We've just heard from NSF that our proposal to study the wetlands of Big Cypress National Preserve will be funded! The Big Cypress landscape is a mosaic of isolated wetlands, grasslands, and pine forests. The core observation that motivates our proposal is that the Cypress wetlands appear to be regularly spaced. This sort of regular pattern occurs in dryland vegetation, in peatlands (including the nearby Everglades) and elsewhere, and is thought to arise from feedbacks that are spatially-dependent. Basically, organisms improve the environment in their immediate vicinity, but that has the effect of making more distant locations unsuitable. In Big Cypress, we think that cypress trees essentially capture water from the surrounding landscape by dissolving the limestone bedrock and creating wetland depressions. Pretty smart! Testing this core hypothesis, and all of its pieces, requires an interdisciplinary team. My colleagues at UF, who are going to do most of the field work, include ecohydrologists, soil scientists, and organic and inorganic geochemists. Brad Murray and I are in charge of developing a model of this landscape. It's gonna be fun.
New paper on hydrologic feedbacks in the Everglades has been published in PLoS One. In this study, we develop a mathematical model of interactions between peat accumulation, vegetation productivity, soil elevation, and water flow. We show that the resulting feedbacks can cause spontaneous divergence of ridges and sloughs, and that these feedbacks act differentially with direction. The model provides a range of predictions that we are hoping to test with data from our Everglades monitoring project. You can download the paper here.
Our paper on ecohydrologic feedbacks and pattern formation has just been accepted for publication in PLoS One. This paper uses a simple quasi-spatial model to show that the need to route water through the Everglades landscape, in conjunction with local positive feedbacks on peat accretion, can produce directional feedbacks that generate flow-perpendicular pattern. The model also makes a number of predictions about relationships between water flow and microtopographic variation that we hope to test with our large-scale Everglades field sampling. Will post a link to the paper as soon as it is in press.
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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