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Harnessing leaf optical properties to assess plant traits, genetics and environmental interactions
No full textPlant trait expression is at the core of ecosystem functioning. Plants produce sources of bioavailable energy, influence nutrient cycling, modulate energy flow, and impact decomposition which has immense impacts on local, regional, and global processes. As climate change intensifies, identifying which plant traits are adaptive in particular environments is imperative for making effective land management decisions. Global climate patterns are predicted to become more extreme and as a result, plant phenotypes which were once adaptive in certain environments may become maladaptive. Developing high throughput phenotyping strategies which can efficiently and cost-effectively survey these dynamics across geographic scales remains an area of high interest to researchers and land managers alike. Hyperspectral technology is one of the most promising avenues for accomplishing this task. We focus on two foundation species, Fremont cottonwood (Populus fremontii), narrowleaf cottonwood (P. angustifolia) and their hybrid (P. × hinckleyana) which have been shown to support diverse communities and regulate ecosystem processes. These obligate riparian species and their associated communities are under increased threat due to aridification, rising temperatures and anthropogenic water resource use. We collected ground-based hyperspectral leaf reflectance from wild and experimental trees across a steep elevational gradient and integrated molecular, morphological, biochemical, and environmental data to test the limits of using leaf spectra to predict ecologically important traits in the wild and climatically dissimilar areas. We addressed three major topics. First, to understand whether leaf spectra vary between genotypes and populations in different environments, we analyzed samples from wild Fremont cottonwood at home sites as well as reciprocally planted clones from three common gardens planted at low, mid, and high elevation sites. Classification models showed that leaf spectra from the visible, near infrared and shortwave infrared wavelengths (500 nm – 2400 nm) possess sufficient variation to correctly predict genotype, population, and environment identity. Our findings also suggest that leaf spectral phenotypes display plasticity in some spectral regions when introduced to novel environments.
Second, we assessed whether leaf reflectance can be used to predict leaf biochemical, morphological and tree architectural traits from reciprocally planted cottonwood clones grown in different environments. We conducted partial least squares analyses to identify which traits and spectral regions are important for predictive modeling. We found that 1) wet leaf reflectance can predict leaf morphological and biochemical traits across common gardens, but not tree architecture, 2) the importance of wavelengths for predictive models varies by trait, and 3) leaf spectra are better predictors of population and environment identity than some traditional leaf traits. Our findings suggest that some (but not all) ecologically important leaf traits may be detectable at the canopy level across climatically different environments.
Third, hybrid vigor has been hypothesized to confer a potential advantage for individuals in the face of climate change. As such, monitoring functional trait differences in hybrid systems as well as range expansion or contraction using remote sensing is of particular interest. To determine whether genetic and morphological differences may be detectible between canopies, we surveyed the spectra of fresh leaves from common garden trees of known ancestral identity. We predicted that 1) Fremont and narrowleaf spectra would be distinguishable and 2) leaf spectra could discriminate hybrids from parental species. Partial least squares discriminant analyses using leaf reflectance as a function of Fremont molecular markers as well as tree identity and leaf morphological traits supported these hypotheses. Our findings suggest that leaf reflectance and foliar trait differences between parental and hybrid cottonwood may be detectable at the canopy level and could be tractable for determining whether hybrid swarms are expanding into parental territory or contracting as global temperatures increase.
The goal of this dissertation was to assess how leaf optical properties can inform conservation and land management practices as well as the ecology and evolution of plant traits in different environmental scenarios. Our exploration into the various scales and facets of this topic provides a proof-of-concept for integrating cottonwood foliar spectra into a diverse range of applications. Based on our findings, we posit that leaf spectra are useful for exploring gene-by-environment interactions and phenotypic variation at the genotype, population, and interspecies levels across multiple geographic and climatic scales
Climate, genetics, and river flow interact to shape riparian plant community structure
Get PDFRiparian plant communities are shaped by hierarchical, interacting factors ranging from climate and river flows to plant traits shaped by genetics and the environment. As increasing temperatures, water use, and river regulation change the conditions that control riparian plant establishment, growth, and survival, a deeper understanding of the interactions between landscape-level environmental pressures and plant-level responses are needed to protect and conserve riparian areas. In this dissertation, I examine interactions among factors driving riparian plant communities at three different scales, using the Colorado River between Glen Canyon Dam and Lake Mead as the study area. In Chapter 1, I introduce the concepts behind riparian plant genetic patterns, potential links between climate adaptation and inundation response, and how river regulation and increasing temperatures could differentially impact riparian species. In Chapter 2, I use simple sequence repeat markers to examine how geography and life history are related to riparian plant population genetics in a restoration context. Here, I show that patterns of genetic variation differ across species and are related to river connectivity, mating system, clonality, and seed dispersal. In Chapter 3, I evaluate how phenotypic variability in growth and resource acquisition characteristics are related to genotype, provenance, and inundation depth using a controlled greenhouse experiment and a clonal, riparian shrub, Pluchea sericea. I show that growth characteristics are more closely related to inundation, while resource acquisition characteristics are more closely related to genotype. In Chapter 4, I examine plant responses to 12 climate, hydrology, and topographic variables and their interactions with site-specific mean annual temperature. I analyze data from a large, 5-year riparian vegetation monitoring dataset, with a focus on eight species representing four functional groups and a variety of hydrological preferences. Analyses were conducted using a Bayesian model structure that simultaneously evaluates plant species absence and cover in the same framework and adjusts for false absences associated with observer error. These results indicate that absence and cover differ in their environmental correlates, hydropower derived flows have unique impacts on riparian plants separate from other hydrological variables, and higher air temperature mediates plant responses to other environmental variables. In Chapter 5, I discuss how conclusions from these studies raise new questions and illustrate connections across multiple drivers of riparian plant responses. Taken together, these studies emphasize the need for comparing multiple riparian species responses to make informed management decisions. Additionally, they show the utility of incorporating plant genetics, river flow, and climate into understanding riparian plant responses
Plasticity in leaf hydraulic architecture varies among genotypes and populations of Populus fremontii
Get PDFClimate means, extremes, and variability are shifting rapidly, which will continue to result in mismatches between climate and locally adapted plant traits. Phenotypic plasticity, the ability of a plant to respond to environmental conditions within a lifetime (e.g., by adjusting the traits of leaves they make each year), may provide a buffer for plants to persist under rapid environmental change. We used three common gardens situated across a temperature gradient to investigate phenotypic plasticity in six populations of Fremont cottonwood (Populus fremontii), an important riparian tree, collected from across a naturally occurring temperature gradient. We focused on the plasticity of leaf venation, a multivariate trait that is linked to plant performance and tolerance of environmental stress. We found that 1) Populations responded differently to a hotter growing environment, with some increasing and some decreasing the density of their leaf venation; 2) Within populations, vein density also differed among genotypes in the hottest growing environment; 3) Locally adapted southern populations trended toward greater vein density and higher growth in the hottest growing environment compared to northern populations. Past studies indicate that high vein density is associated with a suite of characteristics that are likely to support survival in hotter and drier climates (i.e., high leaf hydraulic conductance, high stomatal density, and drought resistance). Results from this study suggest that different P. fremontii populations will vary in their capacity to adjust their leaf venation and support growth in hot environments. Survivorship modeling efforts, restoration project managers, and assisted migration initiatives should consider genetic stock, growing conditions, and multiple dimensions of environmental stress early in the research and planning process to improve predictions and enhance restoration outcomes
The influence of positive behavior interventions on school culture
No full textThe purpose of this study was to determine the influence of positive behavior interventions and supports (PBIS) on school culture at the high school level. PBIS is a three-tiered framework that several schools and organizations use to focus on the positive behavior outcomes over the negative behavior outcomes. Additionally, the effectiveness of the program on school culture is described through a qualitative transcendental phenomenological study.Participants included two administrator and five teacher participants from the study site. The design of this study was a transcendental phenomenology with a focus on qualitative data that was collected, analyzed, and summarized. Additional information was collected from existing archives of student discipline referral records.
Research Question 1 addressed how the use of the PBIS program influences the culture of the school from teachers’ perceptions. Teachers emphasized that the PBIS framework must be implemented with fidelity in order to have a positive effect on the culture of the school. Additionally, they expressed the need for administrators to create buy-in and model the framework for all stakeholders. Overall, the teachers expressed there were only small changes in the culture due to the lack of administrative support and inconsistencies of implementation across campus.
Research Question 2 addressed how the use of the PBIS framework influences the school culture from the administrators’ perception. Administrators stressed the importance of implementing the PBIS framework through the creation of teacher buy-in and administrative initiative. Overall, administrators saw small shifts toward a positive school culture. School data were analyzed by the administrators that measured a decrease in discipline referrals. They also expressed experiencing more interactive relationships between staff and students due to the tangible rewards system associated with the practices of the PBIS framework.
Research Question 3 addressed how the role of administrators influenced the use of PBIS from administrators’ perspective. Administrators emphasized their role was to create teacher buy-in through administrative initiatives and modeling the framework of PBIS. Additionally, they are responsible for identifying the wanted behaviors to ensure all stakeholders understand the expectations.
Research Question 4 addressed how the administrators influence the PBIS framework from the teachers’ perceptions. Teachers emphasized the need for administrative initiative to create teacher buy-in. Additionally, teachers stated that it was the role of the administrator to model the framework of PBIS and that they are responsible for identifying the wanted behaviors to ensure all stakeholders understand the expectations.
Research Question 5 identified the measurements used to determine the success of the PBIS program. These quantitative data were collected from an administrative participant. The data displayed a small decrease in discipline referrals over a three-year period; however, no conclusions could be drawn due to the insufficiency of the data
The application of coercive control theory to youth sex trafficking
No full textThis thesis project investigates the relational aspect of YST victimization and the applicability of the theory of coercive control to YST. It explores the relative similarities between YST experiences and intimate partner violence (IPV) relationships. In pursuit of greater understanding, I reviewed existing literature in the field with a sharpened focus on concepts of vulnerability, agency, social inequality, and coercive control. Utilizing a qualitative methodological approach, I interviewed nine service providers who directly interact with youth who have experienced sex trafficking. Following interviews with service providers, I employed reflexive thematic analysis to extract relevant and meaningful themes from the interview data including but not limited to: 1) coercive control in YST, 2) coercive control influencing the initiation and retention of YST victimized youth, and 3) service providers’ conceptualization of vulnerability and agency among youth in YST situations. Parallels are drawn between YST and IPV according to relationality, barriers to exit, and abuse minimization. In the conclusion, implications of this project for policy focus on improvement in the areas of race, class, and gender inequality, as well as the redistribution of resources, the breakdown of stereotypes, and the restructuring of traditional social expectations nationwide
Latcrit theory online education Latinx students and community college success
No full textThe purpose of this study was to analyze Latinx student success in online education and how culturally responsive pedagogy (CRP) contributes to removing barriers for success. CRP has proven to be successful in small scale studies in K-12 sector. This study analyzed how CRP can be effective in higher education and if applied to online education how it can affect success. Participants of my study included six students all of Latinx backgrounds who have taken a fully online course in a community college setting within the last year. I had three female and three male participants that were of traditional and non-traditional age. The design of this study is qualitative founded on LatCrit theory. I used critical narrative inquiry as my methodology. I setup interviews with my participants and used critical reflection to deconstruct the stories told about their online educational experiences.
Research questions that were addressed is in listening to the critical narratives of the students and how did those narratives relate to culturally responsive pedagogy. What resources and support do Latinx students need to be successful in online education and lastly what barriers are inhibiting students of Latinx backgrounds to be successful in online education at a community college? These research questions were the basis of this study to gain clarity into Latinx academic success and how to eliminate barriers to that success with a focus in online education
Ticks, tortoises and tick-borne relapsing fever in Mojave desert tortoise habitat
No full textArgasid ticks, Ornithodoros parkeri and O. turicata occur throughout the Mojave Desert and are frequently observed on Mojave desert tortoises (Gopherus agassizii; hereafter referred to as desert tortoise). These ticks harbor and transmit tick-borne relapsing fever (TBRF) group Borrelia, resulting in TBRF in people. Tick-borne relapsing fever group Borrelia is endemic in the western U.S.; however, it is typically associated with the bite of an infected O. hermsi tick found in habitats at high elevations (above 1500 feet). This dissertation examines the relationship between O. parkeri and O. turicata, the TBRF group Borrelia species they carry, and their common host, the desert tortoise in Mojave desert tortoise habitat.Chapter two of this dissertation described the first documented cases of TBRF in people associated with Ornithodoros ticks in the Mojave Desert. This case report described TBRF contracted by two tortoise biologists exposed to Ornithodoros ticks when excavating desert tortoise burrows in Clark County, Nevada. A blood sample from one of the cases was able to be sequenced to Borrelia turicatae, a TBRF group Borrelia carried by the tick O. turicata. This chapter emphasized the risk of TBRF for individuals, such as biologists working in Mojave desert tortoise habitat, desert tortoise pet owners, or anyone that interacts with desert tortoises and their burrows where Ornithodoros ticks are commonly encountered.
Despite the risk of contracting TBRF group Borrelia in Mojave desert tortoise habitat, limited research exists examining the relationships between O. parkeri and O. turicata and the desert tortoise. Chapter 3 of this dissertation examined this relationship using data collected from desert tortoise health assessments. As a threatened species, desert tortoise populations are monitored per U.S. Fish and Wildlife Services regulations and the health of individual tortoises is routinely assessed. Presence and abundance of ticks as well as clinical signs of disease and other morphometrics are collected for these health assessments. This chapter analyzed tick presence on desert tortoise health assessments as a function of season, location, sex, foraging behavior and evidence of clinical signs of disease. Ticks were more likely to be present on adult tortoises than juveniles and on captive tortoises versus wild tortoises. Ticks were also more likely to be observed on tortoises with observed clinical signs of disease and on tortoises without evidence of foraging. This analysis provided insight into the biology of ticks in relation to desert tortoises that may be useful for management of threatened tortoise populations where large tick infestations are detected and emphasized the risk of encountering ticks in tortoise burrows.
Notably, no information regarding pathogen prevalence or tick species was collected for these health assessments; chapter four discussed pathogen prevalence and tick species of ticks collected throughout Mojave desert tortoise habitat. Collected ticks were identified to species using morphological characteristics and DNA sequencing. All ticks were also tested for pathogens. A total of 1,165 ticks were collected and identified as O. parkeri and O. turicata. One Otobius megnini was found in a desert tortoise burrow. Twenty-two ticks of the 1,165 tested positive for TBRF group Borrelia, five had enough bacterial DNA to be sequenced to B. turicatae. This study was the largest tick surveillance study conducted in the Mojave Desert and shed light on distributions of tick species and pathogens in Mojave desert tortoise habitat. Research from chapter four determined a low prevalence of TBRF group Borrelia in collected ticks (1.88%, CI = 1.07-3.27); chapter five examined potential borreliacidal (Borrelia killing) components of desert tortoise plasma that may contribute to this low pathogen prevalence in ticks.
Limited research exists on relationships between TBRF group Borrelia and desert tortoises. However, studies of relationships between ticks, other Borrelia spp., and reptile hosts such as lizards, suggest that reptiles are incompetent reservoirs of Borrelia spp. Reptile hosts may reduce the prevalence of Borrelia infections in ticks where reptile hosts are common. For example, in the western US, where there is a high abundance of lizards with documented borreliacidal components in their blood, there is a low prevalence of Borrelia infected nymphal ticks. As noted, the prevalence of TBRF group Borrelia is low in ticks collected in desert tortoise habitat. A simple bactericidal killing assay was used in chapter 5 to determine if desert tortoises have a borreliacidal component in their blood. Results from chapter five showed that TBRF group Borrelia spirochetes do not survive in desert tortoise plasma, suggesting that desert tortoises may have a borreliacidal factor in their blood. The immunological mechanism is yet to be determined, but this borreliacidal factor would help maintain low pathogen prevalence in ticks collected in Mojave desert tortoise habitat.
This dissertation helped close gaps of knowledge in regard to ticks, tick-borne zoonotic disease and desert tortoises in Mojave desert tortoise habitat. This research included the first documented human cases of TBRF in relation to Ornithodoros ticks in desert tortoise habitat, relationships between Ornithdoros ticks and desert tortoises, tick species and pathogen prevalence in a large sample size of ticks collected throughout the Mojave Desert and a potential borreliacidal component in desert tortoises. Although there is much to learn about the relationships between ticks, the pathogens they carry and desert tortoises, work from this dissertation has provided valuable insights into an understudied disease dynamic with likely relevance to disease ecology of wildlife and human infections
Balancing act: entrepreneurial mindset of women leading higher education through the enterprise model
Get PDFThe purpose of this research study was to describe and develop an understanding of how female leaders lead in the current and transitional landscape of higher education, how they perceive and have utilized an entrepreneurial mindset and leadership characteristics, and how they have worked to achieve a delicate balance between feminine and masculine leadership attributes that they authentically have. Participants included female community college leaders who had served for more than two years in a senior-level position. The design of the study was a descriptive case study with a focus on qualitative data that was collected, analyzed, and summarized.
Research question 1 sought to understand the perceptions of female leaders regarding the identified characteristics and traits of an entrepreneurial mindset leader. The participants shared that when they were presented with the developed list of entrepreneurial mindset leadership characteristics, they appreciated the combining of the harder leadership skills with the softer side of being a leader. When asked about the gender association with the entrepreneurial mindset leadership characteristics, there were a variety of viewpoints. Overall, most participants indicated that they either felt or truly saw that these characteristics were gender neutral and that any leader could use them effectively.
Research question 2 asked how the identified characteristics and traits of an entrepreneurial mindset leader have been influential to female community college leaders in their advancement in higher education leadership. Participants shared how the entrepreneurial mindset leadership characteristics have been received and overall the reception was positive. Participants indicated that they were inspired by both men and women using the entrepreneurial mindset leadership characteristics. Female leaders were inspiriting in traits of collaboration, questioning with data, resiliency and continual learning, and confident yet humble, while male leaders inspired more innovative risk taking and focused strategic vision. When asked about the phenomenon of a double-bind, the majority of participants indicated that they had either experienced that phenomenon personally or they had observed other female leaders caught in this dilemma. It was clear that this does occur and women have to find ways to balance agentic leadership characteristics while still behaving like woman
Tracking herbivory from space: a multi-scale remote sensing approach to mapping vegetation biomass and assessing impacts of caribou on vegetation
No full textArctic and boreal ecosystems are warming over three times faster than the rest of the planet. This warming has contributed to significant changes in vegetation community structure and function over the past half century. Changes in vegetation have downstream impacts – affecting nutrient cycling, fire regimes, climate feedbacks and wildlife. Wildlife are acutely affected through alteration of habitat and forage quantity and quality. However, animals also impact vegetation through grazing and trampling. Therefore, they influence the trajectory of vegetation change in Arctic/boreal environments, and play a large role in determining ecosystem responses to climate change. Thus, it is crucial to monitor changes in vegetation across large spatiotemporal scales, especially as they relate to fluctuations in animal populations. Vegetation does not respond uniformly to warming or herbivory, nor does it respond only in two dimensions. Therefore, comprehensive understanding of vegetation change requires monitoring that 1) is parsed by ecologically meaningful taxonomic groups, and 2) incorporates a third dimension e.g. height or biomass. We mapped a 35-year time series of plant functional type aboveground biomass (AGBPFT) across Alaska and northwest Canada at 30m resolution using a multi-scale approach that incorporated field harvest data, unmanned aerial vehicle (UAV) imagery and Landsat seasonal spectral composites. Using a similar product, we assessed the impacts of a growing migratory caribou herd on changes in PFT top cover. We found incorporating UAV imagery improved AGB estimates for some PFTs (deciduous shrubs), but not others. Our AGBPFT maps reveal widespread increases in deciduous (37%) and evergreen shrub (7%) biomass, and decreases in graminoid (14%) and lichen (13%) biomass from 1985-2020. Fire was an important driver of changes in the study area, with the largest changes in biomass associated with historic fire perimeters. We did not find evidence that caribou herbivory stymied Arctic shrub expansion, as deciduous shrub cover increased even in areas with high caribou spatial density. However, we found faster rates of graminoid and lichen decline where caribou spatial density was highest. This suggests increasing caribou populations might lead to density-dependent forage reduction across critical habitat. Our results illustrate the driving trends in vegetation change occurring across the Arctic/boreal region and show that climate-induced shifts in vegetation may be influenced by caribou-plant interactions across the circumpolar region
A case study exploring perceptions of stakeholders in a multidisciplinary school-based health center
No full textThe purpose of this descriptive qualitative single case study was to determine how key stakeholders of a school-based health center (SBHC) partnership between a medical university, school district, nonprofit charitable organization, and federally qualified health center (FQHC) define and perceive the functionality and effectiveness of the school-based health center on student outcomes and community buy-in to medical services on a school campus. This research aimed to provide school leaders with ways to ensure successful implementation, development, and sustainability of an SBHC through the collaborative efforts of myriad stakeholders comprising a multidisciplinary team.Participants of the study included the medical director, the chief executive officer of the nonprofit charitable organization, the school board president, a school principal, four classroom teachers, the school nurse, an office manager, a family support specialist, and an instructional assistant. The design of this study was qualitative. Additional information was collected from existing memorandums of understanding (MOUs) and researcher fieldnotes.
Research Question 1 addressed how significant stakeholders in SBHC implementation narrate their experiences with establishing contracts in the process of SBHC development. Institutional reform efforts were driven by systems thinking and political considerations through collective interest in organizational, community change efforts.
Research Question 2 asked about the perceived strengths and weaknesses of a medical university SBHC regarding their family communication and community buy-in processes. Strengths included the holistic benefit to staff, students, and community, yet growth needs were identified in awareness, intersectional influence, and accessibility.
Research Question 3 asked how a medical university SBHC influenced the organizational structure of a school. Adaptations within the school district were fostered through the explicit parameters of the memorandums of understanding, yet trust, buy-in, and acceptance of the SBHC clinic were partially secured through preexisting charitable and community engagement structures in the school community, through which the incorporation of an SBHC grew a furthered complement to the mission of a holistic social enterprise.
Research question 4 asked how SBHC stakeholders create intersectional systemic collaboration. Requisite of collaboration, distributed leadership conditions and structures were necessary to enact an MOU between a medical university, a nonprofit charitable organization, an FQHC, and many other departments within a school district in order for stakeholders to understand and be involved.
Research question 5 focused on how a school principal contributes to the successful launch and implementation of an SBHC. Principal leadership is required for shared accountability and distributed leadership practices, which hinges upon preexisting leadership change efforts in the school community.
Overall, the data presented consistent themes of the crucial role of informal leadership within a distributed leadership multidisciplinary change movement, with the school nurse and classroom teachers leading the sustainability, community buy-in, and organizational trust of families receiving medical care on a school campus