Everglades (Fla)

While repeated transgressive and regressive sea level cycles have shaped south Florida throughout geological history, modern rates of sea level rise pose a significant risk to the structure and function of the freshwater wetland ecosystems throughout the low-lying Everglades region. Current regionally corrected sea level projections for south Florida indicate a rise of 0.42m by 2050 and 1.15m by 2100, suggesting the salinization of previously freshwater areas of the Everglades is conceivable. As freshwater areas become increasingly exposed to saltwater they experience shifts in vegetation composition, soil microbial populations, plant productivity, and physical soil properties that ultimately result in a phenomenon called peat collapse. Recent work in the Everglades has sought to further explain the mechanisms of peat collapse, however the physical changes to the peat matrix induced by saltwater intrusion are still uncertain. Moreover, the combination of physical alterations to the peat matrix associated with peat collapse and shifts in wetland salinity regimes will also likely disrupt the current carbon gas dynamics of the Everglades.

Peat soils are known to be a significant emitter of atmospheric greenhouse gasses.
However, the spatial and temporal variability in production and release of greenhouse
gases (such as methane) in peat soils remains uncertain, particularly for low-latitude
peatlands like the Florida Everglades, as the majority of studies on gas dynamics in
peatlands focus on northern peatlands. The purpose of the work outlined here is focused
on understanding the spatial and temporal variability in biogenic gas dynamics (i.e.
production and release of methane and carbon dioxide) by implementing various
experiments in the Florida Everglades at different scales of measurement, using noninvasive
hydrogeophysical methods. Non-invasive methods include ground-penetrating
radar (GPR), gas traps, time-lapse cameras, and hydrostatic pressure head measurements,
that were constrained with direct measurements on soil cores like porosity, and gas
composition using gas chromatography. By utilizing the measurements of in-situ gas
volumes, we are able to estimate gas production using a mass balance approach, explore
spatial and temporal variabilities of gas dynamics, and better constrain gas ebullition models. A better understanding of the spatial and temporal variability in gas production
and release in peat soils from the Everglades has implications regarding the role of
subtropical wetlands in the global carbon cycle, and can help providing better production
and flux estimates to help global climate researchers improve their predictions and
models for climate change.

The vulnerability of prey to capture plays a fundamental role in determining
overall prey availability for wading birds. Structural complexity can act to decrease prey
vulnerability and influence foraging habitat selection. To determine how structural
complexity can affect habitat selection I conducted a use vs. availability study throughout
the Florida Everglades in 2005 and 2006. Results indicated that wading birds chose
foraging sites that had less emergent vegetation and a thicker flocculent layer relative to
random sites. Submerged vegetation, and the height of emergent vegetation did not
affect wading bird site selection. A difference in habitat selection between years was
evident due to hydrological conditions. Ideal hydrological conditions are probably the
most important parameter to wading bird success. Other factors affecting prey
vulnerability became increasingly important in years of poor hydrology, probably
because the penalty for choosing low quality foraging habitat would be greater than in
years of more optimal conditions.

In the 1980s, confronted by severe problems created by one hundred years of drainage and flood control in Florida, public officials realized a new policy, while continuing to provide flood protection, must protect the environment and wildlife. This involved restoring the natural water flows to wildlife refuges, Everglades National Park, and other wetland areas. New legislation controlling the water supply, water quality, and the wetlands was passed. The Save Our Everglades program proposed to restore the Everglades (the Kissimmee River Basin, Lake Okeechobee and the Everglades) to look and function more as it did in 1900 than in 1983 when the program was initiated. Problems, primarily caused by increasing population and agriculture, continued to thwart restoration efforts.

Floating islands are common natural features in modern Hillsboro
Marsh. Most floating islands: 1) occur as detached,
free-floating batteries (raft-like peaty masses that rise
from substrate), and 2) form in habitats containing abundant
waterlilies. New batteries are quickly colonized by
marsh, and often terrestrial, plants. Differences in
species diversity and early succession occur between two
ecologically different subareas. In one subarea many
batteries succeed quickly to mixed graminoid-arborescent
vegetation. Floating batteries form hydrologically unusual
Everglades habitats and support some locally rare plants.
Battery formation produces local topographic elevations and
depressions. Apparent size-successional vegetational and
landform continuumns seem to link batteries with small extant
tree-islands. Radiometric evidence suggests presence of
batteries in peat profiles of two tree-islands. Everglades
floating islands most resemble others reported in southeastern
United States and appear dissimilar morphologically and
in mode of origin to those reported from elsewhere worldwide.