Journal cover Journal topic
Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
Hydrol. Earth Syst. Sci., 20, 4457-4467, 2016
http://www.hydrol-earth-syst-sci.net/20/4457/2016/
doi:10.5194/hess-20-4457-2016
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
04 Nov 2016
Hydrologic controls on aperiodic spatial organization of the ridge–slough patterned landscape
Stephen T. Casey1, Matthew J. Cohen1, Subodh Acharya1, David A. Kaplan2, and James W. Jawitz3 1School of Forest Resources and Conservation, University of Florida, Gainesville, FL, USA
2Engineering School of Sustainable Infrastructure and Environment, Environmental Engineering Sciences Department, University of Florida, Gainesville, FL, USA
3Soil and Water Science Department, University of Florida, Gainesville, FL, USA
Abstract. A century of hydrologic modification has altered the physical and biological drivers of landscape processes in the Everglades (Florida, USA). Restoring the ridge–slough patterned landscape, a dominant feature of the historical system, is a priority but requires an understanding of pattern genesis and degradation mechanisms. Physical experiments to evaluate alternative pattern formation mechanisms are limited by the long timescales of peat accumulation and loss, necessitating model-based comparisons, where support for a particular mechanism is based on model replication of extant patterning and trajectories of degradation. However, multiple mechanisms yield a central feature of ridge–slough patterning (patch elongation in the direction of historical flow), limiting the utility of that characteristic for discriminating among alternatives. Using data from vegetation maps, we investigated the statistical features of ridge–slough spatial patterning (ridge density, patch perimeter, elongation, patch size distributions, and spatial periodicity) to establish more rigorous criteria for evaluating model performance and to inform controls on pattern variation across the contemporary system. Mean water depth explained significant variation in ridge density, total perimeter, and length : width ratios, illustrating an important pattern response to existing hydrologic gradients. Two independent analyses (2-D periodograms and patch size distributions) provide strong evidence against regular patterning, with the landscape exhibiting neither a characteristic wavelength nor a characteristic patch size, both of which are expected under conditions that produce regular patterns. Rather, landscape properties suggest robust scale-free patterning, indicating genesis from the coupled effects of local facilitation and a global negative feedback operating uniformly at the landscape scale. Critically, this challenges widespread invocation of scale-dependent negative feedbacks for explaining ridge–slough pattern origins. These results help discern among genesis mechanisms and provide an improved statistical description of the landscape that can be used to compare among model outputs, as well as to assess the success of future restoration projects.

Citation: Casey, S. T., Cohen, M. J., Acharya, S., Kaplan, D. A., and Jawitz, J. W.: Hydrologic controls on aperiodic spatial organization of the ridge–slough patterned landscape, Hydrol. Earth Syst. Sci., 20, 4457-4467, doi:10.5194/hess-20-4457-2016, 2016.
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Short summary
The ridge–slough landscape is a major part of the Everglades, a critically imperiled wetland in south Florida (USA). The landscape consists of two wetland types, shallow water ridges and deep water sloughs, interspersed in a complex pattern. Human changes to hydrology have changed this pattern, impacting water flow, fish movement, and bird habitat. Restoring pattern requires understanding its origins. We describe the pattern in detail, gaining insights relevant for management on its origins.
The ridge–slough landscape is a major part of the Everglades, a critically imperiled wetland in...
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