• Land cover change on the Seward Peninsula: the use of remote sensing to evaluate the potential influences of climate change on historical vegetation dynamics

      Silapaswan, Cherie Sumitra (2000-12)
      Vegetation on the Seward Peninsula, Alaska, which is characterized by transitions from tundra to boreal forest, may be sensitive to the influences of climate change on disturbance and species composition. To determine the ability to detect decadal-scale structural changes in vegetation, Change Vector Analysis (CVA) techniques were evaluated for Landsat TM imagery of the Seward Peninsula. Scenes were geographically corrected to sub-pixel accuracy and then radiometrically rectified. The CVA results suggest that shrubbiness is increasing on the Seward Peninsula. The CVA detected vegetation change on more than 50% of the burned region on TM imagery for up to nine years following fire. The use of both CVA and unsupervised classification together provided a more powerful interpretation of change than either method alone. This study indicates that CVA may be a valuable tool for the detection of land-cover change in transitional regions between tundra and boreal forest.
    • Landfast sea ice formation and deformation near Barrow, Alaska: variability and implications for ice stability

      Jones, Joshua M.; Hajo, Eicken; Shapiro, Lewis; Hutchings, Jennifer; Weingartner, Thomas (2013-12)
      Climate change in the Arctic is having large and far-reaching effects. Sea ice is declining in annual extent and thinning with a warming of the atmosphere and the ocean. As a result, sea ice dynamic behaviour and processes are undergoing major changes, interacting with socio-economic changes underway in the Arctic. Near Barrow, Alaska, landfast sea ice is an integral part of native lñupiaq culture and impacts the natural resource extraction and maritime industries. Events known as breakouts of the landfast ice, in which stable landfast ice becomes mobile and detaches from the coast, have been occurring more frequently in recent years in northern Alaska. The current study investigates processes contributing to breakout events near Barrow, and environmental conditions related to the detachment of landfast sea ice from the coast. In this study, synoptic scale sea level pressure patterns are classified in an attempt to identify atmospheric preconditioning and drivers of breakout events. An unsupervised classification approach, so called Self-Organizing Maps, is employed to sort daily sea level pressure distributions across the study area into commonly observed patterns. The results did not point to any particular distributions which favored the occurrence of breakouts. Because of the comparatively small number of breakout events tracked at Barrow to date (nine events between 2006 and 2010), continued data collection may still yield data that support a relationship between breakout events and large scale sea level pressure distributions. Two case studies for breakout events in the 2008/09 and 2009/10 ice seasons help identify contributing and controlling factors for shorefast ice fragmentation and detachment. Observational data, primarily from components of the Barrow Sea Ice Observatory, are used to quantify stresses acting upon the landfast ice. The stability of the landfast ice cover is estimated through the calculation of the extent of grounded pressure ridges, which are stabilizing features of landfast ice. Using idealized ridge geometries and convergence derived from velocity fields obtained by coastal radar, effective grounding depths can be calculated. Processes acting to destabilize or precondition the ice cover are also observed. For a medium-severity breakout that occurred on March 24, 2010, the calculated atmospheric and oceanic stresses on the landfast ice overcame the estimated grounding strength of ridge keels, although interaction with rapidly moving pack ice cannot be ruled out as the primary breakout cause. For another medium-severity breakout that took place on February 27, 2009, the landfast ice was preconditioned by reducing the draft of grounded ridge keels, with subsequent detachment from the shore during the next period of oceanic and atmospheric conditions favoring a breakout. For both of these breakouts, in addition to their potential role in destabilizing the landfast ice by overcoming the ridge grounding strength, current and/or wind forcing on the landfast ice were found to be important factors in moving the stationary ice away from shore.
    • Landscape Control Of Thunderstorm Development In Interior Alaska

      Dissing, Dorte; Verbyla, David (2003)
      General Circulation Models suggest a future climate of warmer and possibly drier summers in the boreal forest region, which could change fire regimes in high latitudes. Thunderstorm development is a dominant factor in the continental boreal forest fire regime, through its influence as a fire starting mechanism. Global Climate Change research has identified the land-atmosphere interface as a vital area of a needed research in order to improve our predictions of climate change. This dissertation has focused on the development of thunderstorms and lightning strike activity in a boreal forest region in Interior Alaska and on how the underlying surface can influence their development. I have examined the distributions and correlations between lightning strikes, thunderclouds, thunderstorm indices (CAPE and LI), elevation, and vegetation variables in Alaska. The relationships were examined at scales ranging from the Interior region of the state to individual wildfire burn scars, and at temporal scales ranging from the annual to daily. The objective is to understand the influential factors and processes responsible for thunderstorm development in Alaska, such that we may produce well-founded predictions on future thunderstorm regimes caused by a changing climate. The scale-related studies of this dissertation show that both processes and important variables for development of thunderstorms and lightning activity vary within and between the scales. It appears that on the larger scales, the combined effects of boreal forest and elevation on increased lightning strike activity were more prevalent than at the smallest scale (local). When the scale gets too small for the boundary layer to be affected (<10km), land surface effects on lightning cannot be. My results suggest that the underlying surface (in the form of areal forest coverage and vegetation) has more of an influence on convective development on days with airmass storms than on days with synoptic storms.
    • Landscape modeling of threespine stickleback occurrence in small Southeast Alaska lakes

      Gregovich, Dave (2007-12)
      Although threespine stickleback (Gasterosteus aculeatus L) are known to inhabit a wide range of habitats, their distribution in lakes across Southeast Alaska is not known. Threespine stickleback are an important prey item for many consumers in freshwater ecosystems. Additionally, isolated populations may be genetically unique and thus important from a conservation perspective. This study focused on identifying' landscape factors and models useful in predicting the presence of threespine stickleback in small (0.5-5 ha) lakes of Southeast Alaska. Stickleback occurrence was assessed via snorkeling and minnow trapping in 54 lakes, which were divided into calibration (n=36) and prediction (n=18) data sets. A number of models representing four methodologies-generalized linear models, generalized additive models, classification trees, and artificial neural networks-were built based on the calibration set, cross-validated, and evaluated by prediction to the test set of lakes. Lake elevation, distance from saltwater, and slope of lake outlet stream were the most useful predictors of stickleback occurrence. Results suggest that the likelihood of stickleback presence is highest in low elevation lakes near the coast. Human development and recreational activity also tends to be common in these areas, and so land-use planning should account for the high potential occurrence of threespine stickleback here
    • Landscape sensitivity to climate change in northern Alaska: lessons from the past

      Gaglioti, Benjamin V.; Mann, Daniel H.; Wooller, Matthew J.; Arp, Christopher D.; Jones, Miriam C.; Jones, Jeremy B.; Swanson, David K. (2016-05)
      The climate is now changing rapidly at high-latitudes, and observing how the Arctic and sub-Arctic environment responded to prehistoric climate changes can hold valuable lessons as we adapt in the future. This dissertation presents four studies that use biogeochemical proxies to reconstruct environmental changes in northern Alaska over the last 40,000 years (40 ka). These records are used to infer how the environment responded to climate changes at different locations and over varying spatial and temporal scales. The first study presents a time series of stable oxygen isotopes contained in radiocarbon-dated (¹⁴C) willow wood to quantify the nature and rates of climate change on the North Slope of Alaska over the last 40 ka. The second study examines how past temperature fluctuations affected permafrost thaw and the release of ancient carbon over the last 14.5 ka by compiling ¹⁴C-age offsets in the sediment of a small lake in the Brooks Range foothills. In the third study, I document human-caused changes to boreal wildfire frequency near the city of Fairbanks to test whether the primeval forest type and permafrost in the surrounding watershed will be vulnerable to more frequent fires in the future. The fourth study examines how ice age (40-9 ka) climate changes impacted the activity of sand dunes, vegetation productivity, and the dynamics of permafrost recorded in a unique sedimentary exposure located near the Arctic Coastal Plain on Alaska’s North Slope. Overall, I present several new and interesting approaches and findings stemming from this work. Ancient willow isotopes show that between 17 and 8 ka, during the time when ice sheets were in retreat worldwide, temperatures fluctuated widely on the North Slope mostly in concert with those in Greenland. Most notably, rapid changes in temperature and moisture occurred during the initial deglacial warming (ca. 16 ka), and during the Younger Dryas cold period (12.9-11.7 ka). These climate trends were amplified on the North Slope by changes in sea-ice extent in adjacent seas, which also controlled the availability of local precipitation evaporated from these seas. However, these warming and cooling trends were occasionally dampened by the advent of more maritime climate accompanying sea-level rise during the early Holocene, and by the breakdown of the atmospheric circulation patterns created by continental ice sheets in North America during the last glacial maximum. Over the last 7 ka, a gradual, insolation-driven cooling trend ended in ca. AD 1850 when the exceptional rates of recent warming began that continue to today. I found that the vegetation, permafrost and sand dunes in Arctic Alaska were sensitive to external climate forcing, but their responses were moderated by strong, internal feedbacks, including the temperature-buffering effects that thick peat layers have on the underlying permafrost. Prior to peat buildup in the early Holocene, the timing of sedimentary transitions indicate permafrost and aeolian processes were highly responsive to the volatile climate during the last ice age, which included Greenland interstadials. This incessant ice age climate change, coupled with the complex biophysical landscape responses that are particular to the unglaciated Arctic, helped maintain the ecological mosaic of the Mammoth Steppe ecosystem. Prehistoric warming events triggered permafrost thaw and the release of ancient carbon during the Bølling-Allerød (14.5-12.9 ka) and early Holocene warm period (11.7-8.0 ka), and this release is likely to occur again given enough warming. In the boreal forest watershed near Fairbanks, Alaska, the current ecological regime has remained intact despite a three-fold increase in pre-settlement wildfires during the Fairbanks gold rush (1902-1940). Once continued warming surpasses the buffering effects of the current internal feedbacks of the North Slope and boreal forest and the threshold for change is reached, more dynamic aeolian and permafrost processes may again dominate as they did on the more unstable and diverse ice age landscape. Overall, the results of this work will be useful for understanding how climate and landscape change in northern Alaska will respond to global climate forcing in the future.
    • Landscape Structure And Terrain-Based Hunting Range Models: Exploring Late Prehistoric Land Use In The Nutzotin Mountains, Southcentral Alaska

      Patterson, Jody J.; Murray, Maribeth; Gerlach, S. Craig; Irish, Joel; Mann, Dan (2010)
      Striving for better delineation of site function, land use, and settlement patterns, the data and analyses presented in this dissertation aim to explore more robust and objective avenues of inquiry for addressing the variability and distribution of surface lithic scatters using terrain-based hunting range models. Using large mammal distributions, Athabascan hunting ranges, and topography, landscape metrics, and an exploratory data analysis (EDA) framework, landscape structure is quantified and compared across much of the Alaskan Interior to identify reoccurring patterns related to hunting land use and the range characteristics of caribou, moose, and sheep. Key components of the landscape structure are contrasted with topographic matrices associated with protohistoric and late prehistoric sites via discriminant function classification models. Projectile points, scrapers and bifaces from surface scatters in the Nutzotin Mountains are examined in relationship to these models and their constituent elements. The results show that the association of certain chipped-stone tools and landscape structure are highly autocorrelated. This suggests that landscape structure models can be useful in the generation of constructive hypotheses to test ideas concerning inter-assemblage variability, site function and varied forms of land use.
    • Landscape-scale establishment and population spread of yellow-cedar (Callitropsis nootkatensis) at a leading northern range edge

      Krapek, John P.; Verbyla, David L.; Buma, Brian; Hennon, Paul E.; D'Amore, David V. (2016-12)
      Yellow-cedar is a long-lived conifer of the North Pacific Coastal Temperate Rainforest region that is thought to be undergoing a continued natural range expansion in southeast Alaska. Yellow-cedar is locally rare in northeastern portions of the Alexander Archipelago, and the fairly homogenous climate and forest conditions across the region suggest that yellow-cedar's rarity could be due to its local migrational history rather than constraints on its growth. Yellow-cedar trees in northern range edge locations appear to be healthy, with few dead trees; additionally, yellow-cedar tend to be younger than co-dominant mountain and western hemlock trees, indicating recent establishment in existing forests. To explore yellow-cedar's migration in the region, and determine if the range is expanding into unoccupied habitat, I located 11 leading edge yellow-cedar populations near Juneau, Alaska. I used the geographic context of these populations to determine the topographic, climatic, and disturbance factors associated with range edge population establishment. I used those same landscape variables to model suitable habitat for the species at the range edge. Based on habitat modeling, yellow-cedar is currently only occupying 0.8 percent of its potential landscape niche in the Juneau study area. Tree ages indicate that populations are relatively young for the species, indicating recent migration, and that most populations established during the Little Ice Age climate period (1100 -- 1850). To determine if yellow-cedar is continuing to colonize unoccupied habitat in the region, I located 29 plots at the edges of yellow-cedar stands to measure regeneration and expansion into existing forest communities. Despite abundant suitable habitat, yellow-cedar stand expansion appears stagnant in recent decades. On average, seedlings only dispersed 4.65 m beyond stand boundaries and few seedlings reached mature heights both inside and outside of existing yellow-cedar stands. Mature, 100 --200-year-old trees were often observed abruptly at stand boundaries, indicating that most standboundaries have not moved in the past ~150 years. When observed, seedlings were most common in high light understory plant communities and moderately wet portions of the soil drainage gradient, consistent with the species' autecology in the region. Despite an overall lack of regeneration via seed, yellow-cedar is reproducing via asexual layering in high densities across stands. Layering may be one strategy this species employs to slowly infill habitat and/or persist on the landscape until conditions are more favorable for sexual reproduction. This study leads to a picture of yellow-cedar migration as punctuated, and relatively slow, in southeast Alaska. Yellow-cedar's migration history and currently limited spread at the northeastern range edge should be considered when planning for the conservation and management of this high value tree under future climate scenarios.
    • Landslide mapping using multiscale LiDAR digital elevation models

      Miandad, Javed; Darrow, Margaret; Metz, Paul; Daanen, Ronald; Hendricks, Michael (2018-08)
      This study presents a new methodology to identify landslide and landslide susceptible locations in interior Alaska using only geomorphic properties from light detection and ranging (LiDAR) derivatives (i.e., slope, profile curvature, roughness) and the normalized difference vegetation index (NDVI). The study specifically focused on the effect of different resolutions of LiDAR images in identifying landslide locations. I developed a semi-automated object-oriented image classification approach in ArcGIS 10.5, and prepared a landslide inventory from visual observation of hillshade images. The multistage workflow included combining derivatives from 1m, 2.5m, and 5m resolution LiDAR, image segmentation, image classification using a support vector machine classifier, and image generalization to clean false positives. I assessed the accuracy of the classifications by generating confusion matrix tables. Analysis of the results indicated that the scale of LiDAR images played an important role in the classification, and the use of NDVI generated better results in identifying landslide and landslide susceptible places. Overall, the LiDAR 5m resolution image with NDVI generated the best results with a kappa value of 0.55 and an overall accuracy of 83%. The LiDAR 1m resolution image with NDVI generated the highest producer accuracy of 73% in identifying landslide locations. I produced a combined overlay map by summing the individual classified maps, which was able to delineate landslide objects better than the individual maps. The combined classified map from 1m, 2.5m, and 5m resolution LiDAR with NDVI generated producer accuracies of 60%, 80%, 86%, and user accuracies of 39%, 51%, 98% for landslide, landslide susceptible, and stable locations, respectively, with an overall accuracy of 84% and a kappa value of 0.58. The proposed method can be improved by fine-tuning segmented image generation, incorporating other data sets, and developing a standard accuracy assessment technique for object-oriented image analysis.
    • Language Switching On English Compositions Of Latino Students In Alaska And Puerto Rico

      Jimenez-Lugo, Edna; Burleson, Derick (2007)
      The main objective of the research described in this dissertation was to explore how English second language (ESL) writers used their first language (L1) when composing in their second language (L2). This task was undertaken by identifying participants according to their L2 (English) proficiency level, Latino ethnic subgroup, and generational status. Another objective of this study was to better understand the writer's perspective regarding first language use in L2 writing, referred to as language-switching (L-S) in this study. Eight high school Latinos were recruited in Fairbanks, Alaska, and a group of twenty-three college-level participants in Mayaguez, Puerto Rico. Participants were asked to complete a self-report questionnaire, provide a writing sample, and participate in a guided focus group discussion. Findings indicated that participants with low L2 proficiency were more likely to switch languages at the lexical level than participants at an intermediate or advanced level of English proficiency. Switching languages from English to Spanish at the lexical level was of no benefit for text coherence. Lack of L2 linguistic competence was a contributing factor for switching to the L1 as participants compensated for L2 difficulties with their L1 knowledge at the morphological, syntactical, and semantic level. A qualitative analysis of the focus group data suggests that thinking in the L1 is a common strategy for ESL learners, which they perceive to be an advantage for generating ideas faster and to decide what to write. However, participants' perceived writing text in the L1 for later content translation to be counterproductive. An important factor that cannot be discounted and that may have contributed to the language switching frequency among the participants in this study is the learning contexts: learning English in the U.S. versus learning English in Puerto Rico. Additional research is needed to explore the relationship between language switching and learning context. I conclude this dissertation by suggesting pedagogical implications regarding L2 writing instruction and for placement of L2 learners in ESL programs.
    • The Last Great Indian War (Nulato 1851)

      Wright, Miranda Hildebrand; Black, Lydia T.; Schweitzer, Peter P.; Morrow, Phyllis (1995-04)
      In this study, I review the causes of an Athabaskan conflict in western Alaska which occurred in 1851. This hostility is known in published sources as the Nulato Massacre. In oral tradition the same incident is referred to either as the Last Great Indian War or simply "The Nulato War". Critical reading and analysis of primary and secondary historical source materials offer insight into external pressures on the indigenous population, the analysis of oral tradition the resulting internal pressures. The combination of historic documentation and oral tradition provide a basis for the analysis of the Nulato Massacre as an internecine conflict. The Koyukon point of view reveals this conflict to be the result of a shamanistic power contest. While it may be argued that the conflict was precipitated ultimately by economic and social post-contact dislocations, the Koyukon perceive it as a disturbance of their concept of universal psychic unity, an overarching conceptualization which encompasses all aspects of Koyukon worldview. It was imperative in their view to regain control of their lives. The role of the shaman in such restoration was paramount.
    • Latching mechanism between UAV and UGV team for mine rescue

      Hoffman, Sarah; Peterson, Rorik; Hatfield, Michael; Lin, Chuen-Sen (2017-08)
      Safety is a concern in the mining industry when a tunnel collapse could result in the casualties and deaths of workers and rescuers due to the hazards posed to them. The Alaska Center for Unmanned Aircraft Systems Integration (ACUASI) is working on a project to increase mine safety by sending an Unmanned Ground Vehicle (UGV) fit with LiDAR sensors and an Unmanned Aircraft Vehicle (UAV) to map the tunnels and to find a collapsed tunnel in an effort to determine the location and condition of trapped workers. The UGV will drive to the collapsed tunnel, at which point the U AV will launch to find any gap in the tunnel that it could fly through to assess the damage. This overall project requires a releasing and latching system to secure the UAV, allow it to launch at the appropriate location, and dock the UAV when its mission is complete or its battery needs recharging. A simple pin-through design was adopted to latch and release the UAV by implementing a Scotch yoke and servo as the actuator. All necessary components were analyzed for stress using two forces, 16 N (maximum takeoff weight of the potential UAV) and 150 N (im pact force of the maximum w eight of the potential UAV from 0.15 m or just under 6 inches). Three sets of properties for PLA were applied in the stress analyses to thoroughly investigate the feasibility of creating the parts out of PLA, a commonly used plastic for 3D printing. These three property sets were found in literature and consisted of bulk values of PLA, empirically determined values of 3D printed PLA, and values calculated using porosity equations. It was found that most components would function satisfactorily without risking fracture except in extreme conditions. The stress analyses for the landing gear illustrated its weaknesses, revealing a potential need for a different material or redesign. The landing gear as it is could be utilized under nominal operation, but it could not withstand any significant impact such as one that might occur in the event of a hard landing. The latching mechanism itself succeeded in securing the UAV. Future work includes redesigning the landing gear, another design concept for a latching mechanism that may prove more reliable, and adjusting the landing pad in the event a different UAV is selected.
    • Late Cenozoic unroofing sequence and foreland basin development of the central Alaska Range: implications from the Nenana Gravel

      Thoms, E. E. (2000-05)
      Facies architecture analysis, lithostratigraphy, and ⁴⁰AR/³⁹AR analyses of syn-orogenic sediments from the Nenana Gravel consistently demonstrate that deformation and erosion of the Late Cenozoic Alaska Range progressed in a foreland propagating sequence. Alluvial braidplain sediments, the oldest sourced from south of the present range divide, were shed into depozones exhibiting characteristics that indicate the growth of an underlying orogenic wedge primarily controlled deposition. Those characteristics include very immature and locally derived sediments, erosional unconformities, evidence for the competing influences of uplift and subsidence, lithology transitions that are correlated with facies transitions, and evidence for drainages that were defeated by surface uplift. Deposition of the Nenana Gravel took place between roughly 7 and 3 Ma. The Nenana Gravel depositional system changed when deformation within the proximal reaches of the basin brought resistant basement rocks to the surface forcing antecedent drainages to incise and abandon the alluvial braidplain they once fed.
    • Late quaternary and future biome simulations for Alaska and eastern Russia

      Hendricks, Amy S.; Walsh, John; Saito, Kazuyuki; Bigelow, Nancy; Bhatt, Uma (2016-05)
      Arctic biomes across a region including Alaska and Eastern Russia were investigated using the BIOME4 biogeochemical and biogeography vegetation model. This study investigated past (the last 21,000 years), present, and future vegetation distributions in the study area, using climate forcing from five CMIP5 models (CCSM4, GISS-E2-R, MIROC-ESM, MPI-ESM, and MRI-CGCM3). The present-day BIOME4 simulations were generally consistent with current vegetation observations in the study region characterized by evergreen and deciduous taiga and shrub tundras. Paleoclimatological simulations were compared with pollen data samples collected in the study region. Pre-industrial biome simulations are generally similar to the modern reconstruction but differ by having more shrub tundra in both Russia and Alaska to the north, as well as less deciduous taiga in Alaska. Pre-industrial simulations were in good agreement with the pollen data. Mid-Holocene simulations place shrub tundras along the Arctic coast, and in some cases along the eastern coast of Russia. Simulations for the Mid-Holocene are in good agreement with pollen-based distributions of biomes. Simulations for the Last Glacial Maximum (LGM) show that the Bering Land Bridge was covered almost entirely by cushion forb, lichen and moss tundra, shrub tundra, and graminoid tundra. Three out of the five models’ climate data produce evergreen and deciduous taiga in what is now southwestern Alaska, however the pollen data does not support this. The distributions of cushion forb, lichen, and moss tundra and graminoid tundra differ noticeably between models, while shrub tundra distributions are generally similar. Future simulations of BIOME4 based on the RCP8.5 climate scenario indicate a northward shift of the treeline and a significant areal decrease of shrub tundra and graminoid tundra regions in the 21st century. Intrusions of cool mixed, deciduous, and conifer forests above 60°N, especially in southwest Alaska, were notable. Across eastern Russia, deciduous taiga begins to overtake evergreen taiga, except along the coastal regions where evergreen taiga remains the favored biome.
    • 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.
    • Later that night: three studies in horror

      Michael, Kathryn; Kamerling, Leonard; Farmer, Daryl; Carr, Richard (2015-05)
      To write a successful screenplay is to form a blueprint, a set of dramatic instructions; a structural plan to be executed at a later date by film artists and technicians. It is vital not to become attached to the details; components such as character names and place settings will often change as a project undergoes different stages of development. Above all else, what must remain on the page is the story's dramatic structure, its intention. If this is accomplished, the integrity of the screenplay is intact, and the writer is in control. Later that Night: Three Studies in Horror is a compilation of three short screenplays, each showcasing a popular horror subgenre. The screenplays follow Anna and Gabriel, a pair of con-artists, as they try to maneuver their way through the back roads of Nebraska on one fateful summer night. In In Sight, the pair is wrapping up a con job when an unexpected guest turns up on the front porch in need of help, with surprising consequences. In Pit Stop, a routine fill-up at a local gas station takes a bloody turn for the worse when two men attempt a hold-up. Finally, in Overnight Guest, Anna's freedom from Gabriel is cut short when his spirit refuses to grant her peace. These three screenplays are written as stand-alone pieces that can be viewed in chronological order to form a continuous storyline. The purpose of this structure is to highlight specific subgenres of horror in each of the three scripts and to create an understanding of how each functions as a storytelling genre. In Sight is a psychological thriller, focusing on feelings of unease and impending action. Pit Stop is a "gore script", highlighting gratuitous amounts of blood and death. Overnight Guest is a story of the supernatural, with the protagonist's life being directly affected by an angry spirit.
    • Lateral magma transport during the 1912 eruption of Novarupta: insights from magnetic imaging

      Hill, Graham J.; Eichelberger, John; Freymueller, Jeff; Faust-Larsen, Jessica (2003-08)
      The Valley of Ten Thousand Smokes (VTTS), on the Alaska Peninsula, was formed by the cataclysmic eruption of Novarupta (Katmai) in 1912. During the eruption, three magma types were tapped (7-8 km³ of rhyolite, 4.5 km³ of dacite, and 1 km³ of andesite). Contemporaneous collapse of Mount Katmai while Katmai-like andesite and dacite magma joined the eruption at Novarupta provides incontrovertible evidence for magma transport from beneath Mount Katmai caldera to the vent 10 km west at Novarupta (Hildreth and Fierstein, 2000). Shallow storage of the andesite and dacite magmas beneath Mt. Katmai prior to the eruption of 1912 is consistent with the volume of collapse at Katmai, equivalent to the combined volume of andesite and dacite erupted. A ground-based magnetic survey of the area was conducted to characterize the intriguing connection between Mt. Katmai and Novarupta. The magnetic field strength and gradient survey results suggest a linear anomaly that is best modelled by the presence of a shallowly (200-300 m) emplaced dike on the order of 5-10 m wide, which resembles the known physical properties of the 7 m-wide rhyolitic dike discovered during the drilling of Inyo Domes.
    • Latitudinal gradients in leaf litter decomposition in streams: Effects of leaf chemistry and temperature

      Irons, John Gillam, Iii (1993)
      Autumnal leaf litter that falls into streams of forested regions forms a major source of energy for stream food webs. The processing of this litter has been studied for many years, and two generalizations have come from this research: (1) nitrogen concentration is positively correlated with breakdown rate, and (2) temperature is negatively correlated with breakdown rate. Along with investigators in Michigan and Costa Rica, I examined these generalizations by estimating breakdown rates of litter of ten tree species with widely varying nutritional quality along the latitudinal gradient of Costa Rica to Michigan to Alaska. At each site, litter processing experiments were done using leaves of the same ten tree species and the same methods in streams with similar character. We found that (1) condensed tannin, a plant defense against herbivory, was more highly correlated (negatively) with breakdown rates than was nitrogen (positively correlated with breakdown), and (2) breakdown rate showed a complex response to water temperature (i.e., latitude). I propose a model of leaf litter breakdown in which the microbial contribution to litter breakdown is negatively correlated with latitude (i.e., temperature) and the invertebrate contribution to litter breakdown is positively correlated with latitude. In addition, I suggest that secondary compounds of low solubility, especially condensed tannin, should be considered along with nitrogen when evaluating a tree species for leaf litter quality.
    • Latitudinal patterns of amino acid cycling and plant N uptake among North American forest ecosystems

      McFarland, Jack W.; Ruess, Roger; Boone, Richard; Chapin, Stuart F. III; Kielland, Knut; Hendrick, Ronald L. (2008-12)
      Interest in the role of organic nitrogen (N) to the N economy of forest ecosystems is gaining momentum as ecologists revise the traditional paradigm in N cycling to emphasize the importance of depolymerization of soil organic matter (SOM) in controlling the bioavailability of N in forest soils. Still, there has yet to be a coordinated effort aimed at developing general patterns for soil organic N cycling across ecosystems that vary in climate, SOM quality, plant taxa, or dominant mycorrhizal association: ectomycorrhizae (EM) vs. arbuscular mycorrhizae (AM). In this study, experimental additions of 13C15N-glycine and 15NH4+ were traced in situ through fine root and soil N pools for six North American forest ecosystems in an effort to define patterns of plant and microbial N utilization among divergent forest types. Recovery of 15N in extractable soil pools varied by N form, forest type, and sampling period. At all sites, immobilization by the soil microbial biomass represented the largest short-term (<24 h) biotic sink for NH4+ and amino acid-N, but differences in microbial turnover of the two N forms were linked to cross-ecosystem differences in SOM quality, particularly the availability of labile carbon (C). At the conclusion of the experiment, microbial N turnover had transferred the majority of immobilized 15N to non-extractable soil N pools. By comparison, fine root uptake of NH4+ and glycine-N was low (<10% total tracer recovery), but 15N enrichment of this pool was still increasing at the final sampling period. Since there was no significant loss of 15N tracer within the bulk soil after 14 days for any forest type except sugar maple, it suggests plants have the capacity to capitalize on multiple N turnover events and thus represent an important long-term sink for ecosystem N. Plants in all stands had some capacity to absorb glycine intact, but plant N preference again varied by forest type. Relative uptake of amino acid-N versus inorganic N was lowest in tulip poplar and highest in red pine and balsam poplar, while white oak, sugar maple, and white spruce stands were statistically near unity with respect to the two N forms. However, N uptake ratios were threefold higher in EM-dominated stands than in AM-dominated stands indicating mycorrhizal association in part mediated plant N preference. Thus, amino acids represent an important component of the N economies of a broad spectrum of forest ecosystems, but their relevance to plant nutrition likely varies as a function of microbial demand for C as well as N.
    • Launch environment data logger design and implementation for CubeSats

      Johnson, Morgan; Thorsen, Denise; Hawkins, Joe; Raskovic, Dejan (2016-12)
      Designing to the CubeSat standard has allowed many universities the ability to launch satellites missions to space. These small satellites are secondary, or even tertiary, payloads on launch vehicles. In fact, these ride-share payloads are frequently used as ballast for weight and balance of the launch vehicle and are often mounted near the engines. The environment experienced by these CubeSats is not well known. The Launch Environment Data Logger was designed to measure temperature and vibrations of the launch vehicle to better understand what kind of environment these small satellites must survive on their ride to space. Through this thesis the requirements of the Launch Environment Data Logger system are established and the initial design developed.
    • Layout and fabrication process from generic to high speed printed circuit boards (PCBS)

      Reddy, Indrani (2005-12)
      Printed circuit boards (PCBs) are exceeding the limits of the classic board design. The goal of this thesis is to inform the reader about the layout and fabrication of PCBs from generic to high speed designs. In chapter 2, Basic Design and Layout, I provide the generic PCB design that will give a basic understanding of board layout and fabrication using Cadence® software tools, which will simplify understanding of the high speed PCB design. Cadence® provides a path to designing PCBs, but to rapidly prototype the design we need to implement simulations. We accomplished the simulations using the Advanced Design System (ADS) tool which is used for designing high frequency PCBs. In this thesis the reader will see examples developed to illustrate high speed issues in digital designs using ADS and correlated simulated and measured values.