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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Canopy Gaps as Foci of Succession in a Florida Keys Tropical Hardwood Forest

Diamond, Joshua M 24 June 2014 (has links)
Canopy gaps in many forests are thought of as resetting the successional sequence due to increased light availability. In this study, canopy gaps were identified with a LiDAR digital canopy model in a Key Largo hardwood forest. Sapling structure and composition were recorded in the gaps. Weighted averaging calibration was applied to relative abundances of trees to determine the successional age optimum for each tree species, and weighted averaging regression was used to calculate inferred stand ages for each gap’s saplings. The inferred stand ages were greater in young forest gaps than in surrounding, unimpacted forest, suggesting that succession was actually advanced. Canopy heights in Key Largo were shorter than many other tropical and temperate forests, canopy gaps were smaller and therefore light availability did not vary with gap area. This suggests that the largest gaps may not be big enough to produce the light conditions required to reestablish pioneer tree species. Soil and water conditions in young forest gaps may also favor mature rather than pioneer species. Resetting of the forest successional sequence may not occur without intense disturbances such as fires or major hurricanes that remove the entire canopy and consume or erode soils.
2

Habitat and Seasonal Distribution of the North American River Otter (Lontra canadensis) and Vertebrate Species Assemblages in Two Protected Areas of the Florida Everglades

Hamilton, Catherine Faye 01 November 2014 (has links)
The Florida Everglades ecosystem is threatened by human development, increased pollution, freshwater scarcity, and invasive species; factors that have negatively impacted the Everglades and native species health and populations. Man-made canals and levies have redirected the natural flow of fresh water from Lake Okeechobee into the Florida Everglades, starving central and south Florida ecosystems of necessary fresh water and nutrients. Through the efforts of the Comprehensive Everglades Restoration Project (CERP), freshwater is being redirected back into central and south Florida, returning the sheet flow of water back into the Everglades. Monitoring species abundance in the Everglades is a beneficial conservational tool for assessing restoration efforts from CERP. As a semi-aquatic apex predator, river otters (Lontra canadensis) are a useful health bio-indicator for the Florida Everglades. In order to conduct future population studies of river otters in the Florida Everglades, it must first be ascertained where they can be found and what time of year they are most likely to be sighted. For this study, Moultrie infrared game cameras were used to photograph the presence or absence of river otters within the five main habitats in the Everglades; the pinelands, hardwood hammock, cypress swamp, marsh prairie, and mangrove estuary at two protected areas in the Florida Everglades (Big Cypress National Preserve and Fakahatchee Strand State Park). River otters were most frequently sighted in the hardwood hammock habitat, but were also found in the cypress swamp. The large majority of river otter sightings occurred during dry season, which is thought to be a function of restricted water availability and aquatic mobility. Future population studies of river otters would be most productive in the hardwood hammock and cypress swamp habitats during dry season. Game camera images along with field opportunistic sightings, resulted in a variety of species documented. This provided valuable information of species richness and distribution within and amongst the habitats. The hardwood hammock was found to be the most species rich habitat, having over half the species observed in the study in this habitat. The Aves class was the most abundantly observed in the Everglades, and was most frequently sighted during the dry season. As a refuge for migratory birds, the Everglades house the majority of bird species during the winter months, which occur during dry season. The Aves class was most frequently sighted in the pinelands habitat during dry season. This habitat, being the highest in elevation and therefore the driest, shows a stronger resemblance to most northern bird habitats then does the water-saturated wetlands found throughout the Everglades. The mangrove estuary was the most commonly occurring outlier, having the least species overlap when compared to the other habitats. All other habitats in the Everglades are freshwater wetlands, while the mangrove estuary is a brackish environment, which limits the species that are unable to tolerate saline conditions. Further studies of species abundance throughout the Everglades will aid in monitoring CERP restoration efforts over time.

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