Digital Commons Network^™

Drivers Of Decadal Vegetation Change In Northern Alaska, Jacob Allen Harris

Masters Theses

The Arctic is experiencing rapid climate change. This research documents vegetation change near Atqasuk and Utqiaġvik, Alaska. At each location, 30 plots distributed in a matrix across the landscape, were sampled annually from 2010 to 2019 using a point frame. For every encounter we recorded the height and classified it into eight broad functional groups (deciduous shrubs, evergreen shrubs, forbs, graminoids, bryophytes, lichens, litter and standing dead vegetation); for vascular plants we also identified the species. We found a consistent increase in plant stature and cover over time which was dramatic at Atqasuk. Graminoid cover and height increased at both …

Habitat Use Of The Climate-Sensitive Snowshoe Hare (Lepus Americanus) In The Manistee National Forest In Michigan’S Lower Peninsula, Spencer D. West

Masters Theses

Snowshoe hares (Lepus americanus) are a wide-ranging lagomorph that are important forest herbivores and a popular game species throughout their range. Across the southern boundary of their geographic range, snowshoe hares are experiencing population declines and possible extirpation due to increased predation pressure driven by climate change induced camouflage mismatch, competition for forage, degraded and fragmented habitat. One method of reversing the negative trends in snowshoe hare distribution is to increase and improve available hare habitat. A specific habitat analysis for local regions will most effectively advise managers how to target habitat management. I radio-collared 11 snowshoe hares in the …

The Association Between Dietary Niche Variation In Rodents And Climate Change Across The Paleocene-Eocene Thermal Maximum, Hannah K. Vermeer

Masters Theses

Mammalian teeth play a crucial role in food acquisition and breakdown and are therefore closely tied to dietary niche. This study reconstructed the diet of early Paleogene paramyid rodents across the Paleocene-Eocene Thermal Maximum (PETM) climatic event in an effort to understand the role of climate in mammalian dietary niche change. Dietary niches were quantified using three dental topographic measures: Dirichlet normal energy, relief index, and orientation patch count rotated. A Kruskal-Wallis test was conducted over eight time periods to determine if each of the dental topographic measures (i.e., diet) varied over time. Regression analysis of these measures with climatic …

What Happens Now? The U.S.’S Withdrawal From Paris Climate Agreement, Samantha Klann

Honors Projects

This research paper investigates what possible consequences President Trump’s removal of the United States from the Paris Climate Agreement could have on world leadership position, international (trade) relations, innovation, and overall economic development of the U.S. President Trump retracted the U.S. from the agreement in June 2017, and although the withdrawal takes years to officially be completed, it is possible to explore possible ramifications for the U.S.’s future (Friedman, 2017). This paper focuses on analyzing how this withdrawal could affect the U.S. world leadership position, international (trade) relations, and innovation, and the subsequent impact on the economic development of the …

Detection And Attribution Of Long-Term Vegetation Changes In Northern Alaska, Robert Barrett

Masters Theses

Climate change is impacting terrestrial ecosystems world-wide and the Arctic is particularly vulnerable as it is warming faster and with greater magnitude than other regions. Understanding the responses of arctic plants species to abiotic factors is crucial to predicting the impact climate change will have on the Arctic because plants play critical roles in carbon exchange, energy balance, and trophic interactions. Using data from long-term research sites in Barrow and Atqasuk, Alaska, the purpose of this thesis was to investigate how arctic plants respond to 17-19 years of experimental warming, establish the relative strengths of various abiotic factors in predicting …

Toxin Production And Population Dynamics Of Gloeotrichia Echinulata With Considerations Of Global Climate Change, Sarah Stamann

Masters Theses

Global climate change has been identified as a driver for increasing cyanobacteria blooms world-wide. Blooms of the cyanobacterium, Gloeotrichia echinulata, (hereafter, G. echinulata) have been observed in Silver Lake (Oceana County, MI), often forming dense surface scums. This organism is known to produce the hepatotoxin, microcystin- LR, and its growth is linked to phosphorus accumulation from sediment and temperature.

A series of experiments at ambient and elevated temperatures (+2° and +6°above ambient) with sediment from four locations in Silver Lake with varying phosphorus concentrations were conducted to examine the effect of these variables on G. echinulata growth. These …

Wetland Sediment Nutrient Flux In Response To Proposed Hydrologic Reconnection And Climate Warming, James T. Smit

Masters Theses

Wetland restoration and creation are common practices, but wetlands restored or created on former agricultural land may act as a source of nutrients, rather than as a sink. I studied P sediment-water exchange in two flooded celery fields (west and east), which are designated for wetland restoration, in order to assess the effects that hydrologic reconnection of the area to an adjacent creek would have on P dynamics. We also examined the influence of climate change, specifically warming temperatures, by conducting the sediment-water exchange experiments at ambient and plus 2°C temperature conditions. Lab-based sediment core incubations revealed that TP release …

Deglaciation Explains Bat Extinction In The Caribbean, Lilian M. Dávalos, Amy L. Russell

Funded Articles

Ecological factors such as changing climate on land and interspecific competition have been debated as possible causes of postglacial Caribbean extinction. These hypotheses, however, have not been tested against a null model of climate- driven postglacial area loss. Here, we use a new Quaternary mammal database and deep-sea bathymetry to estimate species–area relationships (SARs) at present and during the Last Glacial Maximum (LGM) for bats of the Caribbean, and to model species loss as a function of area loss from rising sea level. Island area was a significant predictor of species richness in the Bahamas, Greater Antilles, and Lesser Antilles …

Estimated Change In Tundra Ecosystem Function Near Barrow, Alaska Between 1972 And 2010, M. J. Lara, S. Villarreal, D. R. Johnson, R. D. Hollister, P. J. Webber, C. E. Tweedie

Peer Reviewed Publications

How the greening of Arctic landscapes manifests as a change in ecosystem structure and function remains largely unknown. This study investigates the likely implications of plant community change on ecosystem function in tundra near Barrow, Alaska. We use structural data from marked plots, established in 1972 and resampled in 1999, 2008 and 2010 to assess plant community change. Ecosystem functional studies were made close to peak growing season in 2008 and 2010 on destructive plots adjacent to marked plots and included measurement of land–atmosphere CH4 and CO2 exchange, hyperspectral reflectance, albedo, water table height, soil moisture, and plant species cover …

Tundra Vegetation Change Near Barrow, Alaska (1972–2010), S. Villarreal, R. D. Hollister, D. R. Johnson, M. J. Lara, P. J. Webber, C. E. Tweedie

Peer Reviewed Publications

Knowledge of how arctic plant communities will respond to change has been largely derived from plot level experimental manipulation, not from trends of decade time scale environmental observations. This study documents plant community change in 330 marked plots at 33 sites established during the International Biological Program near Barrow, Alaska in 1972. Plots were resampled in 1999, 2008 and 2010 for species cover and presence. Cluster analysis identified nine plant communities in 1972. Non-metric multidimensional scaling (NMS) indicates that plant communities have changed in different ways over time, and that wet communities have changed more than dry communities. The relative …

Recent Advances In The Climate Change Biology Literature: Describing The Whole Elephant, A. Townsend Peterson, Shaily Menon, Xingong Li

Peer Reviewed Publications

Climate change biology is seeing a wave of new contributions, which are reviewed herein. Contributions treat shifts in phenology and distribution, and both document past and forecast future effects. However, many of the current wave of contributions are observational and correlational, and few are experimental in nature, and too often a conceptual framework in which to contextualize the results is lacking. An additional gap is the lack of effective cross-linking among areas of research, for example, connection of sea-level rise and climate change implications for distributions of species, or evolutionary adaptation studies with distributional shift studies. Although numerous important contributions …

Projected Climate Change Effects On Nuthatch Distribution And Diversity Across Asia, Shaily Menon, M. Zafar-Ul Islam, A. Townsend Peterson

Peer Reviewed Publications

We used ecological niche modeling approaches to explore climate change implications for one family of birds, the Sittidae, in Asia. Quantitative niche models based on present-day distributions for each of 13 species were projected onto future climate change scenarios. Species’ potential distributional areas tended to be predicted to retract along their fringes, and at lower elevations along mountain ranges. As observed in other studies, montane systems were relatively more robust to the horizontal effects of climate change on species’ distributions compared to flatland systems, so range contractions were focused in Southeast Asia and peninsular India.

Environmental Stress Effects On Vigor, Mortality, And Growth In Northern Hardwood Forests Along A Pollution-Climate Gradient, Neil W. Macdonald, John A. Witter, David R. Reed, Andrew J. Burton, Kurt S. Pregitzer, Hal O. Liechty

Peer Reviewed Publications

Concern exists over the effects of interacting environmental stresses on the ecological integrity of temperate forests. Coincidence of sensitivity to drought, increasing occurrence of defoliation, and elevated pollutant deposition has produced speculation that northern hardwood forests may be susceptible to the increased climatic stresses projected for the Great Lakes region. The objective of our study was to examine relationships among environmental stress factors, vigor, mortality, and growth in northern hardwood forests located along a pollution-climate gradient in the Great Lakes region. Between 1987 and 1993, we quantified climatic variables, pollutant deposition, insect defoliation, and tree vigor and growth at five …