Discharge competence and pattern formation in peatlands: a meta-ecosystem model of the Everglades ridge-slough landscape.

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Regular landscape patterning arises from spatially-dependent feedbacks, and can undergo catastrophic loss in response to changing landscape drivers. The central Everglades (Florida, USA) historically exhibited regular, linear, flow-parallel orientation of high-elevation sawgrass ridges and low-elevation sloughs that has degraded due to hydrologic modification. In this study, we use a meta-ecosystem approach to model a mechanism for the establishment, persistence, and loss of this landscape. The discharge competence (or self-organizing canal) hypothesis assumes non-linear relationships between peat accretion and water depth, and describes flow-dependent feedbacks of microtopography on water depth. Closed-form model solutions demonstrate that 1) this mechanism can produce spontaneous divergence of local elevation; 2) divergent and homogenous states can exhibit global bi-stability; and 3) feedbacks that produce divergence act anisotropically. Thus, discharge competence and non-linear peat accretion dynamics may explain the establishment, persistence, and loss of landscape pattern, even in the absence of other spatial feedbacks. Our model provides specific, testable predictions that may allow discrimination between the self-organizing canal hypotheses and competing explanations. The potential for global bi-stability suggested by our model suggests that hydrologic restoration may not re-initiate spontaneous pattern establishment, particularly where distinct soil elevation modes have been lost. As a result, we recommend that management efforts should prioritize maintenance of historic hydroperiods in areas of conserved pattern over restoration of hydrologic regimes in degraded regions. This study illustrates the value of simple meta-ecosystem models for investigation of spatial processes.





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Heffernan, James B, Danielle L Watts and Matthew J Cohen (2013). Discharge competence and pattern formation in peatlands: a meta-ecosystem model of the Everglades ridge-slough landscape. PLoS One, 8(5). p. e64174. 10.1371/journal.pone.0064174 Retrieved from https://hdl.handle.net/10161/8321.

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James Brendan Heffernan

Associate Professor of Ecosystem Ecology and Ecohydrology

I am interested in major changes in ecosystem structure, particularly in streams, rivers and wetlands. My work focuses on feedbacks among ecological, physical, and biogeochemical processes, and uses a wide range of tools and approaches. I am particularly interested in projects that address both basic ecological theory and pressing environmental problems. Increasingly, we are applying tools and theories developed for local ecosystems to better understand ecological patterns and mechanisms at regional and continental scales.

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