• The Effects Of Changes In Climate And Other Environmental Factors On Permafrost Evolution

      Jafarov, Elchin; Romanovsky, Vladimir; Layer, Paul; Marchuoko, Sergei; Walsh, John (2013)
      Permafrost is a product of a past colder climate. It underlies most of the terrestrial Arctic, where it influences landscape hydrology, biogeochemical environments and human activity. The current thermal regime of permafrost is mediated by different environmental factors, including snow, topography, vegetation and soil texture. The dependence of permafrost on these factors greatly complicates the modeling of permafrost dynamics. Accurate modeling of these dynamics, however, is critical for evaluating potential impacts of climate change on permafrost stability. The objectives of this study were to a) improve modeling of ground temperature during snow season; b) analyze the effects of post-fire environmental changes on permafrost thermal stability; and c) predict 21st century ground temperature dynamics in Alaska with high spatial resolution. To achieve the proposed objectives, near-surface air and ground temperatures were measured at permafrost observation stations across Alaska. Measured ground temperatures were used to evaluate simulated ground temperatures, which were generated with the Geophysical Institute Permafrost Laboratory (GIPL) numerical transient model. The current version of the GIPL model takes into account climate, snow, soil texture, soil moisture, and the freeze/thaw effect. To better model ground temperatures within the soil column, it was necessary to improve the parameterization of snow layer thermal properties in the GIPL model. To improve ground temperature simulations during snow season, daily snow thermal properties were estimated using an inverse approach. Modeling bias was improved by including ground temperatures simulated using estimated daily snow thermal conductivities. To address the effects of fire disturbance on permafrost thermal stability, we applied the GIPL model to lowland and upland boreal forest permafrost environments. The results indicate that permafrost vulnerability depends on pre-fire organic soil layer thickness and wetness, the amount of organic matter burned during the fire, and post-fire soil organic layer recovery rates. High spatial resolution permafrost maps are necessary for evaluating the potential impacts of permafrost thawing on Arctic ecosystems, engineering facilities, infrastructure, and the remobilization of soil carbon. Simulated ground temperatures in Alaska during the 21st century indicate widespread permafrost degradation in the discontinuous permafrost zone. High ground temperature warming trends are projected for most of the continuous permafrost zone north of the Brooks Range.
    • The Foraging Behavior, Habitat Use, And Diet Of Arctic Foxes (Alopex Lagopus) In A Goose Nesting Area Near Kokechik Bay, Alaska

      Stickney, Alice Allgood; Murphy, Edward C. (1989)
      The foraging behavior, habitat use, and diet of arctic foxes were observed in a goose nesting area near Kokechik Bay, Alaska during the summers of 1985 and 1986. The foraging patterns of arctic foxes changed after birds started nesting in the study area, adding an abundant egg resource to a previously limited prey base. The duration of search bouts decreased and success rate increased, yielding an increased prey capture rate. Over 80% of the eggs taken by foxes during the nesting stage were cached, rather than eaten immediately. Differences in search patterns among foxes were probably related to the different prey available within the range of each fox. Egg caches extended fox access to a temporally clumped resource, and increased the impact of foxes on the nesting success of geese. Eggs were the primary prey of foxes during the nesting stage in both years, regardless of variations in microtine abundance. <p>
    • 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.
    • A total environment of change: exploring social-ecological shifts in subsistence fisheries in Noatak and Selawik, Alaska

      Moerlein, Katie J. (2012-05)
      Arctic ecosystems are undergoing rapid changes as a result of global climate change, with significant implications for the livelihoods of arctic peoples. In this thesis, I use ethnographic research methods to detail prominent environmental changes observed and experienced over the past few decades and to document the impact of these changes on subsistence fishing practices in the Inupiaq communities of Noatak and Selawik in northwestern Alaska. Using in-depth key informant interviews, participant observation, and cultural consensus analysis, I explore local knowledge and perceptions of climate change and other pronounced changes facing the communities of Noatak and Selawik. I find consistent agreement about a range of perceived environmental changes affecting subsistence fisheries in this region, including lower river water levels, decreasing abundances of particular fish species, increasingly unpredictable weather conditions, and increasing presence of beaver, which affect local waterways and fisheries. These observations of environmental changes are not perceived as isolated phenomena, but are experienced in the context of accompanying social changes that are continually reshaping rural Alaska communities and subsistence economies. Consequently, in order to properly assess and understand the impacts of climate change on the subsistence practices in arctic communities, we must also consider the total environment of change that is dramatically shaping the relationship between people, communities, and their surrounding environments.
    • Trophic dynamics of boreal lakes in a changing northern landscape: impacts of lake drying and forest fires

      Lewis, Tyler L.; Lindberg, Mark; Schmutz, Joel; Larsen, Amy; Jones, Jeremy; Heglund, Patricia (2015-05)
      The abundant lakes of northern latitudes are the primary breeding grounds for many waterbird species. In recent decades, temperatures in the north have increased by twice the global average. This substantial warming has caused lake drying and increased wildfires, both of which may impact waterbird habitats. Fires release nutrients locked in terrestrial resources, making them available for transport to lakes, while lake drying concentrates nutrients and other solutes into smaller water volumes. Increased nutrients may fundamentally alter ecosystem processes of lakes by changing the timing and abundance of phytoplankton blooms, which in turn affects the abundance of aquatic invertebrates - the primary food source for breeding waterbirds and their broods. I examined effects of forest fires and lake drying on ecosystems of Subarctic boreal lakes in the Yukon Flats, Alaska, documenting changes to (1) aquatic nutrient and chlorophyll concentrations, (2) aquatic invertebrate densities, and (3) abundance and occupancy of waterbirds. Nutrient, chlorophyll, and invertebrate levels were largely unaffected by a recent forest fire. This ecosystem stability transferred upward to waterbirds, as brood abundance was also unaffected by the fire. On drying lakes, nitrogen and phosphorus concentrations increased >200% and >100%, respectively, from the 1980s to present. At the same time, concentrations of 4 major ions increased, including increases of >500% for chloride and >100% for sodium. Nonetheless, chlorophyll levels, aquatic invertebrate abundance, and occupancy of waterbird broods were largely unaffected by these chemical changes on drying lakes. Overall, ecosystems of Yukon Flats were largely resilient to short-term effects of forest fires and rising chemical concentrations associated with lake drying. Moreover, this resilience spanned multiple trophic levels, from phytoplankton to aquatic invertebrates to waterbirds.
    • Trophic pathways supporting Arctic Grayling in a small stream on the Arctic Coastal Plain, Alaska

      McFarland, Jason John; Wipfli, Mark S.; Ruess, Roger; Arp, Chris D. (2015-05)
      Arctic Grayling (Thymallus arcticus) are widely distributed on the Arctic Coastal Plain (ACP) of Alaska, and are one of the few upper level consumers in streams, but the trophic pathways and food resources supporting these fish are unknown. Grayling migrate each summer into small beaded streams, which are common across the landscape on the ACP, and appear to be crucial foraging grounds for these and other fishes. I investigated prey resources supporting different size classes of grayling in a beaded stream, Crea Creek, where petroleum development is being planned. The specific objectives were to measure terrestrial prey subsidies entering the stream, quantify prey ingested by Arctic Grayling and Ninespine Stickleback (Pungitius pungitius), determine if riparian plant species affect the quantity of terrestrial invertebrates ingested by grayling, and determine if prey size and type ingested were a function of predator size. Results indicated that small grayling (< 15 cm fork length (FL)) consumed mostly aquatic invertebrates (caddisflies, midges, and blackflies) early in the summer, and increasing quantities of terrestrial invertebrates (wasps, beetles, and spiders) later in summer, while larger fish (> 15 cm FL) foraged most heavily on stickleback. Riparian plant species influenced the quantity of terrestrial invertebrates entering the stream, however these differences were not reflected in fish diets. This study showed that grayling can be both highly insectivorous and piscivorous, depending upon fish size class, and that both aquatic and terrestrial invertebrates, and especially stickleback, are the main prey of grayling. These results highlight the importance of beaded streams as summer foraging habitats for grayling. Understanding prey flow dynamics in these poorly studied aquatic habitats, prior to further petroleum development and simultaneous climate change, establishes essential baseline information to interpret if and how these freshwater ecosystems may respond to a changing Arctic environment.
    • Trophic pathways supporting juvenile chinook and coho salmon in the glacial Susitna River, Alaska: patterns of freshwater, terrestrial, and marine resource use across a seasonally dynamic habitat mosaic

      Rine, Kristin M.; Wipfli, Mark S.; Jones, Jeremy B.; Stricker, Craig A. (2015-12)
      In large, seasonally dynamic and spatially complex watersheds, the availability and relative importance of various food resources for stream fishes can be expected to vary substantially. While numerous studies have attempted to uncover the trophic linkages that support stream salmonids, much of these efforts have occurred at small scales that disregard variability of food resources inherent in lotic systems. This study aimed to determine large-scale patterns in the contributions of freshwater, terrestrial, and marine-derived food resources to juvenile Chinook and Coho salmon (Oncorhynchus tshawytscha and O. kisutch) in the large, glacially influenced Susitna River, Alaska. I quantified diet patterns both spatially, across different macrohabitat types positioned along a 169-km segment of the river corridor, and temporally, from June to October, using stable isotope and stomach content analyses. To further resolve energy pathways from basal carbon sources to juvenile salmon, I determined the relative roles of terrestrial organic matter and freshwater periphyton food sources to aquatic benthic invertebrate diets. The latter analysis showed that invertebrate consumers were more reliant on freshwater periphyton than on terrestrial organic matter. Bayesian stable isotope mixing models indicated that juvenile salmon in the middle Susitna River were, in turn, largely supported by freshwater invertebrate prey regardless of spatial and temporal context. The relative contribution of marine-derived prey (salmon eggs) to juvenile salmon diets was greatest in the fall within tributary mouth and off-channel macrohabitats during both years of the study. Terrestrial invertebrate prey contributions were generally greatest during mid-summer within all macrohabitat types sampled, however this pattern varied across years. No upstream to downstream diet pattern was apparent from the data. These results underscore the importance of freshwater energy pathways for sustaining juvenile Chinook and Coho salmon in the Susitna River and provide further spatial and temporal context for the importance of pulsed marine and terrestrial prey subsidies. As Pacific salmon stocks continue to decline, management and mitigation efforts should operate on knowledge gained from studies that encompass the largescale spatial and temporal variability inherent in riverine landscapes.
    • 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.
    • The use of aerial imagery to map in-stream physical habitat related to summer distribution of juvenile salmonids in a Southcentral Alaskan stream

      Perschbacher, Jeff; Margraf, F. Joseph; Hasbrouck, James; Wipfli, Mark; Prakash, Anupma (2011-12)
      Airborne remote sensing (3-band multispectral imagery) was used to assess in-stream physical habitat related to summer distributions of juvenile salmonids in a Southcentral Alaskan stream. The objectives of this study were to test the accuracy of using remote sensing spectral and spatial classification techniques to map in-stream physical habitat, and test hypotheses of spatial segregation of ranked densities of juvenile chinook salmon Oncorhynchus tschwytscha, coho salmon O. kisutch, and rainbow trout O. mykiss, related to stream order and drainage. To relate habitat measured with remote sensing to fish densities, a supervised classification technique based on spectral signature was used to classify riffles, non-riffles, vegetation, shade, gravel, and eddy drop zones, with a spatial technique used to classify large woody debris. Combining the two classification techniques resulted in an overall user's accuracy of 85%, compared to results from similar studies (11-80%). Densities of juvenile salmonids was found to be significantly different between stream orders, but not between the two major drainages. Habitat data collected along a 500-meter stream reach were used successfully to map in-stream physical habitat for six river-kilometers of a fourth-order streams. The use of relatively inexpensive aerial imagery to classify in-stream physical habitats is cost effective and repeatable for mapping over large areas, and should be considered an effective tool for fisheries and land-use managers.
    • Variation in age and size at maturity of Lake Clark, Alaska sockeye salmon

      Benolkin, Elizabeth B.; Margraf, Joseph; Woody, Carol Ann; Adkison, Milo (2009-12)
      Salmon returning to Lake Clark, Alaska are a valuable subsistence, commercial and ecological resource, and are an important component of the larger Kvichak River escapement. Average escapement to the Kvichak River declined sharply during 1996-2005, prompting studies to investigate age and size at maturity, key life history traits of salmon linked to reproductive success and survival. We examined potential factors which may influence sockeye salmon Oncorhynchus nerka age and size at maturity: spawning habitat and ocean environment, and examined variation in both traits over time. Sockeye salmon age and length at maturity differed among spawning locations and between brood years, but no consistent patterns were observed among habitat types. Age and length at maturity differed over time; the proportion of older marine age 3 fish was larger in recent brood years, while fish were smaller during 1997-2001 compared to 1976-1980. Sea surface temperatures and coastal upwelling appeared to be important indicators of fish length, highlighting the importance of the ocean environment in salmon growth. These results demonstrate the complexity and importance of both the freshwater and ocean ecosystems in variation in age and size at maturity, and indicate that trends may not necessarily be similar among systems or years.
    • 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.
    • 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.
    • Winter forage selection by barren-ground caribou: effects of fire and snow

      Saperstein, Lisa Beth (1993-05)
      Snow depth and hardness were the most influential factors in selection of feeding areas by caribou (Rangifer tarandus) in late winter in northwestern Alaska. Following a 1988 fire, plots were established in late March through April in burned and unbumed tussock tundra in 1990 and 1991. Snow in both burned and unbumed plots was shallower and softer at edges of caribou feeding craters than at adjacent undisturbed points in both years. There was little difference in snow depth or hardness between burned and unbumed plots, although caribou cratered in shallower snow in burned plots than in unbumed plots in 1990. Crater area was greater in unbumed plots in 1990, but there was no difference in crater area between burned and unbumed plots in 1991. Frequencies of particular plant taxa were only significant in determining selection of crater sites in unbumed plots in 1990, when caribou craters had higher relative frequencies of lichens and lower frequencies of bryophytes than unused areas. Fire reduced relative frequency and biomass of most plant taxa, with the exception of post-disturbance species, which occurred primarily in burned plots. Lichens were reduced in burned plots, and lichens composed 59-74% of the late-winter diet of caribou, as determined by microhistological analysis of fecal pellets. Biomass and relative frequency of Eriophorum vaginatum was greater in burned plots than in unbumed plots in 1991, and protein and in vitro digestibility levels were enhanced in samples of this species collected from burned plots in late winter.
    • 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 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.