In the Gulf of Mexico, barrier islands absorb the majority of the wind and wave action from storms, resulting in modification of dune morphology and vegetation dynamics. Understanding changes in dune vegetation in response to storms can identify the ecological processes occurring in these areas as well as help predict future effects of tropical storms. Since 1999, T. Miller of Florida State University has been collecting data describing the dynamics of dune vegetation on St. George Island. These long-term census data provide an opportunity to investigate the ecology of dune ecosystems. I analyzed this ten-year data set to quantify how vegetation responds to major storms and determine which dune species would be most useful for restoring damaged coastal areas. This approach was tested using six plant species that were identified by T. Miller as particularly robust to the effects of storms. I conducted a transplant experiment with these six species across dune microhabitats and quantified transplant survival and growth over time in each habitat. Results suggest that, while several of these species have significant potential for restoration use, the habitat from which a transplant species originates is not a good indicator of its success in different habitats. Further, it appears that transplants encourage succession on degraded habitat. I explored the potential to extrapolate this restoration technique to a broader group of landscapes using GIS and aerial images to characterize vegetation change over time on St. George Island and compared these data with long-term census data. Additionally, I investigated if remote sensing could be used to identify locations that were similar to St. George in the distribution of dune habitats and the effects of storms across these areas. Results suggest that remote sensing approaches can be useful for a subset of habitat and species types on barrier islands. Lastly, I used estimates of plant growth in good and bad years from the long-term data to build a model that describes succession in dune habitats. The model can be used to identify how dune communities might respond to a change in storm frequency. The model predicts that an increasing frequency of storms will result in plant species turnover in each dune community with the foredune community expressing the most dramatic changes. / A Thesis submitted to the Department of Biological Science in partial fulfillment of the requirements for the degree of Master of Science. / Summer Semester, 2009. / May 19, 2009. / Hurricane, Barrier island, Coastal restoration, Climate change / Includes bibliographical references. / Thomas Edward Miller, Professor Directing Thesis; Alice Winn, Committee Member; Austin Mast, Committee Member; Nora Underwood, Committee Member; Jeff Chanton, Committee Member.

The purpose of these studies was to monitor changes in two aquatic ecosystems that represent end members along a continuum of human impacts. St. Andrew Bay in Panama City, Florida, USA, has been impacted by humans since it formed about 5,000 years ago; however these impacts have accelerated in the last 150 years as industrialization took place. In contrast, the peatlands north of High Level, Alberta, Canada, are located in a region where human population and development are minimal, yet these remote areas do not appear to be immune to the global climate change that resulted from the industrial revolution. This work describes the effects of water quality on seagrass distribution and epiphyte growth in St. Andrew Bay and it shows how climate change affects peat deposits north of High Level. Water quality has been monitored in St. Andrew Bay since 1990 and these data were coupled with seagrass monitoring data collected since 2000 and five aerial photos taken since 1953 to better determine the extent of seagrass losses in the bay system. The St. Andrew Bay system is composed of four smaller bays: West Bay, North Bay, St. Andrew Bay, and East Bay, and although there has been no systemic decline in seagrass coverage in North Bay, St. Andrew Bay, and East Bay, approximately half of the seagrasses in West Bay have been destroyed or degraded since 1953. Comparisons among these smaller bays show higher turbidities, higher chlorophyll a concentrations, and increased epiphyte growth rates in West Bay which result in shallower seagrass depths. Although the initial cause of seagrass loss in West Bay is unknown, the present eutrophication of this area will make it harder for seagrasses to recover. Furthermore, the future development of over 30,000 acres within West Bay's watershed surrounding a new international airport and industrial complex does not bode well for this stressed ecosystem. Although the peatlands of Canada are located in an area where human impacts are minimal, these ecosystems are still at risk from indirect stressors such a global climate change. Peatlands formed approximately 7,000 years ago as shallow lakes filled in with vegetation; eventually the accumulating vegetation insulated the ground allowing permafrost to form. Over the past 60 years however, global temperatures have increased, the direct result of increased carbon dioxide levels that started to climb after the industrial revolution. This warmer climate decreases the ability of peat to sufficiently insulate the ground allowing the permafrost to melt. Relatively small, shallow collapse scar bogs have now formed within the permafrost plateau and this creates wet depressions where primary productivity increases. Peat cores were removed from several bogs north of High Level, Alberta, and the age of the successive layers in the peat were determined using isotopes of 210Pb and the Constant Rate of Supply (CRS) model. Ages derived from the activity of 137Cs in two cores were used to corroborate these results. Peat accumulation rates were determined for each layer in the core based on peat age and cumulative mass depth of the layer. In general, peat accumulation was greatest in bogs 60 miles north of High Level and lowest in bogs 120 miles away. Furthermore, when peat accumulation rates were compared among neighboring cores, changes in peat accumulation rates occurred at similar time intervals. This indicates that local climate factors influence the rate of peat accumulation once these collapse scar bogs form; however, global changes in climate appear to be responsible for the initial formation of these bogs. / A Dissertation submitted to the Department of Earth, Ocean & Atmospheric Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Spring Semester, 2011. / March 21, 2011. / Seagrass, Water Quality, Peatlands, Climate Change / Includes bibliographical references. / Jeffery Chanton, Professor Directing Dissertation; Yang Wang, University Representative; William Burnett, Committee Member; Ian MacDonald, Committee Member; William Landing, Committee Member.

Nitrates (NO3- ) are one of the principal contaminants in ground water. Excess nitrate in ground water is known to cause serious illnesses such as methemoglobinemia, and cancer. In addition to the adverse impact on the health of humans, excess nitrate is known to have unfavorable effects on the ecosystem. One of the major contributors to nitrates in the system are septic tanks. Approximately one-third of Florida's population uses Onsite Wastewater Treatment System (OWTS). In order to quantify the nitrate load to a water body several models have been developed, these models always ignore nitrate from normally working septic tanks and denitrification that occurs between the septic tank drain field and the water body. Additionally these models are often complex and developed specifically for a given site. The aim of this project is to develop a simplified model that can estimate nitrate fate and transport from an On-site Wastewater Treatment System (OWST) to a targeted water body. The Simplified model is developed in two parts, the first to estimate the fate and transport of nitrate and the second the development of a denitrification rate (Rdn). This work focuses on the development of a model to estimate the rate of denitrification using easily available parameters. To estimate the denitrification rate, data was first collated from existing literature values and data available from other researchers. The data collected included the main factors that controlled denitrification i.e. texture, temperature, water filled porosity (WFP), organic carbon, pH, bulk density, soil depth, nitrate concentration and the denitrification rate. A total of 1129 distinct set of parameters and denitrification rates were collected and then statistically analyzed to determine the relationships between the factors and the denitrification rate. The denitrification rates ranged from not detectable up to 157 . Three statistical methods were used to estimate the denitrification rate, linear regressions with Monte Carlo simulation, Multi Regression analysis and the development of a neural network. Denitrification rates were found to be dependent on the WFP as well as organic carbon. For the linear regressions a predictive relationship could not be established between WFP and the denitrification rate. In addition, although an increase in organic carbon content is typically assumed to increase denitrification, a linear relationship between organic carbon and the denitrification rate could not be obtained unless the additional controlling parameters are fixed. Stable isotope data is used to predict the percent of nitrate removed due to denitrification. This method serves as an alternative to estimate the loss of nitrate due to denitrification, but is unable to estimate a rate of denitrification. The developed methods are then applied to three study areas in Jacksonville and the estimated denitrification rates from the methods are compared. Overall the results from the each of the methods except for the multi-regression analysis are a reasonable estimate of the denitrification rate. Due to the complexity of denitrification it is the Neural Networks that are able to best estimate the denitrification rate. Thus by using easily available parameters and existing data the models are able to match or improve the accuracy in predicting the denitrification rate at a fraction of the cost without requiring site specific data. / A Thesis submitted to the Department of Earth Ocean and Atmospheric Sciences in partial fulfillment of the requirements for the degree of Master of Science. / Summer Semester, 2011. / June 15, 2011. / Nitrates, Nitrate Loss, Denitrification, Simplified denitrification models / Includes bibliographical references. / Ming Ye, Professor Directing Thesis; William Parker, Professor Co-Directing Thesis; Yang Wang, Committee Member; Stephen Kish, Committee Member.

As a global pollutant and a metal toxic to living organisms, mercury is one of the most environmentally studied elements. The mercury cycle is a complex phenomenon due to transformations in various media and exchange between them. Thus, there is an incomplete understanding of the mercury cycle in the environment. The recent finding of Mass Independent Fractionation (MIF) of mercury isotopes (Bergquist and Blum, 2007; Ghosh et al., 2008) portend a new understanding of mercury isotopes and the mercury cycle in the environment. Different mercury isotopic features of different materials potentially indicate possible different transformations of mercury. This study attempts to define mercury isotopic features of plants and relate these with different photosynthetic pathways which are obtained by examining carbon isotopic signatures of plants. Plants were sub-sampled into leaves, stems and roots, with the understanding that if fractionation of mercury isotopes occurred in vivo, plants might be isotopically heterogeneous. Soil samples were also analyzed in this study to examine possible differences between plants and soils and also possible transformations inside the plants. Both C3 and C4 plants exhibit mass dependent and mass independent mercury isotope effects. Both C3 and C4 plants are enriched in light isotopes, but the degree of mass fractionation is approximately three times greater in C3 plants, than in C4 plants (-0.29‰/amu compared to -0.09‰/amu). Mercury in both C3 and C4 plants exhibit a MIF isotope effect as well; that being a depletion (generally less than 0.5‰) of the odd mass isotopes 199Hg and 201Hg. The one CAM plant studied contained mercury that is slightly heavy isotope enriched and with no clearly discernable MIF effect. These findings suggest a connection between the isotopic composition of mercury and the photosynthetic pathway of the plants. Leaves are slightly more fractionated than the roots are. The mass dependent effect is a light isotope enrichment of up to 1.54 ‰. Mass independent fractionation is a relative depletion of the odd mass isotopes with Δ199Hg ranging from -0.12 to -0.6 ‰. A difference in the MIF effect of root-leaf pairs seems to require different sources. Soils also showed similar isotopic feature with the plants samples. / A Thesis submitted to the Earth, Ocean, and Atmospheric Science in partial fulfillment of the requirements for the degree of Master of Science. / Summer Semester, 2010. / May 5, 2010. / Plants, Photosynthetic Pathway, Mercury Isotopes, Mass Independent Fractionation / Includes bibliographical references. / A. Leroy Odom, Professor Directing Thesis; Munir Humayun, Committee Member; Yang Wang, Committee Member.

Employing stable carbon and oxygen isotope analyses (including d13C and d18O of structural carbonate in mammalian tooth enamel and d18Op of fish bone samples) to reconstruct paleoecology and paleoenvironments, this dissertation strives to further our understanding of two important yet contentious issues: the late Miocene and Pliocene C4 expansion, and the late Cenozoic uplift history of the Tibetan Plateau. We collected and analyzed a diverse group of mammalian tooth enamel samples including horses, elephants, rhinos, deer, and giraffes from the central Inner Mongolia area (late Oligocene to modern) and Qaidam Basin (late Miocene to modern), and fish bone samples from the Qaidam Basin (late Miocene to modern). The major results are as follows: (1) In the central Inner Mongolia area, the d13C values of 91 tooth enamel samples of early late-Miocene age or older, with the exception of two 13 Ma rhino samples (-7.8 and -7.6‰) and one 8.5 Ma suspected rhino sample (-7.6‰), were all less than -8.0‰ (VPDB), indicating that there were no C4 grasses present in their diets and thus probably few or no C4 grasses in the ecosystems of the central Inner Mongolia prior to ~8 Ma. However, 12 out of 26 tooth enamel samples of younger ages (~7.5 Ma to ~3.9 Ma) have d13C values higher than -8.0‰ (up to -2.4‰), indicating that herbivores in the area had variable diets ranging from pure C3 to mixed C3-C4 vegetation during that time interval. The presence of C4 grasses in herbivores' diets (up to ~76% C4) suggests that C4 grasses were a significant component of the local ecosystems in the latest Miocene and early Pliocene, consistent with the hypothesis of a global factor as the driving mechanism of the late Miocene C4 expansion. Today, C3 grasses dominate grasslands in the central Inner Mongolia area. (2) In the Qaidam Basin, the d13C values of mammalian tooth enamel samples generally show only small variations and are mostly less than 8‰ for modern samples and less than -7‰ for fossils, except a rhino tooth CD0722 from Shengou (late Miocene, with a current best estimated age of ~8–10 Ma) that yielded d13C values up to -4.1‰ - an unambiguous indication of a significant intake of C4 plants in its diet (up to ~56%). If the Qaidam Basin was as arid as today during the late Miocene and early Pliocene, this would indicate that the animals had pure or nearly pure C3 diets and the local ecosystems were likely composed of pure or nearly pure C3 vegetation and that the lone rhino (CD0722) was more likely a migrant primarily lived in places where C4 plants were present and migrated to the Shengou area. If, however, the Qaidam Basin was warmer and more humid during the late Miocene and early Pliocene than today as suggested by geological evidence, then at least a few more samples from Shengou (late Miocene) and Huaitoutala (early Pliocene) in addition to CD0722 indicate significant dietary intakes of C4 plants based on their tooth enamel d13C values. This suggests that the Qaidam Basin very likely had more C4 plants in the local ecosystems during the late Miocene and early Pliocene than today. Moreover, the Qaidam Basin probably also had much denser vegetation at that time to support additional large mammals such as rhinos and elephants. Nonetheless, the C4 plants seemed to have not been consistently utilized because C3 plants, which were more nutritious and easier to digest than C4 plants, were readily available. Today, C3 plants dominated the sparse vegetation in the Qaidam Basin. The d18O values of these samples did not increase monotonously with time. However, the range of variation seems to have increased considerably since the early Pliocene, indicating increased aridification in the basin. The mean d18O values of large mammals and the reconstructed d18O compositions of local meteoric water display a significant negative shift from the Tuosu Nor-Quanshuiliang interval (~11-11.2 Ma) to the Shengou-Naoge interval (~9-9.5 Ma), which is consistent with the marine d18O record showing a cooling trend in the same period as suggested by a positive excursion in the d18O values of benthic forams (Zachos et al., 2001). (3) The oxygen isotope compositions of phosphate (d18Op) from fish bone samples from the Qaidam Basin showed statistically significant enrichment in d18Op from the Tuxi-Shengou-Naoge interval (late Miocene) to the Yahu interval (early Pliocene) and from the Yahu interval to the present day. This is most likely reflecting increases in the d18O of lake water over time. Estimated water temperatures for the modern Qinghai Lake from fish bone d18Op and measured lake water d18Ow using the Longinelli and Nuti (1973) equation range from 19.3 to 23.1 (± 0.3) °C, about 4 to 11°C higher than the reported average temperature of surface water during the summer (~12-15°C). This indicates that the Qinghai Lake fish was not living in the saline Qinghai Lake itself exclusively, but spent at least part of its life in estuary or in the fresh water of an inflow river(s). Temperatures calculated from the average fish bone d18Op values and the average d18Ow derived from structural carbonate d18O of large mammal tooth enamel samples were much too low to be reasonable. Temperatures estimated from d18Op of fish bones and d18Ow estimated from d18O of co-ocurring large mammal tooth enamel samples (including using the highest d18Ow to represent the dry season during which the large mammals presumably had to drink from the lake/lakes) were all lower than the average temperature of the modern Qinghai Lake surface water during the summer, and some were too low to be reasonable – even without considering the observed cooling trend since the late Miocene (which means that lake water probably had higher temperatures during the late Miocene and early Pliocene). These indicate that the fish and the large mammals were not in equilibrium with the same water, which is expected as the d18O values of enamel from large mammals have been shown to generally track the d18O values of meteoric water, whereas the d18O value of lake water as recorded in fish bones often deviates significantly from the d18O of meteoric (source) water due to environmental/hydrological factors such as evaporation. Using the relationship between salinity and d18Ow observed for the modern Qinghai Lake and its surrounding lakes and ponds and assuming that this relationship was applicable in the geological past, we calculated the paleosalinities of lake waters to be from 0.13-0.26 g/l (4°C) to 0.54-1.03 g/l (20°C) for the Tuxi-Shengou-Naoge interval, and from 0.93-2.03 g/l (4°C) to 3.74-8.13 g/l (20°C) for the Yahu interval. The estimated salinity for Yahu is most likely too low, as the extraordinarily thickened skeleton that left little room for muscles would probably require much higher salinity (as well as Ca concentration). In summary, these data, in combination with data from other localities in North China and around the world, provide support for a global factor for driving the late Miocene C4 expansion as suggested by Cerling et al. (1997). The central Inner Mongolia and the Qaidam Basin were warmer and more humid during the late Miocene and early Pliocene, and had significant C4 components in the local ecosystems, but they had different moisture sources: the former from the western Pacific Ocean, while the latter from the Indian Ocean and Bay of Bengal. Further significant uplift of the Tibetan Plateau (at least portions of it) drew some moisture away from the central Inner Mongolia area, diverting it to the Chinese Loess Plateau (CLP) and later the Linxia Basin. The uplift also blocked most of the moisture from the Indian Ocean and Bay of Bengal as well as that from the western Pacific Ocean from reaching the Qaidam Basin. The result is the retreat or significant reduction of C4 grasses in the local ecosystems of the central Inner Mongolia area and the Qaidam Basin after early Pliocene, and the further expansion of C4 plants in the CLP and later Linxia Basin. / A Dissertation submitted to the Department of Earth, Ocean and Atmospheric Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Summer Semester, 2011. / March 25, 2011. / Inner Mongolia, Qaidam Basin, Tibetan Plateau, C4 Plants, Stable Isotopes, Fossil Mammals / Includes bibliographical references. / Yang Wang, Professor Directing Dissertation; Gregory M. Erickson, University Representative; A. Leroy Odom, Committee Member; Stephen A. Kish, Committee Member; Bruce J. MacFadden, Committee Member.

The prediction of tropical cyclone (TC) motion has improved greatly in recent decades. However, similar trends remain absent with respect to TC intensity prediction. Several hypotheses have been proposed attempting to explain why dynamical NWP models struggle to predict TC intensity. The leading candidates are as follows: (1) the lack of an evolving ocean (i.e., sea-surface temperature) boundary condition which responds as a function of the atmosphere (e.g., TC) forcing, (2) inappropriate initial conditions for the TC vortex (e.g., lack of data assimilation methods), (3) NWP model grid-length resolutions which are unable to resolve the temporal and length scale for the features believed responsible for TC vortex intensity. modulations (i.e., eye-wall dynamics, momentum transport, vortex Rossby wave interactions, etc.), and (4) physical parametrization which do not adequately represent the air-sea interactions observed during TC passage. In this study, a coupling algorithm for two independent, high-resolution, and state-of-the-art atmosphere and ocean models is developed. The atmosphere model -- the Advanced Weather Research and Forecasting (WRF-ARW) model is coupled to the HYbrid Coordinate Ocean Model (HYCOM) using a (UNIX) platform independent and innovative coupling methodology. Further, within the WRF-ARW framework, a dynamic initialization algorithm is developed to specify the TC vortex initial condition while preserving the synoptic-scale environment. Each of the tools developed in this study is implemented for a selected case-study: TC Bertha (2008) and TC Gustav (2008) for the coupled-model and TC vortex initialization, respectively. The experiment results suggest that the successful prediction (with respect to the observations) for both the ocean response and the TC intensity cannot be achieved by simply incorporating (i.e., coupling) an ocean model and/or by improving the initial structure for the TC. Rather the physical parametrization governing the air-sea interactions is suggested as the one of the weaknesses for the NWP model. This hypothesis is (indirectly) supported through a diagnostic evaluation of the synoptic-scale features (e.g., sea-level pressure and the deep-layer mean wind beyond the influence of the TC) while the assimilated TC vortex is nudged toward the observed intensity value. It is found -- in the case of TC Gustav (2008) using WRF-ARW, that as the assimilated TC vortex intensity approaches that of the observed, the balance between the mass and momentum states for WRF-ARW is compromised leading to unrealistic features for the environmental sea-level pressure and deep-layer (800- to 200-hPa) mean wind surrounding the TC. Forcing WRF-ARW to assimilate a TC vortex of the observed maximum wind-speed intensity may ultimately compromise the prediction for the TC's motion and subsequently mitigate any gains for the corresponding intensity prediction.Suggestions for additions to the coupled atmosphere-ocean model include a wave-model (WAVEWATCH3), the assimilation of troposphere thermodynamic observations, and modifications to the existing atmospheric boundary-layer parametrization. The current suite of atmosphere model parametrizations do not accurately simulate the observed azimuthal and radial variations for the exchange coefficients (e.g., drag and enthalpy) that have been indicated as potentialpredictor variables for TC intensity modulation. However, these modifications should be implemented only after the limitations for the current coupled-model and TC vortex initialization methods are fully evaluated. / A Dissertation submitted to the Department of Earth, Ocean and Atmospheric Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Fall Semester, 2010. / August 13, 2010. / Tropical cyclone vortex initialization, Coupled atmosphere-ocean model / Includes bibliographical references. / Eric P. Chassignet, Professor Co-Directing Dissertation; Carol Anne Clayson, Professor Co-Directing Dissertation; William K. Dewar, University Representative; Robert E. Hart, Committee Member; Paul H. Ruscher, Committee Member; Mark A. Bourassa, Committee Member; Mark D. Powell, Committee Member.

This study examines the fidelity of the ENSO simulation in two coupled model integrations and compares this with available global ocean data assimilation. The two models are CAM-HYCOM coupled model developed by the HYCOM Consortium and CCSM3.0. The difference between the two climate models is in the use of different ocean general circulation model (OGCM). The hybrid isopycnal-sigma-pressure coordinate ocean model Hybrid Coordinate Ocean Model (HYCOM) replaces the ocean model Parallel Ocean Program (POP) of the CCSM3.0. In both, the atmospheric general circulation model (AGCM) Community Atmosphere Model (CAM) is used. In this way the coupled systems are compared in a controlled setting so that the effects of the OGCM may be obtained. Henceforth the two models will be referred to as CAM-HYCOM and CAM-POP respectively. Comparison of 200 years of model output is used discarding the first 100 years to account for spin-up issues. Both models (CAM-HYCOM and CAM-POP) are compared to observational data for duration, intensity, and global impacts of ENSO. Based on the analysis of equatorial SST, thermocline depth, wind stress and precipitation, ENSO in the CAM-HYCOM model is weaker and farther east than observations while CAM-POP is zonal and extends west of the international dateline. CAM-POP also has an erroneous biennial cycle of the equatorial pacific SSTs. The analysis of the subsurface ocean advective terms highlights the problems of the model simulations. / A Thesis Submitted to the Department of Earth, Ocean and Atmospheric Science in Partial FulfiLlment of the Requirements for the Degree of Master of Science. / Fall Semester, 2010. / August 31, 2010. / General Circulation Model, El Nino, Coupled Model, Climate Model, ENSO / Includes bibliographical references. / Eric Chassignet, Professor Co-Directing Thesis; Vasu Misra, Professor Co-Directing Thesis; Zhaohua Wu, Committee Member.

A total of 123 bulk and serial enamel samples were obtained from modern goats, horses and yaks from southern Tibet for C and O isotope analysis. The δ13C and δ18O values of tooth enamel were compared with the δ13C values of local vegetation and the δ18O values of local waters to examine the relationship between the isotopic composition of modern herbivores and their environment. The δ13C values of enamel samples from horses range from -11.2‰ to -13.9‰ with an average δ13C value of -12.7 ± 1.0‰ (n=13). The δ13C values of yak tooth enamel range from -7.3‰ to -14.2‰, averaging -10.1±1.4‰ (n=84). The goat teeth have δ13C values ranging from -7.8‰ to -12.1‰, with a mean of -10.2 ± 1.2‰ (n=26). These enamel δ13C values indicate that these modern herbivores were feeding predominantly on C3 plants, consistent with the current dominance of C3 vegetation in the region. Some of the samples have δ13C values between -7.3 and -9‰. Although these higher δ13C values could suggest consumption of some C4 plants by the animals, the lack of significant seasonal δ13C variations within individual teeth indicates that these higher enamel δ13C values are more likely due to consumption of C3 plants experiencing water stress and/or some CAM plants. This suggests that the "cut-off" δ13C value for a pure C3 diet can be as high as -8‰ in water-stressed environments. The δ13C variations within and between species primarily reflect the variations in the δ13C values of the C3 plant foodstuffs consumed by the animals. The δ13C values of tooth enamel do not show a trend with increasing elevation. Oxygen isotopic compositions of tooth enamel varied widely within and between species. In contrast to the small intra-tooth δ13C variations within individual teeth, serial enamel samples display large intra-tooth δ18O variations, reflecting seasonal variations in the oxygen isotopic composition of meteoric water. The mean δ18O values of tooth enamel from goats showed a correlation with water δ18O values, suggesting that the δ18O of tooth enamel can be used as a proxy for the δ18O of meteoric water. Unfortunately, the oxygen isotopic compositions of water and tooth enamel do not show a clear trend with increasing elevation in the study area, suggesting that quantitative reconstruction of paleoelevation in this region using reconstructed δ18O values of paleo-meteoric water from fossil tooth enamel or other O-bearing minerals may not be warranted. For a given elevation/environment, horses have the lowest enamel δ18O values while goats display the highest enamel δ18O values among the three species studied. The large inter-species δ18O variations are due to differences in physiology and diet/drinking behavior of the animals. This confirms the importance of species-specific studies when interpreting δ18O data of fossil mammalian teeth in a stratigraphic sequence as a record of paleoclimate changes. / A Thesis submitted to the Department of Geological Sciences in partial fulfillment of the requirements for the degree of Master of Science. / Spring Semester, 2007. / December 15, 2006. / Tibet, Oxygen, Herbivore, Enamel, Carbon, Isotopes, Altitude, Paleoelevation, Paleoclimate / Includes bibliographical references. / Yang Wang, Professor Directing Thesis; A. Leroy Odom, Committee Member; William Parker, Committee Member.

Includes bibliographical references. / The Sverdrupfjella Group in western Dronning Maud Land forms part of a 1200 Ma to 900 Ma orogenic belt which experienced a thermal overprint at around 500 Ma. Although the degree of tectonic reworking during this later event remains uncertain, evidence for late fluid alteration is widespread. In this study, the high-grade metamorphic rocks which make up the Sverdrupfjella Group were sampled in the central Kirwanveggen area. The stable isotope and whole-rock composition of these rocks have been determined, in order to test whether zones of intense fluid-rock interaction can be used as evidence for Pan African overprinting of Grenvillian orogenesis in western Dronning Maud Land.

Nitrogen is the only plant nutrient taken up as both a cation (NH4 +) and anion (NO3-). Nitrate is considered the "safe" form of N and NH/ is generally thought to be toxic, especially at high levels. High NH/ /NO3- ratios are thought to be toxic because they result in a rhizosphere pH low enough to damage root membranes, induced cation deficiencies, and build-up of NH3 caused by delayed NH/ assimilation. These factors can be minimized in hydroponic culture. The objective of these studies was to quantify the effects of high NH4 + IN 0 3- ratios on nitrification and growth of wheat in hydroponics. Two cultivars of wheat (Triticum aestivum L.) were grown to maturity with either 15% or 80% of the N supplied as NH4+. The effect of using CL- versus so/- as counter ions to NH4 + was also examined. Yield was not significantly affected by NH4 + ratio or counter ion. Seed protein was increased from 15 to 19% with high NH4 +. Harvest index was reduced from 52 to 48% with 80% NH4 +, but was unaffected by counter ion. Rates of nitrification in hydroponic culture are not well quantified and could result in significant conversion of NH4+ to NO3- before plant uptake. An isotopic dilution study was conducted to quantify rates of nitrification in hydroponic culture. A 2 x 2 x 2 factorial design was used to examine the effect of pH (5.8 or 7.0), inoculation with nitrifying bacteria, and the presence of plants. This study was done with wheat grown in vigorously-aerated, 2-L bottles. Each bottle contained 10 g of diatomaceous earth to provide surface area for microbial growth. Nitrate began to accumulate in 5 din unplanted, inoculated bottles at pH 7.0; in 20 d at pH 5.8 with inoculation; but did not begin to accumulate in non-inoculated bottles (pH 5.8 or 7.0) until day 30. Nitrate never accumulated in any of the planted bottles, most likely because plants consumed the No 3- that was produced. Calculations from the isotopic dilution measurements indicated that the rate of nitrification averaged 58 μmol No 3- L-1 d-1 in the planted bottles, and averaged 270 μmol NO3- L- 1 d-1 in unplanted bottles. Nitrification was likely reduced in the planted bottles because the reduced concentration of NH4 + limited nitrification. To provide rapid, inexpensive measurement of nutrient concentration in hydroponic solution, five colorimetric tests were evaluated. Tests for NO3- and PO4 were accurate and reliable, but the tests for SO4^2-, Si 0 2, and Fe need additional refinement.