Abstract: Tree islands are considered key indicators of the health of the Everglades ecosystem because of their sensitivity to both flooding and drought conditions. Tree islands also act as a sink for nutrients in the ecosystem and may play an important role in regulating nutrient dynamics. Although management strategies to restore and even create tree islands are being formulated, the published data on their age, developmental history, geochemistry, and response to hydrologic alterations is limited. To address these issues, this project integrates floral and geochemical data with geologic and vegetational mapping activities to establish the timing of tree-island formation and impacts of both flooding and droughts on tree islands throughout the Everglades.
Purpose: Everglades restoration planning requires an understanding of the impact of natural and human-induced environmental change on wetland stability, and this project focuses specifically on three wetland types: tree islands, the sawgrass ridge and slough system, and marl prairies. Tree islands are considered key indicators of the health of the Everglades ecosystem because of their sensitivity to both flooding and drought conditions. Tree islands also act as a sink for nutrients in the ecosystem and may play an important role in regulating nutrient dynamics. Although management strategies to restore and even create tree islands are being formulated, published data on their age, developmental history, geochemistry, and response to hydrologic alterations is limited. This project addresses these issues by integrating floral and geochemical data with geologic and vegetational mapping activities to establish the timing of tree-island formation and impacts of both flooding and droughts on tree islands throughout the Everglades. These data are used to assess the depth and period of flooding that tree islands can tolerate before degradation begins. We are also studying the role of tree islands in the geochemical budget of nutrients in the Everglades and investigating the use of sediment phosphorous as a tracer of historic bird populations in the Everglades. In FY 2003, the project expanded to include examination of the Ridge and Slough system. Resource managers have hypothesized that sawgrass ridges are expanding at the expense of adjacent sloughs; continuation of this trend would result in loss of the ridge and slough structure and development of broad expanses of sawgrass. In addition, performance targets for peat accretion rates in each subenvironment are being considered for CERP efforts, although there is little scientific basis for such targets. Initial analyses of sediment cores from sawgrass ridges and adjacent sloughs indicates that it is possible to distinguish the assemblages in sediment cores. The project will use well-dated pollen records from transects across ridge and slough systems to identify changes in spatial extent of sawgrass ridges and sloughs in both 'pristine' and disturbed areas. These data will be used 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. In Fy 2003-2004 we began research to determine the predrainage extent of marl prairies, particularly in the western Everglades. Marl prairies, with relatively shallow water depths and short hydroperiods, are characterized by a greater abundance of graminoid species compared to sawgrass marshes. Use of well-dated pollen cores to determine the distribution of marl prairies over the past 150 years will facilitate prediction of the impacts of different restoration schemes on this critical region.

Progress: In Work
Update Frequency: As needed

Theme Keywords: none, geochemistry, chemistry, geology, nutrients, tree islands, Ridge and Slough, marl prairies, mapping, vegetation, pollen, Geographic Data - Metadata, ISO 19115:2003(E), TopicCategoryCode, 2003, International Organization for Standardization (ISO), Geneva, Switzerland, biota, environment, geoscientificInformation, inlandWaters, 002, 007, 008, 012
Place Keywords: United States, US, Florida, FL, Collier County, Miami-Dade County, Monroe County, Palm Beach County, Broward County, Everglades National Park, Big Cypress National Preserve, Loxahatchee National Wildlife Refuge, Rattlesnake Ridge, Central Everglades, SW Big Cypress, Water Conservation Area 1, WCA1, Water Conservation Area 2, Water Conservation Area 3, WCA2A, WCA3A, Water Conservation Area 2A, Water Conservation Area 3A

Access Constraints: none
Usage Constraints: These data are subject to change and are not citeable until reviewed and approved for official publication by the USGS