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Project Summary Sheet

U.S. Geological Survey, Greater Everglades Priority Ecosystems Science (PES) Initiative

Fiscal Year 2004 Study Summary Report

Study Title: Development and Stability of Everglades Tree Islands, Ridge and Slough, and Marl Prairies
Study Start Date: 10/1/00 Study End Date: 9/30/07
Web Sites:
Location (Subregions, Counties, Park or Refuge): Loxahatchee NWR, WCA 2, 3, Everglades National Park, Big Cypress National Preserve
Funding Source: USGS Greater Everglades Science Initiative (PES)
Principal Investigator: Debra A. Willard
Study Personnel: C. Bernhardt, M. Corum, C. Holmes, B. Landacre, H. Lerch, M. Marot, W. Orem, T. Sheehan
Supporting Organizations: South Florida Water Management District, Florida Fish & Wildlife Conservation Commission, Loxahatchee NWR, Everglades National Park, Big Cypress National Preserve
Associated / Linked Studies: Interrelation of Everglades Hydrology and Florida Bay Dynamics (Ecology Component), Tides and Inflows in the Mangrove Ecotone (TIME) Model Development, Ecosystem History of the Southwest Coast-Shark River Slough Outflow Area

Overview & Objectives: Everglades restoration planning requires an understanding the impact of natural and human-induced environmental change on wetland stability. This project initially focused on tree-island development and trends and has expanded into two other systems: the sawgrass ridge and slough system and marl prairies. For each system, restoration targets are being proposed, even though little data exists on their predrainage extent and ecosystem dynamics. Initial goals of the project included: determine geologic and hydrologic controls on tree-island formation, development and sustainability; establish vegetational trends in tree-island development; determine the role of tree islands in the geochemical budget of nutrients; and investigate the use of sediment phosphorus as a tracer of historic bird populations in the Everglades.

Investigations of the Ridge and Slough system are directed to: determine the longevity of the features; document changes in spatial extent of sawgrass ridges and sloughs; determine past rates of peat accretion in ridges vs. sloughs; determine whether sawgrass ridges are analogs for sites of tree-island formation; and assess the response of ridges and sloughs to natural and anthropogenic hydrologic changes. Investigations of marl prairies are designed to determine whether the distribution and vegetational composition of marl prairies has changed over the last century.

Status: By the end of FY04, cores will have been collected on 35 tree islands in Loxahatchee NWR, WCA 2A, 3A, 3B, and Everglades National Park (Shark River Slough and Taylor Slough). Pollen and geochronologic data have been generated from 23 cores representing 13 tree islands. Six transects of cores were collected across “pristine” and altered sawgrass ridges and sloughs sites in WCA 3A. From these, pollen analysis is complete on surface samples and four transects, representing a total of 11 cores. In FY03-04, field work included coring of cypress strands in Big Cypress National Preserve, marl prairies in Big Cypress NP, and strand and pop-up tree islands in Loxahatchee NWR. A long core (5 meters) also was collected in Deep Lake (BCP) to evaluate natural and anthropogenic patterns of change in an ancient sink-hole lake in a relatively pristine area of the Preserve. Analysis of sediment cores collected in marl prairies in the western Everglades as a pilot study indicated that pollen, plant macrofossil, and ostracode records all provide good records of vegetational and hydrologic change in marl-accumulating systems, and we intend to sample other such sites to document the timing of vegetational changes and correlate them with specific hydrologic events. In Loxahatchee, we collected cores on nine tree islands and nine marshes in the northern, central, and southern reaches of the Refuge to establish the original ecosystem structure and composition and evaluate changes in response to 20th century management changes.

Recent Products:

Willard, D.A., Holmes, C.W., Korvela, M.S., Mason, D., Murray, J.B., Orem, W.H., and Towles, D.T., 2002. Paleoecological insights on fixed tree island development in the Florida Everglades: I. Environmental Controls. In Sklar, F.H., and van der Valk, A. (Eds.), Tree Islands of the Everglades: 117-152.

Orem, W.H., Willard, D.A., Werch, H.E., Bates, A.L., Boylan, A., and Corum, M., 2002, Nutrient geochemistry of sediments from two tree islands in Water Conservation Area 3B, the Everglades, Florida. In Sklar, F.H., and van der Valk, A. (Eds.), Tree Islands of the Everglades: 153-186.

Willard, D.A. and Orem, W.H. 2003, Tree-Islands of the Florida Everglades - A Disappearing Resource, U.S. Geological Survey Open-file Report 03-26: 2 pp.

Bernhardt, C.E., Willard, D.A., and Holmes, C.W., 2003, Development and Stability of the Everglades Ridge and Slough Landscape. U.S. Geological Survey Open-file Report 03-54: 128.

Willard, D.A., 2004, Tree Islands of the Florida Everglades Long-term Stability and Response to Hydrologic Change, U.S. Geological Survey Open-file Report 2004-3095: 4 pp.

Planned Products:

Willard, D.A., 2004. Tree Islands of the Florida Everglades Long-term Stability and Response to Hydrologic Change, U.S. Geological Survey Open-file Report 2004-3095: 4 pp.

Bernhardt, C.E., Willard, D.A. 2004. Influence of 20th century water management on plant communities in Everglades marl prairies. First National Conference on Ecosystem Restoration (to be held 12-2004, Orlando, FL).

Willard, D.A., Bernhardt, C.E., Holmes, C.W., Landacre, B., and Marot, M., in prep. Tree Islands of the Everglades Ridge and Slough Region: Response to Environmental and Climatic Variability, Ecological Monographs (submission in 2004).

Bernhardt, C.E. and Willard, D.A., in prep. Development and Stability of the Everglades Ridge and Slough Landscape: Records from three transects in Water Conservation Area 3A. U.S. Geological Survey Open-file Report 04 - (completion in FY04).

Specific Relevance to Information Needs Identified in DOI Science Plan in Support of Ecosystem Restoration, Preservation, and Protection in South Florida [See Plan on SOFIA's Web site:]:

This study supports several of the projects listed in the DOI science plan (specifically: Arthur R. Marshall Loxahatchee NWR Internal Canal Structures; Water Conservation Area 3 Decompartmentalization and Sheetflow Enhancement; and Combined Structural and Operational Plan) by (a) documenting the timing of tree-island formation across the region; (b) establishes patterns of vegetation development and geochemical changes on the islands; (c) comparing development of different types of tree islands; (d) developing a model of tree-island formation that may be used in restoration of degraded islands and, possibly, creation of new islands; and (e) determining the duration of flooding or drought that tree islands can tolerate before changes in aerial extent occur.

The study supports the Arthur R. Marshall Loxahatchee NWR Internal Canal Structures project (LNWR; p. 39) as it (1) provides data about historic hydrologic and ecological conditions on the refuge (p. 40) and (2) helps understand the ecological effects of hydrology and water quality on refuge resources (p. 40) The study supports the Water Conservation Area 3 Decompartmentalization and Sheetflow Enhancement project (DECOMP; p. 66) as it (1) helps understand the linkages among the geologic, hydrologic, chemical, and biological processes that shaped the predrainage Everglades (p. 68); (2) helps understand the critical factors for sustaining tree islands, ridge and slough habitats, and marl prairies (p. 68); and (3) helps understand the effects of different hydrologic regimes and ecological processes on restoring and maintaining ecosystem function (p. 69).

This study supports the Combined Structural and Operational Plan project (CSOP and Mod Waters; p. 70) as it (1) generates information that will improve ecological models and make them more suitable for application of the Natural Systems Model (p. 71).

Key Findings:

  1. Tree islands throughout the greater Everglades ecosystem were affected by 20th century hydrologic change, but impacts on plant community composition and tree-island size vary throughout the region.
  2. The basic Ridge and Slough structure of WCA 3A has existed for at least 1,000 years; the position of the ridge-slough transition zone has fluctuated in response to recent changes in hydrology.
  3. Pollen, seed, and ostracode assemblages from cores collected in marl prairies indicate a shift to drier conditions in the early 20th century; pending geochronological analyses will clarify the timing of the change.

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