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1
Broadmeadow, Mark. "Stable carbon isotope discrimination in forest canopies." Thesis, University of Newcastle Upon Tyne, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386693.
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Kim, Moon Koo. "Stable carbon isotope ratio of polycyclic aromatic hydrocarbons (PAHs) in the environment: validation of isolation and stable carbon isotope analysis methods." Diss., Texas A&M University, 2004. http://hdl.handle.net/1969.1/1099.
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Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous, toxic contaminants that are released to the environment from various petrogenic and pyrogenic sources. In an effort to more clearly identify and trace sources of PAHs in the environment, purification and compound specific isotope analysis methods were developed to accurately measure the stable carbon isotope ratio of individual PAHs. Development of the method included improving accuracy and precision of the isotopic measurement by producing highly pure extracts using various chromatographic techniques. The method was refined by improving compound separations using purification techniques and high resolution chromatographic columns. The purification method consists of alumina/silica gel column chromatography, gel permeation chromatography and thin layer chromatography. The mean recovery of PAHs after the purification procedure was approximately 80 %. Sample purities after purification were verified by GC/FID and full scan mass spectrometry. To better resolve peaks and provide more accurate stable carbon isotope measurements, various gas chromatographic conditions were evaluated. The precision of the method ranged between 0.08 and 0.43 . The analytical protocols were evaluated to confirm compositional and stable isotopic integrity during purification and stable isotopic analysis. To confirm the utility of the purification and isotope analysis methods, various environmental samples from marine, land and lacustrine environments were analyzed. The isolates were analyzed for the composition and the stable carbon isotope ratios of PAHs. The stable carbon isotope ratio was measured by GC/IRMS and the results, along with quantitative compound compositions, were used to characterize and identify the contaminant sources. The sources of the PAHs in the study areas were differentiated by PAH molecular ratios and confirmed by stable carbon isotope ratios. This study confirms that compound specific isotope analysis of pollutants by GC/IRMS can be used to identify PAH sources in environmental samples. The study also confirms that the purification and stable carbon isotope analysis methods that were developed can be used to accurately measure the stable carbon isotope ratios of PAHs in environmental samples for the purpose of source identification. GC/IRMS measurement of stable isotopic compositions can be an effective fingerprinting method when used in conjunction with traditional molecular composition methods.
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Eek, Magnus. "Environmental control of stable carbon isotope systematics in Emiliania huxleyi." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0017/NQ52759.pdf.
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Lamb, Clare. "Stable carbon isotope variation during natural chloromethane and bromomethane production." Thesis, Queen's University Belfast, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343035.
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Boller, Amanda J. "Stable carbon isotope discrimination by rubisco enzymes relevant to the global carbon cycle." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4291.
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Five different forms of ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO; IA, IB, IC, ID, II), the carboxylase of the Calvin-Benson-Bassham cycle (CBB), are utilized by plants, algae and autotrophic bacteria for carbon fixation. Discrimination against 13C by RubisCO is a major factor dictating the stable carbon isotopic composition (δ13C = {[13C/12C sample/13C/12C standard] - 1} X 1000) of biomass. To date, isotope discrimination, expressed as ε values (={[12k/13k] - 1} X 1000; 12k and 13k = rates of 12C and 13C fixation) has been measured for form IA, IB, and II RubisCOs from only a few species, with ε values ranging from 18 to 29 /. The aim of this study was to better characterize form ID and IC RubisCO enzymes, which differ substantially in primary structure from the IB enzymes present in many cyanobacteria and organisms with green plastids, by measuring isotopic discrimination and kinetic parameters (KCO2 and Vmax). Several major oceanic primary producers, including diatoms,
coccolithophores, and some dinoflagellates have form ID RubisCO, while form IC RubisCO is present in many proteobacteria of ecological interest, including marine manganese-oxidizing bacteria, some nitrifying and nitrogen-fixing bacteria, and extremely metabolically versatile organisms such as Rhodobacter sphaeroides. The ε -
values of the form ID RubisCO from the coccolithophore, Emiliania huxleyi and the diatom, Skeletonema costatum (respectively 11.1 / and 18.5 /) were measured along with form IC RubisCO from Rhodobacter sphaeroides and Ralstonia eutropha (respectively 22.9 / and 19.0 /). Isotopic discrimination by these form ID/IC RubisCOs is low when compared to form IA/IB RubisCOs (22-29 /). Since the measured form ID RubisCOs are less selective against 13C, oceanic carbon cycle models based on 13C values may need to be reevaluated to accommodate lower ε values of RubisCOs found in major
marine algae. Additionally, with further isotopic studies, the extent to which form IC RubisCO from soil microorganisms contributes to the terrestrial carbon sink may also be determined.
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Carr, R. H. "High sensitivity stable carbon isotope ratio mass spectrometry : instrument development application." Thesis, University of Cambridge, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303835.
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Webb, Megan. "Environmental controls of stable carbon isotope values in freshwater diatom silica." Thesis, Lancaster University, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.747983.
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Improved understanding of the impact of catchment processes on freshwater carbon cycling would aid prediction of carbon flux attributed to changes in climate or land use. Carbon transfer through terrestrial and aquatic environments can be traced using stable carbon isotopic analysis (δ13C). A refined method of δ13C, free from host effects, is the utilisation of diatom-bound carbon (δ13Cdiatom)-
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Burnett, Richard Lee. "Stable Carbon Isotope Evidence of Ancient Maya Agriculture at Tikal, Guatemala." Diss., CLICK HERE for online access, 2009. http://contentdm.lib.byu.edu/ETD/image/etd3135.pdf.
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Vaiglova, Petra. "Neolithic agricultural management in the Eastern Mediterranean : new insight from a multi-isotope approach." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:c8824136-da35-43b2-a700-f458d0cc2fdf.
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The work presented in this dissertation explores the nature of agro-pastoral strategies developed by Neolithic farmers as a way to understand how early food production was inter-twined with environmental and socio-economic opportunities and constraints. Towards this end, a multi-isotope approach is used to address questions of scale and intensity of crop cultivation and animal management at the archaeological sites of Kouphovouno, southern Greece, Makriyalos, northern Greece, and Çatalhöyük, south-central Turkey. Measurements of stable carbon, nitrogen, oxygen and strontium isotope values of carbonized plant remains, human and animal bone collagen and animal tooth enamel are used to examine the similarities and differences in the types of treatments that individual species of plants and animals received during the agricultural cycle at the distinct locations. The results show that farmers at the three sites developed variable methods for exploiting the arable and pastoral landscape and catering to their economic and culinary needs. The discussion considers the implications of these findings to our understanding of the complexity and adaptability of early farming systems.
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Heerden, Leon Andre van. "A nitrogen and carbon stable isotope study of some Western Australian diamonds." Thesis, Open University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262015.
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Mikhail, S. "Stable isotope fractionation during diamond growth and the Earth's deep carbon cycle." Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1333245/.
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The flux of carbon between the mantle and crustal reservoirs can have a large impact on the melting of mantle rocks, the long and short term stability of the climate, and the growth of a very precious mineral; diamond. Diamond can be as young as 200 Ma and as old as > 4000 Ma, which is most of Earth’s entire 4500 Ma history and can also contain samples of the Earth’s mantle over a depth range of > 600 km, from the base of the crust and into the lower mantle. This spatial and temporal sampling of the Earth is unrivalled; therefore the study of mantle diamond is the best way to place constraints on the geodynamic carbon cycle over geological time. This study has used the stable isotopes of carbon and nitrogen in natural diamond of three groups and found that monocrystalline diamonds from Dachine, French Guyana have carbon and nitrogen isotopic compositions consistent with a crustal origin, inferring Phanerozoic type subduction > 2 Ga. The same is true for the source for the same isotopic systems in diamondites; however they appear to be evidence of mobilised subducted fluids that metasomatise primary mantle peridotites and induced melting and contemporaneous diamond formation. This study has also explored the potential effects of isotopic fractionation during diamond growth, y quantifying the magnitude and direction of carbon isotope fractionation between diamond and Fe-carbide in natural and experimental samples. This has shown that carbon isotope fractionation in the lower mantle should be larger than in the upper mantle, despite the higher temperatures. The implications for this new data are discussed in light of terrestrial and extraterrestrial geodynamic carbon cycling.
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Huff, Amy K. "Multiple stable oxygen isotope analysis of atmospheric carbon monoxide and its sources /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1998. http://wwwlib.umi.com/cr/ucsd/fullcit?p9835376.
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Leavitt, Steven W., Austin Long, and Jeffrey S. Dean. "Tree-Ring Dating Through Pattern-Matching of Stable-Carbon Isotope Time Series." Tree-Ring Society, 1985. http://hdl.handle.net/10150/261321.
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Pironti, Concetta. "Innovative applications of stable carbon isotope ratio in environmental and food chemistry." Doctoral thesis, Universita degli studi di Salerno, 2018. http://hdl.handle.net/10556/3022.
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2016 - 2017<br>In the last year, the stable isotope ratio analysis has become a useful tool with many applications in different scientific area. In particular the characteristic isotope signature of materials has permitted to identify authenticity and traceability of food sample and isotope composition has become a valuable marker in environmental studies. This work shows the applicability of analytical methods for isotopic carbon determination in food and environmental samples and the innovative use of δ13C in cultural heritage as valuable tool to trace pollutant fate. The first part is dedicated to the improvement of spectroscopic methods as Fourier Transform Infrared (FT-IR) and Non-Dispersive Infrared spectroscopy (NDIRS) and their application to identify geographical origin in sample like pasta, cocoa, olive oil. The results conducted in order to assess the robustness of the two alternative methods respecting IRMS showed a strong correlation like a demonstration of the positive relationship between the tested analytical methods. A new method was developed 13C NMR spectroscopy to determine the bulk 13C/12C carbon isotope ratio of inorganic carbonates and bicarbonates at natural abundance. In literature the use of 13C NMR spectroscopy was focused on 13C position-specific isotope analysis of organic molecules; in this work it was reported the improvement of NMR methodology able to obtain stable carbon isotope ratio in bulk material using an internal standard...[edited by Author]<br>XXX ciclo
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Lee, Kern Y. "Carbon Cycling in Tropical Rivers: A Carbon Isotope Reconnaissance Study of the Langat and Kelantan Basins." Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/30429.
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Despite the importance of tropical rivers to the global carbon cycle, the nature of carbon cycling within these watersheds has been dealt with by only a handful of studies. The current work attempts to address this lack of information, using stable isotope and concentration measurements to constrain sources and sinks of carbon in two Peninsular Malaysian watersheds. The basins are located on the central-western and northeastern coasts of the Malaysian Peninsula, and are drained by the Langat and Kelantan Rivers, respectively. Water samples were collected from three points along the two rivers twice a month, in addition to the sampling of groundwater in adjacent aquifers.
Principal component analyses (PCA) on water chemistry parameters in the Langat and Kelantan Rivers show the dominance of geogenic and anthropogenic influences, grouped in 4 to 6 components that comprise over 50 % of the total dataset variances. The geogenic input is reflected by components showing strong loadings by Ca, Mg, Mn, Si, and Sr, while anthropogenic influences via pollution are indicated via strong loadings by NO3, SO4, K, Zn and Cl. The carbon isotope and concentration data appear unrelated to these groups, suggesting that the riverine carbon cycle in both locations is dominated by other factors. These may include alternative sources of organic pollution, or inputs from the local vegetation and soils.
The mean riverine 13CDOC of -27.8 ± 2.9 ‰ and -26.6 ± 2.2 ‰ in the Langat and Kelantan Basins, respectively, are consistent with the dominance of C3-type vegetation in both watersheds. Riverine 13CDIC signatures approach C3-like values at high DIC concentrations, with measurements as low as -19 ‰ in the Kelantan Basin and -20 ‰ observed in the Langat Basin, consistent with a biological origin for riverine DIC. However, the average 13CDIC in river water is 13C-enriched by about 10 ‰ relative to the expected C3 source in both rivers, and this 13C- enrichment appears to be largest with smaller DIC concentrations.
Because of the overpressures of CO2 in the rivers, entrainment of isotopically-heavy atmospheric CO2 is not a likely explanation for the observed 13C-enrichment. Theoretically, dissolution of carbonates could be an alternative source of 13C-enriched carbon, but this lithology is scarce, particularly in the Langat watershed. The increase in DIC downstream and generally high pCO2 values in most river sections argues against aquatic photosynthesis as a primary causative factor for the observed isotopic enrichment. This elimination process leaves the speciation of riverine DIC and the evasion of CO2 as the most likely mechanisms for 13C-enrichment in DIC, via isotope fractionation during HCO3- hydration and CO2 diffusion. Potentially, methanogenic activity could also be, at least partially, responsible for the 13C-enrichment in DIC, particularly immediately downstream of the Langat Reservoir, but due to the absence of empirical data, this must remain only a theoretical proposition.
The aquatic chemistry and dissolved carbon data suggests that pollution discharge into the Langat and Kelantan Rivers is the major factor that is responsible for the considerable CO2 overpressures and high DIC and DOC concentrations in the river waters, particularly in the downstream sections. This pollution is likely of biological origin, via sewage and palm oil mill effluent (POME) discharge, and therefore isotopically indistinguishable from natural C3 plant sources.
Carbon budgets of the Langat and Kelantan River show CO2 degassing to be a significant mechanism of fluvial carbon loss, comprising roughly 50 %, or more, of the total riverine carbon export in both watersheds. The remainder of the river carbon is transported to the ocean in the form of DIC, DOC and POC in broadly comparable proportions. However, the combined riverine carbon export from the Kelantan and Langat Basins amount to 2 % or less of the total carbon sequestration of the watersheds. Thus, most of the sequestered carbon is returned to the atmosphere via respiration, with smaller amounts incorporated into ecosystem biomass .
These results highlight the complexity of carbon cycling in tropical rivers, and agree with previous studies in showing riverine systems to be more than simple conduits of carbon from the land to the ocean.
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Cassar, Nicolas. "Carbon-concentrating mechanisms and [beta]-carboxylation their potential contribution to marine photosynthetic carbon isotope fractionation /." Thesis, University of Hawaii at Manoa, 2003. http://proquest.umi.com/pqdweb?index=0&did=765084611&SrchMode=2&sid=6&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1233178277&clientId=23440.
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Trandel, Marlee Anne. "Nitrogen and Carbon Stable Isotopes in Organically and Conventionally Grown Tomatoes." OpenSIUC, 2016. https://opensiuc.lib.siu.edu/theses/2013.
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Tomatoes (Lycopersicon esculentum L.) require high amounts of nitrogen to maximize fruit production. The type of nitrogen and timing of fertilizer applications are important in tomato production systems to reduce nitrogen losses while optimizing yields. A two-year greenhouse study was conducted to determine the effects of organic and inorganic fertilization treatments on nitrogen and carbon isotopic compositions of tomato plant leaves and fruit at immature and mature stages of plant growth. The carbon and nitrogen isotopic ratios together will also help to better depict trends that develop from conventional versus organically grown tomatoes and their resulting water use efficiency (WUE). ‘Better Bush’ tomatoes were grown in 8 L plastic pots filled with 1:1:1 steamed-sterilized sand:silt loam soil:peat mix. Eight fertility treatments were evaluated: no fertility, synthetic Miracle Grow® (MG), organic bonemeal and bloodmeal (BB), BB with liquid Earthjuice (BBL), BB with 25% vermicompost (VC), BBL with 25% VC, MG with 25% VC, and no fertility with 25% VC. The results indicated that for both growth stages, δ15NAir differed (P ≤ 0.05) between fertility treatments, while no major differences were observed for δ13CVPDB (P > 0.05), although conventionally fertilized tomatoes with MG and MG with 25% VC tended to have lower δ13CVPDB values suggesting a greater transpirational water loss through open stomata. The organic treatments with VC had higher δ15NAir values than the conventional or no added fertility treatments for all five leaflets from three different branches, fruit skins from the first two fruit clusters, fruit juices from the first two clusters and soil samples. Generally, the 15N/14N stable isotope values of tomato foliage and fruit are distinctly different between organic and conventional fertilizers, which could provide a powerful forensic tool in fingerprinting tomatoes grown by organic farming methods. Therefore, nitrogen isotopes can distinguish among different fertility treatments and also help to label the VC applications, which are thought to provide better fertility management due to less soil leaching and volatilization.
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Bostic, Joshua Neilson. "Stable Isotope Variability in the American Food Supply: Implications for Dietary Reconstruction Applications." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/73870.
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Stable isotope ratios of carbon (δ¹³C) and nitrogen (δ¹⁵N) in human tissues, which reflect the stable isotope composition of the diet, offer numerous applications in the field of nutrition. One of the biggest contributors to uncertainty in stable isotope dietary reconstruction applications is potential variability in the isotopic composition of foods. No prior studies have evaluated the existing food carbon and nitrogen stable isotope data in an effort to determine broad-scale patterns and characterize the degree of variability of stable isotopes within the American diet.
The purpose of this investigation was to improve our understanding of the isotopic composition of the modern American food supply by 1.) Determining geographically representative means and inter-sample variability of animal foods 2.) Assessing the impact of cooking on food stable isotope composition.To define the range of δ¹³C and δ¹⁵N values of animal proteins within the American food supply, we analyzed nationally-collected milk, fish, and shellfish samples from the USDA’s National Nutrient Database for Standard Reference and compared these to previously published data from the international literature. USDA milk samples were characterized by low overall variability, although regional variations in δ¹³C values were present. In contrast, seafood samples exhibited high overall variability but were consistent throughout the domestic and international samples. No variations in δ¹³C or δ¹⁵N values were detected throughout the baking or fermentation process in yeast buns or cookies.
The representative values determined in this study can be used as a foundation for interpreting the stable isotope composition of the American diet.<br>Master of Science
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Yoshii, Koichi. "Carbon and nitrogen stable isotope study of ecosystem and paleoenvironment in Lake Baikal." 京都大学 (Kyoto University), 1999. http://hdl.handle.net/2433/181447.
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Gromov, Sergey S. [Verfasser]. "Stable isotope composition of atmospheric carbon monoxide : a modelling study / Sergey S. Gromov." Mainz : Universitätsbibliothek Mainz, 2014. http://d-nb.info/1051305497/34.
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Fichtler, Esther, Gerhard Helle, and Martin Worbes. "Stable-Carbon Isotope Time Series From Tropical Tree Rings Indicate A Precipitation Signal." Tree-Ring Society, 2010. http://hdl.handle.net/10150/622616.
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Although studies on stable-carbon isotopes in trees from temperate zones provide abundant
paleoclimatic data, tropical trees are still understudied in this context. Therefore this study examined the variability of intra- and inter-annual stable-carbon isotopic pattern in several tree species from various tropical climates. The 𝛿¹³C values of samples of 12 broadleaved trees (seven species) from various paleotropical and neotropical sites along a climatic moisture gradient were investigated. The inter-annual variability between species and sites was studied. Further the relationship between 𝛿¹³C and precipitation time series was analyzed. Results show that tropical tree species show a similar variability in carbon isotopic composition as temperate tree species. Significant correlations between annual precipitation and tree-ring 𝛿¹³C time series were negative. Successful crossdating of a tree-ring 𝛿¹³C time series highlights the potential of carbon isotope measurements for tropical tree-ring analytical studies. Tropical broadleaved trees are able to capture a carbon isotopic signal in their annual rings even under everwet conditions and show good potential for paleoclimatic research.
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Thomas, Phaedra. "Stable Carbon Isotope Discrimination by Form IC RubisCO from Rhodobacter sphaeroides." [Tampa, Fla] : University of South Florida, 2008. http://purl.fcla.edu/usf/dc/et/SFE0002611.
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Bedaso, Zelalem K. "Stable Isotope Studies of Paleoenvironment and Paleoclimate from Afar, Ethiopia." Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3004.
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ABSTRACT
The sedimentary deposits of the Hadar Formation at Dikika and the Mount Galili Formation at Galili preserve a wealth of paleoenvironmental and paleoclimatic records spanning the last 5.29 Ma. Stable carbon and oxygen isotopic compositions of herbivore tooth enamel were analyzed for more than 600 specimens of 15 different taxa from 10 stratigraphic intervals. The application of carbon and oxygen isotopes here aims
principally at reconstructing shifts in the relative abundance of C4 grasses, and its implications for climate indicators including temperature, aridity, and seasonality. The full range of δ13Cenamel values throughout the Plio-Pleistocene signifies a wide range of foraging strategies by the fauna, which in turn reflects the mosaic of vegetation at Dikika and Galili. Estimates of ecosystem carbon isotope composition (δ13Cecosystem , which is given by average δ13Cenamel of each large vertebrate taxon weighted by the respective faunal abundance and the estimated daily biomass consumption) is used to asses shifts in the ecosystem-scale proportion of C3 and C4 vegetation. In the Plio-Pleistocene, the general paleoenvironmental conditions varied from wooded grassland to grasslands with the total amount of C4 grass cover on the landscape varying between 35% and 91%. Likewise, the paleohabitat reconstructions indicate the presence of grassland, wooded grassland, woodland habitats throughout the Pliocene and in Middle Pleistocene but the relative proportion of the habitats has changed substantially with time. Although this result agrees with the general trend towards more open grassland since the Late Miocene, a rebound of closed habitats and C3 resources from closed canopy woodlands or forests is evident in the middle Pliocene between 3.42 Ma and 3.24 Ma. These changes in the proportion of habitats could have affected the distribution and availability of preferred food resources and has an implication on the interaction of the animals on the paleolandscape and competition for resources.
18Oenamel values also show a wide range of variation within each stratigraphic member and through time. Temporal variation of δ13Cenamel values within a given taxon, as well as differences among sympatric taxa, document different aspects of the environment and climate, including changes in drinking water source, seasonality, and periods of strong
evaporation. Estimated δ13Cmeteoric water based on the most 18O-depleted hippo tooth enamel, displays values of -1.94 / (VSMOW) and -5.24 / (VSMOW) in the Middle Pleistocene of Asbole and middle Pliocene of Galili, respectively. A major shift in the isotopic composition of water at ~ 3.0 Ma was accompanied by a 6.0 / increase from middle Pliocene to the present. While a +3.8 / shift from early to middle Pliocene was documented. The isotopic composition of meteoric water between 4.6 Ma and 4.38 Ma was most 18O-enriched compared to the rest of the Pliocene estimates. Likewise, an increase in the estimated δ13Cmeteoric water values was documented in the Awash Valley and elsewhere in East Africa, which indicate a regional climate change since the early Pliocene. An increase in the aridity, which is expressed as mean annual water deficit (i.e., the difference between potential evapotranspiration and mean annual precipitation) is also evident since the early Pliocene. These changes during the Pliocene in the region may in part be attributed to a regional decrease in the amount of precipitation and changes in the moisture source superimposed on global climate changes.
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Evans, Claire Jane. "Exploring the carbon dynamics of the plant-soil food web using biomolecular and stable carbon isotope approaches." Thesis, University of Bristol, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419146.
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Lockheart, Matthew James. "Isotope compositions and distributions of individual compounds as indicators for environmental conditions : comparisons between contemporary and Clarkia fossil leaves." Thesis, University of Bristol, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389098.
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Wallace, Michael Paul. "Crop watering practices in the Neolithic and Bronze Age : the stable carbon isotope approach." Thesis, University of Sheffield, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.578700.
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In the ancient past, agriculture was central to the daily routines of life and economic organisation. The major limiting factor on crop production in dry regions, such as Western Asia, is the availability of water. In these regions. rainfed crops are susceptible to drought-induced failure and, while farmers can water their crops artificially, this places demands on labour and water supplies. The effort and resources afforded to crops by farmers can indicate the scale of production. whereas the preferential treatment of certain crops over others offers insights into the cultural and economic role of different crops. There are a variety of methods by which crop water status can be inferred from archaeological evidence. One such method is stable carbon isotope analysis of charred crop remains, which are ubiquitous at archaeological sites in dry regions. This thesis assesses the utility of stable carbon isotope analysis as a means of inferring crop water status. Experiments were conducted to establish the relationship between isotopic ratios and water status in modern crops grown in known conditions. Laboratory tests were also undertaken to determine the extent to which isotopic ratios may be altered post-mortem. In light of the findings from these experiments, isotopic analysis was carried out on crop remains from nine archaeological sites, primarily located in Western Asia and of Neolithic and Bronze Age date. Natural variation. unknown differences in growing conditions and plant physiology, and small post- mortem alterations, limit the precision with which crop water status can be inferred from stable carbon isotope ratios. Nevertheless, stable carbon isotope analysis can provide a reliable indication of the water status of ancient crops. On this basis. it is possible to develop interpretations regarding agricultural arrangements at individual sites, and to identify regional trends in ancient crop production.
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Anderson, Kelly C. "Stable carbon and nitrogen isotope analyses of subfossil rats from Liang Bua (Flores, Indonesia)." Master's thesis, University of Central Florida, 2011. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4837.
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This research study investigated the level of bone collagen preservation of rat femora from Liang Bua cave on the island of Flores, Indonesia, as well as conducted carbon and nitrogen stable isotopic analyses on well preserved samples. Although Flores is located in a hot intermediate tropical zone and the burial environment of the bone samples within the cave is considered less than optimal for collagen preservation, significant preservation of the bone collagen was found. Collagen yields, C:N ratio and carbon and nitrogen concentrations were investigated. However, this research study argues that carbon and nitrogen concentrations are an appropriate means to determine preservation on its own. According to the carbon and nitrogen concentration data 32 samples were considered well preserved. Carbon and nitrogen stable isotopic analyses were conducted on the 32 preserved samples. According to the carbon data a significant shift in the [delta][super13]C values from a C[sub3] signature to a C[sub4] signature occurred prior to 2,750 years ago. This shift is indicative of the introduction of a non-endemic C[sub4] plant, which is believed to be either foxtail millet or sugarcane. Since this shift occurs abruptly it indicates that the introduction of agriculture to Flores occurred at one time and has continued to present day.<br>ID: 030423461; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (M.A.)--University of Central Florida, 2011.; Includes bibliographical references.<br>M.A.<br>Masters<br>Anthropology<br>Sciences
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Beramendi, Orosco Laura E. "Catalytic hydropyrolysis of wood to prepare lignin-enriched residues for stable carbon isotope analysis." Thesis, University of Nottingham, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404040.
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Alling, Vanja. "Terrestrial organic carbon dynamics in Arctic coastal areas : budgets and multiple stable isotope approaches." Doctoral thesis, Stockholms universitet, Institutionen för tillämpad miljövetenskap (ITM), 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-43455.
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Arctic rivers transport 31-42 Tg organic carbon (OC) each year to the Arctic Ocean, which is equal to 10% of the global riverine OC discharge. Since the Arctic Ocean only holds approximately 1% of the global ocean volume, the influence of terrestrially derived organic carbon (OCter) in the Arctic Ocean is relatively high. Despite the global importance of this region the behavior of the, by far largest fraction of the OCter, the dissolved organic carbon (DOC) in Arctic and sub-arctic estuaries is still a matter of debate. This thesis describes data originating from field cruises in Arctic and sub-arctic estuaries and coastal areas with the aim to improve the understanding of the fate of OCter in these areas, with specific focus on DOC. All presented studies indicate that DOCter and terrestrially derived particulate organic carbon (POCter) are subjected to substantial degradation in high-latitude estuaries, as shown by the non-conservative behavior of DOC in the East Siberian Arctic Shelf Seas (ESAS) (paper I) and the even more rapid degradation of POC in the same region (paper II). The removals of OCter in Arctic shelf seas were further supported by multiple isotope studies (paper III and IV), which showed that a use of 13C/12C in both OC and DIC, together with 34S/32S is a powerful tool to describe the sources and fate of OCter in estuaries and coastal seas. High-latitude estuaries play a key role in the coupling between terrestrial and marine carbon pools. In contrast to the general perception, this thesis shows that they are not only transportation areas for DOCter from rivers to the ocean, but are also active sites for transformation, degradation and sedimentation of DOCter, as well as for POCter. In a rapidly changing climate, the importance of these areas for the coupling between inorganic and organic carbon pools cannot be underestimated.<br><p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: In press. Paper 2: Submitted. Paper 4: Manuscript.</p>
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Suh, Yeon Jee. "Leaf Wax Stable Isotopes as Paleovegetation and Paleohydrologic Proxies: From a Modern Calibration Study to a Paleoclimate Application." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1512045032087257.
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Czuba, Eva. "Development of a technique to study stable carbon isotope composition of NMHCs in ambient air." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0020/MQ56169.pdf.
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Dethloff, Frederik. "In vivo 13C stable isotope tracing of single leaf development in the cold." Phd thesis, Universität Potsdam, 2013. http://opus.kobv.de/ubp/volltexte/2014/7048/.
Full textAbstract:
Measuring the metabolite profile of plants can be a strong phenotyping tool, but the changes of metabolite pool sizes are often difficult to interpret, not least because metabolite pool sizes may stay constant while carbon flows are altered and vice versa. Hence, measuring the carbon allocation of metabolites enables a better understanding of the metabolic phenotype. The main challenge of such measurements is the in vivo integration of a stable or radioactive label into a plant without perturbation of the system.
To follow the carbon flow of a precursor metabolite, a method is developed in this work that is based on metabolite profiling of primary metabolites measured with a mass spectrometer preceded by a gas chromatograph (Wagner et al. 2003; Erban et al. 2007; Dethloff et al. submitted). This method generates stable isotope profiling data, besides conventional metabolite profiling data. In order to allow the feeding of a 13C sucrose solution into the plant, a petiole and a hypocotyl feeding assay are developed. To enable the processing of large numbers of single leaf samples, their preparation and extraction are simplified and optimised. The metabolite profiles of primary metabolites are measured, and a simple relative calculation is done to gain information on carbon allocation from 13C sucrose.
This method is tested examining single leaves of one rosette in different developmental stages, both metabolically and regarding carbon allocation from 13C sucrose. It is revealed that some metabolite pool sizes and 13C pools are tightly associated to relative leaf growth, i.e. to the developmental stage of the leaf. Fumaric acid turns out to be the most interesting candidate for further studies because pool size and 13C pool diverge considerably. In addition, the analyses are also performed on plants grown in the cold, and the initial results show a different metabolite pool size pattern across single leaves of one Arabidopsis rosette, compared to the plants grown under normal temperatures. Lastly, in situ expression of REIL genes in the cold is examined using promotor-GUS plants. Initial results suggest that single leaf metabolite profiles of reil2 differ from those of the WT.<br>Messungen des pflanzlichen Metaboloms können ein hilfreiches Werkzeug sein, um Pflanzen zu phänotypisieren. Jedoch sind die Änderungen der Poolgrößen teilweise schwer zu interpretieren, weil sich nicht nur die Poolgrößen sondern auch die Kohlenstoffflüsse unabhängig voneinander ändern können. Werden nun zusätzlich Informationen über die Flüsse ermittelt, kann der pflanzliche Phänotyp deutlich genauer beschrieben werden. Die größte Herausforderung für diese Messungen ist die In-vivo-Integration einer stabilen oder radioaktiven Markierung in einer Pflanze, ohne das System dabei zu stören.
In dieser Arbeit wird ein Verfahren entwickelt, um die Verteilung von Kohlenstoffen aus einer gefütterten Vorstufe zu messen. Die Messung basiert dabei auf einem Primärmetabolitenprofil, das mit Hilfe eines Massenspektrometers mit vorgeschaltetem Gaschromatographen erstellt wird (Wagner et al. 2003; Erban et al. 2007; Dethloff et al. eingereicht). Mit dieser Methode ist es einfach möglich, stabile Isotopenprofildaten neben herkömmlichen Metabolitprofildaten zu erzeugen. Die Vorstufe, in diesem Fall 13C Saccharose, wird dazu mit Hilfe eines neuen Petiolen- und Hypokotyl-Fütterungs-Assay in die Pflanze gefüttert. Um die große Menge an Einzelblattproben aufzuarbeiten, die dabei anfallen, wird eine vereinfachte und optimierte Extraktion angewendet. Mit Hilfe einer einfachen Berechnung kann aus den Messdaten eine relative Verteilung des Kohlenstoffs aus 13C Saccharose bestimmt werden.
Die Funktionalität dieses Verfahrens wird an Einzelblättern von Arabidopsis-Rosetten gezeigt, wobei sowohl Primärmetabolitenprofile als auch stabile Isotopenprofile erzeugt und untersucht werden. Es kann hierbei gezeigt werden, dass konventionelle Poolgrößen und 13C Poolgrößen einiger Metaboliten eng mit dem relativen Wachstum einzelner Blattpositionen bzw. mit dem jeweiligen Entwicklungsstadium der Blätter zusammenhängen. Anders als bei den meisten anderen Metaboliten zeigen die konventionellen Poolgrößen und 13C Poolgrößen von Fumarsäure ein unterschiedliches Verhalten in den einzelnen Blättern, was Fumarsäure zum interessantesten Kandidaten für weitere Studien macht. Die beschriebenen Untersuchungen werden weiterhin an in Kälte gewachsenen Pflanzen durchgeführt, wobei erste Ergebnisse ein verändertes Metabolitenprofil in den einzelnen Blättern zeigen. Des Weiteren wird die In-situ-Expression von REIL-Genen mit Hilfe von Promotor-GUS-Reportern untersucht. Erste Ergebnisse von Einzelblatt-Metabolitenprofilen der reil2 zeigen einen deutlichen Unterschied zum WT.
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Rauschenberg, Carlton David. "Microbial carbon sources on the shelf and slope of the northwestern Gulf of Mexico." Texas A&M University, 2005. http://hdl.handle.net/1969.1/4173.
Full textAbstract:
Over the past five years, gas chromatography/combustion/isotope ratio mass
spectrometry (GC/C/IRMS) analyses of phospholipid fatty acids (PLFAs) has been
increasingly used to link organic matter (OM) sources with sedimentary bacteria. This
technique has been applied across diverse estuarine and coastal sediments, including
lower Laguna Madre, TX, an oligotrophic, coastal lagoon dominated by a single OM
source, seagrasses; shelf stations, a eutrophic coastal region receiving multiple sources
of OM, hypoxic regions that occur seasonally and deep slope and abyssal plain
sediments of the Gulf of Mexico (GOM). Previous reports using the Laguna Madre data
as examples, have been used to make comparisons of PLFA 16:0 and PLFA 15:0 isotope
ratios and PLFA 16:0 and total organic carbon isotope ratios. Deviations from the 1:1
line in the former indicate living or recently senescent sources of organic matter are not
predominantly bacterial. Deviations from the 1:1 line in the latter indicate living or
recently senescent sources of organic matter differ isotopically from detrital or older OM
in sediments. Prior to the work of Goni et al. (1998), carbon isotope ratios of OM in
GOM sediments were interpreted as marine in origin. Based on a series of geochemical
measurements, Goni et al. suggested that GOM sediments are largely composed of
terrestrial organic carbon (OCterr). Furthermore, They went on to show that shelf and
slope sediments were primarily C3 and C4 respectively. I report on the preferential
utilization of autochthonous OM by sedimentary bacteria at the sediment surface and the
shift to recalcitrant, terrestrially derived OM with depth.
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Evans, Samantha Lorraine. "Carbon and Nitrogen Stable Isotopic Patterns in South Florida Coastal Ecosystems: Modern and Paleoceanographic Perspectives." FIU Digital Commons, 2008. http://digitalcommons.fiu.edu/etd/189.
Full textAbstract:
Long term management plans for restoration of natural flow conditions through the Everglades increase the importance of understanding potential nutrient impacts of increased freshwater delivery on coastal biogeochemistry. The present study sought to increase understanding of the coastal marine system of South Florida under modern conditions and through the anthropogenic changes in the last century, on scales ranging from individual nutrient cycle processes to seasonal patterns in organic material (OM) under varying hydrodynamic regime, to century scale analysis of sedimentary records. In all applications, carbon and nitrogen stable isotopic compositions of OM were examined as natural recorders of change and nutrient cycling in the coastal system. High spatial and temporal variability in stable isotopic compositions were observed on all time scales. During a transient phytoplankton bloom, ä15N values suggested nitrogen fixation as a nutrient source supporting enhanced productivity. Seasonally, particulate organic material (POM) from ten sites along the Florida Reef Tract and in Florida Bay demonstrated variable fluctuations dependent on hydrodynamic setting. Three separate intra-annual patterns were observed, yet statistical differences were observed between groupings of Florida Bay and Atlantic Ocean sites. The POM ä15N values ranged on a quarterly basis by 7‰, while ä13C varied by 22‰. From a sediment history perspective, four cores collected from Florida Bay further demonstrated the spatial and temporal variability of the system in isotopic composition of bulk OM over time. Source inputs of OM varied with location, with terrestrial inputs dominating proximal to Everglades freshwater discharge, seagrasses dominating in open estuary cores, and a marine mixture of phytoplankton and seagrass in a core from the boundary zone between Florida Bay and the Gulf of Mexico. Significant shifts in OM geochemistry were observed coincident with anthropogenic events of the 20th century, including railroad and road construction in the Florida Keys and Everglades, and also the extensive drainage changes in Everglades hydrology. The sediment record also preserved evidence of the major hurricanes of the last century, with excursions in geochemical composition coincident with Category 4-5 storms.
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Esposito, Mario. "Stable carbon isotope analysis of seawater samples : a new approach to assess CO2 effects on the marine carbon cycle." Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/412277/.
Full textAbstract:
Stable isotope ratio analyses offer a unique opportunity to obtain information about ecosystem dynamics, patterns and processes. The anthropogenic contribution to the global atmospheric CO2 rise through fossil fuel combustion, deforestation and other related human activities has changed the stable carbon isotope composition (δ13C) of the atmosphere over the past 200 years. Changes in the carbon isotopic patterns of terrestrial biosphere, lithosphere and oceans are also expected. The global ocean has been acting as a net sink for CO2 emissions and although it moderates the climate, it is currently in a critical state of health. While the physico-chemical consequences (ocean acidification) of the increasing CO2 uptake by the ocean are fairly well known, the perturbation to marine ecosystems and the related effects on biota still entail large uncertainties. This thesis investigates the feasibility of using measurements of δ13C of seawater samples to increase our understanding of the biogeochemical responses of marine ecosystems to human CO2 perturbation. The isotopic composition of all the individual inorganic and organic carbon species from three long term mesocosm experiments (Sweden 2013, Gran Canaria 2014, Norway 2015) was determined. To have accurate and precise isotopic measurements, mass spectrometry instrument calibrations and method validation procedures were performed. Universal and inter-laboratory accuracy of the analysis was assessed by running standard materials provided by the International Atomic Energy Agency (IAEA, Vienna) and by the Scottish Universities Environmental Research Centre (SUERC) stable isotope laboratory, respectively. Precision and internal consistency was assessed from isotopic measurements of seawater reference materials from A.G. Dickson and D. Hansell for dissolved inorganic and organic carbon, respectively. A novel accurate, precise and rapid method, coupling a Shimadzu 5000A total organic carbon (TOC) analyser to an isotope ratio mass spectrometer (Thermo Scientific Delta V Advantage IRMS), was successfully developed in order to determine the δ13C of dissolved organic carbon in seawater samples which, due to analytical challenges, is currently not a widespread technique. The combination of isotopic and non-isotopic measurements from mesocosm experiments provided a holistic view of the biogeochemical mechanisms that affect carbon dynamics under different CO2 conditions (up to 2000 ppm). A clear CO2 response was detected in the isotopic datasets, but increased CO2 levels had only a subtle effect on the concentrations of the dissolved and particulate organic carbon pools. Distinctive δ13C signatures of the particulate carbon pool both in the water column and the sediments were detectable for the different CO2 treatments and they were strongly correlated with the δ13C signatures of the inorganic carbon but not with the δ13C of the dissolved organic pools. Phytoplankton fractionation was positively affected by high CO2 either because of the higher CO2 availability or because of a shift in phytoplankton community composition, however, phytoplankton bloom intensity and evolution was independent of CO2 concentrations and higher CO2 levels had no significant effect on inorganic nutrient uptake or carbon production/consumption. Overall this study proved the stable carbon isotope approach to be an effective tool for the assessment of the major biogeochemical interactions among individual compartments within the marine system opening the door to new interpretations for past, present and future changes of the global carbon cycle.
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Leggett, Michael Frederick. "Food-web dynamics of Lake Ontario as determined by carbon and nitrogen stable isotope analysis." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ32838.pdf.
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Collett, Martin. "Multi-proxy stable oxygen and carbon isotope evidence for Holocene climate change in western Ireland." Thesis, University of Liverpool, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250327.
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Twiddy, Edward James. "Applications of stable carbon and oxygen isotope analysis to some aspects of coastal environmental change." Thesis, Durham University, 1996. http://etheses.dur.ac.uk/1582/.
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Reitsema, Laurie Jean. "Stable Carbon and Nitrogen Isotope Analysis of Human Diet Change in Prehistoric and Historic Poland." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1330969837.
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Oakes, Joanne. "Microalgae and Mangroves as Carbon Sources for Estuarine Invertebrates: Evidence from Stable Isotope Enrichment Experiments." Thesis, Griffith University, 2007. http://hdl.handle.net/10072/365499.
Full textAbstract:
The importance of different sources of carbon (energy) supporting secondary productivity in estuaries and coastal waters is still rather uncertain, despite decades of research on this topic. One of the major uncertainties is the relative importance of carbon from macrophyte detritus and microalgae, particularly diatoms and cyanobacteria within sediments (microphytobenthos, MPB). Existing methods have been unable to determine their relative contributions to consumer nutrition. This thesis addresses some of the limitations of existing methods, and then uses an innovative combination of techniques to determine the relative contributions of detritus and MPB to the nutrition of consumers within a mangrove forest in southeast Queensland, Australia. To ensure wide applicability, techniques were developed for both mud and sand, encompassing the range of sediments encountered in estuaries and protected coastal waters. Stable isotope analysis is commonly used to resolve food web issues. Difficulty extracting MPB from sediment to obtain a pure carbon isotopic signature (δ13C), however, has hampered efforts to determine the importance of MPB as a carbon source for consumers. I showed that compound-specific isotope analysis of phytol, part of the chlorophyll molecule, can be used to estimate MPB δ13C with enough precision for most food web studies: within 1-1.8‰ of actual values (95% CI) at normal levels of replication (n = 5 or 10). Although the majority of phytol in sediments is produced in situ by MPB, part of the phytol pool is derived from detritus (e.g. 33% for mud, 17% for sand in the current study). In some situations, this could lead to errors in estimating MPBδ13C, realistically by about 1‰ (in sand) or 2‰ (in mud), but an adjustment can be made where necessary. Compound-specific isotope analysis of phytol (the phytol method) can therefore be confidently used to estimate MPB δ13C values in estuarine environments. Where δ13C values of detritus and MPB are similar, natural abundance stable isotopes are unable to resolve their contribution to consumer nutrition. Enrichment of producers with the heavy 13C isotope generates distinct δ13C values that can be traced into consumers. Studies aiming to enrich MPB using 13C-enriched sodium bicarbonate have, however, observed simultaneous enrichment of bacteria. This may simply be due to use of MPB-derived carbon by bacteria, but if bacteria acquire the label directly, enrichment of consumers would indicate use of bacteria, rather than MPB, as a primary carbon source. Application of 13C-enriched bicarbonate resulted in enrichment of MPB in both mud and sand and subsequent secondary enrichment of bacteria. Direct bacterial uptake was trivial in comparison to MPB uptake. Any labelling of animals in subsequent enrichment experiments could therefore be attributed to use of MPB as a primary carbon source. I used a combination of the phytol method, stable isotope enrichment, and compartment modelling within a mangrove forest to examine use of detritus and MPB as carbon sources for common consumers; crabs (Australoplax tridentata and Parasesarma erythrodactyla) and foraminifera (Ammonia beccarii and Trochammina inflata). Compartment modelling quantified the extent of use through comparison of producer and consumer enrichment over time. The main carbon source for T. inflata was unable to be established, but all other species acquired virtually all of their carbon locally (within a 1 m radius), from MPB and/or mangrove detritus. The majority of carbon for A. tridentata was derived from MPB (99%), whereas P. erythrodactyla and A. beccarii predominantly utilised mangrove detritus (88 and 84%, respectively). For the latter two species, the remainder of carbon was derived from MPB. The different strategies in carbon utilisation by the crab species indicate feeding selectivity that may be a strategy to avoid interspecific competition for food resources. The high abundance of benthic invertebrates and their rapid assimilation of local carbon sources highlight their potential importance in influencing carbon cycling and productivity in estuaries. Consumption of benthic invertebrates by more mobile, higher consumers may also allow for transport of locally-produced carbon to adjacent waters via trophic relay. The methods demonstrated in this thesis have potential application in resolving food web issues in a variety of habitats. Further application of these techniques at a variety of temporal and spatial scales would help to develop a broader understanding of the importance of macrophyte detritus and MPB, and establish general patterns in utilisation of carbon sources in estuarine systems.<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>School of Environment<br>Faculty of Environmental Sciences<br>Full Text
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Basapuram, Laxmi Gayatri Devi. "Lake Victoria - Carbon, Nitrogen, Phosphorus and Stable Isotope (δ13C) comparison between lake and catchment sediments". Thesis, Linköpings universitet, Tema Miljöförändring, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-149283.
Full textAbstract:
Lake Victoria situated in East Africa faces an acute problem with eutrophication. Many reasons like agricultural production, industrialization, anthropogenic processes, the introduction of species, and economic activities have caused a stress to the overall well-being of the lake. Excess carbon, nitrogen, and phosphorus drive an increase in productivity which affects eutrophication. Previous studies on sediments and nutrient concentrations in the lake have concluded that nutrient concentrations increase due to release from the catchment. This study focuses on catchment sediments collected from four different sites and compares the results with sediments from two additional sites in the lake. The sediment core from Siaya indicates the highest concentrations of TOC (180 g/kg), TN (13 g/kg) and TP (17000μg/L). It is a rural site and poor agricultural practices such as the burn and slash, use of too many fertilizers, clearance of land, atmospheric deposition and precipitation increase elemental concentrations in the sediments compared to the more urban sites. In the lake sediments, the BILL core had higher concentrations of TP (430g/kg) and TN (16 g/kg) compared to the other site (LV-95) which is located far away from the margins of the lake. This core, however, had high TOC levels (180g/kg). The increase of nutrient levels in lake sediments is thought to be due to non-point sources from the catchment. Analyses of stable carbon isotope were used to infer the different organic matter source in the sediments. Based on the range of values for δ13C vs. C/N it is inferred that aquatic algal production and C4 vascular plants are the dominant sources for the organic matter input. The chemical characterization of catchment and lake sediments provides a qualitative link to nutrient influx and eutrophication in the lake.
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Perkins, Matthew James. "Quantifying the effects of biodiversity on food web structure : a stable isotope approach." Thesis, University of Exeter, 2013. http://hdl.handle.net/10871/13941.
Full textAbstract:
Food web structure is of underlying importance to ecological functions and processes. Whilst it is understood that a range of biotic and abiotic factors affect structure, relatively little is known of the role of biodiversity per se in structuring food webs. In this thesis I utilise novel multi-dimensional estimates of food web structure based on stable isotope ratios of nitrogen (δ15N) and carbon (δ13C) to quantify structural responses to changing community diversity. I additionally investigate methodological aspects of sample preparation and stable isotope quantifications of food chains. Using an arthropod prey-predator system, in chapter 2 I demonstrate that tissue selection and lipid extraction are important methodological procedures for deriving accurate δ15N and δ13C signatures. In chapter 3 I test the utility of δ15N to quantify food chain length, and δ13C to trace primary energy sources through to end consumers. Bayesian resampling of variance in sample means for plant and arthropod food chains produces robust isotopic estimates that match known food chain length well despite some error variance, and estimates of δ13C-range that trace trophic transfers. Chapter 4 represents a change in system from lab to field as I determine δ15N and δ13C signatures for plant and invertebrate species within three grassland communities representing a gradient of biodiversity. Quantifications of community bivariate isotopic space using isotopic metrics revealed that greater taxonomic richness increased both diversity of resource space exploited and overlap in resource space. These results therefore suggest that loss of diversity affected structure through altering relative patterns of niche partitioning in resource exploitation amongst community members. In chapter 5, I additionally find evidence that grassland management mediated changes in food web compartmental structure that were associated with differences in generalist invertebrate predator feeding habits. Taken together, these findings develop and demonstrate the utility of isotopic approaches to quantifying food web structure, and provide evidence of important mechanisms by which biodiversity affects food web structure. I conclude that the preservation of natural food web structure and trophic dynamics are further reasons for halting loss of biodiversity.
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Brookman, Tom Hugo. "Stable isotope dendroclimatology of New Zealand kauri (Agathis australis (D. Don) Lindl.) and cedar (Libocedrus bidwillii Hook. F.)." Thesis, University of Canterbury. Department of Geological Sciences, 2014. http://hdl.handle.net/10092/9027.
Full textAbstract:
This thesis presents research that improves our understanding of the relationship between climate and tree-ring stable isotopes in New Zealand kauri (Agathis australis (D. Don) Lindl.) and cedar (Libocedrus bidwillii Hook. F). As a whole, this research creates a framework from which future investigations of stable isotope dendroclimatology can pursued at high temporal resolution across longer term temporal intervals. Such a framework is required to realize the full potential of New Zealand tree-ring records as archives of palaeoclimatic information. In the Southern Hemisphere, mid-to-high latitude terrestrial climate proxy records are sparse; the long-lived endemic conifers of New Zealand present a rare opportunity to gain valuable insight into Late-Quaternary and Holocene climatic change.
A major barrier to long stable isotope dendroclimatic proxy records has been the time-and-resource intensive nature of associated sample preparation and analytical processes. Through experimental assessment of the SBrendel α-cellulose extraction method, this research demonstrates that this simple processing method can, with some caveats, be successfully applied to resinous conifers, facilitating rapid chemical preparation of samples. Further efficiency gains are documented in through use of dual element low temperature pyrolysis of cellulose, providing carbon and oxygen stable isotope determinations on a single sample, rather than the traditionally separate analyses. These preliminary investigations into methodological efficiency enabled the ~3000 stable isotope determinations on kauri and cedar, on which the following investigations into isotopic variability, chronology quality and climate-isotope relationships are based.
Both kauri and cedar exhibit substantial intra and inter-tree isotopic variability, resulting in greater than normal sample numbers being required to isolate the common variance in composite time-series. Despite sampling 7 trees (18 cores) at one site and 8 trees (21 cores) at another, only oxygen isotope time-series reach an Expressed Population Signal score of 0.85, a common benchmark of chronology quality. Further investigations using high-resolution sequential sampling of single rings show that this variability extends to a sub-annual scale. Within single rings there are large ranges in δ13C and δ18O, generally corresponding with regular annual cycles of up to 4.6‰ for δ13C and 8.1‰ for δ18O. These data show high frequency (sub weekly) changes in δ18O, demonstrating sufficiently fine resolution for event-to-seasonal scale climate/weather reconstruction. However, that potential is complicated by the lack of strong climatic correlations with isotopic cycles.
Due to their stronger common signal, δ18O time series are investigated for inter-annual stable isotope dendroclimatic reconstruction from kauri and cedar. Bootstrapped correlation and multiple regression models show strong relationships between kauri and cedar δ18O and relative humidity, accumulated rainfall and soil moisture deficit. The correlations are strongest for all variables during the period from Autumn prior to growth to the current growth summer. Tree-ring δ18O in kauri and cedar is identified as an effective recorder of regional hydroclimate leading up to and during the Austral growth season.
While it is demonstrated that tree-ring δ18O holds significant promise for inter-annual palaeoclimate reconstruction, it is equally apparent from this research that stable isotope dendroclimatology in New Zealand faces significant challenges. Foremost is gaining an improved understanding of seasonal dendrochemical cycles and their relationship with tree-physiology. Increasing the spatial and temporal coverage of tree-ring isotope records is vital to realising New Zealand’s vast potential for stable isotope dendroclimatic reconstruction.
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Deng, Jia, Carmody K. McCalley, Steve Frolking, et al. "Adding stable carbon isotopes improves model representation of the role of microbial communities in peatland methane cycling." AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/625198.
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Climate change is expected to have significant and uncertain impacts on methane (CH4) emissions from northern peatlands. Biogeochemical models can extrapolate site-specificCH(4) measurements to larger scales and predict responses of CH4 emissions to environmental changes. However, these models include considerable uncertainties and limitations in representing CH4 production, consumption, and transport processes. To improve predictions of CH4 transformations, we incorporated acetate and stable carbon (C) isotopic dynamics associated with CH4 cycling into a biogeochemistry model, DNDC. By including these new features, DNDC explicitly simulates acetate dynamics and the relative contribution of acetotrophic and hydro-genotrophic methanogenesis (AM and HM) to CH4 production, and predicts the C isotopic signature (delta C-13) in soil C pools and emitted gases. When tested against biogeochemical and microbial community observations at two sites in a zone of thawing permafrost in a subarctic peatland in Sweden, the new formulation substantially improved agreement with CH4 production pathways and delta C-13 in emitted CH4 (delta C-13-CH4), a measure of the integrated effects of microbial production and consumption, and of physical transport. We also investigated the sensitivity of simulated delta C-13-CH4 to C isotopic composition of substrates and, to fractionation factors for CH4 production (alpha(AM) and alpha(HM)), CH4 oxidation (alpha(MO)), and plant-mediated CH4 transport (alpha(TP)). The sensitivity analysis indicated that the delta C-13-CH4 is highly sensitive to the factors associated with microbial metabolism (alpha(AM), alpha(HM), and alpha(MO)). The model framework simulating stable C isotopic dynamics provides a robust basis for better constraining and testing microbial mechanisms in predicting CH4 cycling in peatlands.
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Potter, Elyn. "Changes in stable carbon isotopes of methane along a salinity gradient in a hypersaline microbial mat system." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/5089.
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Thesis (M.S.)--University of Missouri-Columbia, 2007.<br>The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on November 1, 2007) Includes bibliographical references.
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Rocheford, MaryKathryn. "An early to middle Holocene carbon isotope and phytolith record from the Sac Valley Archaeological District, southwest Missouri." Thesis, University of Iowa, 2009. https://ir.uiowa.edu/etd/425.
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New pedologic, carbon isotope and phytolith analyses along with stratigraphic correlations to nearby archaeological sites record the spatial and temporal distribution of past vegetation patterns in the Sac Valley Archaeological District of southwest Missouri. Radiocarbon ages obtained from a soil core along Bear Creek, CB5, are related to those from Hajic et al. (1998, 2000) indicating that the CB5 location contains correlative middle Rodgers Shelter submember deposits. This relationship also indicates that sedimentation was approximately two times greater at the CB5 locality than at the Big Eddy (23CE426) archaeological site providing much higher temporal resolution for the alluvial history as well as the vegetation proxies during the early to middle Holocene.
Most midcontinent climate proxy records include indications of an early Holocene warm period when prairie replaced forests, then a cooler period in which trees dominated the landscape, followed by a warmer middle Holocene period when prairie vegetation was dominant. However, the CB5 δ13C profile of mixed C3/C4 vegetation indicates either that the vegetation at this location was not as sensitive to climate change or that this location was buffered from other influences, e.g. fires, which were critical to the expansion of prairie vegetation. On the other hand, the phytolith assemblages at CB5 indicate that there were periods with abundant C4 grasses even though the δ13C values indicate a dominance of C3 vegetation. This indicates that in the mixed forest/prairie ecotone interpretations of past vegetation from either carbon isotopes or phytolith assemblages alone may not accurately reflect patterns of vegetation.
A new core, DDY-KR2, was obtained from the Big Eddy (23CE426) archaeological site and a finer resolution of δ13C values at Big Eddy increased the detail about alluvial activity and revealed subtle changes in the vegetation. The vegetation types suggested by the δ13C values for DDY-KR2 are reflected in the phytolith assemblages validating their usefulness in reconstructing local vegetation history.
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Padgett, Abbey E. "Early-Middle Holocene Cultural and Climate Shifts in NW Africa: Paleoenvironmental Reconstruction Using Stable Isotopes of Land Snail Shells." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1522318834405742.
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Tuerena, Robyn Elizabeth. "Nitrogen and carbon cycling in the South Atlantic Ocean : a stable isotope study along a 40°S transect (UK GEOTRACES)." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/10443.
Full textAbstract:
Fixed N (nitrate, nitrite, and ammonium) is a limiting nutrient for photosynthesis in the surface ocean. The rates and relative importance of N cycling processes, however, are temporally and spatially complex, which hamper their direct measurement and quantification. The South Atlantic subtropical front separates the Atlantic Ocean and the subantarctic, an area which can elucidate information about water masses both entering and leaving the basin. Through the GEOTRACES programme, an oceanographic section across 40°S in the South Atlantic is used to investigate biogeochemical cycling of nitrogen and carbon in this region. Hydrographic data, in combination with the isotopic composition of nitrate (NO3-), particulate organic carbon and particulate nitrogen (δ15NNO3, δ18ONO3, δ13CPOC, δ15NPN), is used to provide integrative measurements for temporally and spatially variable processes of the marine N-cycle and C-cycle. A thorough examination of the stable isotope cycling of particulate and dissolved N across the subtropical front is used to quantify the supply of fixed N to the mixed layer. The relative importance of nitrate from the subsurface, N2 fixation, terrestrial input and atmospheric deposition in supplying production is determined. Typically, 30-50% of the export flux in the subtropical water masses is sourced from N2 fixers and up to 75% within the Brazil Current. This finding suggests that diazotrophs may be abundant in the South West Atlantic providing a source of new N to this region. To assess the basin scale N-cycling processes, the deep water masses were analysed to reveal the origin and history of NO3-. Intermediate waters formed in the subantarctic are enriched in δ15NNO3 and δ18ONO3 from partial utilisation by algae. This enrichment in δ15NNO3 is not present in the subtropical North Atlantic or the return flow of the North Atlantic Deep Water (NADW), which decreases from ~5.9‰ in the newly formed intermediate waters to ~4.8‰ in the NADW at 40°S. The modification of isotopic signatures through the subtropical Atlantic can be calculated as an incorporation of 26-36 Tg N yr-1 of newly fixed N from an isotopic source of -1‰ (N2 fixation). The extent of N addition is higher than estimated rates of N loss within the Atlantic and surpasses the amount of N deficit supplied to the basin. Fixed N inputs and losses through the global ocean are investigated by the assessment of remineralised nitrate added to the ocean interior. A lower δ15N is observed in Atlantic remineralised nitrate in comparison to the Pacific. The relative importance of N2 fixation and pelagic denitrification within each ocean basin is quantified and through this approach, N2 fixation rates are estimated at 92-116 Tg N yr-1 in the Pacific and 24-32 Tg N yr-1 in the Indian Ocean. Combining Atlantic N2 fixation of ~32 Tg N yr-1 with Indo-Pacific, global N2 fixation rates can be estimated at 142-184 Tg N yr-1. The high inputs in the Pacific suggest that excess P is the dominant control on the success of N2 fixers. However, estimates of new N addition to the Atlantic indicate other mechanisms such as the recycling efficiency of P and supply of Fe to the surface ocean increase N2 fixation rates above this threshold. The organic matter supplied to sediments is principally derived from phytoplankton across the subtropical front. High organic content is associated with the productive Brazil-Malvinas Confluence region where a diverse supply of nutrients sustains elevated biomass. The Rio Plata outflow is characterised with high δ15NNO3 and δ15NPN, suggesting denitrification processes occur in the estuary. A low δ13C source associated with high Al concentrations is identified on the western slope, indicating a supply of terrestrial derived C to the deep ocean. The fractionation of C uptake by phytoplankton is assessed in subtropical and subantarctic waters. In the subantarctic, CO2[aq] and growth rates determine the extent of C isotope fractionation. In this region, low species diversity and a small range in cell size enable the fractionation from CO2[aq] and growth rate to be expressed in phytoplankton. In subtropical water masses a larger range of cell size is the principal determinant of C fractionation. Increased surface area to volume is the main mechanism for increasing C uptake, arguing against the use of δ13CPOC as a palaeoproxy. The low δ13CPOC and δ15NPN observed in the subtropics (from C fractionation and N2 fixation) contrast the heavier signatures in the subantarctic. These observations are propagated to the sediments, wherein organic matter shifts are determined by changes in the subtropical front over time. The results of this study have greatly improved knowledge of N and C cycling within the South Atlantic, providing new insight into the cycling of these two important elements in the surface and deep ocean, on a regional and global scale.
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Venkiteswaran, Jason James. "A process-based stable isotope approach to carbon-cycling in recently flooded upland boreal forest reservoirs." Waterloo, Ont. : University of Waterloo, [Dept. of Earth Science], 2002. http://etd.uwaterloo.ca/etd/jjvenkiteswaran2002.pdf.
Full textAbstract:
Thesis (M.Sc.) - University of Waterloo, 2002.<br>"A thesis presented to the University of Waterloo in fulfillment of the thesis requirements for the degree of Master of Science in Earth Sciences". Includes bibliographical references.
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Venkiteswaran, Jason. "A process-based stable isotope approach to carbon cycling in recently flooded upland boreal forest reservoirs." Thesis, University of Waterloo, 2002. http://hdl.handle.net/10012/1238.
Full textAbstract:
Reservoirs impound and store large volumes of water and flood land. The water is used for electricity generation, irrigation, industrial and municipal consumption, flood control and to improve navigation. The decomposition of flooded soil and vegetation creates greenhouse gases and thus reservoirs are a source of greenhouse gases. Reservoirs are not well studied for greenhouse gas flux from the water to the atmosphere. The FLooded Upland Dynamics EXperiment (FLUDEX) involves the creation of three experimental reservoirs in the upland boreal forest to study greenhouse gas and mercury dynamics. The balance of biological processes, decomposition, primary production, CH<sub>4</sub> oxidation and the nitrogen cycle in the reservoirs controls the greenhouse gas flux from the reservoir to the atmosphere. Understanding the importance and controlling factors of these processes is vital to understanding the sources and sinks of greenhouse gases within reservoirs. The carbon and oxygen dynamics near the sediment-water interface are very important to the entire reservoir because many processes occur in this area. Light and dark benthic chambers were deployed, side-by-side, to determine the benthic flux of DIC and CH<sub>4</sub> across the sediment-water interface and to determine the role of benthic photoautotrophs in benthic DIC, CH<sub>4</sub> and O<sub>2</sub> cycling. Benthic chambers have shown photoautotrophs use the decomposing soil, rocks and exposed bedrock as a physical substrate to colonize and the CO<sub>2</sub> produced by the decomposing soil as a carbon source since the delta<sup>13</sup>C-DIC value of the DIC added to light chambers is enriched relative to dark chambers and net photosynthesis rates are linked to community respiration. Benthic photoautotrophs consume 15-33% of the potential DIC flux into the water column. CH<sub>4</sub> produced by the decomposition of soils is partially oxidized by methanotrophs that use the photosynthetically produced oxygen. The delta<sup>13</sup>C-CH<sub>4</sub> values of the CH<sub>4</sub> added to light chambers is enriched relative to dark chambers and 15-88% of the potential CH<sub>4</sub> flux into the water column is oxidized. An isotope-mass budget for DIC and CH<sub>4</sub> is presented for each reservoir to identify the importance of processes on areservoir scale. Input of DIC to the reservoirs from overland flow can be important because concentration is greater and delta<sup>13</sup>C-DIC values are depleted relative to inflow from Roddy Lake. Estimates of total reservoir primary production indicate that 3-19% of the total DIC production from decomposition is removed by photoautotrophs. The carbon cycling in biofilm and the importance of periphytic primary production needs to be better understood. Dissolved delta<sup>13</sup>C-CH<sub>4</sub> values of CH<sub>4</sub> in reservoir outflow enriched 45-60permil, indicating that CH<sub>4</sub> oxidation was an important CH<sub>4</sub> sink within the reservoirs. Stable carbon isotope data indicates that the CH<sub>4</sub> in the bubbles is partially oxidized so the site of bubble formation is the upper portion of the flooded soil. The fraction of CH<sub>4</sub> converted to CO<sub>2</sub> in the FLUDEX reservoirs is similar to that of the wetland flooded for the Experimental Lakes Area Reservoir Project (ELARP). Approximately half of the dissolved CH<sub>4</sub> in the FLUDEX reservoirs was removedby CH<sub>4</sub> oxidation. The ebullitive flux of CH<sub>4</sub> from FLUDEX reservoirs is reduced 25-75% by CH<sub>4</sub> oxidation. The CH<sub>4</sub> flux to the atmosphere from peat surface of the ELARP reservoir became less oxidized after flooding: 91% to 85% oxidized. The floating peat islands of the ELARP reservoir were less oxidized than the peat surface. Similar to the CH<sub>4</sub> in the FLUDEX reservoirs, CH<sub>4</sub> in the ELARP peat islands was oxidized 56%. CH<sub>4</sub> oxidation is an important process because it reduces the global warming potential of the greenhouse gas flux since CO<sub>2</sub> is less radiatively active than CH<sub>4</sub>.