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Research and data collection recommendations

Causes of change
Evidence of change
Formation & Maintenance
Ecological impacts
Performance measure
Very few research studies have been conducted specifically to determine the role of flow in the Everglades ecosystem. Most of the research projects from which data were presented in this paper, while relevant to the role of flow, were not designed to determine the role of flow. It is precisely for this reason that the SCT chose the topic of flow as one of its priorities. Because compartmentalization and drainage of the Everglades almost certainly had a major impact on flow patterns, it is important that appropriate research and data collection occur to best guide future management and restoration decisions. It is with that goal in mind that the following research and data collection recommendations are provided.

It should be noted that listing of these recommendations does not eliminate the need for a thorough science plan for ridge and slough research. It is important that such a plan be developed, with participation by all stakeholders, including restoration managers. The plan should clearly develop priorities for research, so that limited funding can be applied in the most effective manner possible to develop new information. The plan should be revised on a regular basis as new information and knowledge is obtained. Also, because multiple mechanisms of ridge and slough formation and maintenance likely operate, research projects should specifically address the relative importance of the various mechanisms.

The recommendations below are separated into 3 general priorities – higher, medium, and lower – based upon the degree of consensus among the contributors and the reviewers of earlier drafts of this manuscript.

Higher priority

1. A multidisciplinary study of Everglades paleoenvironmental history is essential to determine the historical extent of ridge and slough habitat, the long-term dynamics of this and other landscape types, and more recent dynamics based on impacts from water management activities, barriers to flow, and other disturbance events such as fire. Measurements needed include: sediment stratigraphy; sediment dating; pollen analysis; peat charcoal detection; isotope geochronology; grain size analysis, bulk density measurements; carbon/nitrogen analysis; C3 vs C4 photosynthetic pathways; sediment geochemistry; macrofossil analysis; nitrogen isotope analysis; analysis of lipid biomarker compounds that reveal the origin of organic matter; and analysis of authigenic minerals such as iron sulfides to determine past redox changes.

2. A thorough and broad geomorphic review is necessary to develop competing conceptual models of how the ridge and slough landscape formed and how it is maintained. This review should provide lists of specific questions and hypotheses that would have to be addressed to evaluate each possible mechanism of formation and maintenance. The review should lead to the selection of a few of the conceptual models that would provide a better foundation for large-scale scientific inquiry. The review should evaluate processes of peat formation and vertical accretion of organic material, as these processes are fairly well understood and relevant.

3. Sediment transport distributions (spatially and temporally) should be quantified as a possible mechanism of ridge and slough formation and maintenance. Measurements needed include: distribution of particle size and density in suspended sediments, including floc; thickness and other specific characteristics of the floc layer, including changes over time; interception of suspended sediment by vegetation; the velocity at which suspended sediments will be deposited (sedimentary velocity); the velocity at which sediments are resuspended (erosive velocity); sediment deposition and decomposition rates in sloughs and sawgrass stands; and the typical elevation differences between ridges and sloughs. Collection of suspended sediments under variable flow regimes, both before, during, and after restoration is needed to support these objectives.

4. Synoptic measurements of flow should be conducted over short time scales and large space scales in order to quantify ranges of flow velocity and direction and to delineate major flow pathways. Flow measurements should be made in both intact and degraded ridge and slough habitat, and should include surface and ground water. Vertical profiling of flow should be conducted at specific times and locations to quantify details of the flow in order to understand the processes involved in sediment transport, erosion, deposition, mixing, and transport, and to correlate point measurements to vertical means. Time series measurements of flow should be conducted over long time scales at a limited number of locations in order to quantify the effect of infrequent events, such as the passage of storms, and the effect of low frequency phenomena, such as seasonal variations. Individual flow measurements, coupled with ecological surveys, should be designed to study the specific processes that are hypothesized to most likely alter the landscape and affect transport and mixing. Examples include flows around tree islands, near culverts, in fire-impacted areas, and in the vicinity of canals.

Medium priority

1. Develop a simple carbon balance model as a basis for understanding the biological and geomorphological processes that may differ between ridge and slough habitats, and to address the possible mechanism of differential rates of peat accumulation and decomposition. Model parameters would include: primary productivity; decomposition; carbon inputs and exports, both dissolved and particulate; and methane export. Obviously, the data collection and research necessary to provide these types of inputs to the model would have to be conducted, and coordinated with the collection of hydrological data suggested elsewhere. From this model development, a thorough, data-based, carbon budget could be established. Such an approach would illustrate any differences that may exist between ridges and sloughs, and would provide insight into factors that control carbon flow.

2. Continued collection and analysis of remotely sensed images, either fixed wing or satellite, is required to track trends in ridge and slough landscape patterns, and to track restoration progress, particularly when barriers to flow are removed. Field studies, remote sensing techniques, and system models also should be coordinated to provide a thorough understanding of the mechanisms involved. For instance, remote sensing and surface geophysics could be used to identify areas with strong or weak ridge and slough characteristics and depths of sediment deposition on bedrock, and field research could attempt to quantify environmental conditions leading to both landscape types. Field studies should be able to provide the parameters required by the system models.

3. Develop a seasonal water balance for the entire Everglades, illustrating the relative contribution of regional groundwater, direct precipitation, and surface inflows from the north. This balance would allow estimation of flow availability, quantity, and timing to the ridge and slough landscape prior to and after the water management system was constructed. Even if this water balance is available only as a first-order analysis, it would be useful in assessing the historical and present role of flow in creating and maintaining the ridge and slough landscape pattern.

Lower priority

1. Numerical and analytic techniques, including modeling, are needed to determine the mechanisms of ridge and slough formation and degradation. Numerical modeling of water and sediment flows should be conducted at a variety of temporal and spatial scales in order to provide a physics-based interpolation of the flow field on scales of ecological interest. Modeling also is required to evaluate restoration alternatives. System models that investigate the interactions of important landscape mechanisms would improve our understanding of the relative importance of the environmental factors. These models could also assess potential feedback processes between vegetation and hydrology. A specific example of a model is a ridge and slough patterning model. This model is a simple, grid-based simulation model that has been partially developed by South Florida Water Management District staff (Martha Nungesser, personal communication) but not yet implemented. Another possible approach to understanding the nature of flow and these landscape patterns is to build a simple physical model that tracks how slowly flowing water interacts with a peat-type material.

2. Studies should be conducted to assess the potential for recovery from dense sawgrass stands back to a more diverse wetland mosaic once uninterrupted flow patterns are restored. These studies would address whether the system is resilient enough to recover on its own, or further intervention would be required.

3. Research should be conducted to determine steps that must be taken to ensure that existing ridge and slough landscape can be sustained even in compartmentalized areas of the Everglades.

4. The responses of Everglades animals to flow should be studied, particularly how they may use flow to disperse seasonally to recolonize the system and how flow barriers affect that process.

5. Because of the lack of pre-drainage data, additional historical information concerning pre-drainage vegetation conditions should be sought. In particular, interviews should be conducted with individuals having direct experience in the Everglades prior to the majority of human-induced changes. For example, there may be Miccosukee Tribal elders who lived in the Everglades prior to the construction of the Tamiami Trail.

6. Regular workshops, focused on the ecological effects of flow in the Everglades, should be held. These workshops should involve wide participation of hydrologists and ecologists.

Additional recommendations for future research, both at the one and five-year time horizons, are contained in the flow workshop summary, accessible at http://sofia.usgs.gov/geer.

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Last updated: 04 September, 2013 @ 02:04 PM(TJE)