• Effects of density-dependence, environment and species interaction during spawning and incubation on population dynamics of pink and sockeye salmon in the Auke Lake system, southeast Alaska

      Fukushima, Michio (1996)
      Mechanisms that regulate or influence fry and smolt production of pink and sockeye salmon in the Auke Lake system, southeast Alaska, were studied with special emphases on effects of: (1) density-dependence; (2) environmental effects; and (3) species interaction. There has been an increasing trend in the residuals of spawner-recruit models for pink and sockeye salmon since the late 1970's. A strong positive influence of precipitation was found in sockeye smolt production. Estimated spawner capacity of pink salmon was 15 times greater than sockeye salmon in the system. Pink salmon spawners varied in stream life (5-11 days), spawning efficiency (30-70% of daily cohorts of females retained less than 500 eggs at death), and habitat selection (30-70% spawned in Auke Creek rather than Lake Creek, the inlet stream). Variation of these attributes in female pink salmon was explained by various environmental variables using generalized linear models. Repeated use of limited spawning grounds by Pacific salmon, i.e., redd superimposition, can cause density-dependent mortality. Pink salmon egg loss from part of Auke Creek, estimated by a series of mark and recapture experiments, was roughly proportional to spawner abundance and not related to discharge. The maximum daily egg loss was estimated to be 3-400,000 eggs. Eggs in samples were more advanced in development later in the season. Eggs were washed out from the streambed due to redd superimposition; eggs spawned by early pink salmon spawners suffered higher mortality than eggs spawned by later spawners. The peak sockeye spawning preceded the peak pink spawning by approximately one week in Lake Creek, and the major spawning areas of sockeye salmon occurred approximately 250-350 m upstream from those of pink salmon. Microhabitat selection measured by four variables differed significantly between the species, but discrimination between the species was impossible because of large overlaps. Habitat variation was greater among different runs of sockeye salmon than between the two species. Sockeye salmon shifted spawning sites from riffles to pools as the season progressed.
    • Effects Of Migratory Geese On Nitrogen Availability And Primary Productivity In Subarctic Barley Fields

      Pugin, Jennifer Adrienne; Sparrow, Stephen (1996)
      Agricultural areas are important for migratory geese, providing easy access to high energy foods. Geese affect agricultural production by removing biomass and by depositing fecal nutrients. This study used $\sp{15}$N as a tracer to examine the quantitative effects of fecal nitrogen contributions on agricultural production.<p> During winter 1994-95, 12-week lab incubations were conducted to determine net nitrogen and carbon mineralization potentials in soils amended with barley straw, grain, and goose feces. The greatest rates of nitrogen mineralization occurred in the soil amended with goose feces. Carbon mineralization occurred at the greatest rate in the soil amended with grain.<p> In comparison to barley grain and straw, goose feces provided the greatest amount of available nitrogen to the soil and to subsequent crops, and consequently higher barley yields (59 and 62% increase, respectively). However, supplementary fertilizer is still necessary for farmers to obtain maximum barley yields. <p>
    • Establishment of native plants on disturbed sites in arctic Alaska

      Cargill, Susan Marjorie; Chapin, F. Stuart III (1988)
      Roads, camps and other structures associated with the Trans-Alaska Pipeline were placed on gravel pads to protect underlying permafrost. Gravel was mined from floodplains, resulting in loss of riparian wildlife habitat. Revegetation of abandoned pads using non-native grasses has been unsuccessful. Native plants might be more persistent and contribute to replacing lost habitat. The naturally-occurring pioneer community on gravel pads consists mainly of willows Salix alaxensis and S. glauca, fireweed Epilobium latifolium, horsetails Equisetum arvense and legumes in the genera Astragalus, Oxytropis and Hedysarum, all species of riparian gravel bars. Ten years after abandonment mean total cover of native species on 16 gravel pads was only 2.7% and mean number of species per site was 4.4. Distance from riparian seed sources explained 25% and 40% of variation in cover and diversity respectively. Legumes were more restricted to sites near the river than were fireweed and willows. In the laboratory, no germination of S. alaxensis occurred at water potentials $< -0.2$ MPa, which probably occur often on gravel pads. In the field, germination was increased by watering or by a rough surface which provided moister microsites. Growth of seedlings was limited by the supply of mineral nutrients. Survival was high and not limited by availability of water or nutrients. In the laboratory, few legume seeds germinated at water potentials $< -0.5$ MPa. In the field, germination was higher on a rough surface which provided moister microsites. Greenhouse experiments indicated that symbiotically-fixed nitrogen contributed significantly to the growth of legume seedlings, especially when availability of mineral N was low. Rhizobia-free legume seedlings transplanted to a gravel pad developed nodules whether or not they were inoculated with rhizobia, but total weight and nodule weight tended to be higher in inoculated seedlings. Some native plants, primarily riparian species, are capable of establishing and growing on abandoned gravel pads. The low cover and diversity of naturally-colonized sites are attributed to (1) limited dispersal from riparian seed sources, (2) lack of water for germination, and (3) lack of nutrients to support growth. Both willows and legumes have promise for use in restoration.
    • Foraging ecology of female Dall's sheep in the Brooks Range, Alaska

      Hansen, Michael Charles (1996)
      Most wild sheep (Ovis) are primarily diurnal. Thus, extreme cold, darkness, and limited quantities of low-quality forage during long winters above the Arctic Circle present a formidable challenge for sheep. Further, summer is particularly short at these high latitudes, providing little time for sheep to accumulate energy reserves for winter. This thesis discusses dietary and behavioral responses of wild sheep to the constraints of Arctic environments. Specifically, I determined diet composition and selection, forage quality, nutrient intake, and activity budgets of adult female Dall's sheep (ewes) (Ovis dalli dalli) near the northern extreme of the range of wild sheep for 2 years and constructed a model of the energy relationships of these animals. Ewes primarily consumed forbs and grasses during summer, and strongly selected forbs over other forages in accordance with the predictions of optimal foraging theory. Diets primarily consisted of grasses in early winter, shifted to sedges in February, and back to grasses in early spring. Shrubs were consistently the least selected class of forage. When the diet was composed of forages with varying digestibility, microhistological analyses not corrected for differential digestibility were biased toward less digestible forage. Winter forage available to Dall's sheep in the northern Brooks Range was low in both digestibility and protein content. In early summer ewes foraged during all hours of the day when sunlight was present for 24 hours. Sheep restricted their foraging almost entirely to daylight hours near the equinoxes, and foraged during all available hours of light, as well as 2.8 hours of the night in December. Daily foraging time varied from 12.9 hours in June to 7.9 hours in December, and, when measured on a daily basis, was positively correlated with average windchill and daylength. Ash-free fecal nitrogen and in vitro digestible dry matter were most highly correlated with activity level on a monthly basis. Energetics modeling indicated that ewes were in a negative energy balance for 6-8 months each winter and lost nearly 30% of their body weight. Duration of the short summer growing period was most important for weight gain, and presence of deep snow determined weight loss in winter.
    • Habitat selection by mule deer: Effects of migration and population density

      Nicholson, Matthew Christopher (1995)
      I investigated effects of migration and population density on habitat and diet selection in a population of mule deer (Odocoileus hemionus) in southern California from 1989 to 1991. All male deer were migratory, whereas females exhibited a mixed strategy with both migrant and resident individuals. No difference occurred in sizes of home ranges for migratory or resident deer. Home-range size of deer was smaller in summer than in winter, however. Size of home range was positively associated with proximity to human disturbance and the amount of avoided habitat (use $<$ available) in the home range. Deer avoided human disturbance in all seasons. Clear tradeoffs existed for deer in montane southern California with respect to whether they migrated. Migratory females were farther from human disturbance and used high-quality habitats more often than did their nonmigratory conspecifics. Nonetheless, during migration deer were at increased risk of predation, and in years of low precipitation (low snow) had higher rates of mortality than did resident deer. Thus, in areas with extremely variable precipitation and snow cover, a mixed strategy for migration can be maintained. Migration patterns of deer resulted in drastic shifts of population density between seasons as deer migrated into and out of ranges. Quality of diet (as indexed by fecal crude protein) for deer in a low-density area was higher than that of a high-density area in winter, when deer densities were most different. Diet quality was similar in summer when both areas had similar densities of deer. Contrary to predictions of the ideal-free distribution, diet quality was different between the two areas in autumn when population densities were similar; this may have been due to an elevated availability of graminoids on the high-density area. Niche breadth, as measured by diet diversity, differed in a manner opposite to the predictions of the ideal-free distribution. During winter, when differences in density between the two study areas were most evident, niche breadth along the dietary axis in the low-density group was twice the size of this measure for the high-density area. Theoretical models for changes in niche dimension need to consider such empirical outcomes.
    • Habitat Utilization By Sea Otters (Enhydra Lutris) In Port Valdez, Prince William Sound, Alaska

      Anthony, Jill Ada Marie; Fay, Francis H. (1995)
      Environmental constraints and human activity influence sea otter habitat use in Port Valdez. Nonetheless, a small subpopulation consistently uses food and space resources there. Otter number, distribution, response to human activity, energetics, and behavior in the Alyeska Marine Terminal (an industrial area) were compared to Shoup Bay (an area with low human activity) from September 1989 to September 1991. Low numbers averaged 102 otters monthly and were predominantly juvenile males. Shoup Bay densities were higher than the Terminal. Terminal boat traffic was more than twice Shoup Bay, resulting in more otter encounters with moving boats and more behavioral changes. Petroleum hydrocarbon levels were low or undetectable in mussels, the main otter prey in the port. Diets varied more in the Terminal than Shoup Bay. Despite lower mussel caloric content in Shoup Bay, otters spent significantly more time feeding at the Terminal. Time-activity budgets in Shoup Bay were more variable. <p>
    • Investigations Into Some Of The Major Controls On The Productivity Of A Black Spruce (Picea Mariana (Mill.) B.S.P.) Forest Ecosystem In The Interior Of Alaska (Photosynthesis, Nutrient Use, Soil Temperatures, Moss Microclimate)

      Hom, John Lun (1986)
      The purpose of this study was to determine the major factors which affect tree and moss productivity in a black spruce (Picea mariana Mill. B.S.P.) forest ecosystem, occurring on permafrost dominated soil. The cold, shallow rooting zone was heated 8(DEGREES) - 10(DEGREES)C above ambient which resulted in increased forest floor nutrient cycling and increased productivity in black spruce. The soil heat sum increased from 563 to 1133 soil degree days and the depth of thaw increased from 57 to 115 cm. Heating increased tree ring radius by 33% relative to the control. Foliar analysis showed significant increases in nitrogen (25%), phosphorus (73%) and potassium (14%), indicating that heating increased nutrient availability to the spruce trees. This resulted in a 22% increase in the maximum photosynthetic rates over the control. The 1 year old tissue had the highest photosynthetic rates, whereas the oldest needles maintained 40% of the maximum photosynthetic rates after 13 seasons. The highest levels of nitrogen and phosphorus were measured in the current tissue and declined with age. Nutrient use efficiency was highest in the 1 year old tissue and declined with needle age. Studies on microclimatic limitations to moss production on the forest floor indicated that water content was the most variable and potentially the most limiting factor. Light was also very limiting, but the range of limitation was small between different day types, demonstrating the moderating influence of the spruce canopy. Temperature was not as limiting a factor during the summer growing season. Limitation by microclimate allowed only 1% of maximum photosynthesis by mosses on dry, clear days and 9% on wet overcast days, with a potential of 20% under sunny and wet conditions. When data was combined for all days, moss photosynthesis ranged from 8 - 14% of maximum, similar to the low 13% efficiency of production calculated from biomass studies.
    • Late Quaternary vegetation and lake level changes in central Alaska

      Bigelow, Nancy Horner; Edwards, Mary E.; Powers, W. Roger (1997)
      The threat of significant high-latitude global warming over the next 50 years requires that we assess the response of vegetation to climate change. One approach is to see how plants have reacted to past climate change. In this study high-resolution reconstructions of past vegetation and climate, based on pollen and lake level changes, provide useful insights into vegetation and climate change in central Alaska since 14,000 years ago. Climate changed substantially at about 12,000 years ago, between 11,000 and 10,000 years ago, and about 8,000 years ago. At 12,000 years ago, a significant transition is reflected by the appearance of shrub birch into a region that had been dominated by grass, sage, and sedge. The vegetation became denser; shrubs occupied the moister sites, and herbaceous taxa grew on well-drained, exposed ridges and slopes. Lake levels increased at this time, suggesting the climate became warmer and wetter than it had been previously. Between 11,000 and 10,000 years ago, the vegetation at some sites reverted to a grass and sage-rich flora, suggesting a return to drier and/or cooler conditions. This period of climate change has not been recognized before from pollen records in central Alaska. The timing of this vegetation shift suggests it is related to the Younger Dryas event, a world-wide episode of climatic deterioration. About 8,500 to 8,000 years ago, spruce appeared in the region, coincident with a significant lake level rise, suggesting that the spruce expansion was aided by wetter conditions, as well as warmer temperatures. In central Alaska, periods of past vegetation change are marked by shifts in moisture. Today, central Alaska receives very little rain, and in some areas the vegetation is moisture-limited, suggesting that during the past, changes in moisture could have had a strong effect on the vegetation. In terms of future global change, this study suggests that any shifts in moisture associated with the predicted temperature changes, especially towards drier conditions, will strongly affect the current vegetation distribution.
    • Lynx And Coyote Diet And Habitat Relationships During A Low Hare Population On The Kenai Peninsula, Alaska

      Staples, Winthrop R., Iii; Dean, Frederick C. (1995)
      Food habits and habitat use of lynx and coyote were compared 1987-1991 on the Kenai Peninsula, Alaska when the snowshoe hare population was low ($<$0.5 hares/ha). During snow seasons, lynx fed primarily on hares (64% total items), whereas coyotes relied heavily on moose carcasses (42% total items). Diet overlap was 42% and hare use overlap was 16%. Habitat use overlap was 92%, but coyotes used roads more than lynx. Both carnivores selected 1947 burn and avoided 1969 burn and large expanses of mature forest. I conclude that there was exploitation competition for food between these predators, because both used the same habitats and hares, a major food, were scarce. The coyote, however, may be using resources that were previously used by red fox, which have been reduced to low levels. Lynx displayed little fear of humans and were vulnerable to shooting incidental to hunting and depredation events. <p>
    • Martingales in mark-recapture experiments with constant recruitment and survival

      Humphrey, Patricia Buslee (1995)
      The method known as mark-recapture has been used for almost one hundred years in assessing animal populations. For many years, these models were restricted to closed populations; no changes to the population were assumed to occur through either migration or births and deaths. Numerous estimators for the closed population have been proposed through the years, some of the most recent by Paul Yip which make use of martingales to derive the necessary estimates. The independently derived Jolly-Seber model (1965) was the first to address the open population situation. That method as originally proposed is cumbersome mathematically due to the large number of parameters to be estimated as well as the inability to obtain estimates until the end of a series of capture events since some of the "observed" variables necessary are prospective. It also is cumbersome for the biologist in the field as individual marks and capture histories are required for each animal. Variations have been proposed through the years which hold survival and/or capture probabilities constant across capture occasions. Models based on log-linear estimators have also been proposed (Cormack 1989). This paper builds on the closed population work of Yip in using martingale-based conditional least squares to estimate population parameters for an open population where it is assumed recruitment of new individuals into the population is constant from one capture occasion to the next, and capture and survival probabilities are constant across capture occasions. It is an improvement over most other methods in that no detailed capture histories are needed; animals are simply noted as marked or unmarked. Performance of the estimator proposed is studied through computer simulation and comparison with classical estimators on actual data sets.
    • Maternal Investment And Habitat Selection By Dall's Sheep

      Rachlow, Janet L.; Bowyer, R. Terry (1991)
      Maternal behaviors and selection of habitat during lambing by Dall's sheep (Ovis dalli) were studied in Denali National Park and Preserve, Alaska, from April through July in 1988 and 1989. Climatic conditions in early spring differed between years; plant phenology was delayed by two weeks in 1989. Births were later and less synchronous in 1989. Females appeared to respond to variation in timing of births by modifying patterns of maternal investment; ewes nursed lambs for greater total time following parturition, but reduced total time spent nursing more rapidly in 1989. Selection of habitat characteristics varied with lambing chronology; terrain features related to avoidance of predators and sites with milder climatic conditions were selected during peak lambing. Variation between years in group sizes strongly influenced habitat selection. When corrected for variation in group size, no significant differences between years in selection of habitat were identified. <p>
    • Microbial ecology and long-term persistence of crude oil in a taiga spruce forest

      Lindstrom, Jon Eric; Braddock, Joan F. (1997)
      The microbial ecology of a 1976 experimental crude oil spill in an Alaskan taiga black spruce forest was investigated in this study. Substantial oil residue remained in the soil, and several microbial parameters showed evidence of long-term oiling effects. Overall, the data suggest that the surviving community in the oiled plot has shifted toward using oil C for growth. Numbers of hydrocarbon degrading microbes, and specific hydrocarbon mineralization potentials, were significantly elevated in the oiled (OIL) plot compared to an adjacent oil-free, reference (REF) plot. Glutamate mineralization potentials and soil C mineralization, on the other hand, were not different between treatments, suggesting that OIL plot heterotrophs were well-acclimated to the oil. Despite little difference between OTL and REF soils in total C mineralized in vitro, net N mineralized was lower and net nitrification was absent in OIL soils. Analysis of the residual oil indicated minimal amounts of N were added with the spilled oil. Biomasses of total fungi and bacteria, and numbers of protozoa, showed no consistent effects due to oiling, but metabolically active fungal and bacterial biomasses were uniformally lower in OTL samples. Community-level multiple substrate metabolism (Biolog) was assessed using a new technique for extracting kinetic data from the microplates. This analysis suggested that the microbial population diversity in the OIL soils was lower than in REF soils. Further, these data indicated that the surviving populations in the OIL plot may be considered metabolic generalists. Some evidence of crude oil biodegradation was seen in the chemistry data, but enrichment of the oil residue in higher molecular weight components, duration of contact with soil organic material, and slow rates of C mineralization indicate the crude oil will persist at this site for decades. Contamination of Alaskan taiga soil at this site has yielded observable long-term microbial community effects with larger-scale consequences for ecosystem function.
    • Movements, distribution, and population dynamics of polar bears in the Beaufort Sea

      Amstrup, Steven C. (1995)
      I used mark and recapture, and radio telemetry to describe movements and population dynamics of polar bears of the Beaufort Sea. Rates of movement were lowest for females with cubs in spring, highest for females with yearlings in winter, and varied from 0.30-0.96 km/h. Total distances moved each month and year were 186-492 km and 1,454-6,203 km respectively. Highest and lowest levels of activity were in June and September. Activity levels were highest from mid-day to late evening. Females with cubs were more active than other bears. Annual home ranges varied from 12,730 km$\sp2$ to 596,800 km$\sp2$. The Beaufort Sea population occupied a 939,153 km$\sp2$ area extending 300 km offshore from Cape Bathurst, Canada, to Pt. Hope, Alaska. Maternal denning in the Beaufort Sea region was common, but 52% of discovered dens were on the drifting pack ice. Bears denning on pack ice drifted as far as 997 km (x = 385 km). Bears followed to >1 den did not reuse sites. Consecutive dens were 20-1,304 km apart, but radio-collared bears were faithful to substrate and locale of previous dens. Of 44 polar bears that denned along the Beaufort Sea coast, 80% were located between 137$\sp\circ$00'W and 146$\sp\circ$59'W. Of those 44, 20 (45%) were on the Arctic National Wildlife Refuge, including 15 (34%) in the 1002 coastal plain area, which may contain >9 billion barrels of recoverable oil. Data indicated, however, that spatial and temporal restrictions on developments could prevent most disruptions of denned bears. Survival of adult female polar bears was higher than previously thought ($\ S=0.96).$ Survival of cubs ($\ S=0.65)$ and yearlings ($\ S=0.86)$ was lower than for adults, but increased rapidly with age. Shooting accounted for 85% of the documented deaths of adult females. The population grew to ~1500 animals ($\ge$2% per year) from 1967-1992. Condition of adult females, survival of young, and litter sizes declined, while age of maturity and reproductive interval appeared to increase. The population may have approached carrying capacity by the end of the study.
    • Natural disturbance at the site and landscape levels in temperate rainforests of southeast Alaska

      Ott, Robert A.; Juday, Glenn Patrick (1997)
      Wind disturbance in forests of southeast Alaska is poorly understood. Dynamics of canopy gaps, formed primarily by wind, were investigated in the western hemlock (Tsuga heterophylla)/blueberry (Vaccinium spp.)/shield fern (Dryopteris austriaca) plant association in northern southeast Alaska; twenty gaps were sampled at each of 3 sites. Gaps comprised about 9% of the forest area. The majority of gaps were $<$50 m$\sp2$ in area, had a diameter-to-height (D/H) $<$0.50, were created from the death of 1 or 2 gapmakers, and had experienced gap expansion. Emulating the small-scale natural disturbance regime would be best achieved if single tree selection and small group selection cuts were administered within a stand. Diffuse light levels were greatest and most variable at both the shrub and herb layers in canopy gaps, and lowest and least variable under closed canopy forest. Shrub layer light levels were positively associated with mean and median canopy gap areas. Herb layer light levels, however, were determined by the amount of light interception at the shrub layer and not by canopy gap size. Most species were robust in terms of their light requirements compared to the range of light conditions present in the understory. Sorenson Index values indicated that gaps and closed canopy forest generally were very similar in species composition. Seedling heights suggest that western hemlock and Sitka spruce seedlings benefit from the presence of canopy gaps. However, the ability of Sitka spruce to maintain itself through gap-phase replacement is limited. Techniques are needed that allow forest managers to interpret wind patterns in remote locations, at both site- and landscape-levels, and across complex topography. I demonstrated the use of circular data analysis of treefall directions as a technique to investigate wind flows at the site-level. I also demonstrated the feasibility of mapping wind flows across a large landscape of complex terrain in southeast Alaska using flagged trees, treefall directions of large-scale natural blowdowns, and treefall directions of blowdowns associated with clearcuts.