Life Sciences Commons^™

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 …

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 …

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 …

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 …