Recent Submissions

  • River features associated with chinook salmon spawning habitat in Southwest Alaska

    Jallen, Deena M.; Margraf, F. Joseph; Adkison, Milo (2009-08)
    Chinook salmon (Oncorhynchus tshawytscha) is a highly valued traditional, subsistence, and commercial resource in Southwest Alaska. Stream habitat availability is a major component influencing salmon productivity. The objective of this study is to identify river features associated with spawning habitat, and describe upper and lower boundaries of chinook salmon spawning on the Tuluksak River. River distances, elevation, salmon locations, spawning sites, and habitat observations were collected along 75 river kilometers of the Tuluksak River primarily within the Yukon Delta National Wildlife Refuge. Habitat and salmon observations were grouped into strata along the length of the river for comparison and analysis. Chinook salmon were observed spawning in the upper 45 river kilometers of the study area. Map-based observations of elevation and channel sinuosity correlate better with chinook salmon spawning than in stream habitat measurements along the Tuluksak River. The upper boundary of chinook salmon spawning in the Tuluksak River was outside of our study area. The lower boundary for chinook salmon spawning habitat on similar rivers might be determined by examining elevation, sinuosity, and channel features from remote images or maps prior to conducting field studies.
  • Black bear denning ecology and habitat selection in interior Alaska

    Smith, Martin E.; Follmann, Erich; Dean, Fred; Hechtel, John; Bowyer, Terry (1994-12)
    To identify conflicts between existing black bear (Ursus americanus) management and human activity on Tanana River Flats, Alaska, we monitored 27 radio-collared black bears from 1988-1991. We compared denning chronology, den characteristics, den-site selection, and habitat selection across sex, age, and female reproductive classes. Mean den entry was 1 October and emergence was 21 April, with females denned earlier and emerging later than males. Marshland and heath meadow habitats were avoided, and willow-alder was selected for den-sites. Eighty-three percent of dens were excavated, 100% contained nests, 18% were previously used, and 29% had flooded. Black bears selected black spruce-tamarack and birch-aspen significantly more, and marshland and heath meadow significantly less than available. Marshland and birch-aspen were used significantly more in spring than autumn. Marshland was used less than available by all bears in all seasons. Special habitat or den-site requirements are not critical for management of Tanana River Flats black bears.
  • The effects of permafrost degradation on soil carbon dynamics in Alaska's boreal region

    O'Donnell, Jonathan A. (2010-12)
    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 and permafrost. Fluctuations in active layer depth across stand age and fire cycles determined the proportion of soil C in frozen or unfrozen soil, and in turn, the vulnerability of soil C to decomposition. Under present-day climate conditions, the presence of near-surface permafrost aids C stabilization through the upward movement of the permafrost table with post-fire ecosystem recovery. However, sensitivity analyses suggest that projected increases in air temperature and fire severity will accelerate permafrost thaw and soil C loss from deep mineral horizons. In the lowlands, permafrost thaw and collapse-scar bog formation resulted in the dramatic redistribution of soil water, modifying soil thermal and C dynamics. Water impoundment in collapse-scar bogs enhanced soil C accumulation in shallow peat horizons, while allowing for high rates of soil C loss from deep inundated peat horizons. Accumulation rates at the surface were not sufficient to balance deep C losses, resulting in a net loss of 26 g C m⁻² y⁻¹ from the entire peat column during the 3000 years following thaw. Findings from these studies highlight the vulnerability of soil C in Alaska's boreal region to future climate warming and permafrost thaw. As a result, permafrost thaw and soil C release from boreal soils to the atmosphere should function as a positive feedback to the climate system.
  • Winter habitat of arctic grayling in an interior Alaska stream

    Lubinski, Brian R. (1995-05)
    Placer mining and the lack of information on winter ecology of Arctic grayling Thymallus arcticus. has raised concern for this popular sportfish. A study was designed to validate aerial radio telemetry data and to locate and describe overwinter areas (OWA) of Arctic grayling in Beaver Creek, Alaska. Reliance on aerial data alone resulted in overestimation of survival and misidentification of 14 of 26 designated OWAs. Twenty-one Arctic grayling were tracked downstream 12-58 km to 12 OWAs spanning a 31-km section of Beaver Creek. Radio-tagged and untagged Arctic grayling occupied areas with ice thickness of 0.4-1.4 m overlying 0.06-0.52 m of water, flowing at 0.03-0.56 m/s. During winter, discharge, cross-sectional area, velocities, and water width in four OWAs decreased until late March; then, cross-sectional area increased due to an increase in discharge that pushed the ice upward. Adult Arctic grayling overwintered downstream of habitat disturbances, and occupied much shallower winter habitats than expected.
  • Thermal limitations on chinook salmon spawning habitat in the northern extent of their range

    Decker, Samantha Kristin Strom; Margraf, F. Joseph; Rosenberger, Amanda; Evenson, Matthew (2010-05)
    Pacific salmon (Oncorhynchus) habitat models attempt to balance research efficiency with management effectiveness, however, model transferability between regions remains elusive. To develop efficient habitat models, we must understand the critical elements that limit habitat. At the northern edge of the geographic range for Chinook salmon, O. tschawytscha, water temperature is a probably a limiting habitat factor. This study investigated the spatial and temporal correspondence between water temperature and Chinook salmon spawning on the Chena River, Alaska. Water temperatures were monitored at 21 stations across 220 river kilometers during the 2006 and 2007 spawning seasons and compared to known thermal requirements for egg development. While an absolute upstream thermal boundary to spawning was not discovered, we describe potential temporal limitations in thermal conditions over the spawning season. Our results show that 98.5% of Chinook salmon selected spawning habitat in which their eggs have a 90% probability of accumulating 450 ATUs before freeze up. This suggests not only temperature conditions limit salmon spawning habitat, but also, as expected, water temperatures temporally limit accessible Chinook salmon spawning habitat at the northern edge of their range. This project documents new spawning habitat for the Anadromous Waters Catalog and broadens the geographical range of Chinook salmon thermal habitat research. It also contributes to the understanding of the processes that define salmon habitat, while providing a baseline for further investigations into water temperature in other thermal regimes.
  • Common ravens in Alaska's North Slope oil fields: an integrated study using local knowledge and science

    Backensto, Stacia Ann (2010-05)
    Common ravens (Corvus corax) that nest on human structures in the Kuparuk and Prudhoe Bay oil fields on Alaska's North Slope are believed to present a predation risk to tundra-nesting birds in this area. In order to gain more information about the history of the resident raven population and their use of anthropogenic resources in the oil fields, I documented oil field worker knowledge of ravens in this area. In order to understand how anthropogenic subsidies in the oil fields affect the breeding population, I examined the influence of types of structures and food subsidies on raven nest site use and productivity in the oil fields. Oil field workers provided new and supplemental information about the breeding population. This work in conjunction with a scientific study of the breeding population suggests that structures in the oil fields were important to ravens throughout the year by providing nest sites and warm locations to roost during the winter. The breeding population was very successful and appears to be limited by suitable nest sites. The landfill is an important food source to ravens during winter, and pick-up trucks provide a supplemental source of food throughout the year. Further research will be necessary to identify how food (anthropogenic and natural) availability affects productivity and the degree to which ravens impact tundra-nesting birds.
  • 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.
  • Marine-derived nutrients in riverine ecosystems: developing tools for tracking movement and assessing effects in food webs on the Kenai Peninsula, Alaska

    Rinella, Daniel J. (2010-05)
    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 ([delta]¹³C, [delta]¹⁵N, and [delta]³⁴S) and fatty acid measures of MDN assimilation in stream and riparian biota, and (2) to examine the ability of these measures to differentiate among sites that vary in spawning salmon biomass. For all biota studied, stable isotopes and fatty acids indicated that MDN assimilation increased with spawner abundance. Among Dolly Varden (Salvelinus malma), larger individuals assimilated proportionately more MDN. Seasonal effects were detected for aquatic macroinvertebrates and riparian horsetail (Equisetum fluviatile), but not for Dolly Varden. Of all dependent variables, Dolly Varden [delta]¹⁵N had the clearest relationship with spawner abundance, making this a good measure for monitoring MDN assimilation. Expanding on these results, two chapters examined potential fisheries management applications. The first sought to identify spawner levels above which stream-dwelling Dolly Varden and coho salmon (O. kisutch) parr cease to gain physiological benefits associated with MDN. RNA-DNA ratios (an index of recent growth rate) and energy density indicated saturation responses where values increased rapidly with spawner abundance up to approximately 1 kg/m² and then leveled off. In coho salmon parr, energy density and RNA-DNA ratios correlated significantly with [delta]¹⁵N. These results show strong linkages between MDN and fish fitness responses, while the saturation points may indicate spawner densities that balance salmon harvest with the ecological benefits of MDN. The second application tested a quick and inexpensive method for estimating, spawning salmon abundance based on [delta]¹⁵N in stream-dwelling fishes. Estimates made with coho salmon pair were unbiased, tightly correlated with observed values, and had a mean absolute deviation of 1.4 MT spawner biomass/km. Application of this method would allow estimates of annual escapement to be made on a potentially large number of streams.
  • Ecology of Prince of Wales spruce grouse

    Nelson, Aleya R. (2010-12)
    Recently, spruce grouse on Prince of Wales Island (POW) in southeast Alaska have been proposed as a separate subspecies. Furthermore, life-history of spruce grouse on POW, which is temperate coastal rainforest, varies sufficiently from birds in mainland areas, mostly boreal forest, to warrant specific management. Therefore, I examined the ecology of spruce grouse on POW to determine how timber harvest influences their survival and habitat selection and ultimately to provide recommendations for their conservation. During 2007-2009, we found that the greatest variation in survival probability was attributed to breeding status. The annual survival of non-breeding birds was 0.72±0.082 (S±) while for breeding birds it was 0.08±0.099. Logging did not adequately predict survival, with no differences among habitats. Conversely, I found differences in selection among habitats. At the watershed scale, spruce grouse preferred unharvested forest. At both watershed and homerange scales, spruce grouse avoided edges and preferred roads. Road-related mortality was the largest known source of death. POW spruce grouse and mainland subspecies exhibit sufficiently different survival rates and habitat preference to warrant specific management. We recommend limited road closures during periods when POW spruce grouse are most vulnerable due to the high rates of mortality associated with this preferred habitat.
  • Urban stream management: interdisciplinary assessment of the Ship Creek fishery

    Krupa, Meagan B. (2009-05)
    The Lower Ship Creek Fishery in the city of Anchorage, Alaska is one of the state's most popular sport fisheries. After years of channelization and development, this social-ecological system (SES) continues to experience the effects of urbanization and is struggling to achieve robustness. I applied a robustness framework to the management of management this fishery because of its semi-engineered nature. This framework uses interdisciplinary methods to study the interrelationships between the fishery's socio-economic and ecological components. Robustness is more appropriate than resilience as an analytical framework because of the relative insensitivity of the engineered components to ecological feedbacks. On Lower Ship Creek, the engineered hatchery fish continue to thrive despite declining stream conditions. The robustness of this fishery contributes to the resilience of the city by increasing local food and recreation options and supporting a diverse set of businesses. To study the robustness of this SES in the context of the resilience of Anchorage, I first combined historical photos and existing Ship Creek data with research conducted on other streams to create an environmental history of the creek. This history then was used to describe how eras of urban development have altered the creek's ecosystem processes and created new ecological constraints related to 1) loss of wetlands and riparian vegetation; 2) erosion, pollution, and channelization; 3) loss of fish species; and 4) flow alteration and habitat loss. Using Lovecraft's (2008) typology, I proposed four plausible management scenarios that highlight the trade-offs associated with management of this fishery: 1) Ship Creek Redesign, 2) Mitigation, Construction, and Maintenance, 3) KAPP Dam Removal, and 4) Business as Usual. The second of these scenarios is most consistent with the current ecological constraints, the characteristics preferred by most stakeholders, and current socio-economic trends. Since Scenario 2 will require a large monetary investment, I examined this SES's cost structure and compared it with previously published analyses of the economic benefits of the fishery. By quantifying the costs borne by each agency, I showed how externalities produce intra- and inter-agency tension. These data were used to construct a new cost-sharing framework that provides decision makers with an economic incentive to work more cooperatively in the future. I then explored the interrelationship of the SES's socioeconomic and ecological subsystems, using Anderies et al.'s (2004) framework. I applied Ostrom's design principles (1990) to sport fisheries to explore the reasons why agencies have not cooperated to produce a more robust fishery. This SES fails to meet three of the design principles: it lacks 1) an equal proportion of benefits and costs, 2) collective-choice arrangements, and 3) user and biophysical monitoring. I then suggest how to improve the design and increase the robustness of this SES. This study proposes that the maintenance of semi-engineered systems is important both for local users and for the resilience of states and countries. In the context of global trends toward increasing urbanization, this study provides an interdisciplinary approach to increasing the robustness of urban streams and building resilience within states and countries.
  • Controls on ecosystem respiration of carbon dioxide across a boreal wetland gradient in Interior Alaska

    McConnell, Nicole A.; McGuire, A. David; Turetsky, Merritt R.; Harden, Jennifer W. (2012-08)
    Permafrost and organic soil layers are common to most wetlands in interior Alaska, where wetlands have functioned as important long-term soil carbon sinks. Boreal wetlands are diverse in both vegetation and nutrient cycling, ranging from nutrient-poor bogs to nutrient- and vascular-rich fens. The goals of my study were to quantify growing season ecosystem respiration (ER) along a gradient of vegetation and permafrost in a boreal wetland complex, and to evaluate the main abiotic and biotic variables that regulate CO₂ release from boreal soils. Highest ER and root respiration were observed at a sedge/forb community and lowest ER and root respiration were observed at a neighboring rich fen community, even though the two fens had similar estimates of root biomass and vascular green area. Root respiration also contributed approximately 40% to ER at both fens. These results support the conclusion that high soil moisture and low redox potential may be limiting both heterotrophic and autotrophic respiration at the rich fen. This study suggests that interactions among soil environmental variables are important drivers of ER. Also, vegetation and its response to soil environment determines contributions from aboveground (leaves and shoots) and belowground (roots and moss) components, which vary among wetland gradient communities.
  • Recent changes in plant and avian communities at Creamer's Refuge, Alaska using field and remote sensing observations

    Tauzer, Lila Maria; Powell, Abby; Bret-Harte, Syndonia; Sharbaugh, Susan; Prakash, Anupma (2013-05)
    Plant communities in the north are being profoundly altered by climate warming, but our understanding of the extent and outcomes of this ecosystem shift is limited. Although it was assumed local vegetation changes will affect avian communities, few data exist to investigate this relationship. In an interior Alaska boreal forest ecosystem, this study capitalized on available resources to assess simultaneous change in plant and avian communities over 35 years. Biological changes were quantified in summer avian community data (species composition, diversity, and richness) and in vegetation using archived field data, and supplemented this data with remote sensing observations for a similar time period to assess the validity of this method for documenting environmental change. Field and remote sensing data both documented successional changes resulting in denser, more coniferous-dominated habitats. Birds responded accordingly, which indicates a rapid avian response to habitat change and that they are good indicators of environmental change. Information gained provides more accurate evaluations of habitat dynamics throughout the interior boreal forest and highlights the importance of considering successional change in all long-term climate studies. It allows for better predictions of future habitat change and acts as a strong baseline for future environmental monitoring.
  • Reproductive behavior and related social organization of the muskox on Nunivak Island

    Smith, Timothy E. (1976-05)
    The sexual behavior and social organization of the muskox (Ovibos moschatus wardi Zimmerman) were studied on Nunivak Island, Alaska, in fall 1972 and summer and fall 1973. Observation effort was concentrated on a single harem group for two months, during the height of courtship activity. Movements and fluctuations in the structure of this group are documented. There was no significant change in mean herd size as a result of the rut, suggesting the existence of a basic social unit independent of the influence of harem bulls. Harem bulls were in the 6-10 year age class. They exerted a stabilizing influence on the harem but did not direct its movements. The rut extended from early July to mid-October. Copulation occurred on September 4 and 5. General patterns of sexual and agonistic behavior are described. Changes in activity patterns as a result of the rut are shown. Bulls displayed more marked changes than cows or juveniles. The proportion of time allocated to sexual and agonistic behavior increased at the expense of maintenance activity as the rut progressed.
  • Effects of milk intake, growth and suckling effieciency on suckling behavior of muskox (Ovibos moschatus) calves

    Tiplady, Barbara Ann (1990-12)
    General theory on parental provisioning predicts that mammalian offspring receiving more milk should show longer suckling bouts, greater total suckling time, longer intervals between bouts, and greater suckling success. For muskoxen I found that suckling bout duration and suckling success were positively correlated with milk intake during some but not all stages of lactation. Neither interval between suckling bouts, nor total suckling time, was correlated with milk intake. Growth of calves was positively related to milk intake, and among calves of the same age suckling efficiency (intake/min suckling) was highly related to body weight. Therefore, milk intake affects growth rate, which in turn affects suckling efficiency. The overriding influence of calf body size and suckling efficiency limits interpretation of differences in suckling behavior that can be attributed to milk intake by muskox calves and therefore to the provisioning strategy of the cow.
  • Spatial scales of muskox resource selection in late winter

    Wilson, Kenneth J. (1992-05)
    I examined resource selection by muskoxen in late winter on the coastal plain of the Arctic National Wildlife Refuge, Alaska, by comparing use and availability at regional, meso, local, and micro spatial scales. Use of vegetation types for feeding appears to be based on selection of areas of shallow soft snow with high cover of sedges, dead vegetation, and total vegetation, and on selection against areas of little vegetation cover or deep hardpacked snow. Muskoxen used moist sedge, tussock sedge, and Dryas terrace tundra in proportion to availability and avoided barren ground, partially vegetated, riparian shrub, and Dryas ridge tundra. Selection for areas of shallow snow occurred within vegetation types as well as between vegetation types. Occurrence of sedges and grasses in the diet was greater than availability. Feeding zones were primarily on windblown vegetated bluffs; these areas are distributed in narrow bands along creeks, rivers, and the coastline.
  • Characterization of muskox habitat in northeastern Alaska

    O'Brien, Constance Marsha (1988-12)
    In northeastern Alaska, muskoxen have been most often found in riparian habitats and proximate uplands. Vegetation was studied in nine adjacent river drainages; six of the drainages are regularly used by muskoxen. Twenty-two vegetation/land cover types were described using aerial photographs, point-intercept sampling, and ocular cover estimates. The proportion of each cover type was estimated for each drainage and compared among drainages by MANOVA. There was no significant difference among non-muskox drainages in the average proportion of cover types. A marginally significant difference was found among muskox drainages. There were no significant differences in the proportions of each vegetation type in non-muskox drainages versus muskox drainages. Five vegetation types associated with high forage quality and availability and low snow accumulation were often used by muskoxen. Four of these five vegetation types typically had <7% cover in the nine drainages and are critical habitat components in northeastern Alaska.
  • Habitat relationships and activity patterns of a reintroduced musk ox population

    Jingfors, Kent T. (1981-12)
    A reintroduced muskox herd in arctic Alaska was studied over a 2-year period to assess seasonal changes in activity patterns and feeding behavior. This large herd showed high calving rates and early breeding in females, characteristic of a rapidly expanding population. Age- and sex-specific differences in activity budgets reflect seasonal energy demands of the different cohorts. Comparison with high arctic muskoxen shows that characteristics of suckling behavior provide a more sensitive indicator of differences in range quality than does variation in summer activity patterns. In summer, muskoxen appear to select vegetation types on the basis of abundance and phenological stage of preferred forage species; snow characteristics strongly influence habitat selection in winter. The herd remained within a limited home range with overlapping seasonal ranges and a distinct calving area. The restricted movements and conservative activity budgets permit minimization of energy expenditure and forage requirements, allowing for a year-long existence in areas of low primary productivity.
  • Genetic variation in muskoxen (Ovibos moschatus)

    Fleischman, Claire L. (1986-05)
    Populations of Alaskan muskoxen (Ovibos moschatus) are derived from 34 animals transplanted from East Greenland in the 1930s. The possibility of a founder effect following this transplant was investigated. Muscle, liver and plasma samples from 87 Alaskan animals and 39 Greenlandic animals were analyzed using polyacrylamide and starch gel electrophoresis. A total of 38 enzyme and non-enzymatic protein systems, coded by 58 presumptive loci, was tested for activity; 28 loci were considered usable. One locus (Esterase-2) was polymorphic; the proportion of polymorphic loci was 0.036 (95% criterion). The mean heterozygosity per individual was 0.006 in the Greenlandic population and 0.011 in the Alaskan population. The allele frequencies at the Est-2 locus were similar in both populations. No heterozygote deficiency and no evidence of a founder effect were seen in the Alaskan population. This may be a consequence of the low level of allozymic variation seen in muskoxen in general.
  • Comparative patterns of winter habitat use by muskoxen and caribou in northern Alaska

    Biddlecomb, Mark Edward (1992-09)
    Snow depth and hardness strongly influenced selection of feeding zones, (i.e., those areas used for foraging), in late winter by both muskoxen (Ovibos moschatus) and caribou (Rangifer tarandus grand) in northern Alaska. Snow in feeding zones was shallower and softer than in surrounding zones. Depth of feeding craters was less than the average snow depth in feeding zones. Moist sedge tundra types were used most often by muskoxen, and their diet, based on microhistological analysis of feces, was dominated by graminoids. Moist sedge and Dryas tundra types were most often used by caribou; lichens and evergreen shrubs were the major constituents of their diet. Despite selection of moist sedge tundra types by both muskoxen and caribou in late winter, dietary and spatial overlap was minimal.
  • Effects of antimony mining on stream invertebrates and primary producers in Denali National Park, Alaska

    Wedemeyer, Kathleen (1987-12)
    Heavy metals, primarily antimony, arsenic and manganese from antimony mines in Denali National Park, Alaska impacted all levels of the stream ecosystem. Decreased algal, moss and macroinvertebrate abundance (but not changes in macroinvertebrate trophic organization) were all clearly associated with mining activity in Slate and Eldorado creeks. Crustacea, Chironomidae (Diptera), Hydracarina (Arachnida), Nemouridae (Plecoptera), and Zapada (Nemouridae) decreased in relative abundance with metal pollution while Capniidae (Plecoptera), Nemoura (Nemouridae), and Podmosta (Nemouridae) increased in relative abundance at mine sites. The data from Stampede Creek demonstrated that mineralized but unmined stream reaches may be impacted by heavy metals. Unexpectedly higher selenium levels upstream of the mine may account for the general lack of substantial differences in macroinvertebrates and periphyton upstream and downstream of the mine. However, macroinvertebrate and periphyton abundances were lower at both sites on Stampede Creek than at the unmined control stream, Jumbo Creek.

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