Coffee Hour: Laurel Larsen "Structural and functional connectivity of complex aquatic landscapes"

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Time: 
Friday, September 19, 2014 - 3:30pm to 5:50pm
Place: 
Refreshments are offered in 319 Walker Building at 3:30 p.m. The lecture begins in 112 Walker Building at 4:00 p.m.

Structural and functional connectivity of complex aquatic landscapes

 

About the talk

Structural connectivity is often hailed as critical for aquatic ecosystem function. Channel-floodplain connectivity promotes nutrient and sediment redistribution and water-purification reactions such as denitrification, while longitudinal connectivity provides corridors for transport of organic matter and organisms. Large-scale connectivity can also enhance resilience by facilitating transport and replenishment of organisms, sediment, and/or nutrients lost during a disturbance. However, connectivity can also promote the spread of catastrophe to large scales through the communication of information (e.g., as in popular forest fire models in terrestrial systems). Because connectivity facilitates or indicates transport in aquatic ecosystems, it is often a better indicator of system dynamics than other visual cues such as patch areas, fractal dimensions, etc. Research on the Everglades shows that a catastrophic decline in linear connectivity of flowing waterways preceded a loss in the areal coverage of those waterways; hence, structural connectivity measures provided a warning of an imminent catastrophic shift in landscape structure. Meanwhile, variability in directional connectivity over a range of headings in the landscape provided information about mechanisms of landscape formation and degradation. In other aquatic landscapes, connectivity may suggest how the landscape will respond to “landscape forming” catastrophic events such as floods but, unlike in many terrestrial systems, also reflects how the landscape responds to less frequent events that may additionally be important for driving landscape evolution, including future changes in connectivity.  I propose that quasi-stable aquatic landscapes exhibit a well-defined range of structural connectivity values (such as the newly established directional connectivity index) at different scales that reflect the frequency and magnitude of forcing. Deviations outside that range suggest that the system is undergoing an imminent catastrophic shift or is susceptible to a future catastrophe. Remote sensing of connectivity, therefore, can serve as a tool for dynamic classification of landscapes or detecting early-warning signals of landscape decline. Challenges lie in defining the scales at which different types of landscape dynamics are most susceptible to connectivity and extracting significant trends from high-dimensional connectivity data over geographically broad areas.

 

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About the speaker

Laurel LarsenLaurel Larsen is an assistant professor of Earth Systems Science in the Geography Department at UC Berkeley. She comes from an interdisciplinary academic background, with a Ph.D in Civil Engineering from the University of Colorado at Boulder, a masters in Earth and Planetary Sciences from Washington University in St. Louis, and a B.S. with majors in Environmental Studies and Systems Science and Mathematics from Washington University. Before starting at Berkeley in January 2013, Laurel spent four years as a Research Hydrologist and Research Ecologist in the US Geological Survey's National Research Program in Reston, VA. Laurel's research focuses on understanding the nonlinear interactions and feedback processes that govern environmental responses to change so that anticipatory planning and restoration efforts can be made more effective and efficient. In her free time, Laurel enjoys cycling, running, and triathlon, swimming in the San Francisco Bay, writing poetry, and exploring with her dog.

Angela Rogers  geography@psu.edu