Full 2020 Program


Click on the title of a talk to view the abstract. 


9:00am-9:40am // Clark Hall // Mural Room

Opening Remarks.

9:45am-10:00am // Clark Hall // Mural Room

Session 1.

10:00am-11:30am // Clark Hall // Room 133

10:00-10:15 am Nitrogen and Carbon Dynamics throughout Secondary Succession following Agricultural Abandonment in North-Central Virginia Parisien, Alexandra; Epstein, Howard E.A.
Long-standing theoretical models predict carbon (C) cycle dynamics during succession following agricultural disturbance. Less understood, however, are the interactive dynamics of the nitrogen (N) and C cycles throughout secondary succession, and how plant-available N may or may not limit vegetation transitions and net primary productivity over time. Two chronosequences at the Blandy Experimental Farm in Boyce, north-central Virginia were examined to elucidate N and C cycle dynamics over a temporal successional gradient. Each chronosequence consists of one early, one mid, and one late secondary successional field (~15 years, ~30 years, and ~100 years post agricultural abandonment, respectively). Five 10×10 m plots were established in each of the six fields. Total soil N and C data were collected to 30 cm depth, and net N mineralization and nitrification were measured twice per growing season using an in-situ anion-cation exchange resin bag technique. Live foliar and litter C and N were also examined in each plot, and soil CO2 efflux was measured biweekly. While soil N varied insignificantly across successional stages, soil C was significantly higher in late succession than early succession in the 0-10 cm fraction. Soil C:N peaked in mid succession in the 0-10 cm fraction. Net N mineralization and nitrification both trend upward from early to late succession. Live foliar N increased through successional stage, but litter N sharply decreased in late succession, indicating an increase in N use efficiency. Soil CO2 efflux decreased significantly through successional stages, correlating with a decrease in soil temperature from early to late succession. Previous studies at this location have demonstrated increasing net primary production and therefore net ecosystem production with time since abandonment, suggesting a lack of N limitation. A thorough understanding of N and C cycling dynamics during secondary succession is especially important in the southeastern United States, where a significant amount of previously cultivated land has been abandoned over the past century due to advances in farming efficiency and the move westward to more fertile soils. Much of the southeastern U.S. is now undergoing secondary succession, and quality data on the dynamics of N and C cycling during this procession can help guide future land management decisions and model predictions..
Author affiliations: UVA Department of Environmental Sciences
10:15-10:30 am Regicide: Conopid fly parasitoids are also killing bumblebee queens. Amber Slatosky
Bumblebees are among pollinators found to have declining populations worldwide. To better understand these declines, examination of their interactions with natural enemies is required. Most studies of interactions between parasitoid conopid flies and their bumblebee hosts focus on risks for non-reproductive members of bumblebee colonies because it is assumed queens hibernate too quickly after maturity to experience substantial risk. This work examines parasitism rates for all three castes (worker, male, queen) of a species that experiences risk of infestation during reproductive dispersal. This work examines whether queens are less likely to be infested than males or workers, exposure will be positively correlated with parasitism for all castes, and that queens will be more likely to exhibit a melanization response in the presence of a conopid fly larva. Reported here: the highest rate of queen parasitism on record, that evidence of melanization on conopid larvae is rare and even among all three castes, and that exposure is most important to understanding risk of infestation. These findings suggest queen bumblebees’ parasitoid fly mortality rates may be higher than previously thought for certain species, and that resistance appears to be low.

10:30-10:45 am Insights on vegetation functioning using remotely-sensed measures of solar-induced fluorescence and reflectance spectroscopy Andrew, Jablonski. Xi Yang, Manuel Lerdau The purpose of this talk is to outline the current state of using remote-sensing methods to monitor vegetation functioning – namely carbon and water fluxes. I will identify current outstanding questions and methodological gaps, and demonstrate how my research provides a framework for addressing such questions.

10:45-11:00 am Atmospheric Drivers of the California Current System Daniel F. Schmidt, Dillon J. Amaya, Kevin M. Grise, and Arthur J. Miller
Upwelling in the California Current system is crucial to bringing nutrient-rich water to the photic zone and supporting the associated ecosystem. This upwelling is a result of the wind-driven ocean circulation and is therefore susceptible to changes in the atmospheric circulation. We use both climate models and observational data to explore the response of the California Current to shifts in the Hadley cell and the North Pacific subtropical high–including both shifts due to short-term variability and longer-term shifts in a climate change scenario. We find that the subtropical high has a much stronger influence than the Hadley cell on upwelling in this area, and that uncertainties in the future of the California Current and its ecosystem can be traced in part to uncertainties in the future evolution of the subtropical high.

”11:00-11:15 Houston, Texas is a major U.S. urban and industrial area, where poor air quality is unevenly distributed, with a disproportionate share in low-income, non-white, and Hispanic neighborhoods. We have traditionally lacked city-wide observations with which to fully describe intra-urban pollutant heterogeneities for reactive gases like nitrogen dioxide (NO2). Here, we analyze novel high-spatial-resolution (250 m x 500 m) NO2 vertical columns measured by the NASA GCAS airborne spectrometer, collected over Houston as part of the September-2013 NASA DISCOVER-AQ mission, and quantify differences in population-weighted NO2 distribution with census tract demographics. We find 37  6% higher NO2 in low-income and non-white/Hispanic (LIN) census tracts compared to high-income white (HIW) tracts, and report NO2 disparities separately by race-ethnicity (11–32%) and poverty status (15–28%). We observe substantial temporal variability in LIN-HIW NO2 differences (and other metrics), driven by the greater prevalence of large NOx ( NO + NO2) emission sources in LIN neighborhoods. We use the GCAS dataset to evaluate measurements from the recently-launched satellite-based TROPOMI (3.5 km x 7 km), averaged to 0.01∘ x 0.01∘ using physics-based oversampling, and demonstrate TROPOMI resolves similar relative, but not absolute, differences in census-tract-scale NO2. We utilize the high-resolution FIVE and NEI NOx emission inventories, plus one year of TROPOMI weekday-weekend variability, to attribute tract-level NO2 disparities to industrial sources and heavy-duty diesel vehicles. We evaluate GCAS and TROPOMI observations against in-situ column and surface measurements. We discuss future opportunities for satellite remote sensing to constrain census-tract-level NO2 disparities.

11:15-11:30 am Assessing the Geographical Distribution and Reduction Potential of the Nitrogen Footprint of a Community: A Case Study in Charlottesville, VA Julia Stanganelli
Nitrogen is imperative to life on earth, but excess reactive nitrogen can have harmful effects on marine and terrestrial environments, the atmosphere, and human health. Anthropogenic creation of reactive N (Nr; all N species but N2) and consequent inputs to the environment are associated largely with agricultural production and fossil fuel combustion. A Nitrogen Footprint is a tool created to track the impact of an individual, institution, or community’s impact on excess Nr released to the environment. This study aims to use the community nitrogen footprint tool to ask: 1) what is the geospatial variability of the N footprint in Charlottesville City, and 2) how does it relate to socio-economic patterns such as average household income and racial make-up of a population segment, as well as distance from the University of Virginia? Additionally, 3) where in Charlottesville City are the greatest opportunities for reduction in the N footprint, and 4) how might certain changes in consumer choices offer strategies for reduction? Previous studies have shown that more socioeconomically advantaged populations contribute more to global climate change and environmental pollution. The results of this study may support this theory in terms of unequal impact on Nr additions to the environment.


11:30-12:45pm // Clark Hall // Odum Room

Session 2.

12:45-1:45pm // Clark Hall // Room 133

12:45-1:00 pm Quantifying and mapping intertidal oyster reefs utilizing LiDAR-based remote sensing Sara Hogan, Matthew Reidenbach
The eastern oyster, Crassostrea virginica, is primarily found within intertidal regions on the Eastern Shore of Virginia, USA, although their abundance and distributions are not well known. Here we determine if Light Detecting and Ranging (LiDAR) derived data can be used to classify land cover and identify intertidal oyster reefs. We use the locations of existing reefs to determine the physical characteristics of oyster habitat, through the use of existing elevation, fetch, and water residence time data for the region. We found that oyster patches mapped using LiDAR-based elevation data overlapped greater than 90% with oyster patches mapped in-situ using GPS ground-truth data. Trained with elevation, intensity, and surface slope, and curvature data derived from LiDAR, the land cover classification identified oyster cover with an accuracy of 81 %. Ground-truth patches were small, with the 50th percentile for area and perimeter being 11.6 m2 and 14.5 m. Reefs were also found to exist in a narrow range of elevation (-0.81 to -0.18 m relative NAVD88) and average vertical relief of 0.15 – 0.87 m relative to their surrounding land. Analysis of land cover with similar physical characteristics also suggests there is still ample viable intertidal area for future oyster population restoration. We conclude that LiDAR data, coupled with physical attributes of existing reefs, can help understand oyster distributions and be used to target and prioritize locations for future restoration.

1:00-1:15 pm Getting the timing right: Ice sheet retreat and margin stabilization due to land emergence Marion McKenzie, Lauren Simkins
The Cordilleran Ice Sheet (CIS), arguably the least understood of all former ice sheets and yet the most similar to the modern Greenland Ice Sheet (GrIS), provides an opportunity to enhance our current understanding of interactions between ice sheet retreat behavior and the solid earth on which ice sheets rest. Specifically, I ask: what was the influence of solid Earth rebound, due to ice unloading, on the retreat of the southernmost CIS, and can we use CIS retreat to better understand ice sheet behavior across emergent marine to terrestrial landscapes, a potentially important consideration for contemporary margins of the GrIS? This project aims to answer these questions by mapping and characterizing glacial landforms and lakes in the Puget Lowland using LiDAR data and collecting a series of lake sediment cores and uplifted outcrop sediments during a field expedition to the Puget Lowland, Washington in May 2020. This process-based study using the paleo-record of ice sheet retreat on an emergent bed will help constrain the sensitivity of ice sheets to earth uplift, which is critical for testing coupled solid Earth – ice sheet models used to project future sea level scenarios.

1:15-1:30 pm Odor tracking in marine organisms: the role of temporal and spatial intermittency of the odor signal Brenden Michaelis, Matthew Reidenbach.
Animals use chemical cues to find food, mates, and avoid predators. In both terrestrial and aquatic environments, the instantaneous temporal and spatial distribution of odors is complex and plumes are often composed of intermittent filaments of chemicals at high concentrations that are adjacent to fluid with little or no odor. Navigation in chemical plumes has typically been considered as a spatial information problem where individuals track towards higher concentration. However, within turbulent plumes, concentration information alone is too variable to explain the search speed and accuracy of many animals. Sensory signals, including chemosensory signals, are generally assumed to be encoded by canonical, tonically active receptor neurons that respond to odor concentration. Recently, studies have demonstrated that a significant portion of primary olfactory receptor neurons (ORNs) in some animals are intrinsically rhythmically active or ‘bursting’. Laboratory and computational models show that these bursting olfactory receptor neurons (bORNS) can provide a mechanism for animals to sample and interpret the intermittency (i.e., on/off signal) of an odor environment. To test how organisms can utilize intermittency in search, we developed a computational fluid dynamics simulation of a turbulent odor plume as well as a plume within a large-scale laboratory water flume. We utilized the spiny lobster, Panulirus argus, as our model species. Our results show that utilizing the intermittency in the odor signal, in combination with concentration, greatly increases the efficiency of search and success in finding the source. However, similar to other search strategies, navigating using intermittency directional cues is dependent on a threshold concentration. We found that adaptation to changing background concentration levels must occur for detected intermittency to be within the measured refractory period for bORNs.

1:30-1:45 pm Temperature effects on temperate seagrass metabolism and resilience Amelie Berger
Seagrass meadows are metabolic hotspots in shallow coastal waters and are recognized as ‘blue carbon’ sinks. They are, however, increasingly threatened by climate change and other stressors. An eelgrass (Zostera marina) meadow at the Virginia Coast Reserve Long Term Ecological Research (VCR-LTER) site recently experienced a large-scale die-off, presumably caused by high summertime water temperatures, providing us with an unprecedented opportunity to study in situ seagrass response to thermal stress. This study examined spatial patterns of thermal stress and seagrass resilience in the meadow, as well as the direct effect of temperature on seagrass metabolism using the aquatic eddy covariance technique. This technique produces high-quality benthic metabolism measurements under naturally varying environmental conditions. It therefore allows us, for the first time, to observe the real-time metabolic response of eelgrass to high temperatures, and constrain the optimum temperature threshold for Z. marina under true in situ conditions. The results will provide insights into the potential responses of other temperate systems where warming oceans may lead to more frequent seagrass mortality events.


(15 min)


2:00-3:30 pm // Clark Hall // Mural Room

Keynote Address. DR. Brooke Medley

3:30-4:30 pm // Clark Hall // Room 107

Closing Remarks.

3:30-4:40 pm // Clark Hall // Room 107


4:45-6:00 pm // Clark Hall // Odum Room

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