| The Everglades ridge and slough landscape is a patterned peatland that is topographically and vegetationally distinct and supports a relatively diverse ecosystem. Patterning persisted in dynamic equilibrium with the climate for 2700 years, but over the past century, landscape structure has degraded rapidly. Degradation, which typically manifests itself as topographic flattening and a loss of sloughs, has occurred concurrent with drainage, compartmentalization of the marsh by levees and canals, modified surface water depth/duration patterns, and agricultural release of phosphorus and sulfate. The goal of this study was to understand how these anthropogenic impacts may have adversely affected the trajectory of landscape evolution and to identify strategies to preserve and restore the ridge and slough landscape. Critical to this goal was the need to elucidate physical-biological feedback processes through field and laboratory experimentation and numerical modeling. Results show that two dominant classes of feedback exert control over the vertical and lateral dimensions of the landscape. In the vertical dimension, a differential peat accretion feedback, in which peat accumulates at different rates under ridge and slough vegetation communities in response to hydrologic and biogeochemical forcing, governs the attainment of an equilibrium elevation difference between ridge and slough. In the lateral dimension, feedback between surface water flow, vegetative resistance, and sediment transport governs ridge width, spacing, and elongation. While the timescale of landscape response to perturbations to the differential peat accretion feedback tends to be shorter than the response to perturbations to the flow/sediment transport feedback, both processes are essential to the long-term stability of the landscape. Although the fluorescent fingerprinting of organic carbon shows evidence of limited particulate organic matter redistribution in the present system, sediment transport events are rare. In sloughs populated by abundant Eleocharis (spikerush), it will be impossible to increase bed shear stresses to the sediment entrainment threshold without increasing surface water slope. Overall, results produce restoration recommendations of reducing Eleocharis abundance within sloughs, maintaining hydroperiods and nutrient concentrations near pre-drainage conditions to ensure the appropriate balance between the production and decomposition of organic matter, and periodic pulsed releases of water from impounded areas to redistribute sediment. |
