• Dynamics of the 240 A.D. caldera-forming eruption of Ksudach Volcano, Kamchatka, Russia

      Andrews, Benjamin James (2004-08)
      The Ksudach Volcano KS-1 rhyodacite deposits offer an opportunity to study eruption dynamics and plume stability during a caldera-forming eruption. Stratigraphic relations indicate four phases of eruption, Initial, Main, Lithic, and Gray. Well-sorted, reverse-graded pumice fall deposits overlying a silty ash compose the Initial phase layers. The Main, Lithic and Gray phases are represented by pumice fall layers interbedded with pyroclastic flow and surge deposits (proximally) and co-ignimbrite ashes (distally). Although most of the deposit is <30 wt.% lithics, the Lithic phase layers are>50wt.% lithics. White and gray pumices are compositionally indistinguishable, however vesicle textures and microlite populations indicate faster ascent by the white pumices prior to the Gray phase. The eruption volume is estimated as 7.5 km³ magma (dense rock equivalent) and 2.4 km³ lithics. Isopleth maps indicate mass discharge rates (MDR) ranged from 5-10x10⁷ kg/s in the Initial phase to> 10⁸ kg/s in the Main, Lithic, and Gray phases. Stratigraphic, granulometric, and component analyses indicate simultaneous eruption of buoyant plumes and non-buoyant flows during the Main, Lithic and Gray phases. Caldera collapse during the Lithic phase is reflected by a large increase in lithic particles and the textural change from white to gray pumices; collapse occurred after eruption of 2/3 of the magma.
    • Dynamics of the fur trade on the middle Yukon River, Alaska, 1839 to 1868

      Arndt, Katherine Louise; Black, Lydia T. (1996)
      This study examines the Russian-era fur trade of the middle course of the Yukon River, that section of the river which extends from Fort Yukon down to Nulato, Alaska. For a period of just over twenty years, 1847 to 1868, the Russian-American and Hudson's Bay companies maintained rival establishments at opposite ends of this stretch of river and vied for the trade of the Native populations living in the region between. After reviewing the events leading up to the establishment of the first European posts in the region, the study focuses on the dynamics of the competition between the rival posts and the changing nature of Native, Russian, and British participation in the middle Yukon trade. Most historical summaries of the early (pre-1867) fur trade of the Middle Yukon rely upon a small number of published sources, resulting in a truncated and rather inaccurate version of the region's fur trade history. This study seeks to overcome that problem through utilization of two major archival collections, the records of the Russian-American and Hudson's Bay companies. Together, these sources make possible an account that is more even in temporal coverage and more balanced in its treatment of Russian, British, and Native trade activities. One of the striking features of the early Yukon drainage fur trade is the pivotal role of the Native traders in determining its spatial patterning. Though regional patterns were characterized by a certain overall stability in the period 1830 through 1868, they also underwent marked change. This study examines those changes with regard to the middle Yukon drainage and discusses the influence of material and social factors upon them.
    • Dynamics simulation of human box delivering task

      Owens, Paul Davis; Xiang, Yujiang; Peterson, Rorik; Chen, Cheng-fu (2018-05)
      The dynamic optimization of a box delivery motion is a complex task. The key component is to achieve an optimized motion associated with the box weight, delivering speed, and location. This thesis addresses one solution for determining the optimal delivery of a box. The delivering task is divided into five subtasks: lifting, transition step, carrying, transition step, and unloading. Each task is simulated independently with appropriate boundary conditions so that they can be stitched together to render a complete delivering task. Each task is formulated as an optimization problem. The design variables are joint angle profiles. For lifting and carrying task, the objective function is the dynamic effort. The unloading task is a byproduct of the lifting task, but done in reverse, starting with holding the box and ending with it at its final position. In contrast, for transition task, the objective function is the combination of dynamic effort and joint discomfort. The various joint parameters are analyzed consisting of joint torque, joint angles, and ground reactive forces. A viable optimization motion is generated from the simulation results. It is also empirically validated. This research holds significance for professions containing heavy box lifting and delivering tasks and would like to reduce the chance of injury.
    • Dynamo action in the ionosphere and motions of the magnetospheric plasma

      DeWitt, Ronald N. (1965-05)
      This thesis presents a study of the dynamic interaction which takes place between the magnetospheric plasma and the underlying neutral atmosphere; it is hoped thus to g a m a better understanding of the effects of this interaction upon the steady state configuration of the magnetosphere. The neutral portion of the atmosphere (the neutrosphere) and the overlying ionized regions (the upper atmosphere and magnetosphere) may be regarded as two distinct dynamic domains that interact in a region of transition occurring between 100 and 150 km over the earth. The neutrosphere because of its greater mass will dominate the motion, and the magnetospheric plasma can be expected to undergo motions related to those of the upper neutrosphere and transition region. However, the geomagnetic field restricts the motion of the magnetospheric plasma to a particular class, allowing one to consider the magnetospheric motion to be constrained. Motions in the transition region of the class not permitted the magnetospheric plasma will give rise to forces against the constraint. The reaction of the constraint on the atmosphere of the transition region takes the form of a Lorentz force x B where J is the current responsible for the well known solar quiet day daily magnetic variation (Sq). The explanation for the production of this current in the transition region has traditionally been presented in terms of a dynamo-like electromotive force generated by motions of the conducting atmosphere through the magnetic field, whence the transition region is aptly named the dynamo region. The Lorentz force represented by this current constitutes a significant term in the equation of motion for the dynamo region. Another important term arises from eddy viscous stresses immediately below the dynamo region. The equation of motion for the dynamo region must thus include such forces as well as the pressure gradient and Coriolis terms. However, our almost total ignorance of the eddy viscous stress field at the lower surface of the dynamo layer at present precludes our deducing the entire dynamo layer winds from the observed Sq magnetic variation. The kinematics of the dynamo layer are discussed and the motion or the dynamo layer is divided into a symmetric and an antisymmetric part. The term symmetric is here used to describe winds in the northern and southern hemisphere that are the mirror images of each other with respect to the equatorial plane. It is demonstrated that the symmetric component gives rise to electrostatic fields transverse to the field lines, but to no currents along the field lines, while the antisymmetric case produces the converse effects. The symmetric and antisymmetric winds ape further divided into components according to the horizontal electromotive force they produce. (a) Symmetric Wind In the case of the symmetric wind, only the portion of the wind producing the solenoidal component of the horizontal dynamo electromotive force is effective in producing ionospheric currents. It is demonstrated that only this current producing wind system acts against the constraints imposed by the geomagnetic field on magnetospheric motions. The motion of the magnetospheric plasma driven by each such wind system is discussed. The earlier treatments of the dynamo theory consider the dynamo region to be a single layer in which the wind system and the electric conductivity are assumed to be uniform in height. A new, more general derivation of the layer's dynamo action is given in which no restrictions are placed upon the vertical distributions. An effective wind is defined which permits the use of the earlier equations relating the current function, the electrostatic field, and the scalar field describing the current producing part of the effective wind. The equation relating the electrostatic field and the current function is essentially that employed by Maeda (1956), allowing his solution for the portion of the electrostatic field associated with the current producing wind to remain unaffected by the stratification of the wind system. Mathematical techniques for solving the dynamo equations for the elecrostatic field are developed. These allow for a quite general conductivity distribution over the globe, only requiring that it be expressible in surface harmonics. The effect of undetected zonal currents upon the solution for the electrostatic field is discussed. It is suggested that a considerable diurnal component of electrostatic field and other components as well may be hidden from us by our inability to detect the prevailing magnetic perturbations produced by zonal currents. The electrostatic field associated with the non-current producing components of the symmetric wind is likewise hidden from us. (b) Antisymmetric Wind The equations for the current driven by the antisymmetric component of wind are derived, and some of the effects of such currents are discussed. It is found that the conduction of current along the field lines from one hemisphere to the other is associated with an interhemispheric stress between geomagneticaliy conjugate points of order 3 x 10⁻⁷ newtons/meter². In addition it is found that an antisymmetric layer current density of 5 amperes/km into the polar cap region (across the 75° latitude circle) might give rise to a displacement of about 150 km in the relative position of the conjugate points defined by field lines of the magnetospheric tail. It is suggested that the dynamo action in the 100 to 150 km height plays a role in determining the manner in which the magnetosphere divides itself into the corotating region and the magnetospheric tail.
    • Early height growth patterns of planted white spruce seedlings in Interior Alaska

      Hollingsworth, Jamie (2002-05)
      This study looked at early height growth of planted white spruce Picea glauca (Moench) Voss around the Fairbanks area. The effort focused on two Levels-of-Growing-Stock (LOGS) experimental plantations located in the Bonanza Creek Experimental Forest that incorporated an espacement study. Annual total height was also measured on 16 operational plantations and then compared to LOGS plantations. Average annual total height at Site 2 of the LOGS plantations was significantly greater than at Site 1. A significant difference in height growth between these sites was attributed to differences in aspect. Results showed significant annual total height differences among the espacement plots within the LOGS plantation. The narrowest spacing 1.2 X 1.2 m and widest spacing 3.7 X 3.7 showed a lower annual total height while spacings 1.8 X 1.8 m, 2.4 X 2.4 m, and 3.0 X 3.0 m showed a greater annual total height at age ten. The range of annual total height found at the LOGS sites was not significantly different than the range of annual total height found at the 16 operational plantations. Additionally, path analysis was used to quantify the direct and indirect effects of multiple environmental variables (i.e., percent slope, slope position, competition, aspect, and soil moisture) on growth rate at the operational plantations. It was found that slope position, percent slope, and competition had significant direct effects on growth rate. These results provide insight for resource managers when predicting the height growth of planted white spruce.
    • Early Life History Dynamics Of Lake Sturgeon

      Caroffino, David C. (2009)
      Populations of lake sturgeon Acipenser fulvescens in the Laurentian Great Lakes have not recovered after dramatic declines in the late 1800s despite the implementation of numerous recovery plans. Although extensive lake sturgeon research has and continues to occur, critical knowledge gaps remain. Recruitment of lake sturgeon is variable, but the extent of that variation, its limiting factors, and mortality rates experienced by early life stages are unclear. The purpose of this study was to increase our understanding of lake sturgeon early life stages by examining characteristics of a remnant population in the Peshtigo River, Wisconsin. Specifically, this research sought to empirically estimate rates of early life stage mortality, describe the vertical distribution of drifting larvae, evaluate the impacts of predation on recruitment, and describe patterns in movement and abundance of age-0 juveniles. Extensive sampling of lake sturgeon eggs, larvae, age-0 juveniles, and potential predators occurred during 2006 and 2007. Although drifting lake sturgeon larvae were captured in all parts of the water column, more were found near the surface than the substrate. After drifting to nursery areas, individuals exhibited variable movement patterns. Some fish were never recaptured more than 10 m from the initial capture site, while other individuals moved more than 9 km. Even though absolute abundance of juveniles differed by an order of magnitude between 2006 and 2007, a pattern of steady decline during the summer months was similar during both years. This downstream movement may have resulted in emigration from the Peshtigo River, as there was no evidence of predation on this life stage. Overall mortality from the egg to age-0 juvenile life stage exceeded 99.9% in both study years. Predation on eggs was extensive by both crayfish and fish (white sucker Catostomus commersonii ), but was minimal on other life stages. These results suggest that recruitment can vary significantly, and predation is likely only limiting at the egg life stage. These results will allow more effective monitoring and management of lake sturgeon early life stages, thereby promoting population recovery.
    • Early marine growth patterns of Situk River steelhead, Oncorhynchus mykiss

      Catterson, Matthew R.; McPhee, Megan; Love, David; Sutton, Trent (2017-08)
      Steelhead Oncorhynchus mykiss exhibit complex life-history patterns described by variable freshwater and marine residency periods, maturation patterns, and reproductive characteristics. Over 300 small populations of Steelhead are present in Southeast Alaska, and similar trends in abundance among these populations suggest the influence of population-regulating forces operating on a regional scale. The Situk River, near Yakutat, Alaska, supports the largest known population of Steelhead in Alaska. Stock assessment studies on this river have collected the longest set of biological data and scale samples for Steelhead in the state. For this study, retrospective scale pattern analysis of samples from Situk River Steelhead was synthesized with regional abundance information to investigate patterns in early marine growth among different life-history and demographic groups, as well as to explore linkages between growth, abundance, and marine environmental variables. Positive correlations were identified between freshwater growth, first ocean-year growth, and adult length, while first ocean-year growth was negatively correlated with second ocean-year growth. Early maturing Steelhead were found to have increased first ocean-year growth and reduced adult length relative to later maturing Steelhead, confirming connections between growth and maturation. Correlations in abundance among Southeast Alaska Steelhead populations suggest that marine and climatic drivers may impact these populations in a regionally coherent manner. Correlations among patterns in abundance also varied along a distance gradient: populations located closer to the Situk River were more correlated with the Situk River than more distant populations. Positive relationships between Gulf of Alaska sea surface temperature, North Pacific Gyre Oscillation, and Situk River Steelhead abundance further supported the importance of climate-driven marine conditions to Steelhead productivity. While conservation concerns for Steelhead in Southeast Alaska are currently minimal, proactive investigations into life-history diversity and population linkages may become more relevant with increased marine ecosystem variability related to climate change.
    • Earthquake source mechanisms and three-dimensional wavefield simulations in Alaska

      Silwal, Vipul; Tape, Carl; Christensen, Douglas; West, Michael; Ruppert, Natalia; Freymueller, Jeffrey (2018-08)
      This thesis presents: (1) a set of earthquake source mechanism catalogs for Alaska and (2) a threedimensional seismic velocity model of Alaska. The improved earthquake sources are used within the velocity model for generating synthetic seismograms, which are then compared with recorded seismograms to assess the quality of the velocity model. An earthquake source mechanism can be modeled as a moment tensor, which is a 3 × 3 symmetric matrix. We estimate the moment tensor for earthquakes by comparing observed waveforms (body waves and surface waves) with synthetic waveforms computed in a layered model. The improved moment tensor solutions are obtained by utilizing both the body waves and surface waves at as many broadband stations as possible. Further improvement in the inversion technique is obtained by (1) implementation of L1 norm in waveform misfit function and (2) inclusion of first-motion polarity misfit in the misfit function. We also demonstrate a probabilistic approach for quantifying the uncertainty in a moment tensor solution. Moment tensors can be used for understanding the tectonics of a region. In the Cook Inlet and Susitna region, west of Anchorage, we determined moment tensor solutions for small-tointermediate magnitude (M ≥ 2.5) crustal earthquakes. Analyzing these small earthquakes required us to modify the misfit function to include first-motion polarity measurements, in addition to waveform differences. The study was complemented with the probabilistic hypocenter estimation of large historical earthquakes (Mw ≥ 5.8) to assess their likelihood of origin as crustal, intraslab, or subduction interface. The predominance of thrust faulting mechanisms for crustal earthquakes indicate a compressive regime within the crust of south-central Alaska. Wavefield simulations are performed in three regions of Alaska: the southern Alaska region of subduction, the eastern Alaska region with the accreting Yakutat microplate, and the interior Alaska region containing predominantly strike-slip faulting, including the Minto Flats fault zone. Our three-dimensional seismic velocity model of Alaska is an interpolated body-wave arrival time model from a previous study, embedded with major sedimentary basins (Cook Inlet, Susitna, Nenana), and with a minimum shear wave velocity threshold of 1000 m/s. Our comparisons between data and synthetics quantify the misfit that arises from different parts of each model. Furtherwork is needed to comprehensively document the regions within each model that give rise to the observed misfit. This would be a step toward performing an iterative adjoint tomographic inversion in Alaska.
    • Eating disorder symptomatology among Alaska Native/American Indian and caucasian female university students in the extreme North

      Saunders, Miranda R. (2004-05)
      The purpose of this study was to explore differences in eating disorder symptomatology among a matched sample of 100 Alaska Native/American Indian and Caucasian female university students, using a demographic instrument and the Eating Attitudes Test (EAT-26). Four (8.0%) Native participants and ten (20.0%) Caucasian participants met or exceeded the EAT-26 cutoff score indicative of clinically significant eating disorder symptomatology. There were no significant differences found among the Native and Caucasian participants with regard to eating disorder symptomatology. Rather, eating disorder symptomatology was present in both Native and Caucasian female college students at rates similar to that of previous studies.
    • Ecogeographic, Adaptive, And Phylogenetic Variations In The Crested Duck (Lophonetta Specularioides) And Their Hemoglobins In The Andes

      Bulgarella, Mariana; McCracken, Kevin; Takebayashi, Naoki; Tubaro, Pablo L.; Winker, Kevin S. (2010)
      Tolerance to high-altitude hypoxia in animals varies widely and is a key factor in determining survival at high elevation. The Andean Cordillera of South America, which spans large elevational and latitudinal gradients, enables the study of native highland populations and the characteristics of hemoglobin proteins that are locally adapted for high-altitude respiration. The waterfowl populations of South America are understudied, little data on demographics and behavior are currently available, and only recently have they been investigated using molecular tools. We studied population genetics, phylogeography, and ecogeographic variation in the crested duck ( Lophonetta specularioides). The crested duck is a dabbling duck, and it comprises two subspecies endemic to highland and lowland regions of South America. The primary objective of this study was to investigate the genetic differentiation between highland and lowlands populations of crested ducks using molecular markers with varying modes of inheritance and rates of substitution. The second objective was to evaluate morphological differences between the subspecies to better understand the forces shaping morphology in the two different environments. A third objective was to provide additional information on the taxonomic relationships and natural history of the crested duck. First, we examined the population genetics of the three adult hemoglobins (alphaD, alphaA, betaA), six autosomal introns, and mtDNA. This multi-locus analysis revealed a significant pattern of differentiation between highland and lowland populations. Four hemoglobin amino acid replacements were found in crested duck that may play a role in influencing high-altitude respiration. The lack of evidence for gene flow for hemoglobin alleles between highland and lowland populations and the biochemical properties of the amino acid substitutions themselves are consistent with the effects of selection acting on these loci. Overall body size was larger for the highland subspecies, body size was intermediate in mid-elevation environments, and smaller individuals were found in the lowlands of Patagonia. We also performed a multi-locus phylogenetic analysis to determine the relationships of Lophonetta within the South American duck clade. Finally, we determined the proportion of genes expressed in bone marow of adult crested duck finding mostly genes related to hemopoietic and immune function.
    • Ecological And Physiological Adaptations Of The Porcupine To Winter Alaska

      Coltrane, Jessica A.; Barboza, Perry; Spalinger, Donald E.; Farley, Sean; Barnes, Brian M. (2012)
      Understanding the ecology and physiology of wildlife is paramount to conservation and management of species. North American porcupines (Erethizon dorsatum) are mammalian herbivores that occupy a diverse array of habitats across a broad geographical range. However, few studies have explored the ecology and physiology of porcupines. I used captive and free ranging porcupines to 1) identify the physiological abilities that enable them to survive on low quality winter forage when thermoregulatory demands are high, 2) determine responses of porcupines to winter conditions, and 3) determine how winter conditions influence habitat selection and home range size at the northern limits of their range. My research revealed that the persistence of porcupines at the northern limits of their range is due to plasticity of food intake, as well as physiological tolerance of low-quality diets and low ambient temperatures. Captive porcupines gained mass when high quality diets were available. However, porcupines decreased their dry matter intake throughout winter, indicating a seasonal decrease in metabolic rate. Low requirements for energy and nitrogen minimized the loss of body mass when intakes were low, while plant toxins increased urinary losses of energy and nitrogen. Free-ranging porcupines conserved lean body mass in winter by catabolizing fat stores. Proportional fat loss was correlated positively with total fat mass at the start of winter. Fat losses were minimized by lowering rates of energy expenditure. Water turnovers were slow in wild porcupines and body temperatures were not reduced to save energy. In order to survive winter on a low quality diet of white spruce (Picea glauca ) needles and cambium and paper birch (Betula papyrifera ) cambium, porcupines maintained large home ranges comprised primarily of mixed conifer/hardwood forests. Occupying a mixed forest habitat allowed porcupine to switch their diet between two forage tree species, potentially alleviating saturated detoxification pathways. Overall, porcupines possess the physiological abilities of a specialist herbivore during winter; however, they rely on abundant high quality summer forages to replenish their stores of fat and protein for reproduction and survival in the subsequent winter.
    • Ecological and physiological aspects of caribou activity and responses to aircraft overflights

      Maier, Julie Ann Kitchens (1996)
      I investigated the use of remote-sensing of caribou (Rangifer tarandus) activity to assess disturbance of low-altitude overflights by jet aircraft. Resource management agencies are concerned about the potential effects of these overflights on important species of ungulates. I hypothesized that low-altitude overflights would affect activity and movements of caribou, and thereby constitute a disturbance with negative consequences on energetics. I used caribou of the Delta Herd (DCH) and captive animals at the Large Animal Research Station (LARS) to address the hypotheses: caribou (1) exhibit equal activity day and night; (2) do not time activity to light; and (3) activity patterns do not change seasonally in response to daylength. Caribou were nychthemeral and exhibited uniform activity with no apparent timing to light. DCH caribou responded to seasonal changes in the environment by modifying activity (increased activity in response to insect harassment), whereas LARS caribou altered activity in response to fluctuating physiological variables (increased activity during rut). Changes in daylength did not affect activity. Data on activity from LARS and DCH caribou were compared with extant data on caribou of the Denali and Porcupine herds. Poor quality forage in winter was inferred from long resting bouts, and low availability of forage was inferred from long active bouts of post-calving caribou of the DCH. In midsummer, caribou of the DCH exhibited significantly longer active and shorter resting bouts than did LARS caribou, consistent with a moderate level of insect harassment. Responses of caribou to overflights were mild in late winter and, thus, overflights did not constitute a disturbance. Post-calving caribou responded to overflights by increasing daily activity, linear movements, incremental energy cost, and average daily metabolic rate. Energetic responses and movements were significantly related to the loudest overflight of the day. In the insect season, activity levels increased significantly in response to overflights but with no corresponding increase in linear movements or energetics. My recommendations are to prohibit aircraft overflights of caribou during calving and post-calving periods and during key feeding times in insect harassment seasons. Research indicates the possibility of more severe effects in nutritionally stressed animals.
    • Ecological And Social Influences On Population Dynamics And Genetics Of Moose In Alaska

      Schmidt, Jennifer Irene; McCracken, Kevin (2007)
      I examined social and ecological influences on moose (Alces alces gigas) in Alaska, USA, with respect to hunting success, antler size, and population genetic structure. Catch per unit effort (CPUE) is frequently used to assess hunter success; thus I hypothesized that landscape characteristics and moose density would affect success. Using hunter harvest tickets returned to the Alaska Department of Fish and Game, I modeled CPUE with Weibull regression. I determined success is significantly predicted by hunt location, mode of transportation, hunting regulations, use of commercial services (i.e., guides), year, road density, hunter-to-moose ratio, moose density, and hunter residency status. Antler size is an important factor for hunters and for mating potential in male moose. I hypothesized that moose density, habitat, and use of guides would correlate with antler size of harvested moose. I also predicted that guides would harvest moose with larger antlers and avoid areas where the hunter-to-moose ratio is high compared to nonguided hunters. Results indicated that antler size decreases with increases in moose density and harvest intensity due to density-dependent processes and a younger age structure in heavily harvested areas. Guided hunts tended to harvest larger antlered bulls and avoided areas of high hunter-to-moose ratios. In addition to age and nutrition, genetics influences antler size. I used eight microsatellites and five sample areas to resolve whether population structure exists among moose in Alaska. I hypothesized that population structure does exist given the intense harvest rates, polygynous mating style of moose, and heterogeneous landscape present in Alaska. Dispersal and gene flow between populations was proposed to occur via isolation-by-distance (IBD) with a positive linear relationship between geographic and genetic distance. Results indicated weak but significant population structure for moose in Alaska, and IBD was supported. Pairwise comparisons between populations indicated that moose have established separate populations except for between Tanana Flats and Koyukuk and Koyukuk and the Seward Peninsula. Lastly, I hypothesized incorporation of landscape characteristics and subsequent least-cost path would strengthen the significance of IBD. With an additional population, Tetlin, the significance of IBD as a mechanism for dispersal/gene flow for moose in Alaska was improved.
    • Ecological development of a management plan for reindeer (Rangifer tarandus) on St. George Island, Alaska

      St. Martin, Michelle L. (2012-12)
      Management of an herbivore production system requires a working knowledge of the components and processes of the targeted grazing system. Land owners and stakeholders wish to develop a management plan for reindeer on St. George Island, Alaska. The foci of this study were to determine seasonal diet composition (including forage preference); evaluate nutritional content of Angelica lucid, a potential alternative winter forage; estimate lichen biomass; and estimate reindeer abundance, annual production, and sustainable stocking density. Lichens were the preferred reindeer forage throughout the year, however significant seasonal dietary shifts occurred across the seasons. Fortis and grasses were consumed in significantly greater proportion in spring and summer diets, sedges greater in the fall diets, and mosses greater in the winter diets. Angelica lucida was found in reindeer diets throughout the year. The nutritional profile and available biomass suggest this species may serve as an important forage for growth and maintenance of the reindeer. Both the reindeer population and calf:cow ratio increased from 2007 (290 individuals; 48:100 ratio) to 2008 (320 individuals; 57:100 ratio). The estimated total lichen biomass for the island was ~ 5.4 million kg dry matter which could support a population of 217 reindeer or 2.4 reindeer/ km².
    • Ecological drivers of mercury accumulation in threespine stickleback fish

      Willacker, James J.; O'Hara, Todd; von Hippel, Frank; Buck, Loren; Welker, Jeffrey; Wipfli, Mark (2013-12)
      I utilized the ecological diversity displayed in the Cook Inlet adaptive radiation of threespine stickleback (Gasterosteus aculeatus species complex, hereafter 'stickleback') to examine the drivers of intra- and inter-population variation in total mercury (THg) concentrations. I examined the importance of sex, trophic position (TP), and habitat-specific foraging (measured as the proportion of the diet derived from benthic sources; a) in stickleback from Benka Lake, Alaska, a lake with both benthic and limnetic ecotypes. The results demonstrate that both sex and habitat-specific foraging are important determinants of THg concentrations in this threespine stickleback population. Specifically, male stickleback and stickleback foraging in limnetic habitats had higher THg concentrations than females or benthic foraging individuals. Further, I found that the relationships between THg concentration, TP, and a differed between the sexes such that TP and a were of approximately equal importance in female fish but TP was more important than a in male fish. I assessed the relative importance of these same factors in determining THg concentrations of stickleback from six lakes spanning a range of trophic ecologies. Across populations, I found sex and TP to be more important determinants of THg concentrations than reliance on benthic prey; however, there was substantial variation in the relative importance of these parameters in individual lakes. Across lakes I also found a positive correlation between THg concentrations in stickleback and the reliance on benthic prey, and my data suggest that differences in the bioavailability of Hg in the lakes were responsible for this relationship. I investigated temporal variation in the THg concentrations of Benka Lake stickleback. The temporal patterns observed in stickleback likely result from numerous physiological and ecological processes. I found that the importance and magnitude of these factors acting upon THg concentrations varied between sexes, ecotypes, or both, though the directions of the relationships were consistent across groups. Despite this variation, TP was consistently the most important determinant of Hg concentrations. Collectively, the results of this dissertation demonstrate that the ecological factors driving THg concentrations in stickleback are complex, likely integrate multiple confounding interactions, and often vary by sex, ecotype, and population (lake). To improve our understanding of the mechanisms underlying Hg bioaccumulation, future research should utilize experimental studies and larger numbers of wild populations to examine the independent effects of these variables within the context of varying physiologies and ecologies.
    • Ecological effects of invasive European bird cherry (Prunus padus) on salmonid food webs in Anchorage, Alaska streams

      Roon, David A.; Wipfli, Mark; Prakash, Anupma; Wurtz, Tricia (2011-08)
      Invasive species are a concern worldwide as they can displace native species, reduce biodiversity, and disrupt ecological processes. European bird cherry (Prunus padus) (EBC) is an invasive ornamental tree that is rapidly spreading and possibly displacing native trees along streams in parts of urban Alaska. The objectives of this study were to: 1) map the current distribution of EBC along two Anchorage streams, Campbell and Chester creeks, and 2) determine the effects of EBC on selected ecological processes linked to stream salmon food webs. Data from the 2009 and 2010 field seasons showed: EBC was widely distributed along Campbell and Chester creeks; EBC leaf litter in streams broke down rapidly and supported similar shredder communities to native tree species; and EBC foliage supported significantly less terrestrial invertebrate biomass relative to native deciduous tree species, and contributed significantly less terrestrial invertebrate biomass to streams compared to mixed native vegetation, but riparian EBC did not appear to affect the amount of terrestrial invertebrate prey ingested by juvenile coho salmon (Oncorhynchus kisutch). Although ecological processes did not seem to be dramatically affected by EBC presence, lowered prey abundance as measured in this study may have long-term consequences for stream-rearing fishes as EBC continues to spread over time.
    • Ecological effects of spawning salmon on several southcentral Alaskan streams

      Piorkowski, Robert Joseph (1995)
      The ecological effects of salmon (Oncorhynchus spp.) carcasses on southcentral Alaskan streams were studied by: (1) observing salmon carcass decomposition and use; (2) comparing the macroinvertebrate community structure of streams receiving different inputs of salmon carcasses; and (3) quantifying the amount of marine-derived nitrogen (MDN) entering stream food webs using stable-isotope analysis. Abiotic mechanisms, such as large woody debris and the slow waters of stream margins and eddies were important in initial retention of salmon carcasses. Once entrained, carcasses decayed rapidly due to intense microbial processing. Stream insects and fishes were observed consuming carcasses, eggs, and smolts. Macroinvertebrate communities in streams receiving runs of salmon or in lake outlet streams were more diverse taxonomically. One functional feeding group, filterers (including net-spinning caddisflies (Hydropsychidae) uncommon in Alaska), increased in relative abundance. Although many other taxa also responded positively to enrichment, some taxa responded negatively. A significant difference existed in $\partial\sp{15}$N values between MDN and terrestrial sources but natural dissolved inorganic nitrogen contributions to stream food webs ($\approx$90-95% of total N) from groundwater generally overwhelmed the marine signal ($\approx$5-10% of total N). $\partial\sp{15}$N values generally suggested that some MDN ($\approx$15% of total N) entered into food webs after its incorporation into algal biomass but values for certain macroinvertebrate taxa (Arctopsyche and Plumiperla), salmon fry (Oncorhynchus spp.) grayling (Thymallus arcticus), rainbow trout (O. mykiss) and American dippers (Cinclus mexicanus) suggest these biota directly consume substantial amounts (40%-90%) of salmon protein. $\partial\sp{15}$N values in individual macroinvertebrate taxa usually cycled seasonally. All three elements of this investigation support the hypothesis that salmon carcasses can be important in structuring aquatic food webs.