• Crop modeling to assess the impact of climate change on spring wheat growth in sub-Arctic Alaska

      Harvey, Stephen K.; Zhang, Mingchu; Karlsson, Meriam; Fochesatto, Gilberto (2019-05)
      In the sub-arctic region of Interior Alaska, warmer temperatures and a longer growing season caused by climate change could make spring wheat (Triticum aestivum L.) a more viable crop. In this study, a crop model was utilized to simulate the growth of spring wheat in future climate change scenarios RCP4.5 (medium-low emission) and RCP8.5 (high emission) of Fairbanks, Alaska. In order to fulfill such simulation, in 2018 high quality crop growth datasets were collected at the Fairbanks and Matanuska Valley Experiment Farms and along with historic variety trial data, the crop model was calibrated and validated for simulating days to maturity (emergence to physiological maturity) and yield of spring wheat in Fairbanks. In the Fairbanks 1989-2018 (baseline) climate, growing season (planting to physiological maturity) average temperature and total precipitation are 15.6° C and 122 mm, respectively. In RCP4.5 2020-2049 (2035s), 2050-2079 (2065s), and 2080-2099 (2090s) projected growing season average temperature and total precipitation are 16.7° C, 17.4° C, 17.8° C and 120 mm, 112 mm, 112 mm, respectively. In RCP8.5 2035s, 2065s, and 2090s projected growing season average temperature and total precipitation are 16.8° C, 18.5° C, 19.5° C and 120 mm, 113 mm, 117 mm, respectively. Using Ingal, an Alaskan spring wheat, the model simulated days to maturity and yield in baseline and projected climate scenarios of Fairbanks, Alaska. Baseline days to maturity were 69 and yield was 1991 kg ha-1. In RCP4.5 2035s, 2065s, and 2090s days to maturity decreased to 64, 62, 60 days, respectively, and yield decreased 2%, 6%, 8%, respectively. In RCP8.5 2035s, 2065s, and 2090s days to maturity decreased to 64, 58, 55 days, respectively, and yield decreased 1%, 3%, then increased 1%, respectively. Adaptation by cultivar modification to have a growing degree day requirement of 68 days to maturity in RCP4.5 2035s and RCP8.5 2035s resulted in increased yields of 4% and 5%, respectively. Climatic parameters of temperature and precipitation per growing season day are projected to become more favorable to the growth of spring wheat. However, precipitation deficit, an indicator of water stress was found to stay similar to the baseline climate. Without adaption, days to maturity and yield are projected to decrease. Selection and/or breeding of spring wheat varieties to maintain baseline days to maturity are a priority to materialize yield increases in the area of Fairbanks, Alaska.
    • Evaluation of marine and freshwater growth and survival of Auke Creek coho salmon

      Russell, Joshua R.; Tallmon, David; McPhee, Megan; Adkison, Milo; Vulstek, Scott (2019-08)
      Coho Salmon (Oncorhynchus kisutch) are a species of great social and economic importance for commercial, sport, personal-use, and traditional harvest. We explored factors influencing Auke Creek Coho Salmon smolt production, growth, and marine survival. We analyzed 35 years (1980-2014) of data collected at the Auke Creek Research Station weir in Juneau, Alaska. This extensive data series allowed for an analysis of Auke Creek Coho Salmon growth and survival that is not possible elsewhere. Creek flow best explained variation in smolt-per-adult production. Analysis of freshwater and saltwater scale growth zones failed to identify a specific growth zone with a significant influence on marine survival. Marine survival had a positive relationship with the magnitude of regional hatchery releases and the Pacific Decadal Oscillation. Changes in climate and hatchery production could have negative effects on survival of Auke Creek Coho Salmon, as evidenced by low returns in recent years associated with anomalously high temperatures in the Gulf of Alaska. The impact of climate change and increased hatchery production should be considered in future management decisions.
    • Foliage and winter woody browse quality of an important Salix browse species: effects of presence of alder-derived nitrogen and winter browsing by Alaskan moose (Alces alces gigas)

      Burrows, Justin; Kielland, Knut; Wagner, Diane; Ruess, Roger (2019-12)
      In this study, I examined the relationship between soil nitrogen and winter browsing by moose on the physical and chemical characteristics of Salix alaxensis; specifically stem production, leaf nutritional quality, and stem nutritional quality of tissues produced the following growing season. I measured stem biomass production the 2013 growing season and offtake during the 2013-2014 winter browsing season at 16 sites on the Tanana River floodplain near Fairbanks, Alaska. I revisited the sites the following summer and autumn to assess regrowth and to collect soil, foliage, and stem samples. Browsing intensity and total soil nitrogen were similar in sites with and without alder, a nitrogen-fixing shrub. Soil nitrogen and browsing intensity were not consistently related to changes in stem or leaf quality, although there were significant relationships in some subsets. Soil nitrogen and browsing intensity also did not have consistent relationships with stem regrowth the following growing season. These results indicate that S. alaxensis growing in this system are able to recover from a naturally broad range of browsing utilization, including very high levels of offtake, and continue to produce nutritious leaves and stems.
    • Growth of juvenile chinook salmon (Oncorhynchus tshawytscha) as an indicator of density-dependence in the Chena River

      Perry, Megan T. (2012-08)
      In management of Pacific salmon, it is often assumed that density-dependent factors, mediated by the physical environment during freshwater residency, regulate population size prior to smolting and outmigration. However, in years following low escapement, temperature may be setting the upper limit on growth of juvenile chinook salmon Oncorhynchus tshawytscha during the summer rearing period. Given the importance of juvenile salmon survival for the eventual adult population size, we require a greater understanding of how density-dependent and independent factors affect juvenile demography through time. In this study we tested the hypotheses that (1) juvenile chinook salmon in the Chena River are food limited, and (2) that freshwater growth of juvenile chinook salmon is positively related with marine survival. We tested the first hypotheses using an in-situ supplemental feeding experiment, and the second hypothesis by conducting a retrospective analysis on juvenile growth estimated using a bioenergetics model related to return per spawner estimates from a stock-recruit analysis. We did not find evidence of food limitation, nor evidence that marine survival is correlated with freshwater growth. However, we did find some evidence suggesting that growth during the freshwater rearing period may be limited by food availability following years when adult escapement is high.
    • Linking freshwater growth to size-dependent marine survival of sockeye salmon: interactions between processes of climate, density, and natural selection

      Ree, Marta Elizabeth; Westley, Peter; Finkle, Heather; Beaudreau, Anne (2019-05)
      Due to the mediating role of body size in determining fitness, the 'bigger is better' hypothesis still pervades evolutionary ecology despite evidence that natural selection on phenotypic traits varies in time and space. For Pacific salmon (genus Oncorhynchus), the size at which juveniles migrate to sea (i.e., smolts) has been linked to survival during the early marine period, where larger smolts typically survive at a higher rate than their smaller counterparts. However, the relationship of smolt size and survival becomes more ambiguous when considering confounding factors of age, ocean entry timing, and environmental variability. Despite equivocal results, smolt size appears to be a key trait and therefore changes in freshwater conditions may have consequences for population productivity. Furthermore, due to differences in site-specific habitats, trophic dynamics, and population traits the response of specific populations to these changes is likely to be context specific. The objective of this thesis was to 1) quantify the direction and magnitude of natural selection on smolt size for three age classes of sockeye salmon in a small watershed on Kodiak Island, AK and 2) explore stock-specific effects of temperature and conspecific density on smolt size over a multi-decade time-series to understand historic and possible future trends. To address our first objective, we calculated standardized selection differentials by comparing observed size distributions of out-migrating juvenile salmon to back-calculated smolt length from the scales of surviving, returning adults. Results reveal the magnitude of selection on size was very strong and consistent among years. However, the direction of selection on size consistently varied among age classes. The absolute magnitude of selection was negatively correlated to apparent marine survival and positively correlated to late mean ocean entry timing. To address our second objective, we back-calculated smolt size from returning adult scales to reconstruct a time-series of smolt length of two stocks within a small Alaska watershed on Kodiak Island. Using a dynamic linear model framework, we detected evidence that for one stock, temperature was important in explaining smolt length, and density effects influenced both stocks utilizing the same lakes. Furthermore, forecasts of smolt length showed highly variable responses under scenarios of increasing temperature and high and low densities. Collectively, these results demonstrate that interactions between processes of climate, density, and natural selection are highly context-specific in terms of both inter- and intra- population variability.
    • Paleobiology of ichthyosaurs: using osteohistology to test hypotheses of growth rates and metabolism in a clade of secondarily aquatic marine tetrapods

      Anderson, Katherine L.; Druckenmiller, Patrick; Erickson, Gregory; Horstmann, Lara; Fowell, Sarah (2019-08)
      Ichthyosaurians (Ichthyosauria) are one of the most prominent groups of secondarily aquatic Mesozoic marine reptiles. Over their 160 million years of evolution, the clade evolved a streamlined body plan with paddle-like limbs, convergent with modern cetaceans. Despite the fact that ichthyosaurians have been studied by paleontologists for over a century, very little is known about aspects of their biology, including quantification of their age structure and growth rates. Multiple lines of evidence, including oxygen isotope, swimming modality, and body shape analyses suggest that ichthyosaurians experienced elevated growth rates and likely maintained an elevated body temperature relative to ambient sea water. In this dissertation, I test these hypotheses using osteohistological methods. In the first manuscript, we describe new material of the small-bodied Upper Triassic ichthyosaurian Toretocnemus from the Nehenta Formation and the Hound Island Volcanics (both Norian, Upper Triassic) of Southeast Alaska. During the Upper Triassic, ichthyosaurians experienced their greatest size disparity, with large-bodied species rivaling the size of modern blue whales (Balaenoptera musculus; 20+ m body length) living alongside small-bodied species (1 m body length) like Toretocnemus. Prior to this study, Toretocnemus was known from Carnian deposits of California and possibly Sonora, Mexico. The referred material described here expands its geographic and temporal range. There are very few known ichthyosaurians from the Norian; thus, this material sheds light on the clade's diversity before the end Triassic extinction event. In the second and third manuscripts, we use osteohistological methods to describe the microstructure of various skeletal elements of two species of Stenopterygius from the Posidonia Shale (Lower Jurassic) of Germany. The Posidonia Shale is a Konservat-Lagerstätten that preserves over 3000 ichthyosaurian specimens, approximately 80 percent of which are referable to Stenopterygius. First, we sampled over 40 skeletal elements from one individual specimen referred to Stenopterygius quadriscissus to 1) describe the mineralized tissues across the skeleton, 2) infer relative growth rate, and 3) identify elements with growth marks. Almost all elements described demonstrate fibrolamellar primary bone, indicative of a rapid growth rate. We also identify growth marks in several elements, including the dentary and premaxilla, that will be used in future growth studies. In the third manuscript, we sample a scleral ossicle from Stenopterygius triscissus to describe its microstructure and investigate the use of ossicles for skeletochronology. The use of scleral ossicles for determining age structure has been documented in extant sea turtles as well as dinosaurs. We sectioned one ossicle in three planes and document conspicuous growth banding in the short axis section. Although this method requires further testing, we tentatively determine a minimum age of 7 years at the time of death for this individual. This dissertation lays critical groundwork for future studies of the paleobiology of ichthyosaurians. We are already in the preliminary stages of using these results to 1) quantify age structure and growth rates of an ichthyosaurian (Stenopterygius quadriscissus) for the first time, and 2) test the use of scleral ossicles for skeletochronology of ichthyosaurians. Through addressing these basic aspects of ichthyosaurian biology, we can begin to investigate how ichthyosaurian development and physiology changed over time and space and develop a greater understanding of this clade's 160 million years of evolution.
    • Spatial variation in blueberry (Vaccinium uliginosum) and lingonberry (Vaccinium vitis-idaea) fruit production in Interior Alaska

      Parkinson, Linsey Viann; Mulder, Christa; Hollingsworth, Teresa; Spellman, Katie (2019-05)
      There are over 50 species of plants in Alaska that produce fleshy fruits (hereafter: "berries"), of which people consume 25. Berries are a key cultural and nutritional resource in rural Alaska and an important source of calories for a range of animals including bears (Ursus spp.), foxes (Vulpes vulpes), geese (e.g., Branta hutchinsii), and voles (e.g., Myodes rutilus). Berry production, from bud development to ripe fruit, takes at least 15 months and may be affected by factors even a year or two before that. Many studies in the circumpolar North focus on these interannual effects on fruit production but few assess how local variation within a forested region may affect berry numbers. Changes in the frequency and severity of wildfires in the boreal forest has affected soil conditions and plant community structure, which may alter the range of circumstances a species must respond to, influencing overall fruit production at a site. I studied how fruit production in Vaccinium uliginosum (blueberry) and V. vitis-idaea (lingonberry), responded to factors such as pollen load, floral resources, canopy cover, and soil conditions within forest sites of Interior Alaska. I found two distinct habitat types in the Interior Alaskan forest, upland and lowland, which differed by elevation, soil moisture (lower in upland sites), and active layer (deeper in upland sites). We found lingonberry was more pollen limited than blueberry, and plants in lowland sites were more pollen limited while plants in upland sites were more resource limited. Additionally, canopy cover had a significant negative effect on a ramet's investment in flowers, berries, and leaves, versus structural growth, in upland sites but little effect in lowland sites. I was able to explain more of the variation in berry production and resource allocation in upland sites than lowland sites. Pollen and resource limitation differed between the two species and between uplands and lowlands suggesting Vaccinium berry production and resource allocation is partially defined by spatial variability of the landscape.