Dissertations / Theses on the topic 'Nutrient cycles'
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Abell, Jeffrey Thomas. "Giving a damn about DOM in the subtropical North Pacific : quantifying the role of dissolved organic matter in the cycling of carbon, oxygen and nutrients in the upper ocean /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/11060.
Anderson, Laurence Anthony. "The determination of Redfield ratios for use in global oceanic nutrient cycle models." [Princeton, N.J.] : Princeton University, Dept. of Geological and Geophysical Sciences, Program in Atmospheric and Oceanic Sciences, 1993. http://catalog.hathitrust.org/api/volumes/oclc/75401374.html.
Crump, Byron C. "Bacterial activity and community structure in the Columbia River estuarine turbidity maxima /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/10989.
Mielke, Nora. "The role of nitrogen and phosphorus in carbon and nutrient cycling of bryophyte-dominated exosystems." Thesis, University of Aberdeen, 2016. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=231758.
Neu, Silke, Jörg Schaller, and E. Gert Dudel. "Silicon availability modifies nutrient use efficiency and content, C:N:P stoichiometry, and productivity of winter wheat (Triticum aestivum L.)." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-221008.
Auguères, Anne-Sophie. "Régulation biotique des cycles biogéochimiques globaux : une approche théorique." Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30290/document.
Anthropogenic activities heavily impact global biogeochemical cycles, mainly through nutrient fertilisation of ecosystems; thus it is crucial to assess the extent to which global biogeochemical cycles are regulated. Autotrophs can regulate nutrient pools locally through resource consumption, but most resources are inaccessible to them at global scales. We used theoretical models to assess how organisms respond nutrient fertilisation at global scales and how they can regulate the concentration of these nutrients when their accessibility of is limited. We further investigated the mechanisms driving the regulation of Redfield ratios in oceans, and the effects of nutrient fertilisation on total oceanic primary production. We showed that organisms cannot efficiently regulate nutrient pools. Mechanisms such as coupling of nutrient cycles and competition between functional groups can alter the strength of biotic regulation of global biogeochemical cycles, either positively or negatively. An inefficient regulation of inaccessible nutrient concentration, however, does not exclude a strong biotic regulation of nutrient ratios, as is the case with Redfield ratios in oceans. Nutrient fertilization of oceanic and terrestrial ecosystems is thus likely to have a strong impact on primary production and global nutrient cycles at both small and long timescales
Oates, Richard Hunter. "Phosphate-mineral interactions and potential consequences for nutrient cycling." Thesis, Online version of original thesis, 2008. http://hdl.handle.net/1912/2395.
Neu, Silke, Jörg Schaller, and E. Gert Dudel. "Silicon availability modifies nutrient use efficiency and content, C:N:P stoichiometry, and productivity of winter wheat (Triticum aestivum L.)." Nature Publishing Group, 2016. https://tud.qucosa.de/id/qucosa%3A30213.
Klein, Lawrence S. "An Ecosystem Dynamics Model of Monterey Bay, California." Fogler Library, University of Maine, 2002. http://www.library.umaine.edu/theses/pdf/KleinLS2002.pdf.
Murphy, Conor. "Investigation of rhizosphere priming effects for N mineralisation in contrasting soils." Thesis, University of Aberdeen, 2015. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=228575.
Kwari, J. D. "Effects of straw burning and drying-rewetting cycles on the fertility of some soils of North-East Nigeria." Thesis, University of Aberdeen, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379809.
Hardison, Amber Kay. "Interactions between macroalgae and the sediment microbial community : nutrient cycling within shallow coastal bays /." W&M ScholarWorks, 2009. http://web.vims.edu/library/Theses/Hardison09.pdf.
Chuyong, George Bindeh. "Nutrient cycling in ectomycorrhizal legume-dominated forest in Korup National Park, Cameroon." Thesis, University of Stirling, 1994. http://hdl.handle.net/1893/2640.
Ostrowski, Martin Biotechnology & Biomolecular Sciences Faculty of Science UNSW. "Physiological adaptation to nutrient limitation in a marine oligotrophic ultramicrobacterium Sphingopyxis alaskensis." Awarded by:University of New South Wales. School of Biotechnology and Biomolecular Sciences, 2006. http://handle.unsw.edu.au/1959.4/27422.
Simpson, Kyle G. F. "Nutrient dynamics and nitrogen-based production in the western Canadian Arctic Ocean." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=112363.
Conducted as part of the Canadian Arctic Shelf Exchange Study (CASES), this thesis provides a current review of nutrient dynamics and cycling, and estimates of annual new and net primary production for the Mackenzie Shelf, the Amundsen Gulf and the Cape Bathurst polynya in the southeastern Beaufort Sea in the Canadian Arctic Ocean.
Dam, Oscar van. "Forest filled with gaps effects of gap size on water and nutrient cycling in tropical rain forest : a study in Guyana = Bos gevuld met gaten : de effecten van de grootte kronendakopeningen op de water- en nutriëntenkringloop in tropisch regenwoud : een studie in Guyana /." Georgetown, Guyana : Tropenbos Guyana Programme, 2001. http://catalog.hathitrust.org/api/volumes/oclc/48485430.html.
Human, Lucienne Ryno Daniel. "Reeds as indicators of nutrient enrichment in the East Kleinemonde Estuary." Thesis, Nelson Mandela Metropolitan University, 2009. http://hdl.handle.net/10948/1252.
Stoklas, Ulrica F. "Variation in nutrient dynamics among full-sib families of Picea mariana (Mill.) B.S.P. at two sites differing in water availability." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0004/MQ37169.pdf.
Klenk, Nicole. "Controls on nutrient availability in black spruce forests of northwestern Quebec." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33012.
Tobón, Marin Conrado. "Monitoring and modelling hydrological fluxes in support of nutrient cycling studies in Amazonian rain forest ecosystems." Wageningen, The Netherlands : Tropendos Foundation, 1999. http://catalog.hathitrust.org/api/volumes/oclc/43455503.html.
Dessirier, Benoît, and Safeyeh Soltani. "Dynamics of internal nutrient sources in the Baltic Sea - A comparative modelling study of the Gulf of Finland." Thesis, KTH, Vattenvårdsteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-96110.
Lindsay, Elizabeth A. "The impact of Chrysanthemoides monilifera spp. rotundata (bitou bush) on coastal ecosystem processes." Access electronically, 2004. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20041222.143610/index.html.
Dassonville, Nicolas. "Impact des plantes exotiques envahissantes sur le fonctionnement des écosystèmes en Belgique." Doctoral thesis, Universite Libre de Bruxelles, 2008. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210579.
Dans un deuxième temps, je me suis attaché à identifier les mécanismes de l’impact de Fallopia japonica sur le cycle de l’azote. Cette espèce, perenne rhizomateuse, adopte une gestion très conservatrice de l’azote en retransloquant jusqu’à 80 % de l’azote des tiges et des feuilles vers le système racinaire en automne avant l’abscission des feuilles. La litière restituée est, de ce fait, pauvre en azote. Ce paramètre, combiné à une teneur élevée en lignine, explique sa faible vitesse de décomposition par rapport à celle de la végétation non envahie. Une grande partie de l’azote de l’écosystème tourne donc en cycle quasi fermé entre les organes de réserve et les parties aériennes de la plante, tandis que l’azote restant est en grande partie bloqué dans la nécromasse de la plante et est donc non disponible pour les espèces concurrentes indigènes. Ce mécanisme explique, sans doute, en partie le succès invasif de l’espèce.
A l’avenir, les implications des impacts sur le sol en terme de restauration des communautés devront être étudiées. L’hypothèse d’une influence positive de ces impacts sur l’aptitude compétitive des espèces envahissantes devra être testée. Enfin, une étude plus fonctionnelle des impacts de ces espèces dans des sites contrastés devrait permettre d’identifier les mécanismes impliqués./Biological invasions are a major cause of biodiversity loss worldwide. The direct impact of alien invasive species (AIS) on community structure and composition has been well documented. On the other hand, their impact on ecosystem functioning has been comparatively less studied. In this work, I measured, on the field and in experimental conditions, the impact of 7 highly invasive alien plant species in Europe on soil chemical properties, biomass and aboveground nutrient stock. Despite the high diversity in considered functional groups (from annuals to trees), recurring impacts have been found. AIS had always higher biomass and aboveground nutrient stocks than invaded resident vegetation. Concerning soil, species functional traits did not allow us to predict impact direction and intensity. On the other hand, impacts on soil were partially predictable based on initial ecological conditions (pedologic context). Thus, cations and P availability and organic C and N concentrations increased in initially poor sites and decreased in eutrophic ones. AIS tend to homogenize soil properties across invaded landscapes.
In a second part, i tried to identify the mechanisms of the impacts of Fallopia japonica on N cycling. This perrennial rhizomatous species manage N in a very conservative way. About 80 % of aboveground N is translocated to rhizomes before leaves abscission. The litter is therefore poor in N. This parameter combined with a high lignin concentration explains its slow decomposition rate compared to that of uninvaded vegetation. A big part of the ecosystem N is engaged in a nearly closed cycle between above and belowground organs while the remaining N is blocked in the necromass and is thus not available for the indigenous competitors. This mechanism probably explains the invasive success of this species.
In the future, the implications of soil properties modifications in terms of community restoration should be studied. The hypothesis of a positive influence of these modifications on the competitive ability of AIS should be tested. At last, a functional study of these soil impacts in contrasted sites should allow us to identify the implied mechanisms.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
Human, Lucienne Ryno Daniel. "The contribution of submerged macrophytes and macroalgae to nutrient cycling in the Great Brak Estuary." Thesis, Nelson Mandela Metropolitan University, 2013. http://hdl.handle.net/10948/d1021102.
Haupert, Christie Lynn 1976. "Nutrient limitation dynamics of a coastal Cape Cod pond : seasonal trends in alkaline phosphatase activity." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/55335.
Includes bibliographical references (leaves 144-149).
A bi-weekly seasonal study was conducted in Ashumet Pond (Cape Cod, Massachusetts). The Redfield Ratio (106C:16N:1P) and alkaline phosphatase activity (APA) were utilized in tandem as nutrient deficiency indicators (NDIs) for phytoplankton. The study objective was to evaluate the limiting nutrient status of the pond throughout the growing season. The development of a high throughput method for fluorometrically measuring APA allowed for a large quantity of pond-water samples to be analyzed. The new method utilized a cytofluor, a fluorescence multi-well plate reader, which increased sample throughput by 75% compared to a standard filter fluorometer method. The detection limit, capability to measure APA at different time intervals, and performance at sea were tested. APA measurements made using the cytofluor were comparable to those made using a standard filter fluorometer, thus indicating that the cytofluor is a suitable and preferred replacement to the fluorometer for APA measurements. The presence of alkaline phosphatase, an inducible phospho-hydrolytic enzyme, is commonly used as an NDI diagnostic for phosphate limitation. A nutrient enrichment incubation re-affirmed the use of APA as a robust indicator of phosphate limitation in phytoplankton. APA data indicate that the system experienced episodic periods of phosphate-deficiency, implying that the limiting nutrient regime was not static, but was changeable throughout the growing season. Seasonal trends in dissolved N:P and particulate C:P ratios often contradict the APA results, however, suggesting that the Redfield Ratio is an unreliable indicator of the overall nutrient limitation regime of the pond. The observed discrepancies between C:N:P and APA can be reconciled by taking into account seasonal changes in species composition, which played an important role in driving seasonal APA trends.
by Christie Lynn Haupert.
M.S.
Darrow, Brian P. "Effects of Nutrients From the Water Column on the Growth of Benthic Microalgae in Permeable Sediments." Scholar Commons, 2007. https://scholarcommons.usf.edu/etd/200.
Boucher, Patricia. "Base cation immobilization in the stem of some hardwoods of southern Québec." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ55039.pdf.
Weeber, Russell C. "Nutrient addition and the use of stable isotope techniques in wetlands of the Interlake Region of Manitoba, Canada." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22825.
In general, the effects of nutrient additions were confined to 1992. Treatment enclosure dissolved oxygen levels decreased immediately following fertilization, recovering in the low treatments by early June. Low oxygen conditions persisted in whole high enclosures throughout most of 1992. Dissolved and suspended nutrient concentrations, and phytoplankton chlorophyll a increased but, with the exception of dissolved N, were soon lost from the water column. Treatment enclosure epiphytic algae increased while epipelon did not respond to fertilization. The primary effect of fertilization on invertebrate production was an increase in treatment enclosure chironomid larvae during 1992. As with productivity measures, stable isotope ratio values suggested a temporary presence of alfalfa nutrients in the enclosed food webs. Only the isotope ratios of metaphytic algae and snails collected during August 1992 indicated an incorporation of alfalfa nutrients.
Popendorf, Kimberly J. (Kimberly Julia). "Marine microbial intact polar diacylglycerolipids and their application in the study of nutrient stress and bacterial production." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/79293.
"February 2013." Cataloged from PDF version of thesis.
Includes bibliographical references.
Intact polar diacylglycerolipids (IP-DAGs) were used to study microbial dynamics in the surface ocean. IP-DAGs from surface ocean seawater were quantified using high performance liquid chromatography-mass spectrometry (HPLC-MS), after first developing a sensitive, high throughput molecular ion independent triple quadrupole MS method for quantification. Using this analytical technique I examined the distribution of the nine most abundant classes of IPDAGs across the Mediterranean, and found that phospholipids as a percent of total IP-DAGs correlated with phosphate concentration. Furthermore, phospholipids were a higher percent of total particulate phosphorus where phosphate was higher, ranging from 1-14%. Thus IP-DAGs can play not only a significant but also a dynamic role in defining planktonic nutrient needs and cellular C:N:P ratios in the environment. Additionally, microcosm incubations were amended with phosphate and ammonium, and in the course of several days this elicited a shift in the ratios of IP-DAGs. This study was the first to demonstrate the dynamic response of membrane lipid composition to changes in nutrients in a natural, mixed planktonic community, and indicated that the change in IP-DAG ratios in response to changing nutrients may be a useful indicator of microbial nutrient stress. In the surface waters of the western North Atlantic I used three experimental approaches to identify the microbial sources of the nine most abundant classes of IP-DAGs. Phytoplankton are the primary source of one class of sulfolipid, sulfoquinovosyldiacylglycerol, and one class of betaine lipid, diacylglyceryl-trimethyl-homoserine, while heterotrophic bacteria are the dominant source of the phospholipids phosphatidylglycerol and phosphatidylethanolamine. In regrowth experiments in the Sargasso Sea and the North Pacific I demonstrated that phospholipid specific production rate is representative of heterotrophic bacterial cell specific growth rate. I measured phospholipid specific production rate and bacterial production rate using uptake of 3H-leucine (³H-Leu) and 3H-thymidine (³H-TdR) across the North Atlantic, across the Mediterranean, and in the North Pacific subtropical gyre. I found that phospholipid specific production rates estimate heterotrophic bacterial cell specific growth rates that are on the order of 1 per day, an order of magnitude faster than cell specific growth rates suggested by uptake of ³H-Leu and ³H-TdR.
by Kimberly J. Popendorf.
Ph.D.
Lequy, Emeline. "Dépôts atmosphériques particulaires sur les écosystèmes forestiers de la moitié Nord de la France : influence sur les cycles biogéochimiques." Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0277/document.
Quantifying the little-known inputs of atmospheric particulate deposition (APD) is critically important for a sustainable management of forest ecosystems. Indeed, harvesting and subsequent nutrient losses are going to increase so as to meet the demand in renewable energy, including fuel-wood. This work aims at filling this gap by (i) describing the deposition rate, mineralogical and chemical compositions of APD and (ii) evaluating the influence of APD nutrient inputs on forest biogeochemical cycles. To do so, 4 beech stands in North French forests were equipped for a 4-week sampling. After a metrological development, samplers out of and below canopy were used for a 2-year sampling, as well as methods to separate APD from atmospheric dissolved deposition. These methods were conceived to separate the organic and mineral fractions of APD according to the conceptual model designed in this work. My results validated this model and indicated (i) a quite constant deposition rate of 19±3 kg.ha-1.year-1 of hardly soluble minerals over the North of France, made of various minerals suggesting heterogeneous sources of particles, (ii) nutrient inputs inferior to those of atmospheric dissolved deposition and soil weathering, but improving ecosystem fertility, (iii) an interception effect of the canopy, and (iv) the dissolution of mineral particles in the atmosphere which enriched atmospheric dissolved deposition in nutrients. Extending and optimizing the sampling would allow confirming and clarifying these results, especially concerning high atmospheric load periods and APD below canopy
Bringhurst, Kelly. "The effect of land-use on nutrient cycles of tropical streams on the Osa peninsula, Costa Rica : a paired catchment approach to investigate current conditions and projected changes." Thesis, University of Ulster, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.553867.
Panassa, Essowe [Verfasser], Judith [Akademischer Betreuer] Hauck, Dieter A. [Gutachter] Wolf-Gladrow, and Birgit [Gutachter] Schneider. "Role of Mixed Layer Depth and Subduction Processes for the Southern Ocean Carbon and Nutrient Cycles / Essowe Panassa ; Gutachter: Dieter A. Wolf-Gladrow, Birgit Schneider ; Betreuer: Judith Hauck." Bremen : Staats- und Universitätsbibliothek Bremen, 2018. http://d-nb.info/1160670463/34.
Noble, Abigail Emery. "Influences on the oceanic biogeochemical cycling of the hybrid-type metals, cobalt, iron, and manganese." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/70779.
Cataloged from PDF version of thesis.
Includes bibliographical references.
Trace metal cycling is one of many processes that influence ocean ecosystem dynamics. Cobalt, iron, and manganese are redox active trace metal micro-nutrients with oceanic distributions that are influenced by both biological and abiotic sources and sinks. Their open ocean concentrations range from picomolar to nanomolar, and their bioavailabilities can impact primary production. Understanding the biogeochemical cycling of these hybrid-type metals with an emphasis on cobalt was the focus of this thesis. This was accomplished by determining the dissolved distributions of these metals in oceanic regions that were characterized by different dominant biogeochemistries. A large subsurface plume of dissolved cobalt, iron, and manganese was found in the Eastern South Atlantic. The cause of this plume is a combination of reductive dissolution in coastal sediments, wind-driven upwelling, advection, biological uptake, and remineralization. Additional processes that are discussed as sources of metals to the regions studied during this thesis include isopycnal uplift within cold-core eddies (Hawaii), ice melt (McMurdo Sound, Antarctica), riverine input (Arctic Ocean), and winter mixing (McMurdo Sound). The biological influence on surface ocean distributions of cobalt was apparent by the observation of linear relationships between cobalt and phosphate in mid to low latitudes. The cobalt:phosphate ratios derived from these correlations changed over orders of magnitude, revealing dynamic variability in the utilization, demand, and sources of this micronutrient. Speciation studies suggest that there may be two classes of cobalt binding ligands, and that organic complexation plays an important role in preventing scavenging of cobalt in the ocean. These datasets provided a basis for comparing the biogeochemical cycles of cobalt, iron, and manganese in three oceanic regimes (Hawaii, South Atlantic, McMurdo Sound). The relative rates of scavenging for these metals show environmental variability: in the South Atlantic, cobalt, iron, and manganese were scavenged at very different rates, but in the Ross Sea, mixing and circulation over the shallow sea was fast, scavenging played a minor role, and the cycles of all three metals were coupled. Studying the distributions of these metals in biogeochemically distinct regions is a step toward a better understanding of their oceanic cycles.
by Abigail Emery Noble.
Ph.D.
Abe, Hitofumi. "Forest management impacts on growth, diversity and nutrient cycling of lowland tropical rainforest and plantations, Papua New Guinea." University of Western Australia. School of Plant Biology, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0098.
Andrisoa, Aladin Danoary. "Ecological impacts of groundwater discharge to Mediterranean coastal lagoons." Thesis, Aix-Marseille, 2019. http://theses.univ-amu.fr.lama.univ-amu.fr/190326_ANDRISOA_564o889xp122jxhof868gdfl_TH.pdf.
Whilst the role of groundwater discharge and porewater fluxes (recirculation) as important pathways for nutrient delivery to coastal systems is increasingly being recognized, there remains limited evidence of its “downstream” ecological implications. This thesis aims at investigating the ecological role that groundwater flows play in some aspects of the functioning and vulnerability of coastal lagoonal ecosystems. Two contrasting lagoons on the french mediterranean coastline were studied (La Palme and Salses-Leucate lagoons). Our results show that the recirculation of lagoon water through the lagoon sediments is the main source of both dissolved inorganic nitrogen (DIN) and phosphorous (DIP) to La Palme lagoon. The nitrogen isotopic signatures (δ15N) in primary producers reflect predominantly the nitrogen isotopic signatures of the terrestrial (karstic) groundwater and porewater source in both La Palme and Salses-Leucate lagoons, demonstrating the important role of these sources in supporting primary production. The carbon isotope signatures (δ13C) indicate groundwater discharge as a significant source also of dissolved inorganic carbon to primary producers. Further more, the variations in growth rate and condition index (tissue weight / shell weight) of the Mediterranean mussels growing in and outside groundwater-influence in Salses-Leucate lagoon were examined. Mussels from the groundwater-influenced sites have higher growth rate and condition index compared to those from the control site, likely as consequence of both the higher winter temperatures and the groundwater-driven nutrient supply that increase the food availability to support mussel growth
Becker, Joscha Nico Verfasser], Yakov [Akademischer Betreuer] [Kuzyakov, Michaela [Gutachter] Dippold, Daniela [Gutachter] Sauer, and Sandra [Gutachter] Spielvogel. "Carbon and nutrient cycles depending on climate and land use along the elevation gradient of Mount Kilimanjaro / Joscha Nico Becker ; Gutachter: Michaela Dippold, Daniela Sauer, Sandra Spielvogel ; Betreuer: Yakov Kuzyakov." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2017. http://d-nb.info/1142001520/34.
Bélanger, Nicolas 1971. "Investigating the long-term influence of atmospheric acid deposition and forest disturbance on soil chemistry and cation nutrient supplies in a forested ecosystem of southern Quebec." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=36542.
Soil and soil solution chemistry between unburned and burned zones following fire disturbance seventy-five years ago was examined within the watershed. Results showed two major, statistically significant, differences: (1) higher base status, and (2) lower soil solution N in the burned zone. High quality leaf litter of aspen and birch (burned zone) relative to that of sugar and red maple (unburned zone) has contributed to the enrichment of base cations in the forest floor. The enrichment of the forest floor did not however impoverish the B horizon as seen in other studies. Rather, fire enriched the soil in base cations and buffered the effect of forest regrowth in the B horizon.
The MAKEDEP model was used to reconstruct the time-series input files needed to run SAFE. In MAKEDEP, the availability of N determines tree growth which in turn, affects most of the processes involved in nutrient cycling. Regressions of measured deposition at the Hubbard Brook Experimental Forest and that of simulated deposition at the study site suggest MAKEDEP is suitable to model the deposition trends of all elements except Na.
SAFE was calibrated for the unburned and burned conditions at the study site. Fire disturbance and forest regrowth have produced different soil chemical composition within the zones as discussed above. SAFE was therefore validated at the study site as a function of its ability to reproduce soil chemistry under unburned and burned conditions. The simulated soil chemistry was in close agreement with the measured unburned soil conditions, but some processes would have to be clarified or accounted for with greater accurately, e.g., biological N fixation and N immobilization by myccorhizal fungi, to reproduce more accurately the measured burned soil chemistry. Simulated soil chemistry in the unburned zone reinforced nevertheless the conclusions of a few historical soil chemistry studies supporting the hypothesis that acid-sensitive forest sites of the United States underwent significant acidification during 1930--1980 during major input of acidity from the atmosphere. Model output suggests that cation nutrient deficiencies could occur in the long-term, but future Al phytotoxic responses are unlikely to occur due to a relatively high projected pH. (Abstract shortened by UMI.)
Menoyo, Molins Alexandra. "Nutrient availability regulates cell cycle through a Pho85 CDK-dependent control of Cln3 cyclin stability." Doctoral thesis, Universitat Internacional de Catalunya, 2012. http://hdl.handle.net/10803/101414.
El control del cicle cel•lular per factors tròfics té un paper important en la proliferació cel•lular de tots els organismes. Els nutrients són uns d’aquests factors importants requerits per les cèl•lules per reproduir-se, per tant deuen existir mecanismes molt ben regulats que connecten la disponibilitat de nutrients amb el cicle cel•lular. Per això, l’estudi de com funciona la senyalització cel•lular de nutrients i com afecta a la progressió del cicle és altament rellevant. Cln3, la ciclina de G1 més primerenca a Saccharomyces cerevisiae, és un efector comú de múltiples vies de senyalització de nutrients. A més, el seu paper en el cicle cel•lular és crucial. Per tant aquesta proteïna és una bona candidata per regular la progressió del cicle cel•lular en resposta a la disponibilitat de nutrients. Una qüestió important a resoldre és trobar la proteïna que podria modular directament els nivells de Cln3 depenent de la presència de nutrients. Aquesta proteïna actuaria com a sensor de nutrients i com a reguladora del cicle cel•lular alhora. A la present tesi, es mostra a Pho85 com la proteïna que pot fer aquestes dues tasques, tant per les seves propietats ben conegudes en la detecció de fosfat, com per les seves funcions de CDK modulant el cicle cel•lular. Els resultats d’aquesta tesi demostren clarament que quan el fosfat és present, Pho85 modula els nivells de Cln3 incrementant l’estabilitat de la ciclina mitjançant fosforilacions específiques, promovent la progressió del cicle cel•lular. Per altra banda, sota condicions de manca de fosfat, Pho85 esdevé inactiva i Cln3 és degradada ràpidament, conduint a un arrest del cicle cel•lular per mantenir la longevitat de la cèl•lula.
El control del ciclo celular por factores tróficos tiene un papel importante en la proliferación celular de todos los organismos. Los nutrientes son uno de estos factores importantes requeridos por las células para reproducirse, por lo tanto deben existir mecanismos muy bien regulados que conecten la disponibilidad de nutrientes con el ciclo celular. Por ello, el estudio de cómo funciona la señalización celular de nutrientes y cómo afecta a la progresión del cicle es altamente relevante. Cln3, la ciclina de G1 más temprana en Saccharomyces cerevisia, es un efector común de múltiples vías de señalización de nutrientes. Además, su papel en el ciclo celular es crucial. Por lo tanto esta proteína es una buena candidata para regular la progresión del ciclo celular en respuesta a la disponibilidad de nutrientes. Un tema importante a resolver es encontrar la proteína que podría modular directamente los niveles de Cln3 dependiendo de la presencia de nutrientes. Esta proteína actuaría como sensor de nutrientes y como reguladora del ciclo celular. En la presente tesis, se muestra a Pho85 como la proteína que puede hacer estas dos tareas, tanto por sus propiedades bien conocidas en la detección de fosfato, como por sus funciones de CDK modulando el ciclo celular. Los resultados de esta tesis demuestran claramente que cuando el fosfato está presente, Pho85 modula los niveles de Cln3 incrementando la estabilidad de la ciclina mediante fosforilaciones específicas, promoviendo la progresión del ciclo celular. Por otro lado, bajo condiciones de ausencia de fosfato, Pho85 es inactivada y Cln3 se degrada rápidamente, conduciendo a una parada del ciclo celular para mantener la longevidad de la célula.
Liu, Shibin Verfasser], Yakov [Akademischer Betreuer] [Kuzyakov, Michaela [Gutachter] Dippold, Sandra [Gutachter] Spielvogel, Bruno [Gutachter] Glaser, and Christoph [Gutachter] Leuschner. "Tibetan pasture degradation under the impact of global change: Consequences for carbon and nutrient cycles and recovery strategies / Shibin Liu ; Gutachter: Michaela Dippold, Sandra Spielvogel, Bruno Glaser, Christoph Leuschner ; Betreuer: Yakov Kuzyakov." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2017. http://d-nb.info/113738008X/34.
Gillett, David James. "Effects of habitat quality on secondary production in shallow estuarine waters and the consequences for the benthic-pelagic food web." W&M ScholarWorks, 2010. http://www.vims.edu/library/Theses/Gillett10.pdf.
Saunders, Darla L. "Nitrogen retention in freshwater ecosystems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq64444.pdf.
Mestelan, Silvia A. "Impact of long-term no till and plow till on soil properties and soil nutrient cycling." Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1199221756.
Le, Noë Julia. "Biogeochemical functioning and trajectories of French territorial agricultural systems : carbon, nitrogen and phosphorus fluxes (1852-2014)." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS159/document.
This work investigates agricultural systems from the angle of nitrogen (N), phosphorus (P) and carbon (C) fluxes in French regions from 1852 to 2014, following a socio-metabolic approach stressing out the underlying logic behind these material fluxes. Results brought out by this research highlight the systemic relation between production pattern and N and P balances, and changes in soil organic C stocks in agricultural soil. Intensive specialized agricultural systems generate high environmental losses and resource consumption per unit agricultural surface and present largely open nutrient cycles due to substantial trade flows. Conversely, integrated crop and livestock farming have more limited N and P consumption and lead to lower air and water contamination. Long-term analysis shows that only after the Second World War, under the pressure of strong interventionist policies, some French regions specialized into crop or livestock farming. Particularly, the period from the 1950’s to the 1980’s was marked by a concomitant acceleration in crops yields, livestock production and use of mineral fertilizers. This resulted in increased N and P balances over cropland and grassland and growing C inputs to cropland, causing important losses of N to the hydrosphere and atmosphere, together with the accumulation of P and C stocks in soils. However, C accumulation resulting from increased crop production was permitted by the increased recourse to mineral fertilizers and agricultural machinery which consumes fossil-fuel energy. Therefore, C storage in cropland was a side-effect of the shift from an energy metabolism based on solar energy to one based on fossil-fuel combustion
Fink, Daniel Francis. "Effects of a pulsing hydroperiod on a created riparian river diversion wetland." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1167401886.
Le, Van Khoi. "Nutrient cycle in an integrated recirculating aquaculture system." Thesis, Curtin University, 2012. http://hdl.handle.net/20.500.11937/1916.
Eschrique, Samara Aranha. "Estudo do balanço biogeoquímico dos nutrientes dissolvidos principais como indicador da influência antrópica em sistemas estuarinos do Nordeste e Sudeste do Brasil." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/21/21133/tde-19042012-151614/.
The main proposal of this work was to evaluate the effects of anthropic actions upon estuarine systems, based on biogeochemical balance between forms of nutrients (N, P and Si). Two estuarine systems were studied, localized in extreme points of the coast, one in northeast, Jaguaribe River estuary, in Ceará, and the other in southeast, Cananéia-Iguape estuarine-lagoon complex, in São Paulo. These systems are under different climatic patterns and the study involved: aspects of dry and rainy periods in both locations; tide effects; and fresh water inputs, either in the form of rain, or via continental drainage and dams. The anthropic influence showed action upon the excess of silicon in both systems. Phosphorus was the dissolved element that suffered bigger neutralizing action, being buffered, and so, didn\'t show signals of eutrophication. That is not the case of nitrogen\'s forms, they showed a signature related to anthropic activities that impact each region the most. In the case of Jaguaribe River, the input of organic matter and nutrients, due to shrimp farms activities, contributed to prominent N-ammonium form in medium and lower estuary waters, where shrimp farms are located; the signals in upper estuary were connected to inputs via dam and Aracati city. In the case of Cananéia-Iguape estuarine-lagoon complex, the form nitrate was highlighted by the inputs of Ribeira de Iguape River, through Valo Grande, representing agricultural areas drainage. The south part of the system, Cananéia, showed a quite natural balance between the nitrogen forms, supporting primary production of populations common to the estuarine environment. Meanwhile, values of photosynthetic pigments showed that the composition of planktonic communities adapt itself to the abiotic conditions of the water body. There is production everywhere, but with distinctions between the communities. Seasonal influence occurred, and also degradation of microscopic vegetal biomass, often added to influence of pheopigments of margin communities. The diagnosis made by ASSETS Program is based on nitrogen input, values of chlorophyll and macroalgae presence; nevertheless the equilibrium between nutrients can be an excellent tool for environmental evaluation
Zhang, Hongyan. "Ecological modeling of the lower trophic levels of Lake Erie." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1163785412.
Hollis, S. "The role of pony and cattle excreta in the mineral nutrient cycle of New Forest Grassland and their effect on botanical composition." Thesis, University of Southampton, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355627.
Allan, Elizabeth Louise. "Ecological role of free-living bacteria in the microbial food web of the temporarily open/closed East Kleinemonde Estuary, South Africa." Thesis, Rhodes University, 2008. http://hdl.handle.net/10962/d1005351.
Su, Lin 1966. "Modelling study of nutrients cycles in the North Atlantic Atlantic Ocean." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40002.
The ocean model (Zhang et al., 1992) is based on the planetary geostrophic equations in spherical coordinates. The model equations include the full prognostic temperature and salinity equations. The momentum equations are diagnostic and include geostrophic balance, and a linear friction term in order to provide a western boundary current. The wind stress is applied at the top level of the model. The temperature and salinity distributions used in the surface boundary restoring condition are taken from climatological data. The model domain consists of a flat-bottomed box of 60$ sp circ$ longitude extending between 5$ sp circ$N and 65$ sp circ$N. The horizontal resolution is 2.3$ sp circ$ in both latitude and longitude with 14 levels in the vertical.
The physical model is first coupled to a biological model where new production is given by a restoring condition of surface nitrate towards its observed concentration. The coupled model is used to examine Martin et al.'s (1987) hypothesis that lateral transport and decomposition of slow or non-sinking organic matter can cause a non-local balance between the remineralization rate and the overlying new production rate in open ocean regions. The role of the Gulf Stream in nutrient transport is examined. The model results agree well with the North Atlantic nutrient transport calculated from observed nutrients and hydrographic data. The model results suggest that the thermohaline overturning circulation and the Gulf Stream horizontal recirculation play an important role in the North Atlantic nutrient distribution.
The physical model is then tested in the seasonal mode, and coupled with a biological model which is based on nitrate limiting the rate of new production. The model simulated seasonal oxygen cycle agrees well with the results of observational studies and 1-dimensional model simulations. The oxygen utilization rate below the euphotic zone provides a useful estimate of new production.
A 1-dimensional time dependent particle cycling model with two particle size classes based on Clegg and Whitfield (1990) is then developed. The simulated total organic carbon concentration and large particle flux are consistent with observations and other 1-dimensional model simulations. The downward transport of organic carbon is mainly accomplished by the fast sinking large particles, which comprise a small fraction of the total particulate mass. The steady state version of the particle model is also coupled with the 3-dimensional physical model. The magnitudes of simulated organic carbon flux and total organic matter concentration are comparable with observations.