Gallagher, Jacqueline

The purpose of this thesis was to document human impacts to Grassy Waters Preserve and correlate that to environmental change. Aerial photographs and archives provided a history of human impacts. These impacts included roadways, canals/levees, development, and landfills. To determine if environmental change occurred vegetation maps were digitized and compared from three study areas using 1940 and 1999 aerial photography. These vegetation maps included open water, transitional marsh/prairie, cypress, upland forest and human feature categories. Within all study areas the vegetation maps indicated decreases in the open water community. Within two areas major increases in cypress and uplands occurred. Vegetative shifts varied based on the locations of features like canals and levees. Due to image quality differences statistical analysis of the maps was not possible. However, the magnitude of change suggests that Grassy Waters became more densely vegetated and forested over time.

Loss of species richness and vegetative biodiversity in the Greater Everglades Area is in large part due to human encroachment and compartmentalization causing altered hydroperiods, water levels and surface sheet flow. This study quantifies vegetative complexity, biodiversity and species richness on four tree islands within a near pristine area of the historical northern Everglades ecosystem. A Complexity Index (CI) was formulated by assessing multiple variables; high CI and low herbaceous species richness values are attributed to mature, late successional stage forests. There are structural and population differences on each of the tree islands studied with the more mature tree islands located in the south of the study area, the more disturbed, low CI valued sites to the north. Data from this study is to be used as a baseline study for the area, and will be used to test and track the effects of the Comprehensive Everglades Restoration Plan.

This study focused on whether wetland vegetation could become re-established on a newly restored floodplain of the Kissimmee River if seasonal floodplain inundation were re-established. The wetland was re-created by back-filling a section of the Kissimmee Canal and diverting water flow into remnant river meanders. Seasonal flooding did occur during the study period. There were no other interventions to promote wetland plant growth. Ten vegetation quadrats were stratified between the back-filled canal and adjacent floodplain. These quadrats were monitored for 11 months. Of the 68 plant species recorded, 72% were obligate, facultative wetland or aquatic species. Diversity, richness, and percent cover of wetland plants increased with time. Coverage of broadleaf marsh habitat increased with increasing water depths. Vegetation at the end of the study period was similar to pre-channelized estimates. Restoration of hydrologic fluctuations appears sufficient to re-establish wetland habitat in this area of the Kissimmee River basin.

Lake Okeechobee is one of the largest lakes in the United States, yet its formation, circulation, and geomorphology are not well known. The ridges that occur on the eastern and northern shorelines of the lake have not been studied. Sugar Ridge is the closest ridge to the lake on the central part of the eastern shoreline. It is composed of medium- to fine-grained quartz (sugar sand) sediments in a dynamic form, superimposed upon organic peat and muck layers. It contains centimeter-scale bedding that exhibits many sedimentary structures typical of an accretionary barrier beach. Wind waves are considered the most likely cause of transport of the clastic sediments to the study area. Variations in lake level and wind in the region are such that conditions were favorable for development primarily in the winter. That is when lake levels were high enough to reach the ridge and the winds were strong enough to cause waves to transport sediment. Sediment was transported from the mouth of the Kissimmee clockwise around the northern perimeter. However, today the lake is completely enclosed and its levels are constantly manipulated.