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Research EcologistContact Info
Dr. Laurel Larsen studies the linkages between hydrology, geomorphology, and ecology in streams and wetlands. She has expertise in simulation modeling, fluvial geomorphology, environmental fluid mechanics, and the fate and transport of fine sediment and organic matter and works in diverse environments, ranging from the vast Florida Everglades to headwater urban streams in the mid-Atlantic.
Dr. Larsen received her undergraduate degree in systems science and mathematics and her master’s degree in Earth and Planetary Sciences from Washington University in St. Louis in 2003. A Hertz and National Science Foundation fellow, she completed her Ph.D in civil engineering from the University of Colorado in 2008. She began her career with the USGS National Research Program in 2008.
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My Science Topics
My USGS Science Strategy AreasUnderstanding Ecosystems & Predicting Ecosystems Change
Hydroecology of flowing waters
My research focuses on understanding the complex interactions between physical and biological processes in flowing-water environments in order to predict how the ecological functioning of those environments will change as a result of climate change, urbanization, and restoration management. Areas of particular emphasis include surface-water transport processes and fine sediment dynamics. My typical approach to this work is to perform detailed field and laboratory experimentation to understand the details of processes controlling ecosystem function and then to formulate numerical models that predict changes in ecosystem function in response to changes in driving variables. Multivariate statistics, information theory, and complex systems analysis are tools that I apply to better understand the nature of interactions between multiple environmental variables based on the results of the field, laboratory, and numerical experiments. Current projects are:
The ridge and slough landscape of the Florida Everglades is a patterned ecosystem in which the structure of the landscape is tightly linked to its ecosystem function. Ridges and sloughs provide habitat heterogeneity, which supports high biodiversity, while the connectivity of sloughs in the direction of flow supports fish movement. Recent degradation of the landscape via loss of sloughs and the call to restore landscape form and function as part of the Comprehensive Everglades Restoration Plan have highlighted the need to understand the fundamental processes controlling the past, present, and future evolution of this ecosystem. My work has revealed that this landscape patterning evolves under a precise set of environmental conditions that involve relatively deep levels of inundation, moderate water surface slopes (i.e., moderate flow velocity), and consistent flow direction. Numerical experiments evaluating the relative sensitivity of landscape pattern to these different driving variables has yielded new recommendations for management actions designed to preserve or restore the ridge and slough landscape. Currently I am involved in a large-scale flow release experiment in the Everglades to test our predictions about the ecological impacts of restored flows and better understand additional aspects of the dynamics of flow-vegetation-sediment interactions. Current uncertainties under investigation include (1) landscape pattern sensitivity to flow direction, (2) the differential roles of different classes of fine sediment in landscape evolution, and (3) interactions between water quality, sediment physical and biogeochemical properties, and landscape evolution.
The Influence of Fine Sediment Transport and Stream Restoration on Urban Stream Ecosystem Health
Stream restoration is a multi-billion dollar industry, yet few stream restoration projects are monitored post-installation, and effects on stream ecosystem health are poorly understood. The goal of this project is to attain a process-based understanding of how stream restoration and resulting physical changes to the environment impact stream metabolism (a functional indicator of stream ecosystem health), and the stream reach's contribution to downstream water quality. Stream metabolism is the sum of gross primary production and respiration occurring within a stream reach and, as it results from processes occurring across multiple trophic levels, is a particularly integrative metric of stream ecosystem health. A stream reach's metabolism plays an important role in determining how much organic material that reach exports to downstream ecosystems such as the Chesapeake Bay, where it could contribute to low-oxygen events and fish kills. We are currently conducting long term field experiments to determine controls on stream metabolism in adjacent restored and unrestored streams in Fairfax County, VA. Preliminary findings suggest that a common type of stream restoration that involves channel stabilization and bank regrading results in an increase in the production of algal organic material, which flushes downstream during storm events. Meanwhile, the stream receives less fine mineral sediment from bank collapse events, which may contribute to the lower respiration rates observed in the restored stream and the stream's reduced capacity to process organic material from the watershed. We are moving toward development of a biological response model (USES = Urban Stream Ecosystem Service simulator) that can be used to predict impacts of different types of stream restoration designs on stream metabolism, as well as the likely impacts of climate change on stream ecosystem health.
12201 Sunrise Valley Dr
Reston, VA 20192-0002
703-648-5484 - Fax
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