Dynamics of a large submersed plant bed in upper Chesapeake Bay

A large SAV bed in upper Chesapeake Bay has experienced several abrupt shifts over the past half-century, beginning with near-complete loss after a record-breaking flood in 1972, followed by an unexpected, rapid resurgence in the early 2000’s, then partial decline in 2011 following another major flood event. Together, these trends and events provide a unique opportunity to study a recovering SAV ecosystem from several different perspectives. First, I analyzed and synthesized existing time series datasets to make inferences about what factors prompted the recovery. Next, I analyzed existing datasets, together with field samples and a simple hydrodynamic model to investigate mechanisms of SAV bed loss and resilience to storm events. Finally, I conducted field deployments and experiments to explore how the bed affects internal physical and biogeochemical processes and what implications those effects have for the dynamics of the system. I found that modest reductions in nutrient loading, coupled with several consecutive dry years likely facilitated the SAV resurgence. Furthermore, positive feedback processes may have played a role in the sudden nature of the recovery because they could have reinforced the state of the bed before and after the abrupt shift. I also found that scour and poor water clarity associated with sediment deposition during the 2011 flood event were mechanisms of plant loss. However, interactions between the bed, water flow, and waves served as mechanisms of resilience because these processes created favorable growing conditions (i.e., clear water, low flow velocities) in the inner core of the bed. Finally, I found that that interactions between physical and biogeochemical processes led to low nutrient concentrations inside the bed relative to outside the bed, which created conditions that precluded algal growth and reinforced vascular plant dominance. This work demonstrates that positive feedbacks play a central role in SAV resilience to both chronic eutrophication as well as acute storm events. Furthermore, I show that analysis of long-term ecological monitoring data, together with field measurements and experiments, can be an effective approach for understanding the mechanisms underlying ecosystem dynamics.

Understanding information use in multiattribute decision making

An inference task in one in which some known set of information is used to produce an estimate about an unknown quantity. Existing theories of how humans make inferences include specialized heuristics that allow people to make these inferences in familiar environments quickly and without unnecessarily complex computation. Specialized heuristic processing may be unnecessary, however; other research suggests that the same patterns in judgment can be explained by existing patterns in encoding and retrieving memories. This dissertation compares and attempts to reconcile three alternate explanations of human inference. After justifying three hierarchical Bayesian version of existing inference models, the three models are com- pared on simulated, observed, and experimental data. The results suggest that the three models capture different patterns in human behavior but, based on posterior prediction using laboratory data, potentially ignore important determinants of the decision process.

Principal Effectiveness: Middle School Leaders' Perceptions Of Principal Practices To Improve Middle School Reading Achievement

ABSTRACT Title of Document: PRINCIPAL EFFECTIVENESS: MIDDLE SCHOOL LEADERS’ PERCEPTIONS OF PRINCIPAL PRACTICES TO IMPROVE MIDDLE SCHOOL READING ACHIEVEMENT Kathleen R. Brady, Doctor of Education, 2016 Directed By: Dr. John Norris, Department of Education The purpose of this exploratory and descriptive study was to examine school leaders’ perceptions of leadership practices that contribute to principal effectiveness in improving reading achievement in middle schools in a large public school district. The data was gathered through the use of a Web-based survey that was emailed to 97 school based leaders including 20 principals, 40 assistant principals, 17 reading department chairpersons, and 20 professional development lead teachers in middle schools with grade 6-8 and 7-8 configurations. Data were collected and analyzed in order to make inferences about principal practices at middle school. The findings of this study indicated few differences between middle school principals’, assistant principals’, reading department chairpersons’, and professional development lead teachers’ perceptions of principal leadership practices that are most important to and have the greatest impact on student reading achievement success. Furthermore, the findings indicated that participants’ three top ranked resources needed to increase the effectiveness of principals in order to improve reading achievement at middle schools include implementing a collaborative planning protocol to support literacy instruction, adding a reading coach to the middle school staff, and providing professional development activities focused on literacy instruction across the content areas. The results were used to make recommendations that may contribute to middle school principal effectiveness.