cover, height, leaf area index (LAI) and stem area index (SAI). Canopy complexity determines the amount of the energy that will be available in an ecosystem and will also greatly influence the partitioning of that energy into different land surface processes such as heating the air, evaporating water and warming the ground. Across a gradient of sites in Western Alaska, we found that increasing canopy complexity was linked to increased sensible heating. Thus, vegetation structural changes could represent an important positive feedback to warming. Structural changes in ecosystems are linked to changes in ecosystem function. High latitude ecosystems play an important role in the earth's climate system because they contain nearly 40% of the world's reactive soil carbon. We examined Net Ecosystem Production (NEP) in major community types of Northern Alaska using a combination of field-based measurements and modeling. Modeled NEP decreased in both warmer and drier and warmer and wetter conditions. However, in colder and wetter conditions, NEP increased. The net effect for the region was a slight gain in ecosystem carbon; however, our research highlights the importance of climate variability in the carbon balance of the study region during the last two decades. The next step forward with this research will be to incorporate these results into coupled models of the land-atmosphere system. Improved representations of ecosystem structure and function will improve our ability to predict future responses of vegetation composition, carbon storage, and climate and will allow us to better examine the interactions between vegetation and the atmosphere in the context of a changing climate.
    • Vertex arboricity of triangle-free graphs

      Warren, Samantha; Gimbel, John; Faudree, Jill; Allman, Elizabeth (2016-05)
      The vertex arboricity of a graph is the minimum number of colors needed to color the vertices so that the subgraph induced by each color class is a forest. In other words, the vertex arboricity of a graph is the fewest number of colors required in order to color a graph such that every cycle has at least two colors. Although not standard, we will refer to vertex arboricity simply as arboricity. In this paper, we discuss properties of chromatic number and k-defective chromatic number and how those properties relate to the arboricity of trianglefree graphs. In particular, we find bounds on the minimum order of a graph having arboricity three. Equivalently, we consider the largest possible vertex arboricity of triangle-free graphs of fixed order.
    • Vitamin D, cognitive function, and oxidative stress: clues to overtraining syndrome?

      Jerome, Scott P.; Reynolds, Arleigh J.; Duffy, Lawrence K.; Sheppard, Dani K.; Watts, Phillip B. (2018-05)
      Overtraining syndrome (OTS) is characterized by an unexplainable drop in athletic performance. It affects primarily elite, endurance athletes, though sub-elite athletes are also affected. Although the deterioration in performance is often the most pronounced and troublesome symptoms for athletes, others range from severe fatigue and insomnia to depression and lack of mental concentration. There is no known diagnostic tool except for ruling out all other possible explanations for the abnormal performance. The only known remedy for OTS is rest. Some recover within months while others take a year or more. Some athletes never fully recovery and never return to pre-OTS performance levels. The exact mechanism behind OTS is unknown. Consensus has been reached among exercise science professionals that 1) an imbalance between stress load and recovery leads to OTS; 2) OTS exists on a spectrum of possible outcomes from different exercise/rest ratios; and 3) exercise is only one part of systemic stress that can lead to OTS. In addition to physical exercise, other factors such as environmental conditions, family dynamics, schoolwork, job stressors, and social pressures all contribute to the total stress load on the body. A severe and sustained imbalance between stress and rest is a likely contributor to OTS in athletes. I investigated biomarkers and psychological markers that, in concert, could be used to identify athletes who are at the greatest risk for developing OTS before the onset of symptoms. I examined vitamin D, cognitive function, and oxidative stress status in university cross country skiers in addition to athletic performance status during the competitive ski season. This study's results support three primary conclusions. First, collegiate endurance athletes are more prone to vitamin D insufficiency and deficiency than their sedentary counterparts. Second, collegiate cross country ski racers in the circumpolar North are unlikely to maintain adequate vitamin D during a competition season. Furthermore, vitamin D levels are likely to drop in the post-season, recovery period. Third, cognitive function is likely to be significantly higher in the post-season than during the competition season. Fourth, those who experienced a drop in performance during the competition season are more likely to show signs of oxidative stress. These findings may help to produce a screening tool for OTS.
    • Volcanic, tectonic, and tsunamigenic events recorded in peats near Millers Landing, Homer, Alaska

      Davis, Kathleen Melissa (2006-05)
      The Millers Landing peat deposit is located on the western side of Kachemak Bay, near Homer, Alaska. Distal tephra deposits from past eruptions of Augustine Volcano, Redoubt Volcano, Spurr Volcano, and Katmai Volcano are preserved within the peat. Evidence of active tectonism is found where a meter of marine silt overlies the peat deposits at Millers Landing. The marine mud deposits record co-seismic subsidence and post-seismic uplift as a result of a prehistoric great earthquake, ca. 1000 yr. B.P. along the northern Pacific plate boundary along the subduction interface. The uplift rate of Millers Landing over the past 1000 years has a minimum uplift rate of 3.0 mm/yr. Since 1995 Millers Landing has been an experiencing a post-seismic uplift rate of 5.4 +/- 0.6 mm/yr from the 1964 Prince William Sound earthquake. The Millers Landing peat deposits also contained nine layers of sand and beach gravel. The sedimentology is identical to classic tsunami depositional facies that have been identified in other tectonically active areas and we interpret these deposits as evidence of prehistoric tsunami events. The upper layer of two thick sand units, dated at ca. 3600 yr. B.P. by radiocarbon dating, is directly overlain by a 1.2 cm thick grayish white tephra. The tephra is from Redoubt Volcano and records a tsunami triggered by Mt. Redoubt's debris avalanche and lahar which are also dated at 3600 yrs B.P. The other sand deposits present within the peat are evidence of tectonically-triggered tsunamis. The recognition of tephras, tsunami deposits, and evidence of prehistoric co-seismic subsidence indicates the potential for geohazard assessment of Millers Landing and the entire Homer, Alaska region.
    • Volcanism On Unimak Island, Alaska, Usa: A Petrologic Focus On Shishaldin And Fisher Volcanoes

      Stelling, Peter L.; Eichelberger, John C. (2003)
      Volcanism on Unimak Island, Alaska represents a microcosm of Aleutian arc volcanism in general. This work focuses on two of the most significant features on Unimak Island, Fisher Caldera and Shishaldin Volcano. Despite frequent activity and potential for violent, hazardous eruptions, these volcanoes have been relatively unstudied. The present work details the processes occurring within Shishaldin and Fisher volcanoes, and highlights the complexities of their magma storage systems. Fisher Caldera began as a scattered series of independent stratocones formed from small, independent, non-communicating reservoirs. The 100 km 3 caldera-forming eruption (CFE) resulted from injection of three chemically distinct magmas, one being the largest magma batch to have passed through this system. Extensive fracturing during the CFE destroyed the pre-caldera infrastructure, and subsequent magmatism formed a single mixed reservoir. Post-caldera activity, stemming from this centralized chamber, produced several structurally controlled stratocones that erupted into the newly formed caldera lake. A tsunami generated by an explosive intra-caldera eruption catastrophically drained the caldera lake. Current activity is largely hydrothermal. The progression through which the Fisher system developed is similar to those seen in other caldera systems, yet has not been put forth in the literature as a common process. I suggest the Fisher sequence is an end-member in the spectrum of worldwide caldera formation, and present this process in a global context. Shishaldin Volcano has been formed through the concurrent activity of two separate magma systems, the products of each of which are compositionally distinct. Parental magmas for each series are both basalt, but have different trace-element signatures that require separate protoliths. Furthermore, distinct paths of subsequent chemical evolution are also required. One series shows evidence of ponding at high pressure prior to final ascent, whereas the magmas of the other series are directly emplaced in several small, shallow reservoirs. Results from both volcanoes tend to support a view involving complex magma storage: discrete magma batches with limited interaction rather than simple differentiation in a central chamber.* *This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Adobe Acrobat; Microsoft Office.
    • Volcano Deformation And Subdaily Gps Products

      Grapenthin, Ronni; Freymueller, Jeffrey (2012)
      Volcanic unrest is often accompanied by hours to months of deformation of the ground that is measurable with high-precision GPS. Although GPS receivers are capable of near continuous operation, positions are generally estimated for daily intervals, which I use to infer characteristics of a volcano's plumbing system. However, GPS based volcano geodesy will not be useful in early warning scenarios unless positions are estimated at high rates and in real time. Visualization and analysis of dynamic and static deformation during the 2011 Tohokuoki earthquake in Japan motivates the application of high-rate GPS from a GPS seismology perspective. I give examples of dynamic seismic signals and their evolution to the final static offset in 30 s and 1 s intervals, which demonstrates the enhancement of subtle rupture dynamics through increased temporal resolution. This stresses the importance of processing data at recording intervals to minimize signal loss. Deformation during the 2009 eruption of Redoubt Volcano, Alaska, suggested net deflation by 0.05 km³ in three distinct phases. Mid-crustal aseismic precursory inflation began in May 2008 and was detected by a single continuous GPS station about 28 km NE of Redoubt. Deflation during the explosive and effusive phases was sourced from a vertical ellipsoidal reservoir at about 7-11.5 km. From this I infer a model for the temporal evolution of a complex plumbing system of at least 2 sources during the eruption. Using subdaily GPS positioning solutions I demonstrate that plumes can be detected and localized by utilizing information on phase residuals. The GPS network at Bezymianny Volcano, Kamchatka, records network wide subsidence at rapid rates between 8 and 12 mm/yr from 2005-2010. I hypothesize this to be caused by continuous deflation of a ~30 km deep sill under Kluchevskoy Volcano. Interestingly, 1-2 explosive events per year cause little to no deformation at any site other than the summit site closest to the vent. I derive evidence for a very shallow source, likely within the edifice. This work shows that network design and individual plumbing system characteristics affect the ability to detect motion on subdaily and even weekly time scales, which stresses the importance of network scale considerations.
    • Volcano Seismicity in Alaska

      Buurman, Helena; West, Michael; Freymueller, Jeffrey; Prejean, Stephanie; Thompson, Glenn (2013-05)
      I examine the many facets of volcano seismicity in Alaska: from the short-lived eruption seismicity that is limited to only the few weeks during which a volcano is active, to the seismicity that occurs in the months following an eruption, and finally to the longterm volcano seismicity that occurs in the years in which volcanoes are dormant. I use the rich seismic dataset that was recorded during the 2009 eruption of Redoubt Volcano to examine eruptive volcano seismicity. I show that the progression of magma through the conduit system at Redoubt could be readily tracked by the seismicity. Many of my interpretations benefited greatly from the numerous other datasets collected during the eruption. Rarely was there volcanic activity that did not manifest itself in some way seismically, however, resulting in a remarkably complete chronology within the seismic record of the 2009 eruption. I also use the Redoubt seismic dataset to study post-eruptive seismicity. During the year following the eruption there were a number of unexplained bursts of shallow seismicity that did not culminate in eruptive activity despite closely mirroring seismic signals that had preceded explosions less than a year prior. I show that these episodes of shallow seismicity were in fact related to volcanic processes much deeper in the volcanic edifice by demonstrating that earthquakes that were related to magmatic activity during the eruption were also present during the renewed shallow unrest. These results show that magmatic processes can continue for many months after eruptions end, suggesting that volcanoes can stay active for much longer than previously thought. In the final chapter I characterize volcanic earthquakes on a much broader scale by analyzing a decade of continuous seismic data across 46 volcanoes in the Aleutian arc to search for regional-scale trends in volcano seismicity. I find that volcanic earthquakes below 20 km depth are much more common in the central region of the arc than they are in the eastern and western regions. I tie these observations to trends in magma geochemistry and regional tectonic features, and present two hypotheses to explain what could control volcanism in the Aleutian arc.
    • Volcano Seismology From Around The World: Case Studies From Mount Pinatubo (Philippines) Galeras (Colombia), Mount Wrangell And Mount Veniaminof (Alaska)

      Sanchez-Aguilar, John Jairo; McNutt, Stephen R.; Power, John A.; Freymueller, Jeffrey T.; Christensen, Douglas; Eichelberger, John (2005)
      A compilation of research papers in volcano seismology is presented: (1) to study the configuration of magma systems beneath volcanoes, (2) to describe unexpected effects of the shaking from a regional earthquake on volcanic systems, and (3) to integrate seismicity investigations into a conceptual model for the magma system of a volcano. This work was undertaken because much research in volcano seismology is needed to help in hazard assessment. The possible configuration of magma systems beneath Mount Pinatubo, Philippines, and Galeras Volcano, Colombia, is studied with b-value mapping. We suggest models for earthquake-volcanoes interactions by studying the declines in local seismicity at Mt. Wrangell and Mt. Veniaminof, Alaska, following the 3 November 2002 Denali Fault Earthquake (DFE). Finally, a model for the magmatic-hydrothermal system beneath Mt. Veniaminof is proposed by deriving a velocity model and relocating the earthquakes, and by studying the temporal changes of frequencies and attenuation (Q) at the source of long-period (LP) events. Results from b-value mapping confirm that volcanoes are characterized by localized zones of high b-values, and also indicate that the internal structure of volcanoes is variable. Analyses of the background seismicity at Mt. Veniaminof suggest that earthquakes result from locally-induced stresses and that LP events may represent the response of a shallow hydrothermal system to heat input from below. The study of declines in seismicity at Mt. Wrangell and Mt. Veniaminof volcanoes following the DFE indicates that the dynamic shaking from regional shocks can physically damage a volcano and together with the static stress changes can affect the local seismicity for extended periods. We conclude that the use of simple methods allows a better understanding of the seismicity at volcanoes in Alaska, but most importantly in developing countries where the small number of seismograph stations puts challenging limitations for research.
    • Volume Changes Of Alaska Glaciers: Contributions To Rising Sea Level And Links To Changing Climate

      Arendt, Anthony A.; Echelmeyer, Keith A. (2006)
      We have used airborne altimetry to measure surface elevations along the central flowline of 86 glaciers in Alaska, Yukon Territory and northwestern British Columbia (northwestern North America). Comparison of these elevations with contours on maps derived from 1950s to 1970s aerial photography yields elevation and volume changes over a 30 to 45 year period. Approximately one-third of glaciers have been re-profiled 3 to 5 years after the earlier profile, providing a measure of short-timescale elevation and volume changes for comparison with the earlier period. We have used these measurements to estimate the total contribution of glaciers in northwestern North America to rising sea level, and to quantify the magnitude of climate changes in these regions. We found that glaciers in northwestern North America have contributed to about 10% of the rate of global sea level rise during the last half-century and that the rate of mass loss has approximately doubled during the past decade. During this time, summer and winter air temperatures at low elevation climate stations increased by 0.2+/-0.1 and 0.4+/-0.2�C (decade)-1 respectively. There was also a weak trend of increasing precipitation and an overall lengthening of the summer melt season. We modeled regional changes in glacier mass balance with climate station data and were able to reproduce altimetry measurements to within reported errors. We conclude that summer temperature increases have been the main driver of the increased rates of glacier mass loss, but winter warming might also be affecting the glaciers through enhanced melt at low elevations and a change in precipitation from snow to rain, especially in maritime regions. Uncertainties in our calculations are large, owing to the inaccuracies of the maps used to provide baseline elevations, the sparsity of accurate climate data, and the complex and dynamic nature of glaciers in these regions. Tidewater, surging, and lake-terminating glaciers have dynamical cycles that are not linked in a simple way to climate variability. We found that regional volume losses can depend on one or several large and dynamic glaciers. These glaciers should be treated separately when extrapolating altimetry data to an entire region.
    • Vulture and other ornithological survey data in Annapurna and Manaslu Conservation regions

      Karmacharya, Dikpal Krishna; Gyawali, Seejan; Virani, Munir; Huettmann, Falk (2013-10-01)
      This dataset presents geo-referenced summaries of vulture and raptor sightings (from field work as well as from published sources 1977-2013), as well as general avian species lists and their detected abundances, for the Annapurna (ACA) and Manaslu Conservation Areas (MCA). In addition, compiled 'presence only' data of vultures are provided for Nepal and Northern India as well. The bounding box (decimal degrees) of the data coverage is 77.4966 til 87.0667 latitude and 26.3666 til 28.58333 longitude, and Altitude covers 100m til 7969m. The data consist of MS Excel and include 6 worksheets (all bird list, number of bird sighting and counting, descending number of individuals, vulture survey in ACA, raptors in Manaslu, and compiled presence only sightings of vultures for Nepal and Northern India). While this data set is reatively small, it includes a large and complex set of information for a vast and globally relevant region. The following raptor species are primarily covered in this data set: Upland Buzzard (Buteo hemilasius, TSN 175385), Himalayan Griffon (Gyps fulvus, 175487), Golden Eagler (Aquila chrysaetos, 175407), Himalayan Vulture (Gyps himalayensis,175488), Bearded Vulture (Gypaetus barbatus,175483), Egyptian Vulture (Neophron percnopterus, 175481) and White-Rumped Vulture (Gyps bengalensis, 175485). Smaller predators like Common Kestrel (Falco tinnunculus, 175620), Peregrine Falcon (Falco peregrinus,175604), Shikra (Accipiter badius, 55890), Bonelli's Eagle (Aquila fasciata, 175565), Black Kite (Milvus migrans,175469), Mountain Hawk Eagle (Spizaetus nipalensis, 175580), Spotted Owlet (Athene brama, 555472), Western Osprey (Pandion haliaetus, 175590) and Crested Serpent Eagle (Spilornis cheela, 175506) were also reported, In addition, overall app. 763 sighting locations of 143 species of birds are also featured in the data (english names as well as scientific names). Naturalists, bird watchers, modelers as well as investigators of raptors and other birds in the Nepal and Northern Indian regions will find great value in this data set.
    • Water, behavior, and health in Alaska

      Ritter, Troy L.; Bersamin, Andrea; Lopez, Ellen; Hennessy, Thomas; Johnson, Rhonda; Konkel, Steven (2014-08)
      This dissertation addresses the need for a better understanding of how water and sanitation infrastructure and water use behaviors come together to influence health. The ultimate aim is to inform water infrastructure designs and behavior change programming for the prevention of acute respiratory infections (ARIs), skin infections, and diarrhea. All three diseases are of public health significance in Alaska, and all three can be prevented by proper access and use of water and sanitation services. I begin the dissertation by illustrating that some residents who have access to treated water continue to consume untreated river water and rain. In fact, 82% of respondents (n=172) reported that some of their drinking water came from an untreated source. Motives for drinking untreated water could be categorized into six themes: chemicals, taste, health, access, tradition, and cost. The next chapter describes the design and impact of a health promotion program to increase consumption of treated water. Self-reported data revealed that from pre- to post-intervention, the proportion of households drinking mostly treated water increased by 21% (39% to 60%), p < 0.0001. The third chapter reports changes in water use and health as reported by participants who recently received modern sanitation services. Most participants (n=101; 74%) reported improved community health. A prominent theme was that better access to treated water increased children’s ability to drink treated water and perform hand washing and bathing, practices known to prevent ARIs, skin infections and diarrhea. Based on the findings, I recommend: 1) providing inhouse piped water service where feasible, 2) development of an alternative water and sanitation system that provides adequate quantities of water for homes that may not be provided in-house piped water service, and 3) providing health promotion to encourage healthy water use, either in combination with provision of in-house water service, or as a stand-alone intervention.
    • Waterbird distribution and habitat in the Prairie Pothole Region, U.S.A.

      Steen, Valerie (2010-12)
      The Prairie Pothole Region (PPR) of north-central North America provides some of the most critical wetland habitat continent-wide to waterbirds. Agricultural conversion has resulted in widespread wetland drainage. Furthermore, climate change projections indicate a drier future, which will alter remaining wetland habitats. I evaluated Black Tern (Chlidonias niger) habitat selection and the potential impacts of climate change on the distribution of waterbird species. To examine Black Tern habitat selection, I surveyed 589 wetlands in North and South Dakota in 2008-09, then created multivariate habitat models. I documented breeding at 5% and foraging at 17% of wetlands surveyed, and found local variables were more important predictors of use than landscape variables, evidence for differential selection of wetlands where breeding and foraging occurred, and evidence fora more limited role of area sensitivity (wetland size). To examine the potential effects of climate change, I created models relating occurrence of five waterbird species to climate and wetland variables for the U.S. PPR. Projected range reductions were 28 to 99%, with an average of 64% for all species. Models also predicted that, given even wetland density, the best areas to conserve under climate change are Northern North Dakota and Minnesota.
    • A window to the past: macrofossil remains from an 18,000 year-old buried surface, Seward Peninsula, Alaska

      Wolf, Victoria Goetcheus (2001-12)
      Macrofossil remains and pollen from an 18,000 year old buried surface from the northern Seward Peninsula enable a reconstruction of the full-glacial environment of an upland portion of the Bering Land Bridge. The buried surface represents a dry meadow and herb-rich tundra. Prostrate shrubs were rare on the landscape, but abundant locally. A large and diverse insect fauna populated the surface, preying on the plants and each other. Small mammals and their predators lived on the surface. Large mammals, such as caribou and bison, were present as well. The productivity of the surface was maintained by a continual influx of loess, which replenished the nutrients of the soil. Study of the buried surface provides an important addition to knowledge about the vegetation mosaic of full-glacial Beringia.
    • Winter feeding ecology and biomagnification of organochlorine contaminants in Alaska polar bears

      Bentzen, Torsten W. (2006-12)
      Dietary pathways expose polar bears to a variety of contaminant profiles and concentrations, ranging from bowhead whale (Balaena mysticetus) as one of the least contaminated marine mammals to the more highly contaminated upper trophic level ringed seal (Phoca hispida) which represent the majority of their annual diet. We used stable isotopes [delta]¹⁵N and [delta]¹³C to estimate trophic status of 139 free-ranging polar bears sampled along Alaska's Beaufort Sea coast in spring 2003 and 2004. The [delta]¹⁵N values of polar bear packed blood cells ranged from 18.2% to 21.4% with a mean of 19.5% (SD=0.7) in 2003 and 19.9% (SD=0.7) in 2004. Two-element three-source mixing models indicated that lower trophic level prey, such as scavenged bowhead whale carcasses, may have composed 11-26% (95% CI) of the diet in 2003, and -2-14% (95% CI) of the diet in 2004. Organochlorine (OC) concentrations in subcutaneous adipose tissue were determined for 47 of the polar bears sampled in 2003 and compared to trophic position ([delta]¹⁵N). Although many OCs appear not to biomagnify in polar bears, we found positive relationships with [delta]¹⁵N in both sexes between concentrations of several highly recalcitrant OCs in models incorporating age, lipid content, and [delta]¹³C. [Delta]¹⁵N was important in explaining variation in OC concentrations, indicating structural differences in food webs and biomagnification of OCs among polar bears related to their sex, age, and the apparent use of lower trophic level prey.
    • Winter foraging ecology of moose in the Tanana Flats and Alaska Range foothills

      Seaton, C. Tom (2002-12)
      I studied woody browse distribution, production, removal, species composition, twig size, moose diets, and predicted daily intake of resident and migratory moose in the Tanana Flats and adjacent Alaska Range Foothills, Alaska, 1999-2000. Density of moose in these areas was high (1.1 moose/km²). Moose were experiencing density-dependent effects on reproduction and growth, exhibited by low adult twinning rate (6%) and absence of pregnant yearlings, yet 17.5 kg higher 10-month-old calf body weights in the migratory segment. Of all willow, poplar, and paper birch plants sampled, 74% had a broomed architecture, which I attributed to heavy use by moose. Using a model of daily moose intake based on bite mass and bite density, I estimated that 1) migratory moose met expected intake during winter while intake of resident moose was marginal, 2) moose could not meet their expected daily intake with the mean twig dry mass (0.26 g) remaining unbrowsed at end of winter, and 3) higher predicted intake by migratory moose than resident moose was consistent with their higher 10-month-old calf weights.
    • Winter movements of Arctic foxes in Northern Alaska measured by satellite telemetry

      Pamperin, Nathan J.; Follman, Erich H.; Lindberg, Mark S.; Huettmann, Falk; Person, Brian (2008-12)
      We studied winter movements of 37 arctic foxes (Alopex lagopus) collared within a petroleum development area at Prudhoe Bay, Alaska (n = 20), and an undeveloped area in the National Petroleum Reserve-Alaska (NPR-A, n = 17) during the winters of 2004, 2005, and 2006 using satellite telemetry. Comparing Prudhoe Bay and NPR-A, differences in mean movement rates of juveniles was 23.9 ± 2.7 km per duty cycle and 10.6 ± 2.8 km per duty cycle for adults, and mean difference in maximum distance from capture site for juveniles was 265.2 ± 63.2 km and 205.5 ± 128.9 km for adults. Juveniles and adults collared in NPR-A were highly mobile and made long distance movements (up to 782 km) while foxes from Prudhoe Bay remained in or near the oil field throughout winter. Extensive use of sea-ice by three juvenile foxes from NPR-A was documented during the winter of 2005-2006. Three juvenile foxes traveled long distances (904, 1096, and 2757 km) during the winter and remained on the sea-ice for extended periods of time (76, 120, and 156 days). These findings verify the use of sea-ice by arctic foxes and raise concerns that the diminishing ice cover may negatively impact populations by limiting access to marine food sources. We conclude that the oilfields are having a strong effect on the winter movements of arctic fox and suggest differences in movements are likely attributable to the availability of anthropogenic foods at Prudhoe Bay.
    • Winter Range Studies Of The Western Arctic Caribou Herd, Northwest Alaska

      Joly, Kyle; Chapin, F.S.; Rupp, T.S.; Klein, David R.; Verbyla, David L. (2011)
      Climate change is likely to bring a myriad of interrelated changes to the Arctic. One change is warmer and drier conditions that could increase the prevalence of wildfire in northwest Alaska. Wildfires destroy terricolous lichens that Western Arctic Herd caribou (Rangifer tarandus ) rely on during winter; taking decades to recover. My goals were to assess the recent (1950--2007) fire regime within the herd's range, identify characteristics of habitat selected by overwintering caribou, and determine the potential impacts of climate change on the fire regime and caribou winter range. I used a combination of existing data and information collected at vegetation plots to conduct these analyses. I found that wildfires in the tundra were relatively common from 1950--2007, covering approximately 10% of northwest Alaska. Tundra was > 4.5 times more likely to re-burn than boreal forest. This novel, yet intuitive finding could have serious implications if fire starts to become more common in the Arctic. I found that the average annual area burned more than doubled in years where mean August temperatures exceeded 11.7�C (53�F). Caribou use tundra and forested during winter but avoided recently (< 58 years) burned areas in both habitat types likely because they contained < 1/4 of the abundance of forage lichen species than unburned habitats. I found that lichen abundance was 3 times greater in the herd's current winter range versus its historic range -- supporting the theory that caribou shift ranges to compensate for deteriorating grazing conditions. Stand age was the most consistent correlate with lichen abundance. Dwarf birch (Betula spp.) was more abundant in recent burns which may facilitate the intensification of the future fire regime in the region. My modeling efforts revealed that wildfire is likely to become more prevalent, especially on the herd's core winter range, which could have deleterious impacts on caribou winter range and provide quality habitat for moose ( Alces alces). My results should provide a solid foundation to develop a science-based fire management plan for the Western Arctic Herd.
    • Winter vertebrate browsing of birch: effects on the use of leaf litter leachates by stream microorganisms

      Estensen, Jeffrey L. (2001-05)
      Winter browsing of birch leads to chemical changes in leaves of the following growing season, potentially generating differences in the quality of leachates derived from leaf litter and in leachate use by stream microorganisms. The effects of moose browsing were tested on leachates from leaves collected from browsed and unbrowsed trees and inoculated with microbial communities. Respiration and bacterial abundance were used to assess qualitative differences in leachates. Microbes cultured in leachates derived from leaves of browsed trees had significantly higher rates of oxygen uptake. There were no significant differences in bacterial abundance between treatments. The basis for the qualitative difference in leachates is likely due to an 89% greater concentration of amino acides in leachates derived from leaves of previously browsed trees. This study provides evidence that winter herbivory of birch can influence the use of leaf leachates by stream microbes, demonstrating coupling between riparian zones and stream ecosystems.
    • Wintering strategies of an Arctic-nesting goose: costs of migration and over-wintering for Pacific black brant

      Mather, Danielle D. (2005-05)
      Birds wintering in different climates may have different strategies for storing and using energy. We documented changes in body morphology and composition of Pacific Black Brant (Branta bernicla nigricans) wintering in Alaska and Baja California and modeled the energetic costs of wintering at each location. We compared costs associated with two different wintering strategies: 1) to remain in an unstable and harsh environment but close to breeding grounds, or 2) to migrate long distances to a mild environment, but distant from breeding grounds. Despite dramatic differences in the timing and magnitude of energetic costs between sites, Brant stored similar amounts of lipid and maintained similar body mass throughout winter. Brant operate under similar physiological bounds but changes in organ mass and nutrient storage took place within these bounds. This flexibility allowed Brant to employ two contrasting winter strategies. We suggest that there may be reproductive and energetic advantages associated with shortening migration distance and remaining in Alaska over winter. The number of Brant wintering in Alaska should continue to increase if constraints on food intake do not impede energy storage and survival is similar between sites.
    • X-ray fluorescence spectrometry using synchrotron radiation with applications in unmanned aircraft environmental sensing

      Barberie, Sean Richard Gopal; Cahill, Catherine F.; Hatfield, Michael C.; Iceman, Christopher R. (2015-12)
      In this thesis I present an analytical optimization of the Synchrotron Radiation X-Ray Fluorescence (SR-XRF) technique for applications in unmanned aircraft aerosol studies. In environmental and atmospheric science, there is a pressing need for aerosol measurements at various altitudes in the atmosphere and spanning large regions. This need is currently either ignored, or met to a limited degree by studies that employ manned aircraft. There is, however, a great deal of opportunity to improve and expand on these studies using the emerging technology of unmanned aircraft systems. A newly developed aerosol sampler makes this opportunity a near-reality by its ability to collect aerosol samples in-situ from unmanned aircraft platforms. The challenge lies in analyzing these samples for elemental composition. In airborne aerosol studies, the ability to resolve where a sample was collected both spatially and temporally is limited by the sensitivity of the analysis technique. In aircraft-based aerosol collection, the length of the aerosol sample spot corresponds to distance. Thus the spatial resolution of an airborne study is limited by the amount of mass that must be collected for analysis. The SR-XRF optimizations outlined in this thesis decrease the amount of sample mass required for detectable elemental concentrations, allowing aerosol samples to be analyzed in smaller areas corresponding to smaller time steps. Since, in a flight path, time steps are directly correlated with distance, analysis of smaller time steps results in the ability to measure aerosols at higher spatial resolution. Four SR-XRF analysis configurations were experimentally tested: monochromatic beam, white beam, filtered white beam, and filtered white beam-filtered detector to determine which configuration gave the highest elemental sensitivity and selectivity. Of these tested methods, the straight polychromatic white beam configuration resulted in the best sensitivity for elements across a large range of x-ray energies for small amounts of mass collected on thin film substrates. The research in this thesis provides researchers with an optimized method for non-destructively analyzing a wide variety of environmental samples with high elemental sensitivity and selectivity. This research also has important implications for the ability to perform in-situ aerosol studies with unmanned aircraft on a systematic basis.