Mangrove forests dominate the land-margin ecosystems of the southwestern Everglades. Over 100,000 ha are found in this region (Odum and McIvor, 1990). Mangroves provide considerable goods and services to mankind including: production of commercially and recreationally important fisheries, shoreline stabilization and protection from storm surges, and the improvement of water quality by uptake of nutrients (Ewel and others, 1998). Within the greater South Florida ecosystem, mangrove forests are at the downstream end of the vast "River of Grass" and thus are at the receiving end of upstream water-management decisions (Smith and others, 1989).

In addition to receiving freshwater from upstream sources, mangroves are subjected to periodic catastrophic disturbances, such as Hurricane Andrew, sea-level rise, and occasional freeze events. Significant research activities to understand the ecology of mangroves commenced following the passage of Hurricane Andrew (Smith and others, 1994).

A network of permanent vegetation sampling plots was initially established throughout the mangrove forests along the southwestern coast of Everglades National Park. Plots were located on the upstream downstream gradients of the Shark, Harney, Broad, and Lostmans Rivers in the fall of 1992 and spring of 1993. Subsequently, additional plots were established in the 10,000 Islands National Wildlife Refuge, Rookery Bay National Estuarine Research Reserve, and on the islands and northern shoreline of Florida Bay in Everglades National Park. In many cases, plots have been collocated with sites of other research activity, such as in the vicinity of the surface- and ground-water sampling wells of the South Florida Global Climate Change Program (see Smith, Anderson, Nuttle, this volume). Additionally, a sediment elevation table network is being established at these sites to measure important sedimentological processes (see Cahoon and Smith, this volume).

The plots are circular with a permanent center marker. Every stem over 1.4 meters in height is identified to species and its "diameter at breast height" (dbh) measured. All stems were permanently tagged and the compass bearing and distance from the center stake to each stem recorded. The initial surveys estimated stem damage and tree death caused by Hurricane Andrew. Subsequent surveys have recorded growth (as change in dbh), death and new stems. Also, with each resurvey, the cause of death is recorded if possible (that is, Hurricane Georges in 1998). Sediment porewater chemical parameters (nitrogen, phosphorus, sulfide, and salinity) were measured in a subset of the plots during 1994-95.

The initial surveys revealed catastrophic mortality (100 percent in some cases) from Hurricane Andrew (Smith and others, 1994, Doyle and others, 1995) especially in areas crossed by the eye of the storm. Resurveys over the past 7 years have revealed complex patterns of regrowth and recruitment of new individuals into the forest. The white mangrove (Laguncularia racemosa) has dominated recruitment at many, but not all, plots. Both the red mangrove (Rhizophora mangle) and the black mangrove (Avicennia germinans) have recruited heavily into some plots. Both recruitment and growth showed little correlation with the soil chemical parameters tested to date.

The most upstream plots, those nearest the freshwater Everglades had little damage from Hurricane Andrew, primarily because the trees in these plots are much shorter than trees in downstream plots. However, it is these upstream plots which should exhibit the first measurable changes (for example, growth) to the water-management scenario proposed as part of the south Florida ecosystem restoration. Our mangrove forest permanent plot network is ideally suited for measuring change associated with the hydrological restoration of the Everglades.

A significant part of the funding for this research was provided from the U.S. Department of the Interior, South Florida Ecosystem Restoration Program "Critical Ecosystems Studies Initiative" (administered through the National Park Service); and, in part, from the U.S. Geological Survey, Florida Caribbean Science Center for the project "Disturbance Ecology of Tropical and Subtropical Mangrove Forested Wetland Communities."

REFERENCES

Doyle, T.W., and others, 1995, Wind damage effects of Hurricane Andrew on mangrove communities along the southwest coast of Florida, USA: Journal of Coastal Research (Special Issue #18), p. 159-168.

Ewel, K.C., Twilley, R.R., and Ong, J.E., 1998, Different kinds of mangrove forests provide different goods and services: Global Ecololgy & Biogeographical Letters 7, p. 83-94.

Odum, W.E., McIvor, C.C., 1990, Mangroves, in Myers, R.L., and Ewel, J.J., eds., Ecosystems of Florida: Chapter 15, p. 517-548.

Smith III, T.J., and others, 1989, Freshwater flow from the Everglades to Florida Bay: A historical reconstruction based on fluorescent banding in the coral in the coral Solenastrea bournoni: Bulletin of Marine Science, v. 44, p. 274-282.

Smith III, T.J., and others, 1994, Mangroves, hurricanes and lightning strikes: BioScience, v. 44, p. 256-262.

(This abstract was taken from the Proceedings of the South Florida Restoration Science Forum Open File Report)