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The relative importance of sockeye salmon, invertebrate predators, and other environmental factors in structuring the size and abundance of zooplankton populations was examined in a series of 23 lakes from southern Alaska. Zooplankton abundance was strongly related to sockeye density, along with nutrient availability and alkalinity. The mean size of Bosmina longirostris, the dominant herbivorous cladoceran, was positively correlated with the abundance of the predatory copepod, Cyclops columbianus. Changes in the size and abundance of Bosmina remains over the past 300-500 years were then determined for sediments from two lakes on Kodiak Island, Alaska. The zooplankton communities showed varying responses to past...
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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...
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I examined the foraging ecology of the Yellow-rumped Warbler (Dendroica coronata) several years after an outbreak of spruce beetles (Dendroctonus rufipennis) in the Copper River Basin, Alaska. With increased beetle-induced mortality of white spruce (Picea glauca), a preferred foraging substrate, we predicted warblers would respond through: (1) decreased overall use of white spruce, (2) increased selectivity of live white spruce that remained, and (3) reduced foraging efficiency, reflected by a greater proportion of time spent foraging and lower prey attack rates. We examined warbler foraging behavior and arthropod biomass on commonly used foraging substrates, and in stands with low-moderate (<40%) and heavy (>40%)...
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Summary: "Migratory patterns of Yukon River inconnu Stenodus leucichthys [sheefish] were evaluated using otolith aging and microchemical techniques and radio telemetry. Research was conducted each fall between 1997 and 1999, on inconnu captured at a study site 1,200 river km from the Bering Sea. Biological data were collected to establish maturity and spawning condition. Sagital otoliths were analyzed optically to determine age distribution, and microchemically to determine amphidromy. Inconnu were tagged with radio transmitters and located in upstream spawning destinations. Inconnu captured at the study site were uniformly large, mature fish preparing to spawn. Age estimates ranged from 7 to 28 years. Microchemical...
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Symbioses between plants and nitrogen (N) fixing bacteria are ecologically and economically important interactions with complex evolution and ecology. Theoretical and experimental studies suggest that host specificity and environmental variation are important determinants of both evolutionary and ecological patterns in such interactions, but detailed descriptions of these parameters in natural habitats are lacking for most N-fixing systems. The aim of this set of studies was to provide such information for the symbiosis between alder ( Alnus spp.) plants and Frankia bacteria in interior Alaska. Major objectives were to determine whether: 1) different Alnus species (A. tenuifolia and A. viridis ) associate with different...
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This research had two basic objectives: to assess the capability of macrophytes [non-microscopic plant] indigenous to the subarctic in removal of heavy metals from wastewater and to determine the feasibility of using constructed wetlands for sewage wastewater treatment in a subarctic environment with a focus on rural application. The research consisted of two parts: a greenhouse study in which indigenous macrophytes were subjected to heavy metal pollutants similar to those found in roadway runoff and a constructed wetland built to treat sewage wastewater. Five species of plants were tested in both projects: Arctophila fulva [grass], Carex rhynchophysa [sedge], Menyanthes trifoliata [buckbean], Scirpus validus [bulrush]...
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Snowshoe hares, Lepus americanus, are a 'keystone' prey species in northern boreal forests and experience population fluctuations of 8-11-years. Despite intense responses of both vegetation and predators to changes in hare densities, landscape-scale comparisons of hare populations in Alaska have been limited to qualitative descriptions. We conducted capture-recapture studies of snowshoe hares at 5 locales in the Tanana valley, from Tok in the east to Clear in the west from 1999 to 2002. Snowshoe hare densities were highest in 1999 (x=6.36 ha p- p1, SE=0.63) and declined thereafter. We were unable to detect declines in apparent survival during declining densities in our study populations. Movement distances did not...
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Striving for better delineation of site function, land use, and settlement patterns, the data and analyses presented in this dissertation aim to explore more robust and objective avenues of inquiry for addressing the variability and distribution of surface lithic scatters using terrain-based hunting range models. Using large mammal distributions, Athabascan hunting ranges, and topography, landscape metrics, and an exploratory data analysis (EDA) framework, landscape structure is quantified and compared across much of the Alaskan Interior to identify reoccurring patterns related to hunting land use and the range characteristics of caribou, moose, and sheep. Key components of the landscape structure are contrasted...
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High-latitude regions store large quantities of organic carbon (C) in permafrost soils and peatlands, accounting for nearly half of the global belowground C pool. Projected climate warming over the next century will likely drive widespread thawing of near-surface permafrost and mobilization of soil C from deep soil horizons. However, the processes controlling soil C accumulation and loss following permafrost thaw are not well understood. To improve our understanding of these processes, I examined the effects of permafrost thaw on soil C dynamics in forested upland and peatland ecosystems of Alaska's boreal region. In upland forests, soil C accumulation and loss was governed by the complex interaction of wildfire...
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This dissertation includes three discrete projects addressing various aspects of the neuroendocrine control of song in the Dark-eyed Junco (Junco hyemalis), a migratory songbird. Specifically, the roles of testosterone, photoperiodic condition [length of daylight], opioids, and age were investigated with respect to song production and neural plasticity in the regions of the brain that control song (vocal control regions, VCRs). I found that, in males photoperiodic condition and testosterone interact to regulate seasonal VCR volume plasticity, whereas testosterone alone controls song production. The opioid system is probably not involved in VCR plasticity or song production, but is indicated to play a role in song...
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Summary: "Density estimation of wolves (Canis lupus) requires a count of individuals and an estimate of area those individuals inhabit. With radiomarked wolves, the count is straightforward but estimation of area is more difficult and often given inadequate attention. The population area, based on the mosaic of pack territories, is influenced by sampling intensity similar to individual home ranges. If sampling intensity is low, population area will be underestimated and wolf density will be inflated. Using data from studies in Denali National Park and Preserve, I investigated these relationships using Monte Carlo simulation to evaluate effects of radiolocation effort and number of marked packs on density estimation....
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Harvesting wild berries, firewood, and other non-timber forest products (NTFPs) from the boreal forest in Interior Alaska is a common activity amongst local residents. NTFPs are harvested for personal use, subsistence, and commercial purposes. While these activities contribute to informal household economies and livelihoods, harvest of NTFPs are not well documented in Alaska. Availability of these ecosystem services may be altered under changing management and climate regimes. This interdisciplinary dissertation takes a look at the activities and impacts of current NTFP harvesting practices. Survey results from a forest use survey provide insight into harvest activity in the Tanana Valley. Wild blueberries (38.5%...
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The taxonomy and evolutionary relationships of the Oxytropis arctica and Oxytropis campestris complexes in Alaska are poorly understood. Taxonomic disagreement has centered on which morphological characters are important in circumscribing these taxa. Several of these taxa are endemic to Alaska, including Oxytropis arctica var. barnebyana, which is currently of conservation concern. Internal transcribed spacer sequences and randomly amplified polymorphic DNA markers were employed to circumscribe these taxa. Both lines of evidence revealed one major dichotomy dividing northern populations from western populations. There is weak support for traditional taxonomies. Morphological characters used to separate these taxa...
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Chinook salmon in Alaska support human uses through a variety of fisheries. Age-structured assessment models are rarely used for estimating the abundance of exploited stocks. This thesis develops a model for the Copper River chinook salmon population to show its advantages over typical assessment models. Information consists of catch-age data from three fisheries (commercial, recreational, subsistence), and two sources of auxiliary data (escapement index, spawner-recruit relationship). Four approaches utilizing different information sources are explored. Results suggest that an approach utilizing pooled catch-age data with time-varying brood-year proportions produces the best estimates, although retrospective and...
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Marine-derived nutrients (MDN) delivered by spawning Pacific salmon ( Oncorhynchus spp.) contribute to the productivity of riverine ecosystems. Optimizing methods for measuring MDN assimilation in food webs will foster the development of ecologically based resource management approaches. This dissertation aims to better understand relationships among spawning salmon abundance, biochemical measures of MDN assimilation, and the fitness of stream-dwelling fishes. The goals of my first research chapter were (1) to understand the factors that influence stable isotope (δ 13 C, δ 15 N, and δ34 S) and fatty acid measures of MDN assimilation in stream and riparian biota, and (2) to examine the ability of these measures to...
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Snowshoe hare (Lepus americanus ) survival depends on the interaction of habitat characteristics with numerous biological and environmental variables. In boreal regions where considerable habitat heterogeneity exists, hares balance food availability with predation risk by moving among habitats seasonally, but it is largely unknown how often they move at shorter time scales. I investigated the seasonal effects of habitat, weather, and individual hare characteristics on survival and movement in two common but fundamentally different boreal habitats. Survival was highest in summer, for hares with higher body condition, and in black spruce rather than early successional forest. Hares moved among core use areas in different...
map background search result map search result map Migratory patterns of Yukon River inconnu [sheefish] as determined with otolith microchemistry and radio telemetry Neuroendocrine control of song in the dark-eyed junco (Junco hyemalis) Evaluation of wolf density estimation from radiotelemetry data Phylogenetic relationships of the Oxytropis campestris and Oxytropis arctica complexes in Alaska inferred from non-coding nuclear DNA and RAPD data Constructed wetlands for wastewater treatment in the subarctic The Potential of Lodgepole Pine in Alaska Climate and predictability of Alaska wildfires Geomorphology and Inconnu Spawning Site Selection: An Approach Using GIS and Remote Sensing Holocene vegetation and climate change at Canyon Lake Copper River basin Alaska Birch, berries, and the boreal forest: Activities and impacts of harvesting non-timber forest products in interior Alaska The effects of permafrost degradation on soil carbon dynamics in Alaska's boreal region Landscape structure and terrain-based hunting range models: Exploring late prehistoric land use in the Nutzotin Mountains, southcentral Alaska Marine-derived nutrients in riverine ecosystems: Developing tools for tracking movement and assessing effects in food webs on the Kenai Peninsula, Alaska Winter range studies of the Western Arctic Caribou Herd, Northwest Alaska Sources of variation in the symbiotic association between Alnus and Frankia in interior Alaska Comparison of snowshoe hare populations in interior Alaska An age structured model for assessment and management of Copper River chinook salmon Factors influencing zooplankton populations in Alaskan sockeye salmon (Oncorhynchus nerka) nursery lakes : insights from limnological and paleolimnological analyses Survival and activity patterns of snowshoe hares (Lepus americanus) in interior Alaska Foraging ecology of Yellow-rumped Warblers in response to an outbreak of spruce beetles Neuroendocrine control of song in the dark-eyed junco (Junco hyemalis) Constructed wetlands for wastewater treatment in the subarctic Sources of variation in the symbiotic association between Alnus and Frankia in interior Alaska Comparison of snowshoe hare populations in interior Alaska Survival and activity patterns of snowshoe hares (Lepus americanus) in interior Alaska Holocene vegetation and climate change at Canyon Lake Copper River basin Alaska An age structured model for assessment and management of Copper River chinook salmon Foraging ecology of Yellow-rumped Warblers in response to an outbreak of spruce beetles Geomorphology and Inconnu Spawning Site Selection: An Approach Using GIS and Remote Sensing Marine-derived nutrients in riverine ecosystems: Developing tools for tracking movement and assessing effects in food webs on the Kenai Peninsula, Alaska Factors influencing zooplankton populations in Alaskan sockeye salmon (Oncorhynchus nerka) nursery lakes : insights from limnological and paleolimnological analyses Evaluation of wolf density estimation from radiotelemetry data The effects of permafrost degradation on soil carbon dynamics in Alaska's boreal region Birch, berries, and the boreal forest: Activities and impacts of harvesting non-timber forest products in interior Alaska Winter range studies of the Western Arctic Caribou Herd, Northwest Alaska Landscape structure and terrain-based hunting range models: Exploring late prehistoric land use in the Nutzotin Mountains, southcentral Alaska Climate and predictability of Alaska wildfires Migratory patterns of Yukon River inconnu [sheefish] as determined with otolith microchemistry and radio telemetry Phylogenetic relationships of the Oxytropis campestris and Oxytropis arctica complexes in Alaska inferred from non-coding nuclear DNA and RAPD data The Potential of Lodgepole Pine in Alaska