Life Sciences Commons^™

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 …

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 …

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 …

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 …

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 …

Evaluating Climate And Environmental Drivers Of Tree Species’ Growth Within The Northern Forest, Rebecca Stern

Graduate College Dissertations and Theses

Northeastern forests are in a period of immense change. While forests are inherently dynamic ecosystems, a range of environmental challenges may cause unique and uncertain transformations within forests moving forward. How trees in northern forests respond to these environmental and anthropogenic changes remains uncertain; reductions and increases in the growth of various species and shifts in current species’ ranges may take place.

I analyzed associations between tree growth (assessed using xylem increment cores) and a range of site, climate, and pollution deposition variables for seven major tree species in Vermont. First, I looked at red oak (Quercus rubra L.), a …

Nutritional Ecology Of Aphaenogaster Ants In Response To Climate Change, Katie A. Miller

Graduate College Dissertations and Theses

Climate change is predicted to impact organismal nutritional ecology. Increased temperatures can directly accelerate physiological rate processes, which in turn, impact nutritional requirements. Climate change can also impact organisms indirectly by altering the quality and quantity of nutritional resources, creating the potential for nutritional mismatch between what nutrients are available in the environment and what organisms require. Investigation of organismal stoichiometry, particularly the balance of carbon, nitrogen, and phosphorus content of organisms, can help illuminate the extent to which changes in climate may impact organism nutritional ecology. Ants represent an excellent system to examine stoichiometry because they occur across a …

Remote Sensing Methods And Applications For Detecting Change In Forest Ecosystems, David James Gudex-Cross

Graduate College Dissertations and Theses

Forest ecosystems are being altered by climate change, invasive species, and additional stressors. Our ability to detect these changes and quantify their impacts relies on detailed data across spatial and temporal scales. This dissertation expands the ecological utility of long-term satellite imagery by developing high quality forest mapping products and examining spatiotemporal changes in tree species abundance and phenology across the northeastern United States (US; the ‘Northeast’).

Species/genus-level forest composition maps were developed by integrating field data and Landsat images to model abundance at a sub-pixel scale. These abundance maps were then used to 1) produce a more detailed, accurate …

Quantifying Tree Response To Alterations In Pollution Deposition And Climate Change In The Northeastern Us, Alexandra M. Kosiba

Graduate College Dissertations and Theses

Understanding tree physiological responses to climate change is critical for quantifying forest carbon, predicting species' range change, and forecasting growth trajectories. Continued increases in temperature could push trees into conditions to which they are ill adapted -- such as decreased depth of winter snow cover, altered water regimes, and a lengthened effective growing season. A complicating factor is that in the northeastern United States, climate change is occurring on a backdrop of acid deposition and land-use change. In this dissertation, I used three studies to investigate the spatiotemporal nuances of resultant tree and sapling physiology to environmental change.

First, I …

The Impacts Of Multiple Anthropogenic Disturbances On The Montane Forests Of The Green Mountains, Vermont, Usa, Carolyn Ann Pucko

Graduate College Dissertations and Theses

How and why species’ ranges shift has long been a focus of ecology but is now becoming increasingly important given the current rate of climatic and environmental change. In response to global warming, species will need to migrate northward or upward to stay within their climatic tolerances. The ability of species to migrate will determine their fate and affect the community compositions of the future. However, to more accurately predict the future extent of species, we must identify and understand their responses to past and current climatic and environmental changes. The first place change is expected to occur is within …