Dissertations / Theses on the topic 'Terrestrial carbon'
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Malik, Abdulrahman Ibn. "Terrestrial carbon in Wales." Thesis, Bangor University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.433685.
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Glanville, Helen C. "Carbon dynamics in terrestrial ecosystems." Thesis, Bangor University, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.589388.
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The objective of this thesis was to better understand the mechanistic control of carbon (C) cycling in two terrestrial ecosystems (agricultural grasslands and Arctic tundra), with an aim to identify the contribution of microbial respiration to below-ground C cycling. Firstly, I evaluated different techniques for measuring CO2 evolution from soil. I found that different in-situ chamber-based CO2 gas analyzers gave comparable results across contrasting ecosystems. However, the addition of collars to the CO2 chamber induces variable flux estimates due to the disturbance created upon collar insertion, severing root and mycorrhizal networks. In subsequent studies, I showed that microbial breakdown of individual dissolved organic C (DOC) components demonstrated good reproducibility when performed under either in-situ and ex-situ conditions. After validating the experimental techniques, they were then used to study C turnover in two plant-soil systems. In Arctic tundra, soil temperature was identified as the key driver initiating microbial and vegetation response to snow melt, thereby driving early season CO2 efflux. However, as the growing season progressed, soil water content was hypothesized to become a more important regulator of C turnover with older C compounds becoming more susceptible to decomposition as soil water content increases. In a grassland soil I found that soil microbial community composition does not correlate with increased rates of mineralization across a wide pH gradient. This suggests that abiotic drivers of respiration may directly influence microbial metabolic processes independent of community structure. Further research involving advanced molecular techniques (metabolomics, proteomics, transcriptomics) will help disseminate how metabolic processes are being influenced by different respiration drivers. The application of mathematical models to respiration data provides a more quantitative and mechanistic understanding of processes involved in soil C cycling. I found the fitting of exponential models to respiration data is a reliable proxy for describing substrate mineralization; however, the correct choice of model is critically dependent on the number of measurement points and length of experiment. The modelling approach was subsequently used to quantify the turnover of functional microbial C pools. By combining modelling with experimental measures of soil solution C concentration, we estimated that the microbial contribution to total soil respiration is ea. 18%. This research provides a more detailed understanding of how C constituents are processed by the microbial decomposer community to drive soil respiration. This is crucial to accurately model global terrestrial C fluxes in different ecosystems and to predict how these fluxes are likely to respond to future changes from both natural (e.g. climate change) and anthropogenic (e.g. land-use change) sources.
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Ek, Ella. "Precipitation variability modulates the terrestrial carbon cycle in Scandinavia." Thesis, Uppsala universitet, Luft-, vatten- och landskapslära, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-445453.
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Climate variability and the carbon cycle (C-cycle) are tied together in complex feedback loops and due to these complexities there are still knowledge-gaps of this coupling. However, to make accurate predictions of future climate, profound understanding of the C-cycle and climate variability is essential. To gain more knowledge of climate variability, the study aims to identify recurring spatial patterns of the variability of precipitation anomalies over Scandinavia during spring and summer respectively between 1981 to 2014. These patterns will be related to the C-cycle through changes in summer vegetation greenness, measured as normalized difference vegetation index (NDVI). Finally, the correlation between the patterns of precipitation variability in summer and the teleconnection patterns over the North Atlantic will be investigated. The precipitation data was obtained from ERA5 from the European Centre for Medium-Range Weather Forecasts and the patterns of variability were found through empirical orthogonal function (EOF) analysis. The first three EOFs of the spring and the summer precipitation anomalies together explained 73.5 % and 65.5 % of the variance respectively. The patterns of precipitation variability bore apparent similarities when comparing the spring and summer patterns and the Scandes were identified to be important for the precipitation variability in Scandinavia during both seasons. Anomalous events of the spring EOFs indicated that spring precipitation variability had little impact on anomalies of summer NDVI. Contradictory, summer precipitation variability seemed to impact anomalies of summer NDVI in central- and northeastern Scandinavia, thus indicating that summer precipitation variability modulates some of the terrestrial C-cycle in these regions. Correlations were found between a large part of the summer precipitation variability and the Summer North Atlantic Oscillation and the East Atlantic pattern. Hence, there is a possibility these teleconnections have some impact, through the summer precipitation variability, on the terrestrial C-cycle.Förändringar och variation i klimatet är sammankopplade med kolcykeln genom komplexa återkopplingsmekanismer. På grund av denna komplexitet är kunskapen om kopplingen mellan klimatvariation och kolcykeln fortfarande bristande, men för att möjliggöra precisa prognoser om framtida klimat är det viktigt att ha kunskap om denna koppling. För att få mer kunskap om klimatvariation syftar därför denna studie till att identifiera återkommande strukturer av nederbördsvariation över Skandinavien under vår respektive sommar från 1981 till 2014. Dessa relateras till förändringar i sommarväxtlighetens grönhet, uppmätt som skillnaden i normaliserat vegetationsindex (NDVI). Även korrelationen mellan sommarstrukturerna av nederbördsvariationen och storskaliga atmosfäriska svängningar, s.k. "teleconnections", över Nordatlanten undersöks. Nederbördsdatan erhölls från ERA5 analysdata från Europacentret för Medellånga Väderprognoser och strukturer av nederbördsvariationen identifierades genom empirisk ortogonal funktionsanalys (EOF) av nederbördsavvikelser. De tre första EOF av vår- respektive sommarnederbördsavvikelser förklarade tillsammans 73,5 % respektive 65,5 % av nederbördsvariationen. Strukturerna av nederbördsvariation under vår respektive sommar uppvisade tydliga likheter sinsemellan. Dessutom identifierades Skanderna vara av stor vikt för nederbördsvariationen i Skandinavien under båda årstider. Avvikande år av nederbördsvariation under våren indikerade att sagda nederbördsvariation haft liten påverkan på NDVI-avvikelser under sommaren. Emellertid verkade nederbördsvariationen under sommaren påverkat NDVI-avvikelser under sommaren i centrala och nordöstra Skandinavien. Detta indikerar att nederbördsvariationen under sommaren till viss del styr den terrestra kolcykeln i dessa regioner. För nederbördsvariationen under sommaren fanns korrelation mellan både Nordatlantiska sommaroscillationen och Östatlantiska svängningen. Det finns således en möjlighet att dessa "teleconnections" har en viss påverkan på den terrestra kolcykeln genom nederbördsvariationen under sommaren.
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Hemingway, Jordon Dennis. "Understanding terrestrial organic carbon export : a time-series approach." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/109054.
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Thesis: Ph. D., Joint Program in Chemical Oceanography (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 169-190).
Terrestrial organic carbon (OC) erosion, remineralization, transport through river networks, and burial in marine sediments is a major pathway of the global carbon cycle. However, our ability to constrain these processes and fluxes is largely limited by (i) analytical capability and (ii) temporal sampling resolution. To address issue (i), here I discuss methodological advancements and data analysis techniques for the Ramped PyrOx serial oxidation isotope method developed at WHOI. Ramped-temperature pyrolysis/oxidation coupled with the stable carbon (¹²C, ¹³C) and radiocarbon (¹⁴C) analysis of evolved CO₂ is a promising tool for understanding and separating complex OC mixtures. To quantitatively investigate distributions of OC source, reservoir age, and chemical structure contained within a single sample, I developed a kinetic model linking RPO-derived activation energy, ¹³C composition, and radiocarbon content. This tool provides a novel method to fundamentally address the unknown relationship between OC remineralization rates and chemical structure in various environmental settings. To address issue (ii), I additionally present results from time-series sample sets collected on two end-member systems: the Congo River (Central Africa) and the LiWu River (Taiwan). For the Congo River, bulk and plant-wax-lipid ¹³C compositions indicate that a majority of particulate OC is consistently derived from downstream, C₃-dominated rainforest ecosystems. Furthermore, bulk radiocarbon content and microbial lipid molecular distributions are strongly correlated with discharge, suggesting that pre-aged, swamp-forest-derived soils are preferentially exported when northern hemisphere discharge is highest. Combined, these results provide insight into the relationship between hydrological processes and fluvial carbon export. Lastly, I examined the processes controlling carbon source and flux in a set of soils and time-series fluvial sediments from the LiWu River catchment located in Taiwan. A comparison between bedrock and soil OC content reveals that soils can contain significantly less carbon than the underlying bedrock, suggesting that this material is remineralized to CO₂ prior to soil formation. Both the presence of bacterial lipids and a shift toward lower activation energy of ¹⁴C-free OC contained in soil saprolite layers indicate that this process is microbially mediated and that microbial respiration of rock-derived OC likely represents a larger geochemical flux than previously thought. The results presented in this thesis therefore provide novel insight into the role of rivers in the global carbon cycle as well as their response to environmental perturbations.
by Jordon Dennis Hemingway
Ph. D.
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Krakauer, Nir Yitzhak Schneider Tapio. "Characterizing carbon-dioxide fluxes from oceans and terrestrial ecosystems /." Diss., Pasadena, Calif. : Caltech, 2006. http://resolver.caltech.edu/CaltechETD:etd-05262006-111949.
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Sharma, Benktesh D. "Modeling of forest harvest scheduling and terrestrial carbon sequestration." Morgantown, W. Va. : [West Virginia University Libraries], 2010. http://hdl.handle.net/10450/10900.
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Thesis (Ph. D.)--West Virginia University, 2010.Title from document title page. Document formatted into pages; contains xi, 160 p. : ill. (some col.), col. map. Vita. Includes abstract. Includes bibliographical references.
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Zhu, Dan. "Modeling terrestrial carbon cycle during the Last Glacial Maximum." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLV077.
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Pendant les transitions glaciaire-interglaciaires,on observe une augmentation en partie abrupte de près de 100 ppm du CO2atmosphérique, indiquant une redistribution majeure entre les réservoirs de carbone des continents, de l'océan et de l'atmosphère.Expliquer les flux de carbone associés à ces transitions est un défi scientifique, qui nécessite une meilleure compréhension du stock de carbone ‘initial’ dans la biosphère terrestre au cours de la période glaciaire. L’objectif de cette thèse est d’améliorer la compréhension du fonctionnement des écosystèmes terrestres et des stocks de carbone au cours du dernier maximum glaciaire (LGM, il y a environ21.000 ans), à travers plusieurs nouveaux développements dans le modèle global de végétation ORCHIDEE-MICT, pour améliorer la représentation de la dynamique de la végétation, la dynamique du carbone dans le sol du pergélisol et les interactions entre les grands herbivores et la végétation dans le modèle de la surface terrestre.Pour la première partie, la représentation de la dynamique de la végétation dans ORCHIDEEMICT pour les régions des moyennes et hautes latitudes, a été calibrée et évaluée avec un ensemble de données spatiales de classes de végétation, production primaire brute, et de biomasse forestière pour la période actuelle.Des améliorations sont obtenues avec la nouvelle version du modèle dans la distribution des groupes fonctionnels de végétation. Ce modèle a ensuite été appliqué pour simuler la distribution de la végétation au cours de laLGM, montrant un accord général avec les reconstructions ponctuelles basées sur des données de pollen et de macro-fossiles de plantes.Une partie du pergélisol (sols gelés en permanence) contient des sédiments épais,riches en glace et en matières organiques appelés Yedoma, qui contiennent de grandes quantités de carbone organique, et sont des reliques des stocks de carbone du Pléistocène.Ces sédiments ont été accumulés sous des climats glaciaires. Afin de simuler l'accumulation du carbone dans les dépôts de Yedoma, j’ai proposé une nouvelle paramétrisation de la sédimentation verticale dans le module de carbone dans le sol de ORCHIDEE-MICT. L'inclusion de ce processus a permis de reproduire la distribution verticale de carbone observée sur des sites de Yedoma. Une première estimation du stock de carbone dans le pergélisol au cours du LGM est obtenue, de l’ordre de ~ 1550 PgC, dont 390 ~446 PgC sous forme de Yedoma encore intacts aujourd’hui (1,3 millions de km2).Potentiellement, une plus grande surface de Yedoma pourrait être présente pendant leLGM, qui a disparue lors de la déglaciation.Pour la troisième partie, à la lumière des impacts écologiques des grands animaux, et le rôle potentiel des méga-herbivores comme une force qui a maintenu les écosystèmes steppiques pendant les périodes glaciaires, j'ai incorporé un modèle de d’herbivores dans ORCHIDEE-MICT, basé sur des équations physiologiques pour l'apport énergétique et les dépenses, le taux de natalité, et le taux de mortalité pour les grands herbivores sauvages.Le modèle a montré des résultats raisonnables de biomasse des grands herbivores en comparaison avec des observations disponibles aujourd’hui sur des réserves naturelles. Nous avons simulé un biome de prairies très étendu pendant le LGM avec une densité importante de grands herbivores. Les effets des grands herbivores sur la végétation et le cycle du carbone du LGM ont été discutés, y compris la réduction de la couverture forestière, et la plus grande productivité des prairies.Enfin, j’ai réalisé une estimation préliminaire du stock total de carbone dans le permafrost pendant le LGM, après avoir tenu compte des effets des grands herbivores et en faisant une extrapolation de l'étendue spatiale des sédiments de type Yedoma basée sur des analogues climatiques et topographiques qui sont similaires à la région de Yedoma actuelleDuring the repeated glacialinterglacialtransitions, there has been aconsistent and partly abrupt increase of nearly100 ppm in atmospheric CO2, indicating majorredistributions among the carbon reservoirs ofland, ocean and atmosphere. A comprehensiveexplanation of the carbon fluxes associatedwith the transitions is still missing, requiring abetter understanding of the potential carbonstock in terrestrial biosphere during the glacialperiod. In this thesis, I aimed to improve theunderstanding of terrestrial carbon stocks andcarbon cycle during the Last Glacial Maximum(LGM, about 21,000 years ago), through aseries of model developments to improve therepresentation of vegetation dynamics,permafrost soil carbon dynamics, andinteractions between large herbivores andvegetation in the ORCHIDEE-MICT landsurface model.For the first part, I improved theparameterization of vegetation dynamics inORCHIDEE-MICT for the northern mid- tohigh-latitude regions, which was evaluatedagainst present-day observation-based datasetsof land cover, gross primary production, andforest biomass. Significant improvements wereshown for the new model version in thedistribution of plant functional types (PFTs),including a more realistic simulation of thenorthern tree limit and of the distribution ofevergreen and deciduous conifers in the borealzone. The revised model was then applied tosimulate vegetation distribution during theLGM, showing a general agreement with thepoint-scale reconstructions based on pollen andplant macrofossil data.Among permafrost (perennially frozen) soils,the thick, ice-rich and organic-rich siltysediments called yedoma deposits hold largequantities of organic carbon, which areremnants of late-Pleistocene carbonaccumulated under glacial climates. In order tosimulate the buildup of the thick frozen carbonin yedoma deposits, I implemented asedimentation parameterization in the soilcarbon module of ORCHIDEE-MICT. Theinclusion of sedimentation allowed the modelto reproduce the vertical distribution of carbonobserved at the yedoma sites, leading toseveral-fold increase in total carbon. Simulatedpermafrost soil carbon stock during the LGMwas ~1550 PgC, among which 390~446 PgCwithin today’s known yedoma region (1.3million km2). This result was still anunderestimation since the potentially largerarea of yedoma during the LGM than todaywas not yet taken into account.For the third part, in light of the growingevidence on the ecological impacts of largeanimals, and the potential role of megaherbivoresas a driving force that maintainedthe steppe ecosystems during the glacialperiods, I incorporated a dynamic grazingmodel in ORCHIDEE-MICT, based onphysiological equations for energy intake andexpenditure, reproduction rate, and mortalityrate for wild large grazers. The model showedreasonable results of today’s grazer biomasscompared to empirical data in protected areas,and was able to produce an extensive biomewith a dominant vegetation of grass and asubstantial distribution of large grazers duringthe LGM. The effects of large grazers onvegetation and carbon cycle were discussed,including reducing tree cover, enhancinggrassland productivity, and increasing theturnover rate of vegetation living biomass.Lastly, I presented a preliminary estimation ofpotential LGM permafrost carbon stock, afteraccounting for the effects of large grazers, aswell as extrapolations for the spatial extent ofyedoma-like thick sediments based on climaticand topographic features that are similar to theknown yedoma region. Since these results werederived under LGM climate and constantsedimentation rate, a more realistic simulationwould need to consider transient climate duringthe last glacial period and sedimentation ratevariations in the next step
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Wright, Alison Jane. "Raman spectroscopy of terrestrial analogues for ureilite formation." Thesis, University of Aberdeen, 2010. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=130931.
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This study used Raman spectral analysis to characterise the structural order of carbon in three carbonaceous chondrites and twelve achondrites. The achondrites analysed were a group of carbon-rich meteorites, known as ureilites. These meteorites are composed primarily of olivine and pyroxene and have igneous textures but contain noble gases and primitive oxygen isotopes which appear to contradict their high temperature origin, which has led to the group being described as “enigmatic” by some authors. This study used Raman spectral analysis to show that ureilite carbon is heterogeneous, even at the micrometer scale, and is derived from more than one source. In order to better understand the processes involved in ureilite formation, terrestrial analogues containing carbonaceous material with similar spectral characteristics to the meteorites were identified. Analysis of terrestrial samples showed that the sedimentary carbon can be incorporated into igneous rocks with little structural change, suggesting that the same may be true for carbonaceous material in ureilites. Although the terrestrial carbon is biogenic in origin, it is structurally similar to pre-biotic organic matter found in meteorites. Carbon can be used as an effective tracer for geological events, such as melting and heating, which appear to be ubiquitous in planetary evolution. This study concluded that carbon is a primary component of melts on the ureilite parent body (UPB) and that impact processes have increased the heterogeneity of ureilite carbonaceous material. Carbon is likely to have been remobilised by later impact events, explaining the lack of correlation between carbon content and isotopic values with other geochemical parameters. Spectral analysis suggested that most of the carbon in ureilites is derived from primitive material.
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Borgelt, Jan. "Terrestrial respiration across tundra vegetation types." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-132765.
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Large amounts of carbon (C) are stored in tundra soils. Global warming may turn tundra ecosystems from C sinks into sources or vice versa, depending on the balance between gross primary production (GPP), ecosystem respiration (ER) and the resulting net ecosystem exchange (NEE). We aimed to quantify the summer season C balance of a 27 km2 tundra landscape in subarctic Sweden. We measured CO2 fluxes in 37 widely distributed plots across five tundra vegetation types and in 7 additional bare soil plots, to assess effects of abiotic and biotic components on C exchange. C fluxes in bare soils were low and differed to all vegetation types. Thus, accounting for differences between bare soils and vegetated parts is crucial for upscaling a C balance using a landcover classification map. In addition, we found that both NEE and ER, varied within and across different tundra vegetation types. The C balance model for the growing season 2016 revealed a net C loss to the atmosphere. Most vegetation types acted as CO2 sources, with highest source strength in dense shrub vegetation at low elevations. The only considerable C sinks were graminoid-dominated upland meadows. In addition, we found a shift in C balance between different heath vegetation types, ranging from C source in dense deciduous shrub vegetation (Mesic Heath and Dry Heath) to C sink in low growing shrub vegetation (Extremely Dry Heath). These results highlight the importance to account for differences between vegetation types when modelling C fluxes from plot to landscape level.
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Boysen, Lena. "Potentials, consequences and trade-offs of terrestrial carbon dioxide removal." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2017. http://dx.doi.org/10.18452/17737.
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Die globalen Mitteltemperaturen könnten bis 2100 um 2◦C bis 4.5◦C über vorindustriellem Wert steigen sollten CO2 Emissionen nicht oder nur unzureichend gesenkt werden. Klima-Engineering befasst sich deshalb mit der gezielten Abkühlung des Klimas, z.B. durch terrestrischen Kohlendioxidentzugs (tCDR). Insbesondere wird der Anbau von großflächigen Biomasseplantagen (BP) in Kombination mit der Erstellung von langlebigen Kohlenstoffprodukten wie Bioenergie oder Biokohle in Betracht gezogen. Die vorliegende Doktorarbeit untersucht die tCDR Potentiale und möglichen Konsequenzen von BP auf Nahrungsmittelproduktion, Ökosysteme und das Klima selbst mit Hilfe der Analyse von Landnutzungszenarien simuliert mit einem Biosphärenmodell. Insgesamt wird das tCDR Potential von BP als gering befunden, unabhängig vom Emissionsszenario und ab wann oder wie flächendeckend BP angebaut werden. Demgegenüber stehen meist die zuvor genannten, ungewünschten Konsequenzen. In einem Szenario mit hohen CO2 Konzentrationen kann selbst unbeschränkte Landverfügbarkeit für tCDR die bisherigen Emissionen nicht ausgleichen. Anders jedoch, wenn gleichzeitig Emissionen eingespart. In beiden Fällen führen diese Landumwandlungen jedoch zu sehr hohen “Kosten” für Ökosysteme und die Nahrungsmittelproduktion. Um deren Schutz zu gewährleisten kann die Landverfügbarkeit für tCDR beschränkt werden, was jedoch die tCDR Potentiale trotz baldiger Etablierung sehr einschränkt. Auch die Potentiale des RCP2.6 bleiben deutlich unter den Anforderungen. Das Potential könnte jedoch durch Erhöhung der Umwandlungseffizienzen von Biomasse, neuen Managementoptionen oder der Aufwertung degradierter Flächen durch BP erhöht werden. Diese Doktorarbeit kann abschließend nicht die Annahme unterstützen, dass tCDR eine effektive und umweltfreundliche Methode der Kohlenstoffsequestrierung, und damit eine Ersetzung von strengen Mitigationspfaden, sein könnte.Global mean temperatures could change by 2◦C to 4.5◦C above pre-industrial levels until 2100 if mitigation enforcement of CO2 emissions fails. To counteract this projected global warming, climate engineering techniques aim at intendedly cooling Earth’s climate for example through terrestrial carbon dioxide removal (tCDR). Here, tCDR refers to the establishment of large-scale biomass plantations (BPs) in combination with the production of long-lasting carbon products such as bioenergy with carbon capture and storage or biochar. This thesis examines the potentials and possible consequences of tCDR by analysing land-use scenarios with different spatial and temporal scales of BPs using an advanced biosphere model forced by varying climate projections. Synthesised, the potential of tCDR to permanently extract CO2 out of the atmosphere is found to be small, regardless of the emission scenario, the point of onset or the spatial extent. On the contrary, the aforementioned trade-offs and impacts are shown to be unfavourable in most cases. In a high emission scenario even unlimited area availability for tCDR could not reverse past emissions sufficiently. However, simultaneous emission reductions could result in strong carbon extractions reversing past emissions. In both cases, land transformation for tCDR leads to high “costs” for ecosystems and food production. Restricting the available land for BPs by these trade-off constraints leaves very small tCDR despite a near-future onset. Similarly, simulated tCDR potentials on dedicated BP areas defined in the RCP2.6 scenario stay below the aimed values using current management practices. Some potential may lie the reduction of carbon losses from field to end-products, new management options and the restoration of degraded soils with BPs. This thesis contradicts the assumption that tCDR could be an effective and environmentally friendly way of complementing or substituting strong and rapid mitigation efforts.
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Heck, Vera. "Interference in the Earth system through terrestrial carbon dioxide removal." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2017. http://dx.doi.org/10.18452/17774.
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Biomasseplantagen und Aufforstung zur terrestrischen Kohlenstoffdioxid-Entfernung werden derzeit als Möglichkeit diskutiert um dem anthropogenen Treibhauseffekt entgegenzuwirken. Für die Bewertung solcher Maßnahmen ist ein umfassendes Verständnis ihrer Nachhaltigkeit und möglichen Konsequenzen erforderlich. In dieser Arbeit werden biogeochemische und hydrologische Auswirkungen von Biomasseplantagen und Aufforstung quantitativ und im Kontext der Planetarischen Grenzen (PG) analysiert. Simulationen mit einem globalen Vegetationsmodell zeigen, dass die Auswirkungen von Biomasseplantagen auf die Biosphäre nicht zu vernachlässigen sind und die der historischen landwirtschaftlichen Bodennutzung noch überschreiten können. Außerdem werden Szenarien zur räumlichen Verteilung von Biomasseplantagen unter Berücksichtigung von regionalen und globalen PG für biogeochemische Flüsse, Intaktheit der Biosphäre, Landnutzungswandel und Süßwassernutzung evaluiert. Unter Einhaltung regionaler PG können nur marginale Potentiale erzielt werden. Unter kompletter Ausnutzung des Risikobereichs könnten 1.4-6.9 GtC/a entzogen werden, abhängig von Biomasseverwertungs- und Kohlenstoffspeicherungseffizienzen. Die Relevanz von koevolutionärer Dynamik zwischen dem Kohlenstoffkreislauf und gesellschaftlichem Eingreifen wird mit einem konzeptionellen Modellierungsansatz im Kontext der PG aufgezeigt. Eine Fokussierung auf das Klimaproblem ohne die ganzheitliche Berücksichtigung von erdsystemischen Interaktionen kann ungewollte Überschreitung anderer PG zur Folge haben. Die Kombination von Bevölkerungswachstum und Nahrungsmittelbedarf mit der Minimierung von Kohlenstoff- und Biodiversitätsverlusten zeigt Möglichkeiten und Grenzen für terrestrische Kohlenstoffspeicherung auf. Räumliche Umverteilung in hochproduktive Regionen sowie substantielle landwirtschaftliche Produktivitätssteigerungen ermöglichen die Ernährung von 9 Milliarden Menschen sowie ein Kohlenstoffspeicherungspotential von bis zu 98 GtC.Terrestrial carbon dioxide removal (tCDR) via afforestation or biomass plantations are discussed as options to counteract anthropogenic global warming. Therefore, it is important to understand sustainability limits and implications of tCDR in the context of Earth system dynamics. This thesis provides a model based assessment of biogeochemical and hydrological side-effects of biomass plantations and afforestation in the context of planetary boundaries (PBs), delimiting a safe operating space for humanity. Simulations with a global vegetation model indicate considerable biogeochemical and hydrological consequences of biomass plantations which are even larger than those of historical agricultural land use. Further, land use scenarios of biomass plantations are developed with a multi-objective optimisation model considering the PBs for biogeochemical flows, biosphere integrity, land system change and freshwater use. Respecting PBs yields almost zero tCDR potential. The transgression of PBs into a zone of increasing risk of feedbacks at the planetary scale can provide considerable tCDR potentials of 1.4-6.9 GtC/a, depending on efficiency of biomass conversion and carbon capture and storage. The importance of co-evolutionary dynamics of the Earth''s carbon cycle and societal interventions through tCDR is demonstrated with a conceptual modelling approach in the context of carbon-related PBs. A focus on climate change without an integrated trade-off assessment may lead to navigating the Earth system out of the safe operating space due to collateral transgression of other PBs. Integrating population growth and food demand while minimising carbon and biodiversity loss demonstrates opportunities and limitations for tCDR. Substantial improvements of crop and livestock productivities and the displacement of agricultural production into regions of high productivity yield sustainable terrestrial carbon sequestration potentials of up to 98 GtC while feeding 9 billion people.
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Stapleton, Lee Mark. "Modelling carbon and nitrogen fluxes for two terrestrial ecosystems on Svalbard." Thesis, University of Nottingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.416264.
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Faithfull, Carolyn. "Productivity and carbon transfer in pelagic food webs in response to carbon, nutrients and light." Doctoral thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-43467.
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Some of the major problems we face today are human induced changes to the nitrogen (N), phosphorus (P) and carbon (C) cycles. Predicted increases in rainfall and temperature due to climate change, may also increase dissolved organic matter (DOM) inflows to freshwater ecosystems in the boreal zone. N, P, C and light, are essential resources that most often limit phytoplankton (PPr) and bacterial production (BP) in the pelagic zone of lakes. PPr and BP not only constitute the total basal C resource for the pelagic aquatic food web, but also influence ecosystem function and biogeochemical cycles. In this thesis I studied how N, P, C and light affect the relative and absolute rates of PPr and BP, along a wide latitudinal and trophic gradient using published data, and in two in situ mesocosm experiments in a clear water oligotrophic lake. In the experiments I manipulated bottom-up drivers of production and top-down predation to examine how these factors interact to affect pelagic food web structure and function. The most important predictors of PPr globally (Paper I) were latitude, TN, and lake shape. Latitude alone explained the most variation in areal (50%) and volumetric (40%) PPr. In terms of nutrients PPr was primarily N-limited and BP was P-limited. Therefore bacteria and phytoplankton were not directly competing for nutrients. BP:PPr was mostly driven by PPr, therefore light, N, temperature and other factors affecting PPr controlled this ratio. PPr was positively correlated with temperature, but not BP, consequently, higher temperatures may reduce BP:PPr and hence the amount of energy mobilised through the microbial food web on a global scale. In papers II and III interaction effects were found between C-additions and top-down predation by young-of-the-year (YOY) perch. Selective predation by fish on copepods influenced the fate of labile C-addition, as rotifer biomass increased with C-addition, but only when fish were absent. Interaction effects between these top-down and bottom-up drivers were evident in middle of the food web, which is seldom examined in this type of study. Although the energy pathway from bacteria to higher consumers is generally longer than from phytoplankton to higher trophic levels, increased BP still stimulated the biomass of rotifers, calanoid copepods and YOY fish. However, this appeared to be mediated by intermediate bacterial grazers such as flagellates and ciliates. Light was an important driver of crustacean zooplankton biomass (paper IV), but the light:nutrient hypothesis was inadequate to predict the mechanisms behind the decrease in zooplankton biomass at low light. Instead, it appeared that reduced edibility of the phytoplankton community under low light conditions and reduced BP most strongly affected zooplankton biomass. Thus, the LNH may not apply in oligotrophic lakes where PPr is primarily N-limited, Daphnia is rare or absent and mixotrophic phytoplankton are abundant. N, P, C and light manipulations have very different effects on different parts of the pelagic food web. They influence the relative rates of PPr and BP, affect phytoplankton community composition, alter the biomass of higher trophic levels and change pathways of energy transfer through the pelagic food web. This thesis adds valuable information as to how major changes in these resources will affect food web structure and function under different environmental conditions and future climate scenarios.Lake ecosystem response to environmental change
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Asandei, Ancuta. "Global warming : carbon-nutrient interactions and warming effects on soil carbon dynamics." Thesis, University of Exeter, 2014. http://hdl.handle.net/10871/17537.
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In order to predict how terrestrial ecosystems will respond to global change, there is growing recognition that we need to better understand linkages between plant and soil processes. Previously the factors and processes with potential to influence the terrestrial carbon (C) cycle have been investigated in isolation from each other. This study investigated the interactions of nutrient availability and warming in controlling the soil carbon dynamics, with regards to the fate of already sequestered carbon in soil, under conditions of increasing atmospheric temperatures. The project objectives were addressed by three independent experiments designed to explain specific components of the carbon-nutrient cycle interactions, and the findings brought together to describe the implications for future soil carbon storage. The main measurements collected throughout this project included soil carbon dioxide (CO2) fluxes, partitioned into autotrophic and heterotrophic components, net ecosystem exchange and respiration fluxes, and background soil moisture and temperature data, backed by gas, soil and biomass analyses. In the two field experiments, these measurements were taken from plots with or without any inorganic nutrient additions or in the presence or absence of legumes providing biological nitrogen addition to the ecosystem. In the laboratory, temperature and nutrient availability were manipulated within the ecosystem. The reduction in decomposition rates, without reduction of productivity as a result of inorganic nutrient additions, indicated the potential for increasing C storage. There was also evidence that nutrient availability controls the strength of the link between plant and soil processes in semi-natural grasslands. The yields, decomposition rates and soil C fluxes recorded in the presence and absence of legumes provided some evidence of N2 fixation, improving ecosystem productivity and soil properties while reducing soil C effluxes, in a managed grassland. In the laboratory, the warming of soils from lysimeters with and without plants, receiving or not receiving fertiliser, supported the findings from field experiments regarding the importance of the soil-plant link in controlling C fluxes. However, C stocks and δ13C analyses showed that over a year’s worth of warming and nutrient manipulations made little difference to the amount of C stored in the soil, indicating that edaphic factors have greater control over the response of C dynamics to increased temperatures.
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Shelkov, Denis Alexander. "N and C isotropic composition of different varieties of terrestrial diamonds and carbonado." Thesis, Open University, 1997. http://oro.open.ac.uk/54608/.
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During the course of this research an instrument utilising combustion as a means of gas extraction capable of N, e, Ar and He analysis has been developed and the entire analytical procedure has been automated. N and e isotopic analysis has been performed on eclogitic and peridotitic diamonds (mainly from Yakutian kimberlites and the Roberts Victor kimberlite pipe). Diamonds with unusual (light and heavy relative to the peak of ol3e distribution of mantle diamonds) carbon isotopic signatures were considered for the research so that diamonds in the range of δ¹³C from -30‰ to + 2.8‰ were characterised for δ¹⁵N. The results together with data obtained previously by the others define fields for eclogitic and peridotitic diamonds on a plot of δ¹⁵N vs. δ¹³C. The model of mantle nitrogen and carbon evolution is discussed. A comprehensive comparison between carbonado and other known forms of microcrystalline diamond (framesites and shock diamonds) has been made for a number of parameters: N and e isotopic composition and N content; 4He content; morphology of the inner structure of diamond aggregates. It can be concluded that carbonado is generally similar to frame sites and all facts known about carbonado can be explained on the grounds of common mantle origin involving subducted carbon and nitrogen. Since extremely high 4He concentrations are encountered in carbonado this parameter is considered to be the most singular feature of this diamond variety and the radial distribution of 4He in single diamond crystals has been studied. A 4He content comparable with that in carbonado was found in the 30 J.lm skin of diamond crystals (up to 1.4 x 10⁻²) suggesting that carbonado could acquire high 4He concentration in the same geological processes as single diamond crystals and making carbonado indistinguishable from mantle diamonds in terms of He content. An additional result of the investigation is that the maximum of 4He diffusion coefficient for diamond at mantle P,T conditions can be estimated (≈4x10⁻²¹ ) from the 4He zoning identified in the interior of a diamond crystal from the Finsch kimberlite. A number of diamonds of impact origin from Popigai crater and Ebeliakh river placer deposits were studied for N, C and Ar isotopic compositions. It was concluded that diamonds from these two localities have resulted from separate impact events and that diamond aggregates studied are most probably consist of a mixture of different Ar and N carriers (e.g. two types of diamond grains).
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Warrington, Anita Glasgow. "Stable isotopes of carbon and oxygen in the shells of terrestrial molluscs." Thesis, University of Liverpool, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316976.
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Fornace, Kyrstin L. "Late Quaternary climate variability and terrestrial carbon cycling in tropical South America." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/103257.
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Thesis: Ph. D., Joint Program in Chemical Oceanography (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2016.Cataloged from PDF version of thesis.
Includes bibliographical references.
Characterizing global and regional climate variability and climate-carbon cycle interactions in the past provides critical context for evaluating present and future climate trends. In this thesis, I use stable isotope and radiocarbon analysis of vascular plant biomarkers in lacustrine and marine sediment cores to explore late Quaternary climate variability and connections between past climate change and terrestrial carbon cycling in tropical South America. I investigate temporal and spatial trends in South American Summer Monsoon precipitation by reconstructing hydrologic variability over the past 50,000 years at two sites: the Lake Titicaca drainage basin in the Central Andes and the Pantanal wetlands in the interior lowlands. Diverging hydrologic trends at these two sites during the last glacial period suggest altered monsoon circulation patterns under glacial conditions, while changes in summer insolation appear to be an important control of precipitation at both sites during the Holocene. I next assess the relationship between climate change and the age structure of terrestrial biospheric carbon exported from two tropical catchments over the past 20,000 years. Radiocarbon dating of leaf waxes in Cariaco Basin and Lake Titicaca sediment records indicates that waxes preserved in sediments are likely composed of a fresh component transported to sediments within decades of production by vegetation and an old component derived from aged soil organic matter with an average age on the order of millennia at time of deposition. Results from both sites show that past hydrologic variability had a significant impact on the mobilization and export of different pools of terrestrial biospheric carbon. In particular, results from Cariaco Basin suggest that wetter conditions in the past resulted in increased export of fresh biospheric carbon to the ocean, representing a potentially important climate feedback mechanism on geologic timescales.
by Kyrstin L. Fornace.
Ph. D.
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Blair, David Stanley Hamilton. "Carbon and contaminant trace metal biogeochemistry in surficial organic-rich terrestrial systems." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/16231.
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Peats and organic-rich soils are a key part of the global carbon (C) cycle due to their sequestration and storage of atmospheric C as organic matter. Atmospheric deposition as a result of human activities has led to increased inventories of lead (Pb) and mercury (Hg) in UK peats and organic-rich soils. Ombrotrophic peat bogs, which receive all their nutrients and pollutants from the atmosphere, provide a historic record of Pb and Hg deposition within their solid phase. Organic-rich forest soil systems can also act as sinks for anthropogenic Pb but vertical transport of Pb can distort these temporal records. The long-term outlook may, however, be affected by processes which lead to decomposition of organic matter e.g. drying out of peatlands and soils due to climatic change, since these may release Pb into the aqueous phase and volatile Hg to the atmosphere. The associations and speciation of Pb and Hg within peats and organic-rich soils are not well understood but are key to understanding both the potential for release of these pollutants into other environmental compartments and the risks to ecosystems and human health posed by such a release. Investigation of 4 sites in central Scotland showed that, depending on vertical depth, ~40-99% of Pb in ombrotrophic peat was in association with large (0.22 μm – 100 kDa) humic molecules. Near-surface regions where intact plant material had not yet undergone complete humification showed the lowest proportion of Pb-humic association. Historical Pb deposition was retained to similar degrees across each site with recorded inventories to 1986 of 0.340-0.561 g m-2. However, perturbation of the 206Pb/207Pb isotope ratio profile at Glentress forest indicated that limited migration of petrol-sourced Pb may be occurring. Similarly, perturbation of the 210Pb profile at Auchencorth Moss, in addition to discrepancies in the apparent time period in which peak Pb deposition occurred, indicated that Pb may also be subject to migration within this ombrotrophic system. With respect to Hg, between-site differences in speciation were observed. For example, Hg2+ represented < 25% of the total Hg species in the top 10 cm of solid phase ombrotrophic peat but > 50% of the total in forest soil. In contrast, aqueous phase Hg was entirely in the inorganic form across all sites. The occurrence of a solid phase [Hg] peak in layers corresponding to the ~1955 height of coal burning, in addition to the narrow range of peatland Hg inventories to 1950 (2.20-3.23 g m-2) provide evidence that Hg deposition records may be maintained in organic-rich systems to a greater degree than previously assumed. Differences observed in the associations of Pb and the speciation of Hg between the surface vegetation of ombrotrophic bogs and the underlying peat suggests that plants play an integral role in the biogeochemical behavior and sequestration of Pb and Hg in these terrestrial systems.
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Zaehle, Sönke. "Process-based simulation of the terrestrial biosphere : an evaluation of present-day and future terrestrial carbon balance estimates and their uncertainty." Phd thesis, Universität Potsdam, 2005. http://opus.kobv.de/ubp/volltexte/2005/526/.
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At present, carbon sequestration in terrestrial ecosystems slows the growth rate of atmospheric CO2 concentrations, and thereby reduces the impact of anthropogenic fossil fuel emissions on the climate system. Changes in climate and land use affect terrestrial biosphere structure and functioning at present, and will likely impact on the terrestrial carbon balance during the coming decades - potentially providing a positive feedback to the climate system due to soil carbon releases under a warmer climate. Quantifying changes, and the associated uncertainties, in regional terrestrial carbon budgets resulting from these effects is relevant for the scientific understanding of the Earth system and for long-term climate mitigation strategies.
A model describing the relevant processes that govern the terrestrial carbon cycle is a necessary tool to project regional carbon budgets into the future. This study (1) provides an extensive evaluation of the parameter-based uncertainty in model results of a leading terrestrial biosphere model, the Lund-Potsdam-Jena Dynamic Global Vegetation Model (LPJ-DGVM), against a range of observations and under climate change, thereby complementing existing studies on other aspects of model uncertainty; (2) evaluates different hypotheses to explain the age-related decline in forest growth, both from theoretical and experimental evidence, and introduces the most promising hypothesis into the model; (3) demonstrates how forest statistics can be successfully integrated with process-based modelling to provide long-term constraints on regional-scale forest carbon budget estimates for a European forest case-study; and (4) elucidates the combined effects of land-use and climate changes on the present-day and future terrestrial carbon balance over Europe for four illustrative scenarios - implemented by four general circulation models - using a comprehensive description of different land-use types within the framework of LPJ-DGVM.
This study presents a way to assess and reduce uncertainty in process-based terrestrial carbon estimates on a regional scale. The results of this study demonstrate that simulated present-day land-atmosphere carbon fluxes are relatively well constrained, despite considerable uncertainty in modelled net primary production. Process-based terrestrial modelling and forest statistics are successfully combined to improve model-based estimates of vegetation carbon stocks and their change over time. Application of the advanced model for 77 European provinces shows that model-based estimates of biomass development with stand age compare favourably with forest inventory-based estimates for different tree species. Driven by historic changes in climate, atmospheric CO2 concentration, forest area and wood demand between 1948 and 2000, the model predicts European-scale, present-day age structure of forests, ratio of biomass removals to increment, and vegetation carbon sequestration rates that are consistent with inventory-based estimates. Alternative scenarios of climate and land-use change in the 21st century suggest carbon sequestration in the European terrestrial biosphere during the coming decades will likely be on magnitudes relevant to climate mitigation strategies. However, the uptake rates are small in comparison to the European emissions from fossil fuel combustion, and will likely decline towards the end of the century. Uncertainty in climate change projections is a key driver for uncertainty in simulated land-atmosphere carbon fluxes and needs to be accounted for in mitigation studies of the terrestrial biosphere.
Kohlenstoffspeicherung in terrestrischen Ökosystemen reduziert derzeit die Wirkung anthropogener CO2-Emissionen auf das Klimasystem, indem sie die Wachstumsrate der atmosphärischer CO2-Konzentration verlangsamt. Die heutige terrestrische Kohlenstoffbilanz wird wesentlich von Klima- und Landnutzungsänderungen beeinflusst. Diese Einflussfaktoren werden sich auch in den kommenden Dekaden auf die terrestrische Biosphäre auswirken, und dabei möglicherweise zu einer positiven Rückkopplung zwischen Biosphäre und Klimasystem aufgrund von starken Bodenkohlenstoffverlusten in einem wärmeren Klima führen. Quantitative Abschätzungen der Wirkung dieser Einflussfaktoren - sowie der mit ihnen verbundenen Unsicherheit - auf die terrestrische Kohlenstoffbilanz sind daher sowohl für das Verständnis des Erdsystems, als auch für eine langfristig angelegte Klimaschutzpolitik relevant.
Um regionale Kohlenstoffbilanzen in die Zukunft zu projizieren, sind Modelle erforderlich, die die wesentlichen Prozesse des terrestrischen Kohlenstoffkreislaufes beschreiben. Die vorliegende Arbeit (1) analysiert die parameterbasierte Unsicherheit in Modellergebnissen eines der führenden globalen terrestrischen Ökosystemmodelle (LPJ-DGVM) im Vergleich mit unterschiedlichen ökosystemaren Messgrößen, sowie unter Klimawandelprojektionen, und erweitert damit bereits vorliegende Studien zu anderen Aspekten der Modelunsicherheit; (2) diskutiert unter theoretischen und experimentellen Aspekten verschiedene Hypothesen über die altersbedingte Abnahme des Waldwachstums, und implementiert die vielversprechenste Hypothese in das Model; (3) zeigt für eine europäische Fallstudie, wie Waldbestandsstatistiken erfolgreich für eine verbesserte Abschätzung von regionalen Kohlenstoffbilanzen in Wäldern durch prozessbasierten Modelle angewandt werden können; (4) untersucht die Auswirkung möglicher zukünftiger Klima- und Landnutzungsänderungen auf die europäische Kohlenstoffbilanz anhand von vier verschiedenen illustrativen Szenarien, jeweils unter Berücksichtigung von Klimawandelprojektionen vier verschiedener Klimamodelle. Eine erweiterte Version von LPJ-DGVM findet hierfür Anwendung, die eine umfassende Beschreibung der Hauptlandnutzungstypen beinhaltet.
Die vorliegende Arbeit stellt einen Ansatz vor, um Unsicherheiten in der prozessbasierten Abschätzung von terrestrischen Kohlenstoffbilanzen auf regionaler Skala zu untersuchen und zu reduzieren. Die Ergebnisse dieser Arbeit zeigen, dass der Nettokohlenstoffaustausch zwischen terrestrischer Biosphäre und Atmosphäre unter heutigen klimatischen Bedingungen relativ sicher abgeschätzt werden kann, obwohl erhebliche Unsicherheit über die modelbasierte terrestrische Nettoprimärproduktion existiert. Prozessbasierte Modellierung und Waldbestandsstatistiken wurden erfolgreich kombiniert, um verbesserte Abschätzungen von regionalen Kohlenstoffvorräten und ihrer Änderung mit der Zeit zu ermöglichen. Die Anwendung des angepassten Modells in 77 europäischen Regionen zeigt, dass modellbasierte Abschätzungen des Biomasseaufwuchses in Wäldern weitgehend mit inventarbasierten Abschätzungen für verschiede Baumarten übereinstimmen. Unter Berücksichtigung von historischen Änderungen in Klima, atmosphärischem CO2-Gehalt, Waldfläche und Holzernte (1948-2000) reproduziert das Model auf europäischer Ebene die heutigen, auf Bestandsstatistiken beruhenden, Abschätzungen von Waldaltersstruktur, das Verhältnis von Zuwachs und Entnahme von Biomasse, sowie die Speicherungsraten im Kohlenstoffspeicher der Vegetation. Alternative Szenarien von zukünftigen Landnutzungs- und Klimaänderungen legen nahe, dass die Kohlenstoffaufnahme der europäischen terrestrischen Biosphäre von relevanter Größenordnung für Klimaschutzstrategien sind. Die Speicherungsraten sind jedoch klein im Vergleich zu den absoluten europäischen CO2-Emissionen, und nehmen zudem sehr wahrscheinlich gegen Ende des 21. Jahrhunderts ab. Unsicherheiten in Klimaprojektionen sind eine Hauptursache für die Unsicherheiten in den modellbasierten Abschätzungen des zukünftigen Nettokohlenstoffaustausches und müssen daher in Klimaschutzanalysen der terrestrischen Biosphäre berücksichtigt werden.
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Cunliffe, Andrew Michael. "Understanding structure and function in semiarid ecosystems : implications for terrestrial carbon dynamics in drylands." Thesis, University of Exeter, 2016. http://hdl.handle.net/10871/24329.
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This study advances understanding of how the changes in ecosystem structure and function associated with woody shrub encroachment in semi-arid grasslands alter ecosystem carbon (C) dynamics. In terms of both magnitude and dynamism, dryland ecosystems represent a major component of the global C cycle. Woody shrub encroachment is a widespread phenomenon globally, which is known to substantially alter ecosystem structure and function, with resultant impacts on C dynamics. A series of focal sites were studied at the Sevilleta National Wildlife Refuge in central New Mexico, USA. A space-for-time analogue was used to identify how landscape structure and function change at four stages over a grassland to shrubland transition. The research had three key threads: 1. Soil-associated carbon: Stocks of organic and inorganic C in the near-surface soil, and the redistribution of these C stocks by erosion during high-intensity rainfall events were quantified using hillslope-scale monitoring plots. Coarse (>2 mm) clasts were found to account for a substantial proportion of the organic and inorganic C in these calcareous soils, and the erosional effluxes of both inorganic and organic C increased substantially across the vegetation ecotone. Eroded sediment was found to be significantly enriched in organic C relative to the contributing soil with systematic changes in OC enrichment across the vegetation transition. The OC enrichment dynamics observed were inconsistent with existing understanding (derived largely from reductionist, laboratory-based experiments) that OC enrichment is largely insignificant in the erosional redistribution of C. 2. Plant biomass: Cutting-edge proximal remote sensing approaches, using a remotely piloted lightweight multirotor drone combined with structure-from-motion (SfM) photogrammetry were developed and used to quantify biomass carbon stocks at the focal field sites. In such spatially heterogeneous and temporally dynamic ecosystems existing measurement techniques (e.g. on-the-ground observations or satellite- or aircraft-based remote sensing) struggle to capture the complexity of fine-grained vegetation structure, which is crucial for accurately estimating biomass. The data products available from the novel SfM approach developed for this research quantified plants just 15 mm high, achieving a fidelity nearly two orders of magnitude finer than previous implementations of the method. The approach developed here will revolutionise the study of biomass dynamics in short-sward ecogeomorphic systems. 3. Ecohydrological modelling: Understanding the effects of water-mediated degradation processes on ecosystem carbon dynamics over greater than observable spatio-temporal scales is complicated by significant scale-dependencies and thus requires detailed mechanistic understanding. A process-based, spatially-explicit ecohydrological modelling approach (MAHLERAN - Model for Assessing Hillslope to Landscape Erosion, Runoff and Nutrients) was therefore comprehensively evaluated against a large assemblage of rainfall runoff events. This evaluation highlighted both areas of strength in the current model structure, and also areas of weakness for further development. The research has improved understanding of ecosystem degradation processes in semi-arid rangelands, and demonstrates that woody shrub encroachment may lead to a long-term reduction in ecosystem C storage, which is contrary to the widely promulgated view that woody shrub encroachment increases C storage in terrestrial ecosystems.
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Koren, Lindsey Michelle. "Assessment of Microbial Carbon Processing and its Implications to the Carbon Budget of Lake Superior." VCU Scholars Compass, 2019. https://scholarscompass.vcu.edu/etd/6007.
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Over the past few decades, there has been increased research focus on carbon cycling within aquatic systems, especially with the changing global climate. Inland waters play a major role in the global carbon cycle, but the fundamental features remain poorly understood, particularly the large lakes of the world. Our experimental approach assessing the carbon budget of Lake Superior, the largest freshwater lake by area, provides spatial and temporal variability that has been previously overlooked but may be critical to our understanding on the biogeochemical processes controlling the lake. Multiple stations were chosen across the lake, both nearshore and offshore, to evaluate the variability in physical mixing regimes and biogeochemical processing. Short and long-term carbon consumption measurements were coupled to assess the heterotrophic activity relative to the lability of dissolved organic carbon. Partial pressure of carbon dioxide (pCO2) was directly measured to determine the metabolic nature of the lake and the amount of carbon dioxide (CO2) that fluxes across the air-water interface. The pCO2 results were further coupled with an isotopic approach measuring oxygen-18 (δ18O) to evaluate how the metabolism of Lake Superior has changed over a decadal scale.
A range of environmental factors, including temperature, photodegradation and source/quality of organic carbon, influenced short and long-term carbon consumption. In-situ pCO2 observations supported a temporal switch in metabolism from the lake being a source of CO2 in the spring to being a sink in the summer driven by biological components of the system. When the pCO2 results were coupled with the isotopic measurements over the past decade (1999-2011), Lake Superior was dominated by respiration during isothermal conditions and production during stratification. In the past decade, Lake Superior has experienced increased surface water temperatures, shifting the metabolic state to a shorter net heterotrophic period in the spring and a longer net autotrophic period in the summer. This research highlights fundamental aspects of Lake Superior’s metabolism that have been previously understudied, as well as providing key information about processes controlling its carbon budget, and giving a better understanding of how climate change will continue to impact Lake Superior.
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Zaehle, Sönke. "Process based simulation of the European terrestrial biosphere an evaluation of present-day and future terrestrial carbon balance estimates and their uncertainty /." [S.l. : s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=975648489.
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Wang, Yi 1969. "Simulation of the climate, ocean, vegetation and terrestrial carbon cycle in the holocene." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86064.
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In this thesis, the "green" McGill Paleoclimate Model (MPM) is developed by interactively coupling the five-component physical MPM with a Dynamic Global Vegetation Model (DGVM) known as VECODE (VEgetation COntinuous DEscription model). Three applications to the pre-industrial Holocene climate, ocean, vegetation and terrestrial carbon cycle dynamics are presented, after a new land surface scheme is introduced. In these applications, orbital (Milankovitch) forcing and prescribed atmospheric CO2, starting from eight thousand years before present (8 kyr BP), are applied. In addition, a prescribed retreat of the Laurentide Ice Sheet (LIS) from 8 to 6 kyr BP is introduced. [Note: All acronyms used in this thesis are given in Appendix A.]The first application, in which the atmospheric CO 2 is fixed at 280 ppmv, shows that the vegetation-albedo feedback together with the retreating LIS allows the global annual mean surface air temperature to increase starting from 8 kyr BP and reach a maximum at around 6 kyr BP. The decreasing Northern Hemisphere summer insolation (orbital forcing) together with the vegetation-albedo feedback can explain the gradual cooling during the past 6 kyr. The southward shift of the boreal forest treeline from 6 to 0 kyr BP and the desertification of northern Africa from 8 to 2 kyr BP are also simulated, in good agreement with paleoclimatic reconstructions.
In the second application, the reconstructed (Taylor Dome) atmospheric CO2 is used as a variable radiative forcing, and an inverse method is introduced to investigate the global carbon cycle dynamics. The model results indicate that the retreating LIS, in association with the vegetation-albedo and vegetation-precipitation (biogeophysical) feedbacks, causes the terrestrial carbon store to reach its maximum at around 6 kyr BP. Based on the inverse method, it is inferred that the first 10 ppmv atmospheric CO 2 increase from 8 to 6 kyr BP comes from the ocean carbon pool, which includes sedimentation processes. However, the land carbon release of about 68 PgC (95 PgC without CO2 fertilization) from 6 to 0 kyr BP can only contribute about 5 to 7 ppmv increase in atmospheric CO2; additional carbon sources are needed from the ocean. The simulated desertification results in a 70-PgC decrease in total carbon in the Sahara desert. This decrease is partially compensated by a 40-PgC increase in total carbon in the Southern Hemisphere.
Finally, in the third application, the total volume of meltwater/freshwater from the retreating LIS is estimated, and four discharge scenarios are proposed to investigate the impact of this freshwater on the Holocene ocean, climate and terrestrial carbon cycle. During each freshwater perturbation, the simulated maximum Atlantic meridional overturning circulation (MOC) intensity is reduced, by amounts of up to 8 Sv. However, it rebounds to a higher level than the original state, within 10 to 20 years after the termination of the freshwater input. During the time of a weakened MOC, the SST is reduced in the high-latitude North Atlantic and increased in the Southern Ocean due to decreased northward oceanic heat transport. Only a large freshwater perturbation (>0.1 Sv) has a significant impact on the Holocene climate and terrestrial carbon cycle; it results in an enhanced cooling of about 1°C in the Northern Hemisphere (caused by the appearance of the North Atlantic sea ice) and notable drops in the global net primary productivity (2 PgC/yr) and total land carbon storage (40 PgC).
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Qian, Haifeng. "Variability of terrestrial carbon cycle and its interaction with climate under global warming." College Park, Md.: University of Maryland, 2008. http://hdl.handle.net/1903/8564.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2008.Thesis research directed by: Dept. of Atmospheric and Oceanic Science. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Fang, Linhao. "Terrestrial carbon-isotope stratigraphy : an exploration of the method from Miocene and Jurassic examples." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:883ef59a-f3aa-44ac-b539-d0f81317296e.
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Terrestrial carbon-isotope stratigraphy has proven a promising tool for stratigraphic correlation between the different exchangeable carbon-isotope reservoirs, as well as a powerful approach to reconstructing the evolution of δ13C of atmospheric CO2, which is closely associated with the evolution of palaeoenvironment and palaeoclimate. However, the limited understanding of pitfalls in specific application potentially restricts the method’s utility for stratigraphic correlation and palaeoenvironmental reconstruction. This thesis takes advantage of three case studies at two vital geological intervals which are both characterized by the significant carbon-isotope perturbation in the exchangeable reservoirs, to explore the nature of terrestrial carbon-isotope stratigraphy. Two of the case studies focus on the late Early to Middle Miocene, the period of the so called Monterey Event that is marked by remarkable positive carbon-isotope excursions in benthic and pelagic marine carbonate records. There are few terrestrial carbon-isotope records for the Monterey Event. In the present study, shallow marine sediments were collected from boreholes in the New Jersey margin, USA (IODP, Expedition 313) and North Sea Basin, Denmark. Phytoclasts are concentrated from palynological residues as the basis for a terrestrial carbon-isotope stratigraphy from the two locations. The carbon-isotope curves obtained can be correlated in detail locally, and correlated crudely on a global scale. However, there are no definite positive carbon-isotope excursions observed in the terrestrial isotopic stratigraphic records through the biostratigraphically determined Langhian interval equivalent to the Monterey Event. The reasons for the absence of relatively positive carbon-isotope excursions in terrestrial carbon-isotope stratigraphy might be caused by the reworking deposits of woody phytoclasts from older strata or some other process related to reworking. Another case study centres on the Triassic-Jurassic boundary and Early Jurassic fluvial and lacustrine succession in the Kuqa section, Tarim Basin, NW China. Macrofossil wood samples were collected to generate the terrestrial carbon-isotope stratigraphy. On the basis of the biostratigraphy and potential Stage/Age (sub-) boundaries implied by biological overturns, the terrestrial carbon-isotope stratigraphy in the Kuqa section can be well correlated with both terrestrial and marine carbon-isotope stratigraphic records from UK through the Early Jurassic. For the Triassic-Jurassic boundary, more precise correlation was made globally and an exact the position of Triassic-Jurassic boundary is proposed in the Kuqa section. In light of the biostratigraphy and the carbon-isotope stratigraphy obtained in the present study, an updated age assignment of the lithostratigraphic units is proposed to Age/Stage level in the Early Jurassic across the Northern Tarim Basin. The carbon-isotope stratigraphy thus significantly improves the terrestrial stratigraphic resolution. Terrestrial carbon-isotope stratigraphy is a powerful tool for global stratigraphic correlation and unifies stratigraphic correlation over marine and non-marine strata in cases when potential biasing factors are excluded.
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Vonk, Jorien Elisabeth. "Molecular and isotopic characterization of terrestrial organic carbon released to (sub-)Arctic coastal waters." Doctoral thesis, Stockholm : Department of Applied Environmental Science (ITM), Stockholm University, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-38589.
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Diss. (sammanfattning) Stockholm : Stockholms universitet, 2010.At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Accepted. Paper 4: Manuscript. Härtill 4 uppsatser.
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Rosengren, Emma. "Linking Jet Stream Variability and the NAO to the Terrestrial Carbon Cycle in Europe." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-412827.
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The terrestrial carbon cycle is a part of the global carbon cycle, where one important component is the terrestrial vegetation. Terrestrial vegetation largely controls the land surface carbon exchanges and leverage the atmospheric greenhouse gas concentrations, significantly affecting the trajectory of global warming. It is therefore important to improve the understanding of vegetation response to different climatic factors, in particular for those linked to large-scale climate variability, which is still less studied so far. Vegetation greenness is suggested to be a useful tool in order to understand vegetation response. Looking at Europe, the climate factors that affect vegetation the most are linked to the large-scale atmospheric circulation over the North Atlantic, like the jet stream, which varies in speed and latitude, and the North Atlantic Oscillation (NAO). Here, I compute monthly indices representing the variability of these atmospheric features, and correlate them with monthly vegetation greenness data (NDVI) anomalies over a period of five years. This is done both for regionally-averaged NDVI and the months April-July and as a geographical point-by-point analysis for the month of May. The results show a significant correlation between Scandinavian NDVI and the NAO as well as jet speed at multiple time lags, up until 2 months. The jet latitude, instead, showed significant correlation for three regions in mid/southwestern Europe at longer time lags of 3-4 months. This means that the position of the jet in winter can affect the spring vegetation growth in this area. The jet speed and NAO, however, works mostly at shorter timespans.Den jordbunda kolcykeln, som är en del av den globala kolcykeln, består av olika komponenter där en viktig del är vegetation. Växtlighet på land kontrollerar till stor del utbytet av kol vid jordytan och har därigenom inflytande på atmosfäriska växthusgaskoncentrationer, vilket medför stor påverkan på global uppvärmning. Det är därför viktigt att förbättra förståelsen för hur vegetation reagerar på olika klimatologiska faktorer, särskilt de som är kopplade till storskalig klimatvariabilitet då dessa kopplingar har studerats i mindre utsträckling hittils. Ett bra sätt att mäta den jordbunda kolcyklen på är med grönhet av vegatation. Om vi beaktar Europa så är det främst storskaliga atmosfäriska cirkulatoiner över norra Atlanten av de klimatologiska faktorerna som påverkar vegetation. En av dessa faktorer är jetströmmen, vilken varierar i fart och latitud, samt Nordatlantiska Oscillationen(NAO). I detta arbete beräknar jag index som representerar variationen i dessa i form av månadsgenomsnitt och korrelerar dem med månatlig data över avvikelser i vegetationsgrönhet (NDVI) över en femårsperiod. Det här gjordes för både regionala medelvärden och månaderna april-juli samt en geografisk punkt till punkt analys utförd för maj. Resultatet visar att det finns en signifikant korrelation mellan NDVI i Skandinavien och NAO samt jetfarten vid flera tidsfördröjningar, upp till 2 månader. Jetlatituden visade däremot signifikant korrelation för tre regioner i centrala/sydvästa Europa vid längre tidsfördröjningar på 3-4 månader. Detta innebär att positionen på jetströmmen under vintern kan påverka vegetationstillväxten under våren i detta område. Jetfarten och NAO påverkar däremot mest vid kortare tidsspan.
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Smith, Garrett J. "Microbial contributions to carbon, nitrogen, and greenhouse gas cycling in freshwater terrestrial-aquatic interfaces." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1575380962535345.
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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.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.
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Lefébure, Robert. "Effects of temperature and terrestrial carbon on fish growth and pelagic food web efficiency." Doctoral thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-54028.
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Both temperature and terrestrial dissolved organic carbon (TDOC) have strong impacts on aquatic food web dynamics and production. Temperature affects vital rates of all organisms and terrestrial carbon has been shown to alter the dynamics of phytoplankton and bacterial production and affect the trophic structure of planktonic food webs. As climate change predictions for the Baltic Sea suggests future increases in both terrestrial carbon run-off and increases in temperature, the aim of thesis was to adopt a system-ecological approach and study effects of these abiotic variables, not only on interactions within planktonic food webs, but also on the growth and consumption rates of one of the most common zooplanktivorous fish in the Baltic Sea, the three-spined stickleback Gasterosteus aculeatus. Results showed that three-spined sticklebacks display a high degree of resilience against increasing temperatures, as both growth rates as well as consumption rates on zooplankton were high at temperatures well over 20 °C. Furthermore, it was shown that the minimal resource densities required to sustain individual and population growth, actually decreased with increasing temperatures, implying that sticklebacks around their optimum temperature for growth at 21 °C will actually have an increased scope for growth. As stickleback population densities have increased over the last decade in the Baltic Sea and are now suggested to out-compete other coastal fish species for shared zooplankton resources, the results presented in this thesis suggest that increased water temperatures would only serve to increase sticklebacks competitive advantage. As the structuring role of this small zooplanktivore on pelagic communities might be considerable, further studies investigating competitive interactions as well as patterns of population abundances are definitely warranted. TDOC was overall shown to stimulate bacterial production and the microbial food web. Because of the longer trophic pathways required to transport carbon from bacterial production to higher trophic levels, the addition of TDOC always reduced food web transfer efficiency. However, it became apparent that the full effect of TDOC additions on pelagic food webs was complex and depended heavily not only on the existing trophic structure to which the carbon was introduced, but also on ambient temperature levels. When three-spined sticklebacks were part of food webs with significant TDOC inputs, the presence of fish, indirectly, through predator release of lower trophic levels, amplified the magnitude of the effects of carbon addition on bacterial production, turning the base of the system significantly more heterotrophic, which ultimately, impacted negatively on their own production. However, when a pelagic food web containing sticklebacks was simultaneously subjected to realistic increases in temperature and TDOC concentrations, food web efficiency and fish production increased compared to present day conditions. These results were explained by a temperature dependent increased production potential of zooplankton, sustained by an increased production of heterotropic microzooplankton via TDOC additions, which lead to higher fish production. Although the increased number of trophic linkages in heterotrophic food webs should have reduced energy transfer efficiency, these negative effects seem here to have been overridden by the positive increases in zooplankton production as a result of increased temperature. These results show that heterotrophic carbon transfer can be a viable pathway to top-consumers, but also indicates that in order to understand the full effects of climate change on trophic dynamics and fish production, abiotic variables cannot be studied in isolation.
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Inegbedion, Otaigbe. "The importance of small water bodies for carbon capture in Northumberland." Thesis, Northumbria University, 2017. http://nrl.northumbria.ac.uk/36218/.
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Small water bodies (SWBs) are an important biogeochemical sub-compartment of the global carbon cycle that has been given little or no attention. They have similar capabilities to oceans, large lakes and river systems to exist in flux and could store more carbon in their sediments than the above systems. This research is aimed at determining the number and surface area of inland water bodies in Northumberland, the carbon stocks in the sediments of those water bodies and the microbial influence on the carbon stocks. These further define the Northumberland regional carbon stocks, the level of allochthonous and autochthonous carbon influence in the regional carbon stocks and the effects of surrounding vegetation, sediment wetness, dry bulk density, microbes, anoxia, pond permanence and temporariness on carbon stock variations. The importance of SWBs is in their abundance and the ability to estimate this will aid the understanding of their actual contributions to the global carbon cycle as a net source or sink. Using Landsat-8 and World Imagery data, number and surface area of water bodies in Northumberland were identified by manual digitising of water bodies on ArcGIS 10.0. This showed variation in number and surface area of water body abundance with respect to imagery types, time and scale of analysis. The correctness of estimating water body abundance is subject to the continuous temporal change of small water body abundance. The continuous changes are associated with the nature of water bodies, regional/sub-regional landscape (hypsometry), precipitation and land use. Carbon stock in Northumberland was determined by Total Elemental Analyser (TEA) combustion of sediment from various types and sizes of ponds collected from Druridge Bay, Northumberland. Carbon stocks varied in each ponds type and size range. These variations were influenced by the prevailing environmental/physical, biological and chemical/biochemical factors in pond sediments. The microbial community drives carbon stock by altering the microbial community structure, allochthonous and autochthonous carbon processes and the oxygenation in the ponds. PCR pyrosequencing targeted at the 16s rRNA gene showed diversity in the microbial composition of the Northumberland pond sediments and the results showed a varying level of anoxia triggered by factors such as anoxic Proteobacteria, Bacteroidetes, Chloroflexi, Cyanobacteria and Chlorobi dominance. These dominant phyla also influenced other phyla to develop anoxic ecological relationships and produce predominantly anoxia based processes like methanogenesis and fermentation. Anoxic pond bottoms were also triggered by high terrestrial inputs amongst other factors. This research shows for the first time that carbon stock in a region’s SWBs varied because of numerous physical/environmental, chemical and biological factors. Also, SWBs stock carbon from the terrestrial environment and in-situ aquatic processes. Northumberland water body distribution has shown that more carbon is stocked in the small sized water body systems than larger water body system and their global abundance places them as an important carbon capture mechanism.
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Scholze, Marko. "Model studies on the response of the terrestrial carbon cycle to climate change and variability." Hamburg : Max-Planck-Inst. für Meteorologie, 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=968442625.
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Swain, Eleanor Yvonne. "Molecular characterization of terrestrial organic carbon in some organic-rich soils in the northern latitudes." Thesis, University of Newcastle upon Tyne, 2013. http://hdl.handle.net/10443/2232.
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Northern peatlands store around one third of the global soil carbon, however over the past 100 years significant areas of these peats and peaty gley soils have been drained and planted with coniferous forest. Afforestation could accelerate peat decay due to land disturbance causing the peatland to become a net carbon source, alternatively carbon may accumulate due to increased carbon fixation, causing the peatland to remain a net carbon sink. Despite the global importance of these mechanisms, our understanding of the fate of soil carbon stores in afforested carbon-rich soils (i.e. peaty gley and peat soils) remains unclear. Peat and litter were analysed using thermally assisted hydrolysis and methylation (THM) in the presence of 13C-labelled and unlabelled tetramethylammonium hydroxide (TMAH) which revealed the distribution, degradation transformations and turnover rates of vascular plant- and Sphagnum-derived phenols in carbon-rich soil profiles. The studied sites included afforested peaty gley soils under a first- and second-rotation Sitka spruce plantation, unplanted moorland, and self seeded Sitka spruce on unprepared moorland, all of which are located in Kielder Forest, northern England. A pristine peatland in central Sweden was also extensively sampled to assess the carbon related processes occurring in carbon-rich soils prior to afforestation. The effects of afforestation on total carbon stocks were also investigated. The establishment of coniferous forests on peaty gley soils led to a net accumulation of soil carbon during the second rotation, surpassing the moorland carbon capacity. Whilst the encroachment of Sitka spruce on to open moorland via self seeding has resulted in a decreased carbon stock. The phenol composition of soil horizons displayed a maximum lignin content at deep soil across the afforested sites caused primarily by the horizon inversion that occurred prior to planting. Sphagnum acid THM products were identified across the peatland and serve as putative biomarkers for the contribution of Sphagnum-derived organic matter in peats and afforested peatlands, as well as showing potential to provide information on peatland oxic conditions. Sphagnum phenols accumulate preferentially in the anoxic saturated peat, suggesting changes introduced via land-use change or climate change could affect the water table, and thus increase the potential peat decomposition, and the subsequent loss of carbon in peatlands.
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Liu, Yongwen, Shilong Piao, Xu Lian, Philippe Ciais, and W. Kolby Smith. "Seasonal Responses of Terrestrial Carbon Cycle to Climate Variations in CMIP5 Models: Evaluation and Projection." AMER METEOROLOGICAL SOC, 2017. http://hdl.handle.net/10150/625331.
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Seventeen Earth system models (ESMs) from phase 5 of the Coupled Model Intercomparison Project (CMIP5) were evaluated, focusing on the seasonal sensitivities of net biome production (NBP), net primary production (NPP), and heterotrophic respiration (Rh) to interannual variations in temperature and precipitation during 1982-2005 and their changes over the twenty-first century. Temperature sensitivity of NPP in ESMs was generally consistent across northern high-latitude biomes but significantly more negative for tropical and subtropical biomes relative to satellite-derived estimates. The temperature sensitivity of NBP in both inversion-based and ESM estimates was generally consistent in March-May (MAM) and September-November (SON) for tropical forests, semiarid ecosystems, and boreal forests. By contrast, for inversion-based NBP estimates, temperature sensitivity of NBP was nonsignificant for June-August (JJA) for all biomes except boreal forest; whereas, for ESM NBP estimates, the temperature sensitivity for JJA was significantly negative for all biomes except shrublands and subarctic ecosystems. Both satellite-derivedNPP and inversion-based NBP are often decoupled from precipitation, whereas ESM NPP and NBP estimates are generally positively correlated with precipitation, suggesting that ESMs are oversensitive to precipitation. Over the twenty-first century, changes in temperature sensitivities of NPP, Rh, and NBP are consistent across all RCPs but stronger under more intensive scenarios. The temperature sensitivity of NBP was found to decrease in tropics and subtropics and increase in northern high latitudes in MAM due to an increased temperature sensitivity of NPP. Across all biomes, projected temperature sensitivity of NPP decreased in JJA and SON. Projected precipitation sensitivity of NBP did not change across biomes, except over grasslands in MAM.
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Gilbert, Peter. "The power of ponds? : quantifying sediment carbon stocks within, and fluxes from, small ponds." Thesis, Northumbria University, 2016. http://nrl.northumbria.ac.uk/32560/.
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The role of ponds within the terrestrial carbon cycle has been receiving increasing interest. Existing evidence suggests that they have substantial global coverage, with ecosystem function rates disproportionately intense for their size making them significant cyclers of atmospheric carbon. This project aims to: (1) provide a comprehensive survey and quantification of carbon stocks within lowland ponds from a diverse range of ecological pond types; (2) provide a comparison of carbon stocks from pond sediments across significantly different biogeographical regions across England; and (3) monitor the temporal and spatial variability of carbon fluxes from ponds. Carbon stocks were surveyed in 40 ponds across Druridge Bay, Northumberland. These ponds were selected for their distinct plant communities and hydrological patterns that form four broad pond types: dune-slack ponds; arable field ponds; pasture field; and classically vegetated ponds. High measures of percentage carbon were found within the sediments, however, when quantified in terms of carbon (C) stock, (kg-1 C m-2 < upper 10 cm), little difference was observed among classically vegetated, arable, and pasture pond types (means = 3.14, 3.17, 4.94 kg-1 C m-2 < upper 10 cm respectively); only sediment C stocks of dune-slack ponds (6.18 kg-1 C m-2 < upper 10 cm) were significantly different from other pond types. Equally, the heterogeneity of C stocks among dune-slack ponds varied markedly, with ponds in arable fields being fairly consistent. No significant difference was observed between C stocks in the pond sediments compared to those in surrounding soil. This does not mean that they play a similar role in the carbon cycle, but highlights the importance of acquiring sediment burial rates within these systems in order to quantify their role as C stores. To test if the patterns of C storage could be generalised beyond the Northumberland ponds to other regions in the England, 15 ponds were surveyed, 5 each from 3 separate regions of England with differing climatic influences and biogeographical characteristics: temporary ponds on the Lizard Peninsula, Cornwall, with Mediterranean climate; pingo ponds of Thomspon Common, Norfolk; and peat excavation ponds at Askham Bog, Yorkshire. Sediment C stocks of ponds sampled in Cornwall (mean = 2.6 kg-1 C m-2 < upper 10 cm), were > 43 % lower compared to those in Yorkshire (6.0 kg-1 C m-2 < upper 10 cm) and Norfolk (7.7 kg-1 C m-2 < upper 10 cm). However, cumulatively, the variation observed among all sites was comparable to the high level of variation observed in the comprehensive survey of ponds at Druridge. The absence of detailed C flux rates from small water bodies, especially from desiccated sediments during summer dry phases, is a key factor constraining their inclusion in terrestrial carbon budgets. Thus, CO2 fluxes were monitored from 26 neighbouring experimental ponds of known age, history and ecology, focusing on short-term hydrological changes over two, two-week periods, comprising a drying phase and re-wetting phase. During the drying phase flux rates exhibited a 9-fold increase resulting in a shift from a net intake of CO2 to a net site emission whilst the reverse was observed during the rewetting phase. Moreover, significant variability in fluxes of CO2 were observed among ponds on individual sampling days; the highest range observed was -2154 to 10658 mg m-2 d-1. The result is marked spatial variability in CO2 processing. The large degree of temporal and spatial heterogeneity repeatedly observed throughout this study, both in sediment carbon stocks and CO2 fluxes, highlights the complexity of carbon processing within small aquatic systems such as ponds. This study specifically highlights the need for accurate measures of burial rates within pond systems in order to fully assess their carbon capture capability.
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Liu, Qing. "land surface modeling with enhanced consideration of soil hydraulic properties and terrestrial ecosystems." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5154.
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This thesis research consists of two separate studies. The first study presents the assessment and representation of the effects of soil macropores on the soil hydraulic properties in land surface models for more accurate simulations of soil moisture and surface hydrology. Hydraulic properties determine the soil water content and its transport in the soil. They are provided in most current climate models as empirical formulas by functions of the soil texture. Such is not realistic if the soil contains a substantial amount of macropores. A two-mode soil pore size distribution is incorporated into a land surface model and tested using an observational dataset at a tropical forest site with aggregated soils. The result showed that the existence of macropores greatly affects the estimation of hydraulic properties. Their influence can be included in land models by adding a second function to the pore-size distribution. A practical hydraulic scheme with macropore considerations was proposed given that the existing schemes are not applicable for large-scale simulations. The developed scheme was based on the physical attributes of the water in soil capillary pores and the statistics of several global soil databases. The preliminary test showed that it captures part of soil macropore hydraulic features without sacrificing the estimation accuracy of hydraulic properties of water in soil matrix.
The second study presents the development of an integrated land/ecosystem model by combining the advanced features of a biophysically based land model, the Community Land Model, and an ecosystem biochemical model. The results from tests of the integrated model at four forest sites showed that the model reasonably captures the seasonal and interannual dynamics of leaf area index and leaf nitrogen control on carbon assimilation across different environments. With being coupled to an atmospheric general circulation model (AGCM), the integrated model showed a strong ability to simulate terrestrial ecosystem carbon fluxes together with heat and water fluxes. Its simulated land surface physical variables are reasonable in both geographic distribution and temporal variation with considering the interactive vegetation parameters.
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Chaanda, Mohammed Suleiman. "Cenozoic terrestrial palaeoenvironemtal change : an investigation of the Petrockstowe and Bovey basins, south west United Kingdom." Thesis, University of Plymouth, 2016. http://hdl.handle.net/10026.1/5347.
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The Petrockstowe and Bovey basins are two similar pull apart (strike slip) basins located on the Sticklepath – Lustleigh Fault Zone (SLFZ) in Devon, SW England. The SLFZ is one of the several faults on the Cornubian Peninsula and may be linked to Variscan structures rejuvenated in Palaeogene times. The bulk of the basins’ fill consists of clays, silts, lignites and sands of Palaeogene age, comparable to the Lough Neagh Basin (Northern Ireland), which is also thought to be part of the SLFZ. In this study a multiproxy approach involving sedimentary facies analysis, palynological analysis, stable carbon isotope (δ13C) analysis and organic carbon palaeothermometer analyses were applied in an attempt to understand the depositional environment in both basins. A negative carbon isotope excursion (CIE) with a magnitude of 2‰ was recorded at ~ 580 m in the siltstone, silty clay to clay lithofacies in the lower part of Petrockstowe Basin, with minimum δ13CTOC values of -28.6‰. The CIE spans a depth of 7 m. Palynological characteristics of this excursion are correlated with the Cogham Lignite in the southern UK, which is the only established PETM section in the UK, and other continental sections to test whether the palynology associated with this CIE can be used to date it. The age model proposed herein correlates the CIE to the Eocene Thermal Maximum -2 (ETM2; ~ 52.5Ma) event. Key pollen and spore assemblages found in the lower Petrockstowe Basin are Monocolpopollenites, Inaperturopollenites, Laevigatisporites, Bisaccate conifer pollen and Tricolporopollenites, which suggest an Eocene age, while those occurring in the upper part of the Petrockstowe and Bovey basins are Arecipites, Inaperturopollenites, Monocolpopollenites, Tricolporopollenites, Sequoiapollenites, and Pompeckjodaepollenites, which have suggested botanical affinities to modern tropical to sub-tropical genera signifying a climate that was frost-free at the time of sediment deposition. This assemblage further suggests that these sediments are Oligocene to middle Oligocene in age. In the upper part of the Petrockstowe Basin, reconstructed mean annual air temperatures (MAT) demonstrate a clear departure from the mean temperature of 24.5oC at 10 m to 19.5oC towards the top of the core, indicating a steady continuous decline similar to the temperature departures seen in the Solent Group in the Hampshire Basin, Isle of Wight, UK which has an established Eocene – Oligocene succession.
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Taylor, Scott. "Exploring factors driving organic carbon burial and storage in small constructed ponds : an experimental approach." Thesis, Northumbria University, 2017. http://nrl.northumbria.ac.uk/36143/.
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The significance of ponds in the terrestrial carbon cycle has received increasing attention in recent years. Evidence suggests that ponds exhibit rates of biogeochemical cycling orders of magnitude greater than larger water bodies and, cumulatively, the storage of organic carbon (OC) in small ponds may equal or possibly surpass that of large water bodies. This project furthers our understanding of OC storage within ponds, combining survey and experimental approaches to accurately quantify sediment carbon stocks and accumulation rates. It incorporates four distinct, yet complimentary components aiming to: i) Evaluate the accuracy of estimating OC storage in entire ponds from sediment cores; ii) Monitor physicochemical dynamics and quantify OC storage across newly constructed ponds; iii) Quantify OC storage across a suite of mature ponds and assess the impact of vegetation community development; iv) Identify variations in microbial communities between different ponds in relation to sediment physicochemistry and vegetation coverage, exploring the implications for OC storage and burial. Carbon stocks were surveyed in 12 mature ponds across an experimental field site at Druridge Bay, Northumberland. Comprehensive historical ecological data was used to separate these ponds into three distinct groups based on hydrology and vegetation. One pond was selected from each of the resulting three groups and exhumed in its entirety to accurately quantify OC storage. Three sediment cores were taken beforehand in a novel attempt to evaluate the percentage difference between sediment core estimates and whole pond sediment OC storage. Whole pond exhumation suggests that the three ponds stored between 1565 – 2288 g OC m2, whilst results from the cores alone gave estimates within a 10-15% range. A further three ponds from each group were selected to quantify burial rates using sediment cores. Results suggest the ponds have stored between 1413 – 4459 g OC m2 over 20 yrs, equating to around 67 – 212 g OC m2 yr-1. OC storage was greater in ponds that had undergone the fastest establishment of vascular plant communities. Three new ponds were constructed at the Druridge site. Physicochemical parameters were monitored at approximately fortnightly intervals across a period of three years. All three ponds were hyper-eutrophic, dominated by algae. However, OC storage was negligible, further suggesting that OC burial is only significant upon the establishment of vascular plant communities. Sediment samples were subject to 16s rRNA analysis to identify microbial communities involved in carbon cycling. Variations in microbial community composition between ponds were observed and showed complex relationships with sediment physicochemistry and vegetation coverage. Microbial diversity was significantly higher in ponds storing more OC. Ponds dominated by Juncus vegetation, had lower diversity and a greater abundance of facultative anaerobic bacteria, and stored less OC. The intense rates of OC burial observed in this study demonstrate the functional capacity of constructed ponds to operate as significant sinks of OC. High rates of OC accumulation compared to the surrounding terrestrial landscape highlights the potential for their construction across landscapes to act as versatile, yet effective carbon mitigation features.
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Dogrul, Selver Ayca. "The effect of global climate change on the release of terrestrial organic carbon in the Arctic Region." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/the-effect-of-global-climate-change-on-the-release-of-terrestrial-organic-carbon-in-the-arctic-region(64ed1c27-07ff-42b3-83a7-7803b4b697f4).html.
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The Arctic Region is currently experiencing an amplified warming if compared to the rest of the world. The soils in this region store approximately half of the global soil organic carbon (OC), mainly locked in the permanently-frozen ground (permafrost). This carbon sink is sensitive to global warming meaning that the predicted warming will likely increase the thaw-release of this ‘old’ carbon. However, what happens to this remobilized OC once it is transported to the Arctic Ocean, including the potential conversion to greenhouse gasses causing a positive feedback to climate warming, remains unclear. In this work, we further investigate the fate of terrestrial derived OC (terrOC) in the Eurasian Arctic Region. The key findings of this work are: • Glycerol dialkyl glycerol tetraethers (GDGTs) and bacteriohopanepolyols (BHPs) are present in marine sediments of the Eurasian Arctic Region and the associated Branched and Isoprenoidal tetraether (BIT) and Rsoil indices can be used to trace terrOC in marine realm. However, a slight modification in the Rsoil index is suggested (R’soil). • Analyses indicate that the behaviour of BIT is largely controlled by a marine GDGT contribution while the R’soil index is mainly controlled by the removal of soil marker BHPs. Although both indices suggest a non-conservative behavior for the terrOC, this leads to differences in the estimations for the percentage terrOC present. A multi-proxy approach is essential since the use of a single-proxy approach can lead to over/under estimation.• Comparison of BIT and 13Csoc indices across the East Siberian Shelf indicates that the BIT index is possibly reflecting a predominantly fluvial input while 13Csoc represents a mixed fluvial and coastal erosion input.• The macromolecular terrOC composition varies along a west-east Eurasian Arctic climosequence and is mainly controlled by the river runoff of surface derived terrOC and wetland coverage (sphagnum vs. higher plants) but is not affected by the presence/absence of continuous permafrost. • The phenols/(phenols+pyridines) ratio was suggested as a proxy to trace terrOC at the macromolecular level along the Kolyma River-East Siberian Sea transect. The results indicate a non-conservative behavior of the macromolecular terrOC comparable to the bulk of the terrOC.All molecular analyses/based proxies used showed that the remobilized terrOC in the Eurasian Arctic region behaves non-conservatively potentially causing a positive feedback to global climate change.
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Brown, Jennifer Louise Dickson. "Optical properties of chromophoric dissolved organic matter as a tracer of terrestrial carbon to the coastal ocean." View electronic thesis (PDF), 2009. http://dl.uncw.edu/etd/2009-2/r1/brownj/jenniferbrown.pdf.
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Slevin, Darren. "Investigating sources of uncertainty associated with the JULES land surface model." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/18757.
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The land surface is a key component of the climate system and exchanges energy, water and carbon with the overlying atmosphere. It is the location of the terrestrial carbon sink and changes in the land surface can impact weather and climate at various time and spatial scales. It's ability to act as a source or a sink can influence atmospheric CO2 concentrations. Both models and observations have shown the reduced ability of the land surface to absorb increased anthropogenic CO2 emissions with results from the Coupled Climate-Carbon Cycle Model Intercomparison Project (C4MIP) and phase 5 of the Coupled Model Intercomparison Project (CMIP5) have shown that the terrestrial carbon cycle is a major source of model uncertainty. Land surface models (LSMs) represent the interaction between the biosphere and atmosphere in earth system models (ESMs) and are important for simulating the terrestrial carbon cycle. In the context of land surface modelling, uncertainty arises from an incomplete understanding of land surface processes and the inability to model these processes correctly. As LSMs become more advanced, there is a need to understand their accuracy. In this thesis, the ability of the Joint UK Land Environment Simulator (JULES), the land surface scheme of the UK Met Office United Model, to simulate Gross Primary Productivity (GPP) fluxes is evaluated at various spatial scales (point, regional and global) in order to identify and quantify sources of uncertainty in the model. This thesis has three main objectives. Firstly, JULES is evaluated at the point scale across a range of biomes and climatic conditions using local (site-specific), global and satellite datasets. It was found that JULES is biased with total annual GPP underestimated by 16% and 30% across all sites compared to observations when using local and global data, respectively. The model's phenology module was tested by comparing results from simulations using the default phenology model to those forced with leaf area index (LAI) from the MODIS sensor. Model parameters were found to be a minor source of uncertainty compared to the meteorological driving data at the point scale as was the default phenology module in JULES. Secondly, in addition to evaluating simulated GPP fluxes at the point scale, the ability of JULES to simulate GPP at the global and regional scale for 2000-2010 was investigated with being able to simulate interannual variability and simulated global GPP estimates were found to be greater than the observation-based estimates, FLUXNET-MTE and MODIS, by 8% and 25%, respectively. At the regional scale, differences in GPP between JULES, FLUXNET-MTE and MODIS were observed mostly in the tropics and this was the reason for differences at the global scale. Simulating tropical GPP was found to be a major source of uncertainty in JULES. JULES was found to be insensitive to spatial resolution and when driven with the PRINCETON meteorological dataset, differences between model simulations driven using WFDEI-GPCC and PRINCETON occurred in the tropics (at 5°N-5°S) and extratropics (at 30°N-60°N). Finally, the response of JULES to changes in climate (surface air temperature, precipitation, atmospheric CO2 concentrations) was explored at the global and regional scale. Simulated GPP was found to have greater sensitivity to changes in precipitation and CO2 concentrations than air temperature at the global scale while LAI was sensitive only to changes in temperature and insensitive to changes in precipitation and CO2 concentrations. It was found that model sensitivity to climate at the global scale was determined by its behaviour at the regional scale.
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Mieres, Dinamarca Francisco. "Production, sorption and pathways for dissolved organic carbon flow in the Krycklan catchment. : Modelling with focus on the terrestrial forest ecosystem." Thesis, KTH, Mark- och vattenteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-190613.
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Dissolved Organic Carbon accounts for many different functions in the boreal forest ecosystem. It is the main vehicle for organic carbon transport from the litterfall to the forest soil profile and together with water drainage it can be transported to streams. In boreal forests, the DOC transport have gain attention because of recently documented rise in concentration. Several models have been proposed, first to gain understanding in the main cauces of this increase in concentration, and then to simulate the transport of DOC in the landscape. An exploratory work was made to identify the extent of physical control and hydrological pathways for DOC discharge and the long-term biological control over DOC production, transport in the soil profile and discharge in 2 different situations. A 22-year dataset from the Krycklan Catchment site was used. Meteorological data was used as driving variables to calibrate DOC concentration and runoff in a small catchment (Site C7). The CoupModel was set up to represent the described vegetation and documented soil characterization and then calibrated to fit the measured variables. A stepwise calibration process was preferred to promote the understanding of the different components of the landscape in the organic carbon cycle. Results point to soil heat and water transfer processes as the most relevant group to explain both water runnof and DOC discharge, with increasing relevance in the deeper layers, explaining up to 97% of short-term variability in DOC discharge for the 27-35 cm layer. Soil organic carbon pools showed to have relevance in organic carbon stock balance along the soil profile. Conclusions state that, In concordance with other authors, there is a hydrological primary control over DOC discharge, but that soil organics and especially vegetation perform a relevant role in long-term balance of the organic carbon cycle. Further studies with this model could include time-series of atmospheric deposition of Sulphur and nitrogen and running the model in cascade.
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Garbulsky, Martín Fabio. "On the remote sensing of the radiation use efficiency and the gross primary productivity of terrestrial vegetation." Doctoral thesis, Universitat Autònoma de Barcelona, 2010. http://hdl.handle.net/10803/3713.
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La captación de carbono por la vegetación es a escala global el flujo más grande de CO2 e influencia en gran medida el funcionamiento de los ecosistemas. Sin embargo, su variabilidad temporal y espacial sigue siendo poco conocida y difícil de estimar. Las técnicas de teledetección pueden ayudar a calcular mejor la producción primaria bruta (GPP) terrestre, que es la expresión a nivel de ecosistemas del proceso de la fotosíntesis. El objetivo principal de esta tesis fue encontrar una manera de estimar la variabilidad espacial y temporal de la eficiencia en el uso de la radiación (RUE) a escala de ecosistema y por lo tanto mejorar la estimación de la GPP de la vegetación terrestre por medio de datos de teledetección. Se abordaron cuatro objetivos específicos. El primero fue analizar y sintetizar la literatura científica sobre la relación entre el Índice de Reflectancia Fotoquímica (PRI), un índice espectral vinculado a la eficiencia fotosintética, y diversas variables ecofisiológicas a través de un amplio rango de tipos funcionales de plantas y ecosistemas. El segundo objetivo fue analizar y sintetizar los datos de la variabilidad espacial de la GPP y la variabilidad espacial y temporal de la RUE y sus controles climáticos para un amplio rango de tipos de vegetación, desde la tundra a la selva tropical. El tercer objetivo fue comprobar si diferentes índices espectrales, es decir, el PRI, el NDVI (Normalized Difference Vegetation Index) y EVI (Enhanced Vegetation Index), derivados del Moderate Resolution Imaging Spectroradiometer (MODIS) son buenos estimadores de la captación de carbono a diferentes escalas temporales en un bosque mediterráneo. El cuarto objetivo fue evaluar el uso de MODIS PRI como estimador de la RUE en un amplio rango de tipos de vegetación mediante el uso de datos sobre la captación de carbono de la vegetación derivados de las torres de covarianza turbulenta.
Las principales conclusiones de esta tesis son que hay una coherencia emergente de la relación RUE-PRI que sugiere un sorprendente grado de convergencia funcional de los componentes bioquímicos, fisiológicos y estructurales que afectan la eficiencia de captación de carbono a escala de hoja, de cobertura y de ecosistemas. Al complementar las estimaciones de la fracción de radiación fotosintéticamente activa interceptada por la vegetación (FPAR), el PRI permite mejorar la evaluación de los flujos de carbono a diferentes escalas, a través de la estimación de la RUE. Una segunda conclusión apoya la idea de que el funcionamiento anual de la vegetación es más limitado por la disponibilidad de agua que por la temperatura. La variabilidad espacial de la RUE anual y máxima puede explicarse en gran medida por la precipitación anual, más que por el tipo de vegetación. Una tercera conclusión es que, si bien EVI puede estimar el incremento diametral anual de los troncos, y el PRI puede estimar la fotosíntesis neta diaria nivel de hoja y la eficiencia en el uso de radiación, el papel del NDVI es más limitado como un estimador de cualquier parte del ciclo del carbono en bosques mediterráneos. Por lo tanto, el EVI y el PRI son excelentes herramientas para el seguimiento del ciclo del carbono en los bosques mediterráneos. Por último, el PRI derivado de información satelital disponible libremente, presenta una relación positiva significativa con la RUE para un amplio rango de diferentes tipos de bosques, incluso en años determinados, en bosques caducifolios. En general, esta tesis proporciona un mejor entendimiento de los controles espacial y temporal de la RUE y abre la posibilidad de estimar RUE en tiempo real y, por tanto, la captación de carbono de los bosques a nivel de ecosistemas a partir del PRI.
Carbon uptake by vegetation is the largest global CO2 flux and greatly influences the ecosystem functions. However, its temporal and spatial variability is still not well known and difficult to estimate. Remote sensing techniques can help to better estimate the terrestrial gross primary production (GPP), that is the ecosystem level expression of the photosynthesis process or the rate at which the ecosystem's producers capture CO2. The main objective of this thesis was to find a way to estimate the spatial and temporal variability of the Radiation Use Efficiency (RUE) at the ecosystem scale and therefore to arrive to more accurate ways to estimate GPP of terrestrial vegetation by means of remotely sensed data. Four specific objectives were addressed in this thesis. The first objective was to examine and synthesize the scientific literature on the relationships between the Photochemical Reflectance Index (PRI), a narrow-band spectral index linked to photosynthetic efficiency, and several ecophysiological variables across a wide range of plant functional types and ecosystems. The second objective was to analyze and synthesize data for the spatial variability of GPP and the spatial and temporal variability of the RUE and its climatic controls for a wide range of vegetation types, from tundra to rain forest. The third objective was to test whether different spectral indices, i.e. PRI, NDVI (Normalized Difference Vegetation Index) and EVI (Enhanced Vegetation Index), derived from the MODerate resolution Imaging Spectroradiometer (MODIS) can be indicators of carbon uptake at different temporal scales by analyzing the relationships between detailed ecophysiological variables at the stand level in a Mediterranean forest. The fourth objective was to assess the use of MODIS PRI as surrogate of RUE in a wide range of vegetation types by using data on carbon uptake of the vegetation derived from eddy covariance towers.
The main conclusions of this thesis are that there is an emerging consistency of the RUE-PRI relationship that suggests a surprising degree of functional convergence of biochemical, physiological and structural components affecting leaf, canopy and ecosystem carbon uptake efficiencies. By complementing the estimations of the fraction of photosynthetically active radiation intercepted by the vegetation (fPAR) PRI enables improved assessment of carbon fluxes at different scales, through the estimation of RUE. A second conclusion supports the idea that the annual functioning of vegetation is more constrained by water availability than by temperature. The spatial variability of annual and maximum RUE can be largely explained by annual precipitation, more than by vegetation type. A third conclusion is that while EVI can estimate annual diametric wood increment, and PRI can estimate daily leaf level net photosynthesis and radiation use efficiency, the role NDVI is more limited as a surrogate of any part of the carbon cycle in this type of forest. Therefore, EVI and PRI are excellent tools for vegetation monitoring of carbon cycle in the Mediterranean forests, the first ones we tested in this thesis. Finally, the PRI derived from freely available satellite information was also found to present significant positive relationship with the RUE for a very wide range of different forest types, even in determined years, the deciduous forests. Overall, this thesis provides a better understanding of the spatial and temporal controls of the RUE and opens the possibility to estimate RUE in real time and, therefore, actual carbon uptake of forests at the ecosystem level using the PRI.
Keywords carbon cycle, Normalized Difference Vegetation Index, Enhanced Vegetation Index, Photochemical Reflectance Index, primary productivity, photosynthesis, remote sensing, climatic controls, eddy covariance, radiation use efficiency, terrestrial vegetation.
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Birchall, Jennifer. "The study of modern freshwater and terrestrial ecosystems using carbon, nitrogen and hydrogen isotopes : implications for palaeodietary studies." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275730.
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Franz, Martina [Verfasser], and A. [Akademischer Betreuer] Arneth. "Modelling the impact of air pollution on the terrestrial carbon and nitrogen cycling / Martina Franz ; Betreuer: A. Arneth." Karlsruhe : KIT-Bibliothek, 2020. http://d-nb.info/1204132658/34.
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Dunlap, Thomas M. "Aquatic Priming Effects in the York River Estuary and Implications for Dissolved Organic Carbon Mineralization." VCU Scholars Compass, 2014. http://scholarscompass.vcu.edu/etd/3624.
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The priming effect (PE), characterized as the enhanced microbial processing of bio-recalcitrant organic matter with the addition of labile substrates, has been hypothesized to moderate carbon (C) cycling in aquatic systems. In this study, aquatic PEs were evaluated through bacterial respiration and dissolved organic C consumption in incubations of water collected from three locations along the York River estuary. Incubations from White’s Landing on the Pamunkey River, a tidal freshwater tributary of the York, and from Croaker Landing in the middle of the estuary, displayed positive PEs when amended with labile C. In contrast, amended incubations from Gloucester Point, near the mouth of the estuary, displayed negative PEs, or reduced relative C metabolism, based on our calculations, This study provides empirical evidence for the occurrence of aquatic PEs and serves to elucidate how they may enhance or retard the processing and mineralization of organic C during transport to the ocean.
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Becher, Marina. "Cryogenic soil processes in a changing climate." Doctoral thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-112509.
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A considerable part of the global pool of terrestrial carbon is stored in high latitude soils. In these soils, repeated cycles of freezing and thawing creates soil motion (cryoturbation) that in combination with other cryogenic disturbance processes may play a profound role in controlling the carbon balance of the arctic soil. Conditions for cryogenic soil processes are predicted to dramatically change in response to the ongoing climate warming, but little is known how these changes may affect the ability of arctic soils to accumulate carbon. In this thesis, I utilize a patterned ground system, referred to as non-sorted circles, as experimental units and quantify how cryogenic soil processes affect plant communities and carbon fluxes in arctic soils. I show that the cryoturbation has been an important mechanism for transporting carbon downwards in the studied soil over the last millennia. Interestingly, burial of organic material by cryoturbation appears to have mainly occurred during bioclimatic events occurring around A.D. 900-1250 and A.D. 1650-1950 as indicated by inferred 14C ages. Using a novel photogrammetric approach, I estimate that about 0.2-0.8 % of the carbon pool is annually subjected to a net downward transport induced by the physical motion of soil. Even though this flux seems small, it suggests that cryoturbation is an important transporter of carbon over centennial and millennial timescales and contributes to translocate organic matter to deeper soil layers where respiration proceeds at slow rates. Cryogenic processes not only affect the trajectories of the soil carbon, but also generate plant community changes in both species composition and abundance, as indicated by a conducted plant survey on non-sorted circles subjected to variable differential frost heave during the winter. Here, disturbance-tolerant plant species, such as Carex capillaris and Tofieldia pusilla, seem to be favoured by disturbance generated by the differential heave. Comparison with findings from a previous plant survey on the site conducted in the 1980s suggest that the warmer temperatures during the last decades have resulted in decreased differential heave in the studied non-sorted circles. I argue that this change in cryogenic activity has increased abundance of plants present in the 1980s. The fact that the activity and function of the non-sorted circles in Abisko are undergoing changes is further supported by their contemporary carbon dioxide (CO2) fluxes. Here, my measurements of CO2 fluxes suggest that all studied non-sorted circles act as net CO2 sources and thus that the carbon balance of the soils are in a transition state. My results highlight the complex but important relationship between cryogenic soil processes and the carbon balance of arctic soils.
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Heimhofer, Ulrich. "Response of terrestrial palaeoenvironments to past changes in climate and carbon-cycling : insights from palynology and stable isotope geochemistry /." Zurich : [Swiss Federal Institute of Technlogy], 2004. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=15463.
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Baranchenko, Yevhen. "Collaboration and carbon : the environmental benefits of the co-operative business model in the food sector." Thesis, Northumbria University, 2011. http://nrl.northumbria.ac.uk/2282/.
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Ekumankama, Chinedu. "Effect of heavy metal co-contamination on the biodegradation of polycyclic aromatic hydrocarbons in an urban soil with high organic carbon content." Thesis, Northumbria University, 2015. http://nrl.northumbria.ac.uk/30323/.
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Biodegradation is a commonly used approach for the removal of organic contaminants from soil, relying on naturally present microorganisms that utilise the pollutants as an energy source. Often these sites are co-contaminated with heavy metals and the aim of the current research was to investigate how this affects the biodegradation of 16 US EPA priority polycyclic aromatic hydrocarbons (PAHs), both in terms of removal rates and the overall functioning of the soil microbial community. Soil samples were obtained from a Greenfield site in Newcastle upon Tyne. The soil had a high organic content (11.0 %) and also contained elevated lead concentrations as a result of past atmospheric deposition from adjacent industrial activities. PAHs were applied to the soil using a coal tar source dissolved in acetone, giving a total PAH concentration in the spiked soil of 2166 mg kg-1. Individual PAH concentrations ranged from 1.44 mg kg-1 (acenaphthylene) to 325 mg kg-1 (benzo[b]fluoranthene); the benzo[a]pyrene concentration was 255 mg kg-1. The effect of heavy metal co-contaminants on the biodegradation was investigated using separate amendments of cadmium and lead to give respective total concentrations ranging from 133 to 620 mg kg-1 and 340 to 817 mg kg-1. Mercury amendment was used to give an abiotic control. The study was carried out over 40 weeks. For all treatments, the degradation of PAHs was observed to be biphasic. A novel kinetic model was developed to explain this dependence. In the absence of metal amendment, it was found that PAHs comprising two and three benzene rings generally degrade at a faster rate than four- five and six-membered rings. In the presence of metal amendments, overall % biodegradation after 40 weeks is relatively unaffected for two to four-ring PAHs but shows significant impairment for five and six-ring PAHs. Nevertheless, degradation rates generally decrease with increasing metal concentration, as do soil respiration rate, Shannon Diversity Index, and microbial biomass content. Lead appears to exert the greatest inhibitory effect. The novelty of this study arises from the integrated approach to investigating the effect of metal co-contaminants on the biodegradation of all 16 US EPA priority PAHs together with parameters relating to the functioning and diversity of the soil microbial community.