Life Sciences Commons^™

The Effects Of Ericoid Inoculum Source And Nutrient Addition On Growth And Reproduction In Highbush Blueberry, Ilana Williams

Graduate College Dissertations and Theses

Ericoid mycorrhizal fungi (EMF) form symbiotic relationships with ericaceous plants such as Vaccinium corymbosum, or highbush blueberry and assist in nutrient acquisition. EMF help plants thrive in stressful environments by increasing the area in which roots can uptake water and nutrients. In plant-mycorrhizal symbioses, nutrient uptake may depend on the identity of the fungal partner. Therefore, differently sourced mycorrhizal fungi could show differences in nutrient uptake ability. Here, I hypothesized that inoculation of V. corymbosum with EMF would enhance plant growth and investment in reproduction, and that effect would be more pronounced for plants in low nutrient conditions. I also …

Forest Management In The Context Of Global Change: Impacts Of Disturbance, Adaptive Management, And Invasive Species On Northeastern Forests, Jennifer Santoro

Graduate College Dissertations and Theses

Climate change is predicted to have variable and uncertain effects on forested ecosystems globally. In the northeastern US, natural disturbances have historically been a central driver of forest successional dynamics, but as climate warming is projected to alter the frequency and severity of these events, post-disturbance management strategies to sustain biodiversity and ecosystem services must adaptively change to promote forest resilience. A suite of adaptive silvicultural actions has been proposed to promote forest resilience in the face of uncertainty, but due to the multi-decadal scale of forest management, initial field experiments are only beginning to show results. To address these …

Applications Of Bayesian Hierarchical Detection Models, Emily Beasley

Graduate College Dissertations and Theses

Bayesian hierarchical detection models are useful for addressing uncertainty in datasets in the form of detection error and can be adapted to a variety of research questions. This dissertation uses three case studies to highlight advantages of Bayesian hierarchical detection models: 1) using prior information to model undetected species, 2) efficiently modeling a naturally hierarchical system, and 3) correcting for observation bias in two interconnected ecological metrics for effective disease management.Detection error can bias ecological observations, especially when a species is never detected during sampling. In many communities, the probable identity of these species is known from previous research, but …

Paleolimnological Data Synthesis To Assess Long-Term Ecological Change In Vermont Lakes, Ismar Biberovic

Graduate College Dissertations and Theses

Lakes are excellent early indicators of environmental change on a landscape scale. Due to their connectedness in the landscape, any alteration of land-cover extends beyond a single watershed and can only be amplified by the effects of climate change. These processes can reflect differently across lakes of various characteristics, however, combined, they can leave a lasting impact on biogeochemical processes of a lake, resulting in profound effects on biological communities residing in it. Lake sediments are terrific archives that integrate and preserve this evidence, which then allows us to investigate the extent to which a lake has changed given its …

Short- And Long-Term Impacts Of Forest Management In Response To The Invasive Emerald Ash Borer In New England Forests, Hanusia Higgins

Graduate College Dissertations and Theses

As non-native forest pests disperse across the United States, the emerald ash borer, Agrilus planipennis (EAB), has emerged as one of the most costly and destructive invaders. In response to EAB, forest management practices, including pre-salvage logging, "phloem reduction" (large ash removal), and strategies to improve future ash regeneration, have been implemented to meet economic, ecological, cultural, and safety objectives. Although many studies have quantified the impacts of EAB on mortality of ash trees (Fraxinus spp.), less is known about the short- and long-term ecological impacts of forest management in response to this pest. In summer 2020, we measured forest …

Exploring Mycorrhizae In Riparian Restoration To Enhance Phosphorus Mitigation And Pollinator Habitat On Unceded Territory, Jessica Ann Rubin

Graduate College Dissertations and Theses

When land degradation imperils freshwater quality, land managers can restore ecosystem functions. The premise of three published/accepted thesis chapters is that mycorrhizae can enhance water quality function of riparian buffers and pollinator habitat through diverse, native polyculture associations.

Where water quality is threatened through excess phosphorus (P) loads from agriculture, riparian buffers are considered Best Management Practices (BMPs). They intercept agricultural nutrients before reaching waterways. However, their seasonal cycles, saturation capacity, and often degraded conditions limit their ability to protect water quality. In particular, riparian buffers can transition from sinks to sources of P when agricultural practices chronically contribute P, …

Elements Of Biocontrol Strategies For Pheretimoid Earthworms, Maryam Nouri-Aiin

Graduate College Dissertations and Theses

Jumping worms (Megascolecidae) in the pheretimoid complex, have raisedconsiderable environmental concerns with conservationists, ecologists, policy makers, and the public. Their impacts on North American forests and high density is distinct from earthworms in other families. Most of the infested forests are near horticultural settings. Practicable options to manage their dispersal into forests do not exist. This dissertation examines the potential of an entomopathogenic fungus to control them in horticulture. It also investigates major barriers to managing their spread and studying their ecology including species identification, phenology, and genetic diversity. First, to discover the best time to apply biocontrol agents, I …

Drought Tolerance In Native And Invasive Populations Of The Centaurea Jacea Hybrid Complex, Zoe Portlas

Graduate College Dissertations and Theses

Introduced plants face many ecological and evolutionary challenges when establishing in a new range, such as strong abiotic stressors and potentially novel selective environments. One such abiotic stress is water availability, which is a strong selective force shaping physiological and phenological traits that enable plants to tolerate or avoid drought stress. Despite the challenges of establishing in a new range, thousands of species have become invasive in recent centuries. Two hypotheses that may explain how a species is able to withstand stress in its introduced range are preadaptation, which posits that species are adapted to similar environments in their native …

A Global Understanding Of The Factors Facilitating Plant Invasions., R. Kirsten Tyler

Graduate College Dissertations and Theses

Globalization has resulted in the anthropogenic movement of plant species, many of which have established and become invasive in their secondary ranges. A fundamental goal in invasion ecology is to understand the factors that contribute to successful establishment and spread of invasive species on a global scale. Given the likelihood of a future with increased international connections leading to introductions of plant species, understanding why some species are successful invaders and which ecosystems are susceptible to invasion continues to be crucial to development of effective preventative policy and management strategies. Although there is a large body of literature on determinants …

Soil Invertebrates In Agriculture: Assessing Ecosystem Services, Biodiversity Impacts, And Farmer Perceptions, Eva Kinnebrew

Graduate College Dissertations and Theses

Harmonizing biological diversity and crop production is a major goal towards building more sustainable food systems. Soil invertebrates are diverse and abundant organisms in agriculture, but relatively little is known about their benefits or how agricultural management impacts them. In this dissertation, I dig into the complex interactions between agricultural land use and soil invertebrate biodiversity to better inform farmer decision-making. I find that soil invertebrate communities have major potential contributions to agroecosystems (Chapter 2) and are shaped heavily by agricultural land use (Chapters 3, 4), but remain too uncertain to contribute to farmers’ management choices (Chapter 5). First, I …

Diversity And Distribution Of The Malaria Parasites (Genus Plasmodium) Of The Common Loon (Gavia Immer) And Of Vermont Mosquitoes, Alyssa Neuhaus

Graduate College Dissertations and Theses

The emergence of infectious diseases has become an urgent concern for human and wildlife populations alike. Malaria parasites (genus Plasmodium), which are transmitted by mosquitoes, are major pathogenic disease agents in human and wildlife populations with numerous non-exclusive factors, including climate change and range shifts, acting to increase their threat. The malaria parasites that infect the Common Loon (Gavia immer) serve as an ideal system for studying emerging infectious disease threats with warming temperatures as the Common Loon is a northerly distributed, immunologically and evolutionary naïve species and of conservation concern across parts of its breeding range. I investigated the …

The Effect Of Amphibian Host Ecology And Evolution On The Pathogen Dynamics Of Ranavirus, Lauren V. Ash

Graduate College Dissertations and Theses

Emerging infectious diseases threaten amphibian species around the globe. Ranavirus (Family: Iridoviridae) is associated with the majority of amphibian deaths in North America, with some species exhibiting mass mortality events in short periods of time. In contrast, some amphibian species show the capacity to resist or tolerate infection. Resistant individuals exhibit reduced infection intensity, while tolerant individuals display reduced fitness effects given the infection intensity. My research focused on how amphibian host dynamics at community, population, and individual-level scales relate to the wide variation in Ranavirus prevalence and severity. Through my work, I documented the first reports of Ranavirus in …

Spiny Spiders And Spiny Trees: Molecular Phylogenetics And Biogeographic Reconstruction Reveal History Of Recurrent Overwater Dispersal Events, Single-Island Endemics, And New Species Of Caribbean Micrathena (Araneae: Araneidae), Lily Kay Shapiro

Graduate College Dissertations and Theses

Elucidating the processes responsible for the provenance of taxon biodiversity on islands can help us to understand macroevolutionary mechanics in addition to specific organismal histories. Current species distributions are a result of an admixture of both abiotic (i.e. geologic) and biotic (i.e. dispersal capability, speciation and extinction rates) factors. The heterogeneous tectonic histories and local ecological differentiation among islands within the Caribbean contribute to high levels of endemicity and diversity. Differential historical biogeographic processes, namely vicariance (physical separation of populations by barriers) or long-distance dispersal, represent hypotheses to explain current distributions of species on islands resulting from colonization followed by …

Investigating Routes Of Pollinator Exposure To Pesticides, Jessica Cole

Graduate College Dissertations and Theses

Pesticides are widely used in agriculture to minimize the negative impact of harmful pests. However, the use of pesticides also has non-target effects on beneficial insects such pollinators. In addition to the direct harm to pollinators foraging on crops during pesticide application, pesticides are also frequently utilized in non-agricultural settings, and can drift to non-target areas via the wind and water. Plants growing in such contaminated soils may absorb pesticides and express them in their flowers, specifically the pollen and nectar upon which pollinators rely. This is particularly important because encouraging wildflower growth alongside fields is a common strategy to …

Revealing The Direct And Indirect Effects Of Climate Change On Soil Nutrient Dynamics And Forage Resources In Mountain Ecosystems, Kenna Elizabeth Rewcastle

Graduate College Dissertations and Theses

Modern climate change is already altering the structure and function ofecosystems around the world in nontrivial ways. Mountain ecosystems in particular will continue to experience a greater magnitude and rate of climatic warming than the global average, threatening the stability of key ecosystem processes like nutrient cycling as well as the supply of benefits from ecosystem services provided by mountains. While significant advancements have been made to address the direct effects of rising temperatures on nutrient cycling dynamics, our understanding of the synergies between the direct effects of warming and the indirect effects of climate change, mediated by the response …

Changing Environmental Conditions And The Response And Potential Adaptability Of Freshwater Whitefishes, Taylor R. Stewart

Graduate College Dissertations and Theses

Changes in winter conditions, such as increased temperatures and decreased ice coverage, have been observed worldwide. The responses of many lake fish populations to changing winters are projected to be inadequate to counter the speed and magnitude of climate change. Such environmental changes have been hypothesized to explain the low recruitment observed in freshwater whitefishes (Salmonidae Coregoninae). My research focused on measuring the impact changing winter conditions may have on coregonine reproductive phenology and developmental and morphological traits to better predict changes in coregonine populations as a result of climate change.

I used experimental incubation methods and modeling to explore …

Phosphorus Dynamics In Restored Riparian Wetlands On Former Agricultural Land In Vermont, Adrian Robert Hendrick Wiegman

Graduate College Dissertations and Theses

Wetland restoration has numerous potential ecological and societal benefits, one of which is the retention of phosphorus (P) and consequent protection of downstream water bodies from eutrophication. Past studies focused on influents to and effluents from a variety of wetland types have documented net P retention. However, some wetland systems are less effective at P capture and wetland P retention capacity can change over time. Certain wetland types - especially riparian wetlands restored on former agricultural land - remain understudied. In Vermont, most of the over 4000 potential wetland restoration sites in the Lake Champlain Basin are located on current …

Copepods As A Model System For Exploring The Impacts Of Climate Change On Marine Ectotherms, Lauren Ashlock

Graduate College Dissertations and Theses

Marine ecosystems provide essential habitat to ecologically and economically impactful species and provide humans with a wealth of ecosystem services. With climate change, marine ecosystems are increasing in mean temperature and temperature variability. Marine ectotherms are vulnerable to this change and are important sentinels of warming, as their internal physiology is dependent on the external thermal environment.

Copepods are marine ectotherms that play a critical role in trophic transfer and nutrient cycling. Importantly, copepods are relatively short-lived, allowing them to track ocean change as it happens. Together, these qualities make copepods a reliable model for understanding the impacts of global …

Effects Of Changing Winter Severity On Plankton Ecology In Temperate Lakes, Allison Rose Hrycik

Graduate College Dissertations and Theses

Climate change has rapidly altered winter conditions in temperate regions of the globe. Over the last several decades, snowpack has decreased, spring snowmelt is earlier, and ice cover has declined. Associated changes in lake mixing, inflow, nutrient cycling, and light transmission during winter can affect lake biota both under ice and into the open-water season. Unfortunately, under-ice lake research is limited compared to open-water research. Recent winter limnology research, however, suggests that ecosystem processes do not stop under ice, and many questions remain about the drivers of phytoplankton and zooplankton dynamics in winter. My research aimed to uncover mechanisms by …

Sarracenia Purpurea As A Model System For Aquatic Ecosystem State Changes And Their Impact On Bacterial Communities, Amanda Claire Northrop

Graduate College Dissertations and Theses

Aquatic ecosystems can undergo abrupt and long-lasting transitions from one state to another, often with negative ecological and economic consequences. With anthropogenic enrichment, aquatic ecosystems such as lakes and ponds may shift rapidly from an oligotrophic, clear water state to a eutrophic, turbid state. These shifts, or state changes, generally occur due to a phenomenon called hysteresis in which the relationship between a driving variable and ecosystem variable depend on the current state of the ecosystem. Such dynamics often make recovery difficult or impossible. Though state changes in aquatic ecosystems have been studied extensively since the 1970s, there have been …

Spillover, Dilution, And Coinfection: Understanding The Spread Of Disease Within Managed And Native Bee Communities., Phillip A. Burnham

Graduate College Dissertations and Theses

Maintaining healthy pollinator communities is vital both for ensuring food securityand ecological diversity. However, managed honeybees and wild bee communities are under threat from an array of stressors including habitat loss, global change, pesticide use, poor beekeeping, and various pests and pathogens. Pathogens have been shown to be spilling over from managed bees into wild bee populations and are known to adversely affect colony function as well as increase mortality. Understanding transmission mechanisms related to general dynamics in this system will not only benefit pollinator health, but also gives us insight into important and understudied topics in disease ecology. In …

Assessing Chemical And Biological Recovery From Acid Rain Deposition In Montane Vermont Lakes, Sydney Diamond

Graduate College Dissertations and Theses

Vermont’s inland lakes are changing rapidly in response to anthropogenic disturbance pressures. While changes in water chemistry are well documented across the state, the biological response of primary producer communities to these shifts remains poorly understood. This project investigated the response of phytoplankton communities to the interacting effects of recovery from acidification and climate change in high-altitude lakes. We analyzed long-term monitoring and meteorological data in four of Vermont’s acid-impaired lakes and found that as pH and acid-neutralizing capacity has increased, so have concentrations of dissolved organic carbon (DOC) in most lakes. To assess the biological response to these processes, …

The Role Of Higher Education In Intergenerational Mobility, Amanda Davis Simpfenderfer

Graduate College Dissertations and Theses

Within the US, higher education is viewed as a stepping stone to economic and social mobility, where the promise of improved socioeconomic outcomes continues to draw many students to enroll despite the increasing cost of attendance (National Center for Education Statistics, 2019). The implicit (and sometimes even explicit) promise is that a post-secondary degree is a pathway to upward mobility for all individuals. Yet, higher education is not a monolith, nor are the students attending a homogenous population. Students experience differential outcomes based on their demographics (Baum et al., 2013), as well as institutional type (Thompson, 2019). The purpose of …

Forest Development And Regeneration Dynamics In The Context Of Global Change And Associated Adaptation Strategies, Peter Clark

Graduate College Dissertations and Theses

Over the past century, forested ecosystems in northeastern North America have undergone significant changes characterized by the recovery from intensive land use and impacts from the introduction of invasive insects and disease. These changes, coupled with emerging threats posed by a changing climate present challenges to the maintenance and conservation of biodiversity, ecological functions, and delivery of critical forest ecosystem services. While management strategies to increase forest resilience and mitigate impacts from climate change have been broadly proposed, there are nascent empirical evaluations of their effectiveness. To address this uncertainty, this dissertation couples field manipulations with long-term measurements to examine …

Pacific Northwest To New England: Exploring The Intersections Of Invasive Ecology, Forest Management, And Alternative Energy, Alexandra N. Neidermeier

Graduate College Dissertations and Theses

Invasive species exact important ecologic, economic, and cultural tolls in forests. This research focused on the intersections of invasive ecology, forest management, and a forest commodity. Invasive ecology was explored through an assessment of two potential biological control agents of hemlock woolly adelgid. The two species of silver fly (Leucopis spp.) from the Pacific Northwest were first examined for temporal resource partitioning patterns. The niches of these species were then examined spatially by developing a species distribution model. Leucopis spp. exhibited sinusoidal patterns of daily emergence when examined over a 29-day period, with peak daily abundances that were inversely related. …

The Environmental Microbiome In A Changing World: Microbial Processes And Biogeochemistry, Stephanie Juice

Graduate College Dissertations and Theses

Climate change can alter ecosystem processes and organismal phenology through both long-term, gradual changes and alteration of disturbance regimes. Because microbes mediate decomposition, and therefore the initial stages of nutrient cycling, soil biogeochemical responses to climate change will be driven by microbial responses to changes in temperature, precipitation, and pulsed climatic events. Improving projections of soil ecological and biogeochemical responses to climate change effects therefore requires greater knowledge of microbial contributions to decomposition. This dissertation examines soil microbial and biogeochemical responses to the long-term and punctuated effects of climate change, as well as improvement to decomposition models following addition of …

Consumption Of Microplastics Impacts The Growth And Fecal Properties Of The Marine Copepod, Acartia Tonsa, Emily Ann Shore

Graduate College Dissertations and Theses

Microplastics (mm) are ubiquitous in the global environment and are increasingly recognized as a biological hazard, particularly in the oceans. Due to the small and pervasive nature of these particles, zooplankton have been known to consume and egest microplastics. Though zooplankton play critical roles in marine food webs and in carbon storage through carbon rich fecal pellets, we know little about the effects of microplastics on early life stage growth, reproductive output, and carbon storage. Here, I investigated the effects of ingestion of low-density Polystyrene beads (5 µm) by the copepod Acartia tonsa on (1) early life stage (naupliar) growth, …

Effects Of Ericoid Mycorrhizal Fungi On Reproductive Traits In Vaccinium Corymbosum, Erin O'Neill

Graduate College Dissertations and Theses

Most angiosperms rely on animal pollination to reproduce and the majority of these also interact with mycorrhizal fungi. Although these interactions have been studied separately, few studies have examined their combined effects on host plants. Linking above and belowground interactions has become an exciting new field of study.

Ericoid mycorrhizae (ericoids) are the relationship between certain taxa of fungi and plants in the Ericaceae, including Vaccinium corymbosum, the highbush blueberry. Here, I asked whether inoculation with ericoid mycorrhizal fungi altered resource allocation to floral buds and flowers of V. corymbosum. Different fungi may vary in their ability to assist their …

Mitigating Gaseous Nitrogen And Carbon Losses From Northeastern Agricultural Soils Via Alternative Soil Management Practices, Kyle Michael Dittmer

Graduate College Dissertations and Theses

Traditional agricultural practices often result in gaseous losses of nitrous oxide (N2O), ammonia (NH3), and carbon dioxide (CO2), representing a net loss of nutrients from agricultural soils, which negatively impacts crop yield and requires farmers to increase nutrient inputs. By adopting best management practices (BMPs; i.e., no-tillage, cover crops, sub-surface manure application, and proper manure application timing), there is great potential to reduce these losses. Because N2O and CO2 are also greenhouse gases (GHGs), climate change mitigation via BMP adoption and emissions reductions would be an important co-benefit. However, adopting a no-tillage and cover cropping system has had setbacks within …

From Maintenance To Stewardship: Green Stormwater Infrastructure Capacity In Vermont Towns & Design And Participatory Processes To Provide Cultural Ecosystem Services, Holly Lee Greenleaf

Graduate College Dissertations and Theses

The impervious surfaces of built landscapes create stormwater runoff that causes water quantity and quality problems downstream, upsetting natural hydrology and harming aquatic ecosystems. Green stormwater infrastructure (GSI) includes practices that reduce the amount of stormwater runoff and the pollutants it carries utilizing plants, soils, and other materials to capture, store, reuse, infiltrate, evapotranspire, and filter stormwater. GSI helps to restore developed landscapes, mimicking natural hydrologic processes and providing important water treatment functions as well as beneficial green spaces in urban areas. However, there are many challenges associated with the implementation and maintenance of GSI in our communities and cultures. …