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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

Emergent Insect and Neotropical Migratory Bird Interactions and Responses to Habitat, Hydrology, and Progressive Urbanization in the Tampa Bay Region

Goddard, Nathaniel Lee 02 November 2015 (has links)
The growing human population threatens the many of the earth’s biological systems. In the last 600 years extinction rates risen from 1 extinction per million species per year (E/MSY) in the 1400’s to 50 E/MSY today. During this time period 1.5% of all known birds have gone extinct, because they could not adapt quickly enough to human mediated changes. The goal of this dissertation was to determine how urbanization and anthropogenic services needed to support urban areas impact cypress dome wetland aquatic insect and migratory bird populations that depend on them. In Central Florida cypress dome hydroperiods are driven by seasonal rainfall conditions and fill June and July with the onset of the Florida rainy season then begin drying beginning in October with the onset of the dry season. Some wetlands were strongly influenced by groundwater pumping and dried out quicker than others, a characteristic that reduced annual insect emergence. Decreased adult insect populations were associated with lower emergence rates early in the dry season led to lower utilization by insectivorous birds. Winter migratory birds significantly related with adult insect abundance during winter months (r = 0.578, p=0.049), and utilized this region at the peak in adult insect populations. Conversely, Neotropical migrants travel through the region during spring when insects are scarce, and adult insects began sharp decline suggesting that Neotropical migrants depleted populations possibly leading to interspecies competition. Neotropical migrants strongly avoided urban areas and declined by 70% in urban areas, which may contribute to declining Neotropical migratory bird populations as a lack in adequate stopover sites may limit entire species. If they are not able to adapt foraging patterns that utilize urban areas in Central Florida where urban development is increasing rabidly populations may continue to decline.
2

Land Subsidence and Earth Fissures Due to Groundwater Pumping

Adiyaman, Ibrahim Bahadir January 2012 (has links)
In this research, the fundamental mechanics for the changes in stresses and strains states due to groundwater pumping is formulated. This was accomplished by developing a 3D closed form solution. The results from this research are compared with results of finite element (FE) analyses and data obtained from interferometric synthetic aperture radar (InSAR). Land subsidence (LS) due to groundwater pumping from a single well for different geological profiles and the reason why LS continues after groundwater pumping cessation were investigated. FE analyses for four different scenarios were used to investigate the effects of cemented layers and non-cemented layers above the aquifer on EF initiation. A practical method which is based on the stiffness and cementation strength of the cemented layer and the gradient of the slope of the subsidence bowl (ɑ) was proposed to determine earth fissure (EF) initiation. Three-point bending beam test was conducted in the lab to determine the mode of failure and the modulus of rupture of a local cemented soil that occurs in areas where EFs were observed. The major findings are as follows. LS due to groundwater pumping consists of i) isotropic compression and ii) simple shear on vertical planes with rotation. For a parabolic distribution of groundwater level in a homogenous aquifer, simple shear on vertical planes will be dominant when the characteristic length of the aquifer is larger than √2 times the aquifer thickness. Fine-grained soils are responsible for LS occurring after the cessation of pumping and for sagging in LS profiles. Regardless of the stiffness and cementation strength of the top layer above the aquifer, EF will not initiate if ɑ is less than 8x10⁻⁵. When the stiffness of the top cemented layer increases, it becomes more prone to EF initiation. However if the layer is stiff enough to be classified as "rock" then a higher value of ɑ is needed to initiate an EF. The experiments show that the preferred mode of failure of a cemented soil is shear rather than bending and existing cracks significantly influence the results of EF formation.
3

Analysis Of Groundwater Dynamics In Semi-Arid Regions : Effect Of Rainfall Variability And Pumping

Javeed, Yusuf 10 1900 (has links) (PDF)
No description available.

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