Members of the Heffernan Lab and our colleagues in the Duke River Center made the trek to Portland last week to participate in the first ever Joint Aquatic Sciences Meeting, which convened members of the four largest freshwater scientific societies. Jim Heffernan demonstrated that the Everglades has alternative stable landscape states and (filling in for Martin Doyle) discussed the timescales of reservoir management. Anna Braswell presented evidence that local feedbacks influence continental scale distribution of salt marshes. Chelsea Clifford presented her research on artificial streams in California. Megan Fork used an interactive poster to show how DOC concentrations and fluxes are changing across the US. Heffernan Lab Alumni were out in force as well: Ewan Isherwood talked about vegetation distinctness in the Everglades, Alison Appling talked about greenhouse gas concentrations in Northeastern Lakes, and Meredith Steele somehow wove together urban hydrography and Mermaids. Work from the Heffernan lab was also mentioned in two of the Plenary sessions, via presentations by Laurel Larsen and Pat Soranno. We capped off a succesful meeting by having lunch with members of the Sponseller lab. Now, back to work!
Our paper on the landscape pattern of cypress dome wetlands in Big Cypress National Preserve, led by Adam Watts, is available online at Earth Surface Processes and Landforms. Using a variety of lines of evidence, we show that cypress domes are regularly distributed, and that this pattern is more strongly reflected in the bedrock and vegetation than in soil elevations. We also expand on and refine our conceptual model of how this pattern arises. In brief, we propose that cypress domes are drilling into the limestone bedrock via the acidity of organic matter and CO2 production by vegetation. This local positive feedback expands wetland basins vertically and laterally. As wetlands expand, they essentially come into competition for runoff from the adjacent uplands, which ultimately limits the size and density of wetlands on the landscape. Patterns of soil phosphorus suggest that P mobilization by this dissolution may amplify this biogeomorphic feedback. This paper lays the foundation for our new NSF grant, which will support more mechanistic study of the processes that create these wetland basins and control their distribution on the landscape.
This is the homepage of the Heffernan Lab at Duke University. Here you can find all sorts of information about our research, teaching, and outreach. If you have any questions, contact Dr. Heffernan.
Dr. Jim Heffernan
I am an Assistant Professor in the Nicholas School of the Environment at Duke University. My research is focused on the causes and consequences of major changes in ecosystem structure, mostly in streams and wetlands.
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