Environmental Studies Independent Research and Study Papers
Environmental Studies and Science Majors engage in a variety of types of research. The projects listed here are 1 or 2 semester independent study or independent research projects that are conducted under the guidance of a faculty advisor and follow the department *guidelines* for research. To request access to a hard copy or pdf version of the papers associated with these projects, please contact the Environmental Studies Technician by emailing firstname.lastname@example.org. Independent Research Papers are also available through the Dickinson College Library.
Caroline R. Kanaskie, "Foliar Chemistry of the Eastern Hemlock (Tsuga canadensis)"
The eastern hemlock (Tsuga canadensis (L.) Carrière) plays a unique, important role in forest ecosystem dynamics in eastern North America in its contribution to leaf litter and by providing habitat for vertebrates and shade for small streams. The eastern hemlock has been threatened throughout most of its native range by the hemlock woolly adelgid (Adelges tsugae Annand). The hemlock woolly adelgid is an invasive insect that feeds on xylem at the base of hemlock needles, causing a decline in tree health and eventually mortality. This research builds on 4 years of adelgid abundance and hemlock health surveys in the Cumberland Valley region of Pennsylvania. We seek to investigate the role of foliar nitrogen (N) content on patterns of adelgid abundance and hemlock health. This study, coupled with Yueli Liang's soil nutrient study, aims to further characterize 16 hemlock stands that have been studied since 2014. We found higher %N in new growth than in old growth; subsequently, we found a lower C:N ratio in new growth. Adelgids were more abundant at high elevation than at low elevation in 2014, 2015, and 2016, while adelgid abundance did not differ with elevation in 2017. Adelgid abundance decreased significantly from 2014 to 2015, but has been increasing since then. More new growth was found in valley sites than hilltop sites in 2014, while new growth did not differ with elevation in 2017 (2015 and 2016 data in progress). Crown density was higher in valley sites than hilltop sites in 2014, 2015, 2016 and 2017. Crown ratio was higher in valley sites than hilltop sites in 2017. Overall, we found significant differences among site pairs for most of these analyses, even though they are geographically close in proximity. We found a significant negative correlation between adelgid abundance and the C:N ratio of old growth foliage, with more adelgids found on old growth foliage with a lesser C:N ratio. It is possible that the differences we see in adelgid abundance are because of an intricate adelgid-host relationship, in which adelgid populations thrive when nutrients are avalable, and in turn, deplete nutrients over time, causing a population decline. I suggest further foliar chemical analyses, tree coring, and a 15-N pulse-chase study to better understand how adelgids have been impacting hemlocks in this region for the past 30+ years.
Yueli Liang, "Soil, Adelgids, and the Health of Eastern Hemlock Trees"
Biological invasions have great potential to change ecosystem structure and processes. Hemlock wooly adelgid, Adelges tsugae Annand (Homoptera: Adelgidae) is an invasive insect from Japan causing defoliation and mortality in the eastern hemlock tree, Tsuga canadensis Carrière. Eastern hemlock is an important native tree species that grows in the northeastern United States. Eastern hemlock plays an important and unique role in the forest ecology, because it is a shade-tolerant, long-lived tree species that can provide dense evergreen canopy for many forest organisms. Different from the hemlock tree in Asia, the eastern hemlock is intolerant of adelgid feeding. The adelgids feed on the ray parenchyma cells at the needle bases on young hemlock twigs and inject a toxic saliva which causes needle, bud, and branch loss and eventually kills the tree in as little as four years. Hemlock woolly adelgid reproduces in two generations per year, and it is easy to spread by wind, birds, mammals, and human activities. A previous study in 2014 conducted by Dr. Loeffler, Rosabeth Link and Jill Hautaniemi showed that the eastern hemlock trees' health is greater at low elevation (the stream valleys) than at high elevation (the hilltops) and the adelgid abundance is greater at hilltops than in stream valleys in Pennsylvania. By continuing their study, I found out that the adelgid presence declinded from 2014 to 2015 and then rose through 2016 to its highest level in 2017. Adelgid presence was significantly higher in high elevation sites in 2014, 2015, and 2016 but not in 2017 when adelgid presence was high. The new growth of trees increased significantly between 2014 and 2017. Also, in 2017, new growth was no longer significantly different between high and low sites, possibly because adelgids were equally present at high and low sites. In addition to the annual survey, I also analyzed the soil nutrient content in the fall 2016 to determine if nutrient availability is a factor impacting the abundance of adelgids or the amount of new growth produced by the trees. The soil analyses showed that phosphorus and manganese concentration were significantly higher at hilltops than at stream valleys, and copper and magnesium concentration were significantly higher in stream valleys than at hilltops. Levels of any of the soil nutrients that differed between stream valley and hilltop sites may have affected concentration of nutrients in the foliage which may have affectted adelgid presence, thus indirectly affecting hemlock health. Further study is needed to determine major factors that cause the different pattern of adelgid presence and the mortality of eastern hemlocks.
Natalie McNeill, "Aquatic Citizen Scientist Motivations: Implications for Civil Society"
Changes in Pennsylvania's watersheds from agriculture, development, and hydraulic fracturing (fracking), plus reduced government spending, increase the importance of water quality data. Citizen scientists who voluntarily collect water quality data can help identify pollution events or sites for governmental agencies to prioritize (Jalbert et al. 2014). Involving citizens in the data collection process promotes community development, civic engagement, and scientific literacy (Stepenuck and Green 2015, Alender 2016). Research indicates that volunteers who fulfill their motivations are more likely to continue volunteering (Clary et al. 1998). For this study, qualitative interview methods were used to understand what motivates citizen scientists to monitor water quality in two different geographies: shale gas regions with active or proposed fracking (fracking volunteers) and regions with no active fracking (non-fracking volunteers). Twenty-one volunteers were interviews (12 fracking and 9 non-fracking). Ten motivators for why volunteers monitor their local waterways were identified. Overall, volunteers emphasized being motivated by threats to water quality from fracking the most. Other important motivators are stewardship, community awareness, and data collection. The rest of the motivators identified are relatively consistent between the two groups and/or did not play a large role in the interviews. While there are similarities between the two groups of volunteers, it is necessary to consider the importance of place and how people's environments affect their motivations to monitor. In order to successfully recruit and retain volunteers, these differences should not be ignored because each monitoring group is unique and operates under different circumstances.
Robert F. Page, "The Influences of Soil Characteristics on Nest-Site Selection in Painted Turtles (Chrysemys picta)"
Nest-site selection is important for species with temperature dependent sex determination (TSD) because attributes of the nest not only determine incubation temperatures and therefore hatchling sex but also performance, survivorship and phenotype. However, suitable nesting habitat may be limited for aquatic species such as the painted turtle (Chrysemys picta) that nest on land fragmented by anthropogenic activity and impacted by global increases in temperature. By investigating nest-site selection we can examine to what extent these species can shift nest characteristics to compensate for these environmental changes. The purpose of this study was to examine nest-site selection in painted turtles inhabiting an anthropogenic pond in south central Pennsylvania. Visual surveys were conducted for nesting females along a perimeter dirt path and along an adjacent railroad access road. From 2010-2013 we documented nest location, depth, width, temperature, canopy coverage, clutch size, and hatch success for a total of 31 nests. Nests at our site were shallower than those in other studies and were linearly aggregated north of the pond both on a dirt path and adjacent to an active railroad. To address the influence of soil characteristics on nest selection, in 2016 we analyzed soil samples collected from: 1) actual nests that were depredated, 2) false nests, incomplete nests aborted during digging prior to nest completion, and 3) randomized locations. Analysis revealed that depredated nests had a higher proportion of coarse grains and a lower proportion of small grains relative to false nests and random locations. Nests along the railroad had a higher proportion of total carbon compared with nests on the dirt path. Overall, nest success was lower compared to other studies but was similar between dirt path and railroad locations. We interpret these results to mean that female turtles at this site actively selected nest sites with more coarse and less fine grained soils but that anthropogenic activities appear to limit the availability of suitable nesting sites throughout our site that ultimately decreased hatch success.
Helen Schlimm, "Long-Term Records of Climate-Induced Changes in the Zooplankton of West Greenland Lakes"
Recent research documents climate-induced changes in the algal communities of West Greenland lakes; however, less is known about the response of zooplankton to climate change effects in this region. Zooplankton are predominantly the top predator in these lakes, and thus may be changing due to direct climate effects on physical lake habitat and chemistry or indirect effects on their food source. Cladoceran remains from two lake sediment cores were collected in the Kangerlussuaq region of southwest Greenland: SS1341, located midway between the Greenland ice sheet and the coast, and SS901, close in proximity to the ice sheet. Modern zooplankton data were analyzed from a suite of 26 lakes across both regions and utilized neo- and paleolimnological methods to characterize shifts in zooplankton communities. Paleolimnological results suggest a shift to increased dominance of a particular pelagic genus, Bosmina, over the benthic genus Chydorus in modern times. This trend differs from an established long-term record of zooplankton change from another lake in this region that observed a modern decline in pelagic genera, suggesting variability among systems in zooplankton community response to climate change. Similar variability within paleolimnological records in this region has been observed for small centric diatom species. Modern analysis yielded a correlation of Bosmina and Eubosmina spp. distribution to increased lake clarity and reduced algal biomass, suggesting the effects of climate change may be mediated by bottom-up food web mechanisms. By pairing modern and paleoecological approaches, we are better able to understand the mechanisms driving long-term shifts in plankton communities in these Arctic lakes.
Tiffany Chin, "Differing Seasonal Succession of Phytoplankton in Lakes with High and Low Dissolved Organic Carbon Concentrations: Implications for Long-Term Community Shifts"
In recent decades, rates of acidic deposition from sulfur and nitrogen emissions have been declining across North America (Stoddard et al. 1999). These declines, largely attributed to regional and national emissions regulations, have allowed for the recovery of aquatic ecosystems across the Northeast US and elsewhere. The effects of acid deposition on aquatic ecosystems are dependent on the rate at which deposition occurs and the acid neutralizing capacity (ANC) of each system (Driscoll et al. 2001). Acidic deposition has the greatest impact on perched seepage lakes, which are affected primarily by direct precipitation (Driscoll et al. 2001). High levels of acid deposition in past years have lead to decreases in pH and increases in aluminum concentrations in many ecosystems across the Northeast US, contributing to a decline in species richness and abundance (Driscoll et al. 2001).
In addition to the effects of changing rates of acidic deposition, recent climatic changes in this region are also impacting aquatic ecosystems. Annual temperatures have increased in the northeastern US by 0.08 ±0.01°C per decade over the past century, and this rate has increased to 0.70 ±0.05°C per decade over the past 45 years (Hayhoe et al. 2008). Annual precipitation has also increased over the last century by 9.5 ±2 mm per decade, and climate models predict that these precipitation increases will occur largely during the winter rather than other seasons (Hayhoe et al. 2008). These climatic changes have been observed in conjunction with reductions in the length of ice cover on lakes and changes to ratio of snow to total precipitation (Hayhoe et al. 2008). Such changes can impact the amount of snowmelt entering aquatic ecosystems as well as terrestrially derived dissolved organic carbon. Shifts in the length of ice cover on lakes may also affect the succession of species that are temperature-cued, as the timing of full mixing of the lake will shift.
Max Egener, "The Effects of Extreme Rain Events on Water Transparency and Stratification in Central Pennsylvania Reservoir Ecosystems"
Recent research suggests that the frequency of extreme rain events is increasing in the Mid-Atlantic region of the United States (84% increase since 1948 in this study region). Three reservoirs in central Pennsylvania with varying catchment land use and morphology were monitored over the open water period to measure the effects of extreme rain events (>2.54 cm in 24 hours) on reservoir water transparency, stratification, transparency relevant chemistry (total suspended solids, chlorophyll-a, and dissolved organic carbon), and nutrient chemistry. Reservoir maximum depths were 3.5 m, 7.0 m, and 16.0 m. The catchment land use of Laurel Lake and Fuller Lake is 92% forested, and the catchment land use of Opossum Lake is 44% agricultural and 40% forested. Measurements were collected from Laurel Lake and Opossum Lake on ten days from mid-May to November, as well as within twenty-four hours before and within forty-eight hours after a spring and a fall extreme rain event. High frequency temperature and oxygen sensors were deployed at varying intervals throughout the water columns of all three reservoirs to monitor changes in thermal stratification at the event-scale. Reservoirs with different catchment characteristics experienced dissimilar alterations in water transparency following the spring and fall extreme rain event. Changes in transparency relevant chemistry reflected changes in water transparency. Nutrient chemistry following both extreme rain events suggested that light availability is the primary driver of primary production in Laurel Lake and Opossum Lake. A weakening of stratification occurred more frequently following extreme rain events in reservoirs with shallower maximum depths. These differing responses to extreme rain events in each reservoir warrant reservoir-specific management programs to address ecological changes in response to this local effect of climate change. Further research should seek to understand the long-term effects of these short-term changes on reservoir ecology.
Rachael Sclafani, "Garlic Mustard: Impacts on Understory Diversity and Competitive Interactions"
Garlic mustard is a Western European plant invasive in the United States. It has a number of traits that allow it to be highly invasive in the forest understory such as allelopathy, tolerance of low-light conditions, and phenology that allows it to outcompete other species early in the growing season. On a community level it has been found that Garlic Mustard causes decreases in diversity in the forest understory, however in greenhouse experiments it has been seen that the competitive advantage of Garlic Mustard varies. This study is intended to determine how Garlic Mustard impacts understory diversity at different densities using an observational field study and how it interacts competitively against Japanese Stilt Grass and Japanese Honeysuckle in a greenhouse competition study. In the field 30 1m2 quadrats were sampled recording abundance and percent cover. The greenhouse experiment was set up to vary the density and proportion of each species. In the field study Japanese Stilt Grass showed a negative relationship with Garlic Mustard, however it was not negatively impacted by Garlic Mustard in the greenhouse study. Japanese Stilt Grass seemed to be able to negatively impact the growth of Garlic Mustard. This incongruity is potentially due to an allelopathic effect of Japanese Stilt Grass on Garlic Mustard in the dense conditions of the greenhouse that was not a large factor in the less-dense field. Japanese Honeysuckle showed a positive relationship with Garlic Mustard in the field, but a strong negative relationship with Garlic Mustard in the greenhouse. The incongruity might have been due to the ability of Garlic Mustard to shade out the Japanese Honeysuckle in the greenhouse, whereas in the field the Japanese Honeysuckle can be rooted away from the Garlic Mustard, avoiding this impact.
Tabea K. Zimmermann, "Reconstructing the Effects of Multiple Stressors on Algal Communities in Lakes with Differing Concentrations of Dissolved Organic Carbon"
Inland waters are particularly sensitive to environmental changes and a growing body of research points to lakes as sentinels, integrators and regulators of large-scale stressors such as climate change (Carpenter et al. 2007, Pham et al. 2008, Williamson et al. 2008, Adrian et al. 2009). As low points in the landscape, inland waters receive and process inputs from the surrounding terrestrial environment and atmosphere and respond quickly to changes in precipitation, wind and solar irradiance (Williamson et al. 2009). The reactions of these sensitive ecosystems to landscape and climatic changes are stored in lake sediments, which serve as archives to aquatic and terrestrial-ecosystem response to changing conditions in the past (Williamson et al. 2009).
Alexandra Raczka, "Privilege and the Food Environment in Carlisle, Pennsylvania"
This study looks at the food environment of Carlisle, Pennsylvania. It is specifically focused on food access and food preferences, and the relationships between a person’s educational background, household income and geographic location and what they choose to eat based on what they have access to.
Anna E. McGinn, "Quantifying and Understanding Ecological Literacy, A study of first-year students and liberal arts institutions"
Ecological literacy measures a person’s knowledge of ecological systems, care for their immediate and global environment and level of action to reduce their personal and communal impact on the environment. This study investigates the level of ecological literacy of first-year students who entered seven liberal arts colleges in Pennsylvania in the fall of 2013. The institutions included in the study are Allegheny College, Bryn Mawr College, Bucknell University, Dickinson College, Gettysburg College, Haverford College and Swarthmore College. 426 students were surveyed during their first three months of college, and the data was processed to quantify the number of students who are ecologically literate and to examine the potential triggers for and pathways toward ecological literacy. The study shows that 58 percent of students have some level of ecological literacy while the remaining students are ecologically illiterate. In addition to questions that tested for ecological literacy, the survey collected demographic information and gauged a student’s level of exposure to nature. This study does not find that these factors are predictors of a person’s level of ecological literacy. Between the three sections of ecological literacy, a student’s level of care does correlate with a student’s level of action, but neither action nor caring correlate with knowledge. The aim of this research is to support schools in better catering their sustainability efforts towards students with low levels of ecological literacy, so all students who reach the undergraduate level of education will leave the educational system with a basic understanding of the major environmental issues facing today’s world, a feeling of responsibility to address these challenges and the competencies to contribute positively toward building a more sustainable society.