South Florida Terrestrial Ecosystems Lab
Southeast Environmental Research Center

Coastal Wetland Projects

2015-2018 Ecosystem dynamics in the White Zone: history, drivers, and restoration impacts:
In a comprehensive follow up of studies of landscape change in the Southeast Saline Everglades (Egler 1952, Meeder et al. 1996), this project revisits and expands on prior sampling to determine drivers of productivity in the marsh and tree islands of the coastal ecotone, including the low productivity "White Zone". We analyze vegetation based on field sampling and remote sensing techniques, examine patterns in soil and water characteristics, and employ mollusk and diatom composition as an indicator of environmental change. Our objective is to better understand the responses of the ecosystem to disturbance and saltwater intrusion in the coastal zone. The information we acquire will help managers to anticipate and respond to the combined impacts on these wetlands of future sea level rise and hydrologic restoration activities.

2004-2006 - Large scale assessment of landscape changes and recovery in forest structure of mangrove wetlands subject to human, freshwater diversion, and natural disturbances  using enhanced Shuttle Radar Topography Mission data:
Mangrove wetlands are found primarily in the tropics and sub-tropics along coastlines or river deltas, and are part of a coastal biological complex that also includes seagrass beds, and coral reefs.  Mangroves are especially vulnerable to global changes and human impact. In partnership with the Jet Propulsion Lab & NASA, we used LIDAR to determine the consequences of climate and sea level changes and increased human activities on coastal regions.  We generated enhanced SRTM elevation data to estimate vegetation height in wetlands dominated by mangroves, with concurrent LIDAR mapping, semi-empirical modeling of radar scattering in mangroves to correct for the height bias and differential height measurements. We also estimated productivity within the complex mangrove mosaic, in the process improving our understanding of its underlying controls.  We extended production models to regional scales, and developed a landscape-scale understanding of recovery from disturbance, which is of course related to the innate productivity of the site.

 2002 — Multi-taxon Analysis of the "White Zone", a Common Ecotonal Feature of South Florida Coastal Wetlands:
 A common feature of many South Florida coastal areas is a zone of low plant cover, clearly recognizable as a white band on black and white or color infrared photos, sandwiched between more densely vegetated fringing mangrove and interior ecosystems. The position of the sparsely vegetated white zone seems to provide an effective indicator of the extent of marine influence. Furthermore, between 1940 & 1994 the inner boundary of the white zone had shifted toward the interior by an average of 1.5 km, with maximum change in areas cut off from upstream water sources by canals or roads. To clarify the significance of the white zone within coastal wetlands, and to elucidate its relationship with the local biota, we undertook a detailed examination of a single transect in the easternmost portion of the Southeast saline Everglades, bordering on southwestern Biscayne Bay in order to aid in developing indices of changing environmental conditions. 

1995-2001 – Aboveground Biomass and Production in Mangrove Communities of Biscayne National Park, Florida (USA):
  Many ideas have been advanced regarding the principal causes of variation in the biomass or productivity of mangrove ecosystems.  A complex of proximate factors which may be involved include salinity (Cintron et al. 1978), salinity variation (Ball 1988; Lin and Sternberg 1992), accumulation of sulfides or other toxic substances (McKee 1993), soil redox conditions (Pezeshki et al. 1997), and nutrient limitation (Feller 1995; Boto and Wellington 1983).  Efforts to test the importance of alternative environmental variables on the functioning of mangrove ecosystems require precise measurements of community response, including biomass and production. In 1993, we initiated a study of tall fringe and dwarf mangrove forests.  Our objective was to compare the production and allocation of aboveground biomass in these two forests. The dramatic transition in forest structure that characterized the pre-hurricane mangrove zone in much of southern Biscayne Bay was entirely disrupted by Hurricane Andrew (August, 1992).  Tall Fringe forests adjacent to the coast were leveled by intense winds which reduced the total aboveground biomass by about 200-fold, while Dwarf forest communities a few hundred meters inland were relatively unaffected. Five years later, the initial structural gradient was becoming reestablished, with annual aboveground production in the Fringe forest 3.5 times greater than in the Dwarf forest. This contrast in production between the two forest types was not evenly distributed among woody and photosynthetic tissues; Fringe production rates were approximately two, six, seven, and nine times higher for leaves, stems, branches, and proproots, respectively. Our research calls attention to the dynamic nature of community structure in hurricane-prone mangrove ecosystems, especially the size and distribution of aboveground biomass components.

 1994-1999 The Southeast Saline Everglades Revisited: A half-century of coastal vegetation change:
Coastal wetlands reflect a dynamic hydrologic balance between the marine and upstream or upslope terrestrial ecosystems which bound them on all sides. In these transitional settings, ecological responses which arise principally as a result of changes in the marine system may be modified by physiography, management, or land use patterns in the terrestrial environment, or vice versa. One example of these interactions is found in the response of mangrove ecosystems to sea level rise, which varies in rate or even direction in different physical settings or under alternative water management scenarios (Meeder et al. 1993). At a landscape scale, the anticipated response of coastal wetlands to change in sea level is even more complex, especially if the dramatic vegetation zonation typical of many coastal wetlands is incorporated. Since the mid 1940’s, the boundary of the mixed graminoid-mangrove and sawgrass communities shifted inland by as much as 3.3 km. Moreover, the interior boundary of a low-productivity zone appearing white on both B&W and CIR photos moved inland by an average of 1.5 km.  A smaller shift in this "white zone" was observed in an area receiving fresh water overflow through gaps in one of the canals in the coastal zone, while greater change occurred in areas cut off from upstream water sources by roads or levees. These large-scale vegetation dynamics are apparently the combined result of sea level rise - approximately 10 cm since 1940 – and water management practices in the Southeast Saline Everglades.

 1994-1996 — Vegetation Analysis in the C-111/Taylor Slough Basin:
 Marsh and adjacent tree island vegetation were examined in the Southeastern Saline Everglades (SESE), a broad zone between the Atlantic Coastal Ridge and the Florida and Biscayne Bay Shorelines in SE Florida. SESE marshes were arranged in well-defined compositional zones parallel to the coast, with mangrove-dominated shrub communities near the coast giving way to graminoid-mangrove mixtures, and then sawgrass marsh. The compositional gradient was accompanied by an interiorward decrease in total aboveground biomass, and increases in leaf area index and periphyton biomass. Tree island composition also exhibited a zonal pattern along the coastal gradient, with stands dominated by salt-tolerant and tropical tree species gradually replaced by forest communities of more freshwater and temperate affinity. The objective was to detect changes in the coastal gradient that had taken place since earlier descriptive studies by Egler (1952) and Tabb (1967). Fifty-five sites were sampled in 1994 and 1995. Changes were described in the C111 research report.