Theses for the School of Natural Resources & Agricultural Sciences

Recent Submissions

  • Remote sensing aspen leaf miner (Phyllocnistis populiella chamb) infestations near Ester Dome in Fairbanks, Alaska

    Smart, Douglas D. (2008-12)
    "Mapping trembling aspen stands (Populous tremuloides Michx.) versus Alaskan birch (Betula neoalaskana Sarg.) in interior Alaska is possible as a byproduct of remote sensing aspen leaf miner (Phyllocnistis populiella Chamb.) damage. P. populiella is a defoliator of trembling aspen that has been observed in epidemic proportions in Alaska since 2001. Where it is observed it is ubiquitous. Unlike most remote sensing studies of insect damage, I found no significant change in the near-infrared related to leaf miner damage. The feeding morphology of P. populiella is different from most other leaf defoliating insects. P. populiella feeds only in the epidermal tissue of aspen leaves whereas most other leaf mining insect pests consume mesophyll tissue. This means that P. populiella causes no significant change in near-infrared reflectance whereas most other defoliators do. This lack of change in near-infrared range coupled with the timing of leaf miner foraging can be used to discriminate P. populiella damage from that of other leaf defoliators. The ability to remotely sense damage in aspen stands provides an opportunity to identify P. tremuloides in locations where damage is epidemic. If new image acquisition and historic image purchases are timed to correspond with P. populiella outbreak conditions, it will be possible to identify areas that are P. tremuloides stands and not other species"--Leaf iii
  • Sensitivity of boreal forest carbon dynamics to long-term (1989-2005) throughfall exclusion in Interior Alaska)

    Runck, Sarah A.; Valentine, David; Chapin, Terry; Yarie, John (2008-12)
    "The objective of this study was to assess the effect of throughfall exclusion (1989-2005) on forest vegetation and soil in upland and floodplain landscape positions. In uplands, imposed drought reduced soil moisture at 5, 10, and 20 cm depths and increased soil C storage by slowing decomposer activity at the surface. In the drought plots, aboveground tree growth was reduced and root biomass in mineral soil was increased. In floodplains, imposed drought did not reduce soil moisture as strongly as it did in uplands, though near-surface soil C storage was still increased as a result of reduced decomposer activity. Floodplain vegetation response to imposed drought differed from that of uplands; imposed drought did not reduce aboveground tree growth but instead reduced root biomass in mineral soil. At both landscape positions, imposed drought accelerated the loss of understory vegetation. Overall, the results of the throughfall exclusion indicated that chronic soil drying is likely to increase forest C storage only in floodplains. In uplands, where soil moisture is more limited, forest C storage is not as likely to change because an increase in soil C may be offset by reduced tree growth"--Leaf iii
  • Assessing utilitarian wildlife value orientations of Alaska residents: an urban and rural perspective

    Tracy, Quinn G. (2009-05)
    "A large body of literature supports value theory as an integral component to the management of natural resources. Value theory provides managers with an effective tool for natural resource allocation and stakeholder mitigation by predicting attitudes and behaviors of populations. This study explored the protection or use wildlife value orientation dimension of 2,264 Alaskans with an emphasis on comparing urban and rural populations, and new and long term residents. This study also investigated relationships among value orientations, demographic characteristics, and outdoor activity participation. Data were collected using a mail survey sent to a random sample of 10,003 people registered to vote in Alaska. In an effort to achieve adequate representation from rural Alaskans, the sample was stratified into five geographic regions, with a goal of receiving at least 400 returned surveys from each region. As hypothesized, rural and long term residents were more use oriented or 'utilitarian' than urban and short term residents. As hypothesized, and supported by existing literature, value orientation differences were found within gender, education, and age. Females, educated, and younger residents were more protection oriented then their counterparts. Significant relationships were found between value orientations and outdoor activity participation; however, correlations were too weak to provide predictive capabilities. Although, this study compared rural areas, with predominately Native populations, to urban areas, with predominately non-Native populations, race comparisons were not analyzed, but results signify that differences may exist. Future research should seek to validate value orientation differences by culture and race and longitudinal studies should assess shifting value changes over time"--Leaf iii
  • Factors influencing the development of wind power in rural Alaska communities

    Maynard, Jill Erin; Joly, Julie Lurman; Lovecraft, Amy; Rose, Chris; Chapin, Terry III (2010-05)
    "The state of Alaska is endowed with extensive and developable wind resources. The greatest areas of class seven, "superior" wind resources in the entire United States are located in Alaska. Developing these resources has the potential to play a pivotal role in reshaping Alaska's future by providing reliable, local, and stable-priced power. Despite this tremendous natural asset and the immeasurable benefits it harbors, Alaska's wind resources remain largely untapped and underutilized. Rural Alaskan communities, classified by their remote locations, small populations, and consequent low electric demands and high electric costs, possess some of the greatest wind resources in Alaska. The challenge, however, is to overcome the current social, political, technical, economic, and environmental constraints. This thesis aims to identify factors that contribute to and constrain the successful development of wind power projects in rural Alaska and to recommend solutions to overcome specific barriers. The findings demonstrated that the primary influencing factors included leadership, coordination at local and state levels, access to information and assistance, and local human, technical, and financial capacity. Such factors must be an integral part of planning efforts in order to advance wind power development in rural communities"--Leaf iii
  • How does improved access to clean water impact rural communities? Evaluating impact of water projects in the Ajumako-Enyan-Essiam district in Ghana

    Sam, Josephine-Mary O.; Todd, Susan; Anahita, Sine; Shapiro, Lewis; Chapin, F. Stuart III (2011-12)
    Research has shown that rural water programs benefit communities by promoting women's empowerment, and improving children's education and the health of residents. However, the tendency for such programs to be short-lived (as water pumps break down and villages are unable to repair them) erodes any benefits and sets villages back on the path toward using unsafe and inconvenient water sources. The incidence of failed rural water projects has prompted calls for a more holistic approach to addressing rural water supply issues. Two development organizations, the Nyarkoa Foundation (NF) and the Rural Education and Development Program (REDEP), implemented a water program in villages located in the Ajumako-Enyan-Essiam District of Central Region, Ghana, where earlier water programs had been unsuccessful. Using a new approach, the program focused on gender-sensitive planning, financing for maintenance and participatory governance. Through interviews, focus group discussions and participant observation, this study evaluates the impacts of the NF/REDEP water program in two villages, Ofosu and Awordo. Findings showed that improved access to clean water enhanced economic opportunities for women and children's education in both villages. There was also evidence that equitable and participatory decision-making engendered cooperation and efficient management of the water program, while exclusionist policy making led to apathy and noncompliance. However, the combined usage of the water pumps with unprotected water sources threatened to negate its health benefits, while the absence of effective women's involvement in the management of the program raised questions about its capacity to truly empower women. These findings reveal the need for increased sensitization on the risks of using unsafe water and a review of the program management approach.
  • Remote sensing of browning trends in the Alaskan boreal forest

    Parent, Mary Elizabeth; Verbyla, David; Juday, Glenn Patrick; Heiser, Patricia (2011-12)
    Vegetation health can be monitored using a time series of remotely sensed images by calculating the Normalized Difference Vegetation Index (NDVI). We assessed temporal trends throughout an NDVI time series with three sensors: Advanced Very High Resolution Radiometer (AVHRR), the Moderate Resolution Imaging Spectroradiometer (MODIS) and Landsat Thematic Mapper/Enhanced Thematic Mapper Plus (TM/ETM+). There has been debate over the reliability of AVHRR sensor NDVI data in the circumboreal region. Therefore, the purpose of this paper was to first use MODIS and Landsat TM/ETM+ data and assess declining trends within twelve Landsat scene footprints across boreal Alaska and second use Landsat TM/ETM+ data to assess NDVI trends at a stand-level in eastern boreal Alaska. For the first objective, there were significant (p-value <0.05) declining trends in eastern boreal Alaska and no significant trends in the western region due to an east-west climate gradient. For the second objective, there were significant declining trends scattered across our two research areas. It was determined that many factors need to be included when determining where declining stands in NDVI are located such as site climate, site landscape position and other unique site conditions.
  • Human well-being in recreation: an investigation of the expectancy-valence theory

    Harrington, Andrew M. (2011-05)
    Over the past 50 years, numerous approaches exploring the recreation experience have offered a multitude of concepts and terminology, resulting in a debate over which best represent recreation behavior. This study adopts one of these approaches, the motivational approach, and explores its underpinning theory, expectancy-valence; addresses its limitations presented in the literature; and investigates the potential for the integration with other approaches. A modified analytic induction methodology was applied to address five hypotheses developed to address study questions. Longitudinal, qualitative data were collected through two separate interviews one week apart with 16 individuals that captured their thoughts regarding their recreation activities. A codebook was developed and a kappa statistic revealed an acceptable (K = 0.61 to 0.80) level of inter-coder reliability. Codes were developed based on constructs from the expectancy-valence framework prior to examining the transcripts. Evidence of these codes in the transcripts provided support for the theory. Consistent with modified analytic induction, some hypotheses were confirmed, while one was modified when evidence to the contrary was found. Further examination of the data revealed the potential for integration of other approaches.
  • Arctic sea ice: satellite observations, global climate model performance, and future scenarios

    Rogers, Tracy S.; Rupp, Scott (2011-08)
    This thesis examined Arctic sea ice trends through observational records and model-derived scenarios. A regional analysis of Arctic sea ice observations 1980-2008 identified regional trends similar to the pan-Arctic. However, winter maximum (March) extent in the Atlantic quadrant declined faster. Through an analysis of Atlantic Ocean temperatures and Arctic winds, we concluded that melting sea ice extent may result in increased Atlantic Ocean temperatures, which feeds back to further reductions in Atlantic quadrant extent. Further, Arctic winds do not appear to drive Atlantic ice extent. We evaluated performance of 13 Global Climate Models, reviewing retrospective (1980-2008) sea ice simulations and used three metrics to compare with the observational record. We examined and ranked models at the pan-Arctic domain and regional quadrants, synthesizing model performance across several Arctic studies. The top performing models were able to better capture pan-Arctic trends and regional variability. Using the best performing models, we analyzed future sea ice projections across key access routes in the Arctic and found likely reduced ice coverage through 2100, allowing increasingly longer marine operations. This unique assessment found the Northwest and Northeast Passages to hold potential for future marine access to the Arctic, including shipping and resource development opportunities.
  • Spatial and temporal trends in vegetation index in the Bonanza Creek Experimental Forest

    Baird, Rebecca A. (2011-08)
    Climate has warmed substantially in boreal Alaska since the mid-1970s. The direct effects of rising temperatures on sub-Arctic ecosystems are already being observed in the form of drought stress, increased fire frequency and severity, and increased frequency and severity of herbivorous insect outbreaks. These effects of climate change are having a direct impact on the vegetation of the boreal forest and leading to a decreased remotely sensed normalized difference vegetation index (NDVI), which is an effective proxy for landscape-scale plant productivity and photosynthesis. Therefore, NDVI is a useful tool to examine landscape-scale changes in vegetation over time, especially in the context of known climate change. The overarching goal of my research was to assess the change in vegetation index at multiple scales over a period of 23 years at Bonanza Creek Experimental Forest. I used a combination of remote sensing and field sampling to examine trends in NDVI across landscape units, topographic classes, and plant communities. My project consists of two main parts: 1) Create a floristically-based landcover classification through field sampling and incorporating the field data into a map using satellite imagery and 2) Examine trends in the vegetation index using 11 Landsat TM and ETM+ images from 1986-2009. By using Landsat imagery and doing a landcover classification of my study area I was able define trends in NDVI to specific landscape units, topographic classes, and plant communities in the study area.
  • Ecological development of a management plan for reindeer (Rangifer tarandus) on St. George Island, Alaska

    St. Martin, Michelle L. (2012-12)
    Management of an herbivore production system requires a working knowledge of the components and processes of the targeted grazing system. Land owners and stakeholders wish to develop a management plan for reindeer on St. George Island, Alaska. The foci of this study were to determine seasonal diet composition (including forage preference); evaluate nutritional content of Angelica lucid, a potential alternative winter forage; estimate lichen biomass; and estimate reindeer abundance, annual production, and sustainable stocking density. Lichens were the preferred reindeer forage throughout the year, however significant seasonal dietary shifts occurred across the seasons. Fortis and grasses were consumed in significantly greater proportion in spring and summer diets, sedges greater in the fall diets, and mosses greater in the winter diets. Angelica lucida was found in reindeer diets throughout the year. The nutritional profile and available biomass suggest this species may serve as an important forage for growth and maintenance of the reindeer. Both the reindeer population and calf:cow ratio increased from 2007 (290 individuals; 48:100 ratio) to 2008 (320 individuals; 57:100 ratio). The estimated total lichen biomass for the island was ~ 5.4 million kg dry matter which could support a population of 217 reindeer or 2.4 reindeer/ km².
  • 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.
  • Multiresolution digital soil mapping of permafrost soils using a random forest classifier: an investigation along the Dalton Highway corridor, Alaska

    Paul, Joshua D.; Ping, Chien-Lu; Prakash, Anupma; Rossello, Jordi Cristobal; Libohova, Zamir (2018-12)
    In order to complete soil inventories in the remote permafrost zones of Alaska, there is a need to develop efficient digital soil mapping tools that can be applied over large areas using a minimum of ground truth data. This investigation first used a random forest classifier to test combinations of environmental input data at multiple resolutions (10m, 30m, and 100m). Five tiers of soil taxonomic units were predicted: Order, Suborder, Great Group, "Series Concept", and Particle Size Class. Model outputs are compared quantitatively via estimated out-of-bag accuracy, and qualitatively via visual inspection by soil scientists. Estimated out-of-bag accuracy ranged from ~45% to ~75%, with results improving when fewer classes were modeled. Model runs at 10m and 30m resolution performed comparably, with 100m resolution performing ~5-10% worse in most cases. Increasing the number of trees used, including categorical environmental input data (e.g. landforms), and replacement of environmental covariates with principal component analysis (PCA) bands did not significantly improve model performance. The random forest classifier was then used in a digital soil mapping pilot study along the Dalton Highway in northern Alaska. Parameters suggested in the initial study were used to predict multiple soil taxonomic classes from a basic collection of environmental covariates generated using high resolution (10m) satellite images and sparsely sampled pedon data. Covariates included maximum curvature, multiresolution valley bottom flatness, normalized height, potential incoming solar radiation, slope, terrain ruggedness index, and modified soil and vegetation index. Five tiers of soil taxonomic units were predicted: Order, Suborder, Great Group, "Series Concept", and Particle Size Class. Model outputs are compared quantitatively via estimated out-of-bag accuracy. Estimated out-of-bag accuracy ranged from ~45% to ~75%, with results improving when fewer classes were modeled. We suggest future research into optimized sampling to ensure an adequate distribution of samples across the feature space, and the incorporation of expert knowledge into accuracy assessments. Overall, digital soil mapping with random forest classifiers appears to be a promising method for completing the soil survey of Alaska.
  • A study of soil topo-sequences in the Steese and White Mountains of Alaska

    Geisler, Eric S.; Ping, Chien-Lu; Juday, Glen; Swanson, David (2018-08)
    The Steese Mountains of Alaska present a complex landscape on which to study soil formation and characteristics in relation to topographic position. The White and Steese Mountains of Alaska are located approximately 70 to 220 km northeast of Fairbanks. Ten toposequences with 3 or 4 sites each were described in the field, sampled, and analyzed in the laboratory in order to determine the relationship between soil morphology and soil-forming factors. Permafrost is discontinuous within the study area and vegetation ranges from tundra on summits to boreal stands of resin birch, quaking aspen, black spruce and white spruce along the lower elevations. There have been many wildfires over time that may have altered the soils and affected the vegetation successional patterns. The processes through which various soil patterns have formed and the unique characteristics of the soils are described here based on field data obtained from both burned and unburned sites. The analysis includes biophysical settings, parent material, texture and nutrient concentrations. Organic horizons were common on most of the transects and play a key role in the depth of the active layer where they exist. Nutrient concentrations are also closely tied to the presence and depth of the organic horizons. Some patterns described in other areas of the boreal region were not observed in this study. There were some soil properties that are not readily described under the current taxonomy protocols which are suggested to be added in a future revision of Soil Taxonomy.
  • Temporal and spatial variation of broadleaf forest flammability in boreal Alaska

    Wehmas, Maija I.; Verbyla, David; Mann, Daniel; Hollingsworth, Teresea (2018-08)
    The boreal forest is a carbon reservoir containing roughly 40% of the world's reactive soil carbon, which is mainly cycled by wildland fires. Climate warming in boreal Alaska has changed the wildfire regime such that an increase in broadleaf forest relative to conifer forest is likely, which may reduce landscape flammability. However, the current and future flammability of broadleaf forest in a warming climate is not well understood. We used pre-fire and post-fire geospatial data to investigate the flammability of upland boreal forest patches in Interior Alaska in relation to summer weather conditions. Our objectives were to assess burning of broadleaf forest patches during "Normal" vs. "Large Fire Years", by week within a fire season, and by topographic position. Using 30-meter land-cover and fire-severity grids, we estimated the flammability of upland broadleaf forest patches during Large and Normal Fire Years. We then tested for topographic effects using a solar radiation index to eliminate potential deviations within the vegetation. Finally, Moderate Resolution Imaging Spectroradiometer (MODIS) hotspots were used to track the spatial extent of burns during the fire season by examining the periods of fire activity and intensity. Flammability of broadleaf forest patches varied both in time and space. Even during Normal Fire Years, broadleaf forest patches exhibited substantial flammability, with a mean of over 50% patch area burned. Patch flammability was significantly higher during Large Fire Years. Burning of broadleaf patches varied with topographic position and correlated with potential insolation. Broadleaf forest patches burned most frequently in late June-early July. Contrary to "conventional wisdom", broadleaf forest patches in boreal Alaska are susceptible to burning even during Normal Fire Years. With climate warming, the flammability of broadleaf forest is likely to increase due to more extreme fire weather events. Thus, although the frequency of broadleaf forest patches on the landscape is likely to increase with more frequent and severe wildfires, their effectiveness as a fire break may decrease in the future.
  • Birch, Berries, And The Boreal Forest: Activities And Impacts Of Harvesting Non-Timber Forest Products In Interior Alaska

    Maher, Kimberley Anne C.; Juday, Glenn P.; Barber, Valerie; Gerlach, S. Craig; Watso, Annette (2013)
    Harvesting wild berries, firewood, and other non-timber forest products (NTFPs) from the boreal forest in Interior Alaska is a common activity amongst local residents. NTFPs are harvested for personal use, subsistence, and commercial purposes. While these activities contribute to informal household economies and livelihoods, harvest of NTFPs are not well documented in Alaska. Availability of these ecosystem services may be altered under changing management and climate regimes. This interdisciplinary dissertation takes a look at the activities and impacts of current NTFP harvesting practices. Survey results from a forest use survey provide insight into harvest activity in the Tanana Valley. Wild blueberries (38.5% of households with mean harvested amount of 7.7 quarts) and firewood (25.0% of households with a mean harvest amount of 4.7 cords) were reported harvested with greatest frequency, and harvesting activities were mostly concentrated around larger population centers. Interviews were conducted with personal use and subsistence NTFP harvesters from Interior Alaska. Participants enjoy harvesting from the forest, and that the importance of harvesting is a combination of both the intangible benefits from the activity and the tangible harvested items. Harvested NTFPs were seen as high-quality products that were otherwise unavailable or inaccessible. Birch syrup is a commercially available NTFP produced in Alaska by a small number of companies. Similar to maple syrup, producing birch syrup is a labor intensive process with marginal profits. Interviews were conducted with workers in the Alaskan birch syrup industry, who reported that they were seeking an alternative to the traditional employment. The effects from mechanical damage from tapping for spring sap on birch's vigor are of concern to birch syrup producers and natural resource managers. This study compared the annual increment growth of Alaskan birch trees, Betula neoalaskana, between tapped and untapped trees. No significant difference was detected from tapping, but annual variability in growth was strongly significant. A temperature index accounted for nearly two-thirds of the annual variability. Pairing this index with two climate scenarios, birch growth was extended out through the 21st century. As temperatures rise, birch in Interior Alaska are projected to face a critical threshold, which may limit or extinguish their ability to sustain growth and yield a sustainable sap resource. Integrating the survey, interview, and dendroclimatological data provides a richer picture of how NTFP harvesters actively use the forest and about the benefits derived. These findings can assist resource managers in balancing these needs with those of other forest uses on public land.
  • Anatomical And Mechanical Characteristics Of Woods Used To Manufacture Bassoons

    Levings, Carolyn K.; Barber, Valerie; Alix, Claire; Hulsey, Leroy; Keating, Richard; Rydlinski, George (2012)
    The purpose of this dissertation was three-fold -- 1) to determine if anatomical characteristics and mechanical characteristics derived from tapping (the act of striking an object lightly) can be used to more accurately describe bassoon resonant wood than the characters in use now, 2) to determine if any Alaska hardwoods can be used to construct bassoons, and 3) to produce lists of potential North American hardwoods and resonant bassoon wood characters. The bassoon resonant woods (Acer spp., Dalbergia melanoxylon, and Pyrus spp.) were compared to a known non-resonant bassoon wood (Juglans nigra). Vessel length and width, fiber length, and axial parenchyma width were measured in sectioned and macerated wood slides, along with the ratios of crystalline cellulose, lignin, pectin, and other aromatics in the cell wall. Partial frequencies created from tapping specimens on each longitudinal face were measured from melodic and peak partial spectrograms, as well as the spectrum obtained from the beginning of the sound. MANOVA and univariate ANOVA showed the resonant woods were significantly different from the non-resonant Juglans nigra using the characters measured. These characters were then used to compare two Alaska hardwoods (Alnus rubra and Betula neoalaskana) to the temperate resonant woods (Acer spp. and Pyrus spp.) and the non-resonant Juglans nigra using k-means clustering, MANOVA, and univariate ANOVA. Both Alaska hardwoods grouped with the non-resonant Juglans nigra. Lastly a list of potential North American hardwoods to be checked anatomically was compiled, as well as a list of characters that combine those used now as well as characters found in this study.
  • Soil Fertility And Corn And Soybean Yield And Quality In A Six-Year Nitrogen And Phosphorus Fertilization Experiment

    Anthony, Peter M.; Sparrow, Stephen; Malzer, Gary; David, Valentine,; Zhang, Mingcho (2012)
    Optimum management of nitrogen (N) and phosphorus (P) fertilizers for corn [Zea mays L.] and soybean [Glycine max (L.) Merr.] production requires quantitative understanding of multiple soil processes and crop responses, including supply and immobilization of N and P by soil, the response of yield and quality to nutrient availability, and the relationships and interactions between N and P cycling, crop response, and other soil physical and chemical variables. We conducted a six-year experiment on two 16-ha fields on glacial-till soils in south-central Minnesota. In each year of a corn--soybean rotation, we measured soil physical and chemical parameters and grain yield and quality at a 0.014-ha resolution within each field. These observations coincided with placement of a randomized complete block, split plot design of N and P fertilizer treatments. Spatial patterns of mineralizable N were consistent over time. Mineralizable N was highly correlated to soil nitrate at a well-drained site, but not at a poorly-drained site. Increases in available soil P per kg of net P addition were significantly related to soil pH. Within fields, spatial patterns of soybean yields were highly correlated across years, and we observed consistent relationships between yield and soil variables. Overall, soybean yield related positively to soil P and Zn and negatively to pH at all site-years. Quadratic-plateau regression models of soybean yield in relation to soil P and Zn indicate that in high pH soils at these sites, yield is optimized when soil P and Zn levels are higher than current recommendations. Corn yields responded significantly to N rate and N rate by P rate interaction in all site-years. Whole-field economic optimum N rate differed significantly by site-year and by P treatment at some site-years. Site-specific P fertilization should account for spatial variation in soil P buffering capacity. Nitrogen mineralization and NxP nutrient interactions should be accounted for in agronomic management decisions for corn production. The consistent influence of soil pH on nutrient cycling and crop response indicates the potential benefit to amelioration of high pH in calcareous glacial-till soils. Results highlight the significance of spatial variability in nutrient cycling to crop management.
  • Diversity In The Boreal Forest Of Alaska: Distribution And Impacts On Ecosystem Services

    Young, Brian D.; Yarie, John; Chapin, F. Stuart; Greenburg, Josh; Huettmann, Falk; Verbyla, David (2012)
    Within the forest management community, diversity is often considered as simply a list of species present at a location. In this study, diversity refers to species richness and evenness and takes into account vegetation structure (i.e. size, density, and complexity) that characterize a given forest ecosystem and can typically be measured using existing forest inventories. Within interior Alaska the largest forest inventories are the Cooperative Alaska Forest Inventory and the Wainwright Forest Inventory. The limited distribution of these inventories constrains the predictions that can be made. In this thesis, I examine forest diversity in three distinct frameworks; Recruitment, Patterns, and Production. In Chapter 1, I explore forest management decisions that may shape forest diversity and its role and impacts in the boreal forest. In Chapter 2, I evaluate and map the relationships between recruitment and species and tree size diversity using a geospatial approach. My results show a consistent positive relationship between recruitment and species diversity and a general negative relationship between recruitment and tree size diversity, indicating a tradeoff between species diversity and tree size diversity in their effects on recruitment. In Chapter 3, I modeled and mapped current and possible future forest diversity patterns within the boreal forest of Alaska using machine learning. The results indicate that the geographic patterns of the two diversity measures differ greatly for both current conditions and future scenarios and that these are more strongly influenced by human impacts than by ecological factors. In Chapter 4, I developed a method for mapping and predicting forest biomass for the boreal forest of interior Alaska using three different machine-learning techniques. I developed first time high resolution prediction maps at a 1 km2 pixel size for aboveground woody biomass. My results indicate that the geographic patterns of biomass are strongly influenced by the tree size class diversity of a given stand. Finally, in Chapter 5, I argue that the methods and results developed for this dissertation can aid in our understanding of forest ecology and forest management decisions within the boreal region.
  • Conditions For Effective Use Of Community Sustainability Indicators And Adaptive Learning

    Powell, James E.; Kofinas, Gary (2012)
    As the number of community sustainability indicator programs (SIPs) increases in many regions of the world, including in the United States, questions continue to arise regarding how decision makers can use sustainability indicators (SIs) to contribute in a meaningful way to their efforts to build resilient and sustainable communities. Through an analysis of the sustainability activities in sample cities from across the U.S. and a case study of one city that adopted SIs but has yet to implement them, this study seeks to uncover the conditions for effective SI implementation and use. The study began with a review of the literature on communities' sustainability efforts and the historical roots of sustainability and resilience theory leading up to today's sustainability indicator projects. A heuristic model for adaptive learning is presented to illustrate the relationships among sustainability, resilience, and administrative concepts, including the goals and domains of sustainability indicators. The study's data collection and analysis began with an Internet-based investigation of 200 U.S. cities. A five-tiered system was devised to categorize findings regarding sustainability patterns and trends in studied cities, ranging from an absence of sustainability activities through fully implemented sustainability indicators. The second phase of data collection employed an electronic survey completed by informants from a 38-city sample of the 200 investigated cities, followed by phone interviews with informants from cities that ranked high for developed sustainability programs. A case study using focus group research was then conducted of one small U.S. city, Juneau, Alaska, where local government adopted sustainability indicators in the 1990s but fell short of implementing them. Most cities in the U.S. have not developed sustainability indicator projects, and, among those that have, few have been able to implement them fully. Among highly ranked cities with sustainability indicators, several approaches, including innovative organizational structures and adaptive learning processes, were found to be present. Recommendations for incorporating such innovations and for grounding sustainability indicator projects in sustainability science, resilience thinking, and public administration theory are offered to help ensure sustainability indicators become fully operational in Juneau, as well as in other communities seeking to establish successful sustainability indicator programs.
  • Assessment And Prediction Of Potentially Mineralizable Organic Nitrogen For Subarctic Alaska Soils

    Zhao, Aiqin; Zhang, Mingchu (2011)
    The objective of this study was to identify a rapid laboratory technique to predict potentially mineralizable organic N for subarctic Alaska soils. Soil samples were taken from major agricultural area of subarctic Alaska. Laboratory incubation followed by kinetic model fit was first used to select a best model to estimate potential soil N mineralization. By correlating the model estimated organic N pool sizes and different chemical extracted organic N, I then found the best chemical method to estimate soil potentially mineralizable N. Spectroscopic properties of water extractable organic matter were also determined and correlated with model estimated organic N pool sizes in order to improve the estimation of soil mineralizable N pool. Finally, the best chemical method and spectroscopic property were used in the selected best kinetic model for the prediction of soil N mineralization in field incubation. Model comparisons showed that models with fixed rate constants were better than that the ones with rate constants estimated from simulation. Among models with fixed rate constants, fixed double exponential model was best. This model differentiated active mineralizable organic N pool with a fixed rate constant of 0.693 week-1 and slow mineralizable organic N pool with a fixed rate constant of 0.051 week-1. By correlating model estimated organic N pool size and chemical extracted organic N amount, I found that the potentially mineralizable organic N size was closely correlated with hot (80 �C) water extractable organic N or 1 M NaOH hydrolysable organic N. By correlating model estimated organic N size and spectroscopic characteristics of water extractable organic matter, I found that the active mineralizable organic N pool was correlated with humification index in cold (22 �C) water extraction (R 2=0.89, p<0.05), which indicates that characterizing extracted organic matter was a useful tool to improve the estimation of soil organic N pools. In summary, potential mineralizable organic N in soils from subarctic Alaska can be estimated by hot water extractable organic matter or 1 M NaOH hydrolysable organic N, which accounted for 70% and 63% of the variation in potentially mineralizable organic N, respectively. This approach will provide fundamental insight for farmers to manage N fertilizer application in agricultural land and also provide some basic information for ecologists on predicting N release from Alaska soil that can be used for assessing the N impact on ecosystem.

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