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1
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.
Testo completo
2
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.
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3
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.
Testo completo
4
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.
Testo completoAbstract (sommario):
Bryophytes form an important component of northern vegetation communities. Mosses efficiently capture aerially deposited nutrients, restricting nutrient availability to the soil. Given that key ecosystem processes of northern ecosystems are nutrient-limited, understanding nutrient cycling of the moss layer is key to understanding ecosystem nutrient and C cycling in these systems. However, the role of the moss layer in regulating ecosystem-scale nutrient and C cycling, while potentially significant, is largely unknown. The aim of this thesis is to investigate the effect of the relative availability of N and P on aspects of bryophyte nutrient uptake, retention and C acquisition. The hypothesis investigated is that the availability of one nutrient will influence the demand for the other and thereby moss nutrient acquisition and retention mechanisms. To test this hypothesis, various aspects of moss nutrient cycling in response to the relative availability of N and P were investigated. As the C cycle is tightly linked to the N and P cycles, the hypothesis extended to include bryophyte C assimilation and decomposition processes of an arctic tundra. Bryophyte nutrient demand was chiefly governed by the tissue N:P ratio. Consequently, nutrient uptake, both from aerially deposited nutrients and through moss-cyanobacteria N2 fixation, and nutrient losses after a simulated rainfall event were mostly in response to the relative availability of N and P rather than the availability of one nutrient alone. This thesis provides novel evidence that ectohydric mosses have the ability to internally translocate nutrients. In conjunction with efficient nutrient capture, this trait makes mosses strong nutrient sinks which are likely to exert considerable control over ecosystem nutrient cycling. The relative availability of N and P played a role in C uptake of mosses. Through the production of recalcitrant litter and their insulating effect on soil microclimate mosses exerted an influence over ecosystem C cycling.
5
Neu, Silke, Jörg Schaller e 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.
Testo completoAbstract (sommario):
Silicon (Si) is known as beneficial element for graminaceous plants. The importance of Si for plant functioning of cereals was recently emphasized. However, about the effect of Si availability on biomass production, grain yield, nutrient status and nutrient use efficiency for wheat (Triticum aestivum L.), as one of the most important crop plants worldwide, less is known so far. Consequently, we assessed the effect of a broad range of supply levels of amorphous SiO2 on wheat plant performance. Our results revealed that Si is readily taken up and accumulated basically in aboveground vegetative organs. Carbon (C) and phosphorus (P) status of plants were altered in response to varying Si supply. In bulk straw biomass C concentration decreased with increasing Si supply, while P concentration increased from slight limitation towards optimal nutrition. Thereby, aboveground biomass production increased at low to medium supply levels of silica whereas grain yield increased at medium supply level only. Nutrient use efficiency was improved by Si insofar that biomass production was enhanced at constant nitrogen (N) status of substrate and plants. Consequently, our findings imply fundamental influences of Si on C turnover, P availability and nitrogen use efficiency for wheat as a major staple crop.
6
Auguères, Anne-Sophie. "Régulation biotique des cycles biogéochimiques globaux : une approche théorique". Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30290/document.
Testo completoAbstract (sommario):
Les activités anthropiques affectent les cycles biogéochimiques globaux, principalement par l'ajout de nutriments dans les écosystèmes. Il est donc crucial de déterminer dans quelle mesure les cycles biogéochimiques globaux peuvent être régulés. Les autotrophes peuvent réguler les réservoirs de nutriments par la consommation des ressources, mais la majorité des ressources leur sont inaccessibles à l'échelle globale. Par des modèles théoriques, nous avons cherché à évaluer la manière dont les autotrophes répondent à la fertilisation à l'échelle globale et leur capacité à réguler les concentrations des nutriments quand leur accessibilité est limitée. Nous avons également étudié les mécanismes qui déterminent la régulation des rapports de Redfield dans l'océan, ainsi que les effets de l'ajout de nutriments sur la production primaire océanique totale. Nous avons montré que les organismes ne régulent pas efficacement les réservoirs de nutriments. Le couplage des cycles biogéochimiques et la compétition entre groupes fonctionnels peuvent altérer, négativement ou positivement, la régulation des cycles biogéochimiques globaux par les organismes. Une régulation inefficace des concentrations de nutriments n'exclut par contre pas une forte régulation des rapports entre ces nutriments, comme dans le cas des rapports de Redfield. La fertilisation des écosystèmes terrestres et océaniques risque donc de fortement impacter la production primaire et les cycles biogéochimiques globaux, à de courtes comme à de grandes échelles de tempsAnthropogenic 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
7
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.
Testo completo
8
Neu, Silke, Jörg Schaller e 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.
Testo completoAbstract (sommario):
Silicon (Si) is known as beneficial element for graminaceous plants. The importance of Si for plant functioning of cereals was recently emphasized. However, about the effect of Si availability on biomass production, grain yield, nutrient status and nutrient use efficiency for wheat (Triticum aestivum L.), as one of the most important crop plants worldwide, less is known so far. Consequently, we assessed the effect of a broad range of supply levels of amorphous SiO2 on wheat plant performance. Our results revealed that Si is readily taken up and accumulated basically in aboveground vegetative organs. Carbon (C) and phosphorus (P) status of plants were altered in response to varying Si supply. In bulk straw biomass C concentration decreased with increasing Si supply, while P concentration increased from slight limitation towards optimal nutrition. Thereby, aboveground biomass production increased at low to medium supply levels of silica whereas grain yield increased at medium supply level only. Nutrient use efficiency was improved by Si insofar that biomass production was enhanced at constant nitrogen (N) status of substrate and plants. Consequently, our findings imply fundamental influences of Si on C turnover, P availability and nitrogen use efficiency for wheat as a major staple crop.
9
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.
Testo completo
10
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.
Testo completoAbstract (sommario):
In the context of nutrient cycling in soil, plant-mediated mineralisation of carbon (C) and nitrogen (N) is poorly understood. The broad focus of this thesis was to investigate the potential importance of plant-mediated mineralisation (i.e.priming) on C and N mineralisation in soils with contrasting crop productivities. The studies focus on two soils, which had similar chemical and physical properties but contrasting plant productivities relating to their N supply capacity. These soils were used to investigate the potential importance of priming processes in contributing to the contrasting capacities of these soils to supply N for plant growth. 13C and 15N stable isotopes were used to measure specific gross C and N fluxes. Sole C or N and combined C with N treatments were established to disentangle the effect of carbon and nitrogen availability on plant-mediated mineralisation. The addition of labile C increased gross carbon and nitrogen fluxes from native soil organic matter (SOM) but the effect was soil specific. The addition of nitrogen did not affect SOM mineralisation in either soil. The much lower C-to-N ratio of the 'primed' flux compared to the 'basal' flux indicated that the primed flux utilises different OM pools highlighting that primed and basal mineralisation may be distinct processes. The priming response (i.e. positive or negative and associated mechanisms) was different depending on carbon and nitrogen supply to the microbial community. Overall, the studies in this thesis places the microbial community as the focal point of soil N supply. This data strongly supports the concept that the release of labile carbon from plant roots functions as a nutrient acquisition response, increasing mineralisation of SOM. From the data a conceptual model of priming mechanisms, based on nutrient availability to the microbial community, was established. This could be used as the foundation to develop key concepts for sustainable agricultural practice.
11
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.
Testo completoAbstract (sommario):
The effects of straw burning and drying-rewetting cycles on nutrient availability were studied in an attempt to assess the practical importance of the yearly precropping practice by farmers of burning off excess crop residues and of the seasonal climate of North-East Nigeria. Changes in soil properties resulting from heating three soils up to 700°C and from field burning of straw on three soils were determined. Heating to 250° did not affect soil texture but increased exchangeable NH4+-N, available P, Fe, Mn and phosphate adsorption. A peak of NH4+-N representing decomposed organic N, retained by cation exchange sites was observed after heating at 250°. Soil physical and chemical properties were changed by heating to ≥500^o, resulting in fusion of clay particles into sand-sized particles, decomposition of soil organic matter and alteration of soil minerals with a corresponding increase in non-exchangeable cation status of the soils. The changes observed after field burning of straw were mainly due to deposition of ash; these include a dramatic increase in phosphate adsorption and addition of considerable amounts of inorganic P and exchangeable cations. The availability to maize of the inorganic P returned in ash after field burning or released as a result of laboratory heating of soils was assessed over a 7 day period. The increased P status of the soils after straw burning or heating was not significantly reflected in plant uptake of P but K adsorption was enhanced from the ash. Fertilization of heated and field burnt + overlying ash soil samples resulted in adsorption of P with a corresponding reduction of P concentration in the soil solution and P uptake. The N mineralized after rewetting air-dried clay soils or those containing very low organic matter was insignificant. Investigations also showed that, when dried soils were rewetted, the flush of mineral N was derived mainly from soil organic matter and not from killed microbial cells.
12
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.
Testo completo
13
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.
Testo completoAbstract (sommario):
Patterns and rates of nutrient input to the forest floor in litterfall, throughfall and stemflow were investigated in plots of low and high abundance of ectomycorrhizal species. The aim of the study was to examine the comparative advantage of the ectomycorrhizal species in nutrient acquisition and cycling on nutrient-poor soils in Korup. Litterfall was similar in both forests with annual estimates of 9.00 and 8.33 t ha-1 yr-1 for LEM and HEM forests respectively. Litterfall distribution followed a mono-modal pattern, with peaks in the dry season in both forests and the HEM forest showing stronger seasonality. The concentrations N, K and Ca in total litterfall were higher in the LEM forest while those of P and Mg were higher in the HEM forest. The bulk of nutrients in total litterfall was in leaf litter with the reproductive fractions having the highest concentrations of nutrients. Ectomycorrhizal species showed lesser internal redistribution of nutrients than non-ectomycorrhizal species which resulted in their higher leaf litter concentrations of nutrients. Breakdown of litter was relatively faster in the LEM forest with an annual decomposition constant (KL) of 3.21 compared to 2.43 for the HEM forest. The reproductive fractions had relatively higher annual decomposition constants of 8.20 and 4.27 in the LEM and HEM forests respectively compared to the other fractions. The overall element mobility in decomposing leaf litter was similar in both forests and in the following order: Mg>K>Ca>P>N. Mineralization of N, P and K in the decomposing leaf litter was similar in both forests and higher in the HEM forest for Mg and Ca. Throughfall was 96.6% and 92.4%, and stemflow 1.5% and 2.2%, of gross rainfall in LEM and HEM forests respectively. Considerable amounts of Ca, Mg and P were brought to the forest canopy in gross rainfall (24-45% of total input through this route) with higher amounts of K and Ca leached from plant parts by the rainwater. The amounts of P, K and Ca in stemflow and throughfall were of the same magnitude in both forests with the enhancement of N slightly higher in the LEM forest and Mg in the HEM forest.
14
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.
Testo completoAbstract (sommario):
Sphingopyxis (formerly Sphingomonas) alaskensis, a numerically abundant species isolated from Alaskan waters and the North Sea represents one of the only pure cultures of a typical oligotrophic ultramicrobacterium isolated from the marine environment. In this study, physiological and molecular characterization of an extinction dilution isolate from the North Pacific indicate that it is a strain of Sphingopyxis alaskenis, extending the known geographical distribution of this strain and affirming its importance as a model marine oligotroph. Given the importance of open ocean systems in climatic processes, it is clearly important to understand the physiology and underlying molecular biology of abundant species, such as S. alaskensis, and to define their role in biogeochemical processes. S. alaskensis is thought to proliferate by growing slowly on limited concentrations of substrates thereby avoiding outright starvation. In order to mimic environmental conditions chemostat culture was used to study the physiology of this model oligotroph in response to slow growth and nutrient limitation. It was found that the extent of nutrient limitation and starvation has fundamentally different consequences for the physiology of oligotrophic ultramicrobacteria compared with well-studied copiotrophic bacteria (Vibrio angustum S14 and Escherichia coli). For example, growth rate played a critical role in hydrogen peroxide resistance of S. alaskensis with slowly growing cells being 10, 000 times more resistant than fast growing cells. In contrast, the responses of V. angustum and E. coli to nutrient availability differed in that starved cells were more resistant than growing cells, regardless of growth rate. In order to examine molecular basis of the response to general nutrient limitation, starvation and oxidative stress in S. alaskensis we used proteomics to define differences in protein profiles of chemostat-grown cultures at various levels of nutrient limitation. High-resolution two-dimensional electrophoresis (2DE) methods were developed and 2DE protein maps were used to define proteins regulated by the level of nutrient limitation. A number of these proteins were identified with the aid of mass spectrometry and cross-species database matching. The identified proteins are involved in fundamental cellular processes including protein synthesis, protein folding, energy generation and electron transport, providing an important step in discovering the molecular basis of oligotrophy in this model organism.
15
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.
Testo completoAbstract (sommario):
Inclement climate conditions have made the Arctic Ocean logistically difficult to study, and thus, our historical knowledge of Arctic Ocean processes are limited. Recent observations indicate rapid and abrupt changes in climate. These changes are thought to includes rising temperatures, increase storm activity, altered freshwater balance and a notable decrease in the concentration and extent of sea ice covering the Arctic Ocean. Increasing awareness of these changing conditions and our poor knowledge of how the physical environment influences carbon fluxes, planktonic productivity and biogeochemical cycling have lead to international efforts to address these questions. The data presented here addresses biogeochemical cycling and phytoplankton primary production in the pelagic ecosystem. Given the pace of environmental change in the arctic (rapid ice retreat, record minimum ice extents, and temperature rise) and the relatively little historical data that is available for the region, the data presented here can also be used as a baseline data set from which predictions can be made and future observations can be compared.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.
16
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.
Testo completo
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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.
Testo completoAbstract (sommario):
The release of nutrients (nitrogen and phosphorus) via land clearing, application of fertilisers, discharge of human waste and combustion of fossil fuels, is one of the most harmful effects of anthropogenic stresses on aquatic environments. This study investigated the use of reeds as indicators of nutrient input to estuaries. Small estuaries such as the oligotrophic East Kleinemonde where the research was mostly conducted are sensitive to nutrient enrichment from septic tanks, stormwater runoff and fertiliser application to lawns in close proximity to the estuary. Nutrient concentrations were sampled at different positions, in the groundwater, at the water’s edge, in the reed bed and in the main estuary channel at five sites in the East Kleinemonde Estuary. The NH4+ and SRP concentrations showed a definite trend as concentrations decreased from the groundwater or water’s edge into the main estuary channel. Groundwater introduced nutrients to the estuary which were then taken up by the fringing reeds (Phragmites australis (Cavinelles) Trinius ex Steudel). The water column nutrients were either below detectable limits or in very low concentrations. Low TOxN concentrations were consistently found at the different sites and probably resulted from P. australis assimilating N-TOxN for growth more efficiently than N- NH4+. The roots, rhizomes, stems and leaves of the reeds were measured for δ15N as an indicator of nutrient enrichment as nitrogen stable isotope analysis of plant tissue is an effective method for assessing and monitoring septic tank and other anthropogenic inputs. All plant parts for the three sampling sessions at Site 1 (mouth region) in the East Kleinemonde Estuary had significantly higher δ15N signatures (~20 percent) than the leaves at Site 5 (upper reaches). These differences were related to the surrounding land-use of the East Kleinemonde catchment, where the lower part of the estuary has moderate to low residential development and the upper reaches are utilized mainly for livestock farming. The high δ15N signatures at Site 1 were attributed to septic tank wastewater and stormwater run-off entering the estuary. Nutrient enrichment also influenced the morphology of the reeds. Reed biomass, height and stem density was significantly higher at Site 1 compared to Site 5. Similar studies were conducted in August 2008 in the Sundays Estuary and October 2008 in the nearby Mtati and Mpekweni estuaries to see if the results were similar. iii The same patterns were found where the groundwater NH4+ and SRP concentrations were higher than the estuary channel in the Mtati and Mpekweni estuaries. In the Mpekweni and Sundays estuaries Phragmites australis leaves had high δ15N signatures (10 and 11 percent) similar to that of Site 1 in the East Kleinemonde Estuary. Lower signatures (-2 to +4 percent) were found in the Mtati Estuary. This sampling site was sheltered by a bridge with a steep slope and the concentrations were similar to Site 3 and 5 in the East Kleinemonde Estuary where the derived nutrient was the result of stormwater runoff or fertilisers. Density and biomass of reeds in the Sundays and East Kleinemonde (Site 1) estuaries were similar and this could be related to different nutrient sources, agricultural return flow and septic tank input respectively. Reeds in the Sundays Estuary were significantly taller than in the other estuaries which showed that factors such as shelter and salinity also influence reed growth and therefore morphology alone would not be a good indicator of nutrient enrichment. Indicators of nutrient enrichment are important as the status of temporarily open / closed estuaries in South Africa is threatened by deteriorating water quality. Measurements of the water column may provide an inaccurate assessment of water quality whereas macrophytes are outstanding potential indicators of nutrient enrichment as they are widely distributed, abundant and long-lived. The findings from this study indicate that δ15N concentrations in reeds can be used to indicate nutrient loading.
18
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.
Testo completo
19
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.
Testo completoAbstract (sommario):
The presence of mosses in black spruce forests is known to have an important impact on the availability and abundance of nutrients in this ecosystem. Mosses contribute to long-term accumulation of organic matter and storage of nutrients as well as to short-term nutrient release. In the boreal forest of northwestern Quebec, the effect of mosses on nutrient cycling was examined within the framework of a chronosequence ranging from 25 to 300 years of age. Laboratory and buried bag incubations, total nutrient digests, respirometric and root abundance measurements as well as moisture and temperature measurements were done to characterize the nutritional status of the organic matter profiles. In general, no change in moss accumulation, or nutrient storage or availability across the chronosequence could be detected. There were, however, differences between feather mosses and Sphagnum mosses, the latter having significantly lower levels of nutrients than the former in terms of mineralizable nitrogen and total carbon, nitrogen, phosphorus, magnesium and potassium content. The nutritional profile of moss cores showed different horizons, reflecting differences in organic matter quality down the organic layer. More specifically, nitrogen availability on a concentration basis as well as root abundance decreased with depth. Forest floor temperature seemed to confine the most biologically active horizon, referred to as the active layer, to a shallow depth, however neither temperature nor moisture seemed to explain the nutritional differences between feather mosses and Sphagnum mosses. These results may lead to practical consequences in that they show a clear distinction between the effects of feather mosses and Sphagnum mosses in nutrient cycling, suggesting that moss cover, might be useful as an indicator of site nutritional status. The results also show that accumulation of nutrients in organic surface horizons, as has been observed elsewhere, does not appear to occur in blac
20
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.
Testo completo
21
Dessirier, Benoît, e 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.
Testo completoAbstract (sommario):
For decades the Baltic Sea has been subject to eutrophication due to heavy anthropogenic nutrient loads on the aquatic ecosystem. Quantitative projections of its effects require an understanding of its driving mechanisms, i.e., the hydrodynamics that are responsible for the physical transport and mixing and the biogeochemical nutrients pathways within the algal ecosystem and between the particulate and dissolved phases in the water and in the sediments. A simple basin-scale hydrodynamic framework is set for the Gulf of Finland to test different descriptions of the biogeochemical transformations and determine the most robust modelling strategy. A recently developed criterion to determine the occurrence of anoxic events, based on the amount of fresh carbon detritus in the sediments is implemented in comparison with the classical criterion based on the oxygen concentration in the bottom water. Time-averaging of the hydrodynamics over larger than daily intervals is proved to hinder the capture of rapid mixing events jeopardizing irremediably the water quality simulation. The new carbon based criterion for anoxia shows a better dynamic response and is less sensitive to the model’s internal parameters. An internal source in the sediments correlated to the amount of fresh detritus, to represent the release of iron-bound phosphorus is confirmed as a versatile modelling assumption.
22
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.
Testo completo
23
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.
Testo completoAbstract (sommario):
Les invasions biologiques sont une cause majeure de perte de biodiversité à l’échelle mondiale. L’impact direct des espèces exotiques envahissantes (EEE) sur la structure et la composition des communautés a été bien documenté. Par contre, leur impact sur le fonctionnement des écosystèmes a été comparativement moins étudié. Dans le présent travail, j’ai mesuré sur le terrain et en conditions expérimentales l’impact de 7 espèces de plantes exotiques particulièrement envahissantes en Europe sur les propriétés chimiques du sol, sur la productivité et sur le stock d’éléments minéraux dans la biomasse. Malgré la diversité des groupes fonctionnels considérés dans notre échantillon (des espèces annuelles aux arbres), des impacts récurrents ont pu être mis en évidence. Les EEE ont toujours une biomasse et une productivité supérieures à celles de la végétation qu’elles envahissent. Il en va de même pour le stock d’éléments minéraux dans la biomasse aérienne. En ce qui concerne le sol, les traits fonctionnels des espèces ne permettent pas de prédire la direction et l’amplitude des impacts. Par contre, ces impacts sur le sol se sont révélés partiellement prévisibles en fonction des conditions écologiques initiales (contexte pédologique). La disponibilité des cations et du P et la concentration en C et N organiques augmentent suite à l’invasion dans les sites initialement pauvres alors que ces mêmes paramètres baissent dans les sites plus eutrophes au départ. Les EEE entraînent, dans une certaine mesure, une homogénéisation des conditions écologiques dans les écosystèmes envahis. 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
24
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.
Testo completoAbstract (sommario):
An ecological reserve study by the Department of Water Affairs on the Great Brak Estuary stated that there was a need to determine how much nitrogen and phosphorus was flowing through the estuary as well as how effective the macroalgae were at removing N and P. The objective of this study was to investigate the physico-chemical characteristics in the estuary and the influence of these on the submerged macrophytes and macroalgae. A nutrient budget for the estuary was developed in order to quantify the contribution of the submerged macrophytes and macroalgae relative to other contributing sources. The Wolwedans Dam located 3 km upstream from the estuary has reduced the amount of freshwater flow to the estuary by as much as 56 percent. The estuary has been allocated 2 x 106 m3 per annum of freshwater (ecological reserve) that is used to breach the mouth once or twice a year in spring or summer. Even though this water has been made available it is not sufficient to flush the estuary. Reduced flushing has led to an accumulation of organic matter and degradation in the water quality. Physico-chemical measurements between September 2010 and July 2012 showed that dissolved oxygen values were generally below 6 mg l-1. The average NH4+ concentration in the estuary was 7 μM and increased with depth to 12 μM at 2 m depths. Concentrations >45 μM were found in February and April 2011 at the 5 m deep hole at 3.4 km upstream. Negative correlations between dissolved oxygen and NH4+ during November 2010, February 2011, April 2011 and July 2011 (r = -0.68; -0.67; -0.63; -0.96) indicated that remineralisation of organic matter had occurred. Soluble reactive phosphorus (SRP) followed a similar trend to the NH4+ and was generally below 1 μM in the water column for most months, and had peaks at 1.0 km and 3.4 km in the bottom water. The abundance of submerged macrophytes and macroalgae below the N2 bridge were mostly influenced by mouth state and river inflow. During the closed phase the dominant macroalga Cladophora glomerata had an area cover ranging from 3000 to 6000 m2 while Zostera capensis and Ruppia cirrhosa covered an area of 2000 to 3500 m2 and 1500 to 2900 m2, respectively. After an artificial breach in February 2011, water drained out of the estuary leaving the alga stranded on the marshes and as the flood tide entered the macroalga was once again redistributed in the lower reaches. The alga utilised the available nutrients in the water column and expanded its area cover from 35000 m2 in February 2011 to 64000 m2 in March 2011. However, after the floods in June 2011, Cladophora glomerata had been washed out of the system while the submerged macrophytes responded positively extending their area cover. By comparing the artificial breach with the natural breach, and the effect on the estuary, an important observation was highlighted. Increasing the current allocated ecological reserve, and using a larger volume of water to breach the mouth artificially, would result in better scouring of sediment and associated organic matter out of the estuary. This would enable better oxygenation of the water column, reduce remineralisation and minimise algal blooms.
25
Charberet, Samuel M. "Animal-mediated terrestrial nutrient dynamics : investigating wastes, trophic transfer, and isotopic patterns". Electronic Thesis or Diss., Sorbonne université, 2023. http://www.theses.fr/2023SORUS523.
Testo completoAbstract (sommario):
Certains éléments chimiques sont particulièrement importants pour les organismes. Le carbone (C), le squelette des biomolécules, l’azote (N) des protéines essentielles à toute fonction, et le phosphore (P), au cœur de l’énergie chimique de l’ATP sont si importants que la structure des écosystèmes terrestres, dépend en partie des flux de ces éléments, ainsi que de leur proportion relative, ou stœchiométrie, dans le sol. Or, les animaux se nourrissent et produisent des déchets sous forme de fèces et d’urine contenant ces mêmes éléments (C, N, P), dont le devenir dépend fortement de la quantité et de la qualité de ces déchets. Cependant, la quantité et la qualité des déchets varient entre espèces, a priori en fonction de paramètres physiologiques et alimentaires, mais cette relation est peu documentée. En particulier, la masse corporelle, qui détermine le taux métabolique de l’individu, et le régime alimentaire (herbivore, carnivore, omnivore, détritivore), la richesse nutritionnelle ou la quantité disponible de la ressource sont tous des facteurs susceptibles d’influencer la qualité et la quantité des déchets produits par les animaux, mais aussi leur homéostasie chimique. Afin d’étudier les facteurs déterminants la composition chimique des fèces et l’homéostasie chimique de l’animal à une large échelle phylogénétique, nous avons assemblé des données bibliographiques sur un grand nombre d’espèces animales terrestres. Pour compléter la gamme d’espèces, nous avons par ailleurs effectué de nouvelles mesures. L’analyse montre que le régime alimentaire et la qualité de la ressource sont les facteurs principaux affectant la composition des déchets. La taille corporelle, quant à elle, a peu d’effets. Nous avons également mené une expérience au niveau intraspécifique pour déterminer l’effet de la quantité de ressource sur l’homéostasie chimique, le temps de rétention et les propriétés chimiques des fèces chez Spodoptera littoralis, et ce tant sur les éléments (C, N, P) que sur certains isotopes du carbone et de l’azote. La réduction de la quantité de ressource induit des changements physiologiques importants, dont l’augmentation de l’efficacité d’absorption élémentaire et des isotopes lourds, et réciproquement une réduction de l’excrétion des nutriments (dont N et P). Cela provoque une augmentation du temps de rétention des nutriments dans la biomasse ainsi qu’une diminution de la qualité et de la quantité des déchets. En somme, le recyclage est ralenti lorsque la ressource devient rare. L’ensemble de ces résultats montrent que les animaux sont des noeuds biogéochimiques capables d’adaptations qui interagissent avec le cycle des nutriments et les propriété des chaînes trophiquesCertain chemical elements are particularly important for organisms. Carbon (C), the skeleton of biomolecules, nitrogen (N) from proteins essential to all functions, and phosphorus (P), at the heart of the chemical energy of ATP, are so important that the structure of terrestrial ecosystems depends in part on the flow of these elements, but also on the relative proportion, or stoichiometry, of these elements in the soil. Heterotrophs, particularly animals, feed and produce waste in the form of faeces and urine containing these elements (C, N, P), the fate of which highly depends on the quantity and quality of this waste. Quantity and quality vary between species depending on physiological and dietary parameters, but this relationship is poorly documented. Body mass, which determines an individual’s metabolic rate, as well as diet (herbivore, carnivore, omnivore, detritivore), resource quantity and quality are all factors likely to influence the quality and quantity of waste produced by animals, as well as the chemical homeostasis of their own body. To study the factors determining the chemical composition of faeces and the chemical homeostasis of the animal on a broad phylogenetic scale, we assembled bibliographical data on a large number of terrestrial animal species and carried out new measurements. The analysis of this dataset shows that diet and resource quality are the main factors affecting waste composition. We also conducted an experiment to determine the effect of resource quantity on the chemical homeostasis, retention time and chemical properties of faeces in Spodoptera littoralis, both for the elements (C, N, P) and for certain isotopes of carbon and nitrogen. The reduction in the quantity of resources induces major physiological changes, including an increase in the efficiency of elemental absorption and of heavy isotopes, and conversely a reduction in the excretion of nutrients (including N and P). This leads to an increase in the retention time of nutrients in the biomass and a reduction in the quality and quantity of waste products. In short, recycling slows down when resources become scarce. These results show that animals are biogeochemical nodes capable of adaptations that interact with the nutrient cycle and the properties of trophic chains
26
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.
Testo completoAbstract (sommario):
In some continental shelf sediments integrated benthic microalgal biomass is greater than the integrated phytoplankton biomass in the overlying water column. In addition, benthic microalgae may account for up to 10% of the primary production responsible for the coastal fishery yield of the eastern United States.
A three-dimensional model of the eastern Gulf of Mexico examines the effects of water-column nutrient sources on the growth of benthic microalgae. To parameterize the exchange of nutrients across the sediment/water interface in these permeable sediments, a non-local exchange submodel was constructed and tested within the framework of the model's grid.
Based on the results of the three dimensional simulations, the growth of benthic microalgae from water-column nutrients is highly dependent on the light limitation of overlying phytoplankton. When light is available to phytoplankton in high enough quantities, water-column nutrients are used up before reaching the sediments. When the overlying phytoplankton are light limited, nutrients are able to reach the sediments where the shade adapted benthic microalgae can grow.
27
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.
Testo completoAbstract (sommario):
Thesis (M.S.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), February 2001.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.
28
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.
Testo completo
29
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.
Testo completoAbstract (sommario):
This study examines the relationship between nutrient additions and algae and invertebrate productivity in a nutrient-poor wetland of the Interlake Region of Manitoba, Canada. Alfalfa hay was added to experimental enclosures in May 1992. Alfalfa additions were made in unprocessed and ground forms and consisted of three treatments: ground low, whole low, and whole high. Dissolved oxygen, surface water nutrients, algae standing crop, and invertebrate production were monitored at open marsh sites and in treatment and control enclosures during 1992 and 1993. Stable $ sp{13}$C, $ sp{15}$N and $ sp{34}$S isotope ratios were determined for the alfalfa additions, and for surface water, algae, macrophytes, sediments and invertebrates.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.
30
Yan, Xingcheng. "Greenhouse gas emissions and nutrient retentions in reservoirs of the Seine Basin : budget and modelling". Electronic Thesis or Diss., Sorbonne université, 2022. http://www.theses.fr/2022SORUS152.
Testo completoAbstract (sommario):
L'impact des barrages–réservoirs sur les émissions de GES (gaz à effet de serre, CH4: méthane, CO2: dioxyde de carbone, et N2O: protoxyde d’azote) et sur les cycles biogéochimiques du C (carbone) et des nutriments (N: azote, P: phosphore, et Si: silice) a fait l'objet d'une attention croissante depuis plusieurs années. Après un premier travail d'estimation des émissions de GES par les réservoirs mondiaux, et l’examen de leur évolution à long terme, les travaux se concentrent sur les trois principaux réservoirs du bassin de la Seine, afin de déterminer leur contribution aux émissions de GES et leur impact sur les concentrations de CO2 et de nutriments, dans la Seine à leur aval. Enfin, une version actualisée du modèle biogéochimique BarMan est appliquée aux réservoirs du bassin de la Seine afin d’identifier et quantifier les principaux processus affectant le devenir des nutriments et la dynamique du CO2. À l'échelle mondiale, les flux moyens de CH4, CO2 et N2O s’élèvent respectivement à 125,7 ± 21,2 mg C m–2 d–1, 415,7 ± 36,0 mg C m–2 d–1 et 0,28 ± 0,11 mg N m–2 d–1. En s’appuyant sur un recensement mondial des barrages et réservoirs (base de données GranD v. 1.3), nous avons estimé que les émissions annuelles de GES des réservoirs mondiaux s’élèvent à 12,9 Tg CH4–C an–1, 50,8 Tg CO2–C an–1, et 0,04 Tg N2O–N an–1. L'accroissement de ces émissions entre 1950 et 1980, a suivi l'augmentation rapide du nombre et de la superficie des réservoirs mondiaux. Dans le bassin de la Seine, deux ans de campagnes de mesures ont permis de mettre en évidence des tendances saisonnières marquées pour le CH4 et le CO2 dans les trois principaux réservoirs. Les concentrations de CH4 dans ces réservoirs sont élevées en été–automne, faibles en hiver–printemps, et apparaissent significativement et positivement corrélées avec la température de l'eau et la saturation en oxygène dissous. Des tendances inverses ont été mises en évidence pour le CO2 avec des concentrations les plus basses en été, au maximum de l’activité photosynthétique. Au final, les trois réservoirs apparaissent comme des sources relativement faibles de GES, avec des valeurs moyennes de 6,6 mg CH4–C m–2 d–1, 132,7 mg CO2–C m–2 d–1 et 0,03 mg N2O–N m–2 d–1, assez largement inférieures aux valeurs moyennes des réservoirs mondiaux. Des chroniques longues d’observations des Grands Lacs de Seine (1998–2018) sur la qualité de l'eau ont été complétées par nos mesures sur le terrain (2019–2020). Le calcul des bilans entrées–sorties montre une rétention importante dans les réservoirs (16–53% pour le DIN: azote inorganique dissous, 26–48% pour les PO43–: orthophosphates, 22–40% pour la DSi: silice dissoute et 36–76% des MES: matières en suspension). Les réservoirs modifient ainsi considérablement la qualité des eaux réceptrices en aval. Tout en diminuant les concentrations de DIN, PO43– et DSi, ils augmentent les concentrations en COD (carbone organique dissous) et CODB (COD biodégradable), ainsi que celles du CO2 pendant leurs périodes de vidange, en fin d’été et en automne. Une analyse quantitative montre que les évolutions saisonnières de la qualité de l'eau des réservoirs sont déterminées tant par la dilution de l'eau entrante (quantité et qualité) que par les processus biogéochimiques dans ces réservoirs. Le modèle BarMan a permis de simuler de manière satisfaisante les variations saisonnières de la qualité de l’eau des trois réservoirs, pour les concentrations en nutriments et pour le CO2, et a par ailleurs permis de mieux caractériser le devenir du C et des nutriments (N, P et Si) dans les réservoirs de la Seine. L'assimilation des NO3–, PO43–, et DSi par le phytoplancton et la dénitrification benthique (pour NO3–) apparaissent comme les principaux processus gouvernant l'élimination des nutriments. La précipitation de CaCO3 (Carbonate de calcium) et l'émission de CO2 sont responsables de l'élimination du DIC dans les trois réservoirs. Des explorations par le modèle montrent [...]The impacts of reservoirs on greenhouse gas (GHG, including CH4: methane, CO2: carbon dioxide, and N2O: nitrous oxide) emissions and the biogeochemical cycling of nutrients (including C: carbon, N: nitrogen, P: phosphorus, and Si: silica) have received widespread attention. This work first estimates GHG emissions from global reservoirs and examines their long-term evolution, and then focuses on the main reservoirs in the Seine Basin to elucidate their contribution to GHG emissions and their impact on downstream nutrient and CO2 concentrations. Finally, the updated process-based Barman model was applied to these reservoirs to unravel the nutrient fates and CO2 dynamics in these reservoirs. At the global scale, the average fluxes of CH4, CO2, and N2O were 125.7 ± 21.2 mg C m-2 d-1, 415.7 ± 36.0 mg C m-2 d-1, and 0.28 ± 0.11 mg N m-2 d-1, respectively. Combing with the GranD database (global reservoir and dam database, v 1.3), we estimated that the annual GHG emission from global reservoirs amounted to 12.9 Tg CH4-C yr-1, 50.8 Tg CO2-C yr-1, and 0.04 Tg N2O-N yr-1. A high increase rate of GHG emissions occurred from 1950 to 1980, due to the rapid increases of the numbers and surface areas of global reservoirs at the same period. Focusing on the three main reservoirs of the Seine Basin, obvious seasonal patterns of CH4 and CO2 were observed, CH4 concentrations in these reservoirs were high in summer and autumn and low in winter and spring, and were significantly and positively correlated with water temperate and SDO (saturation of dissolved oxygen), which is in contrast to CO2. The three reservoirs were slight sources of GHG, with the average values of 6.6 mg CH4–C m–2 d–1, 132.7 mg CO2–C m–2 d–1, and 0.03 mg N2O–N m–2 d–1, which were lower than the average values of global reservoirs. Based on the long-term (1998-2018) water quality data and our field measurements (2019-2020), we found that the reservoirs significantly change their downstream water quality. They increase DOC (dissolved organic matter) and BDOC (biodegradable DOC) concentrations, while decrease the concentrations of DIN (dissolved inorganic nitrogen), PO43- (orthophosphate), DSi (dissolved silica), and CO2 during their emptying periods. The mass-balance calculation revealed that these reservoirs retained 16-53%, 26-48%, 22-40%, and 36-76% of the inputs of DIN, PO43-, DSi, and SM, respectively. Qualitative analysis suggested that the mixing effect of entering water (quantity and quality) and biogeochemical processes in these reservoirs are the two dominant factors affecting reservoir water quality changes, and thus resulting in the changes in downstream water quality. The application of the Barman model satisfactorily simulates the changes of water quality variables (nutrients and CO2) and explicitly unravels nutrient (C, N, P, and Si) fates in these reservoirs. The phytoplankton assimilation (for NO3-, PO43-, and DSi) and benthic denitrification (for NO3-) are the dominant processes in removing nutrients. The precipitation of CaCO3 and CO2 emission are responsible for the DIC removal in these reservoirs. The results of scenario analysis suggested that reservoir trophic states (P concentrations) and morphological characteristics (mean depth) would significantly affect the retention efficiencies of NO3- and DSi, and thus its biogeochemical functions to downstream reservoirs
31
Tisserand, Romane. "The Ni biogeochemical cycle in a tropical agromining crop system". Electronic Thesis or Diss., Université de Lorraine, 2021. https://docnum.univ-lorraine.fr/ulprive/DDOC_T_2021_0115_TISSERAND.pdf.
Testo completoAbstract (sommario):
L'hyperaccumulation est un phénomène qui a été découvert il y a 45 ans seulement, il a fait l'objet de nombreuses recherches, en raison du comportement inhabituel des métaux dans l'écosystème et en raison du potentiel de solutions fondées sur la nature qui en découle. La description du cycle biogéochimique du Ni des plantes hyperaccumulatrices est nécessaire pour élucider leur rôle écologique dans leur environnement naturel, mais aussi pour comprendre leur comportement potentiel dans des cultures tropicales d’agromine. L'exploitation agricole et l'exportation de la biomasse riche en Ni interrompront le cycle du Ni. Il est donc important de comprendre les mécanismes qui régissent le cycle biogéochimique du Ni dans les systèmes naturels et de cultures : Quels sont les cycles du Ni et leur impact sur le fonctionnement écologique des forêts tropicales d’hyperaccumulateurs ? Quelle est la vitesse des flux de Ni à travers les compartiments sol-plante et quelle est la dynamique et le renouvellement du Ni dans un système tropical d'hyperaccumulateurs ? À quelle vitesse une culture tropicale Agromine peut-elle épuiser le Ni dans le sol ? Comment pouvons-nous gérer la fertilisation des sols pour une culture d’agromine tropicale de Ni durable ? Les objectifs de ce doctorat étaient donc les suivants (i) d'étudier le cycle biogéochimique d'une forêt naturelle de Phyllanthus rufuschaneyi afin d'évaluer les flux de Ni dans l'écosystème ; (ii) de manipuler un tel écosystème afin d'effectuer un test de sensibilité de l'écosystème pour le flux suivant : retour de la litière au sol ; de l'absence de retour (exportation) à un doublement du retour ; (iii) d'optimiser le système de culture de P. rufuschaneyi pour l'agromine du Ni. Deux peuplements parallèles de P. rufuschaneyi ont été instrumentés, surveillés et comparés pendant deux ans (2018 et 2019), (i) une forêt secondaire naturelle de 100 m2 et (ii) un champ densément planté dans lequel les retours de litière au sol ont été calibrés ; de l'absence de retour (exportation) à un doublement du retour. Cette étude n'a pas révélé l'allopathie des plantes hyperaccumulatrices tropicales. Les plantes hyperaccumulatrices de Ni influent sur la constitution des stocks de Ni disponibles dans les couches arables. Le cycle du Ni est principalement régi par des flux internes, notamment la dégradation et le recyclage de la litière. Ce pourcentage de renouvellement du Ni ne semble pas être influencé par le taillis à court terme mais par la présence initiale de litière sur le sol. La fertilisation NPK n'a aucun effet sur le rendement en Ni à court terme (75 kg Ni ha-1 an-1), même si la fertilisation en azote a tendance à réduire le rendement en Ni de P. rufuschaneyi. Il convient de tenir compte du renouvellement du nickel lors de la conception des cultures d’agromine tropicales. Une étude plus approfondie de l’altération permettrait de préciser son rôle dans la reconstitution des stocks de Ni disponible et de nutrimentsHyperaccumulation is a phenomenon that was only discovered 45 years ago, it has been the focused of very intensive research because of the unusual behaviour of metals in the ecosystem and also because it offers a vast potential for nature-based solutions. Describing the Ni biogeochemical cycle within the soil-hyperaccumulator plants ecosystem is necessary to elucidate the ecological role of hyperaccumulator plants in their natural environment, but also to understand their potential behaviour under tropical agromining systems. Agromining and exporting Ni rich-biomass will interrupt the cycle. It is therefore important to understand the mechanisms which govern the Ni biogeochemical cycle in both natural and agromining systems: What are the Ni cycles (internal and external) and their impact on the ecological functioning of tropical hyperaccumulator forest? How rapid are the Ni fluxes across the soil-plant compartments, and what is the turnover of Ni in a hyperaccumulator tropical system? How fast can a tropical Agromining crop deplete Ni in soil? How can we manage soil fertilisation for a sustainable tropical Ni agromining crop? Therefore, the objectives were: (i) to study the biogeochemical cycling of a natural forest of Phyllanthus rufuschaneyi in order to assess and evaluate the natural fluxes of Ni in the ecosystem; (ii) to manipulate such an ecosystem in order to perform a sensitivity test of the ecosystem for the following flux: litter return to the soil; (iii) to optimize the cropping system of P. rufuschaneyi for Ni agromining. Two parallel stands of P. rufuschaneyi were instrumented, monitored and compared over two years (2018 and 2019), (i) a natural secondary 100-m2 forest and (ii) a densely planted field in which litter returns to the soil were calibrated; from no return (export) to a doubling of the return.This study did not prove allelopathy of tropical hyperaccumulator plants, despite the extreme influence of Ni hyperaccumulators in building up available Ni stocks in topsoils. Nickel cycle was mainly driven by internal fluxes, i.e. degradation and recycling of the hyperaccumulator biomass. The percentage of Ni recycled by litterfall tended to decrease with increasing litter addition to the soil and was not influenced by coppicing, at least in the short term. Major nutrient (NPK) fertilisation did not affect Ni yield (i.e. 75kg Ni ha-1 yr-1) in the short term either, even if N fertilisation reduced Ni concentrations in leaves and plant biomass production. Nickel turnover should be taken into account when designing tropical agromining crops and natural secondary forests are a good surrogate to evaluate the long term impacts of agromining. Further study of the weathering processes would help to precise the contribution of bedrock and soil mineral horizons in the Ni and nutrient budgets of the system
32
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.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Biology; and the Woods Hole Oceanographic Institution), February 2013."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.
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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.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2012.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.
34
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.
Testo completoAbstract (sommario):
Quantifier la totalité des apports atmosphériques, notamment particulaires, est nécessaire pour mieux comprendre les cycles biogéochimiques en vue d'une gestion durable des écosystèmes forestiers. En effet, l'intensification des récoltes de bois-énergie induit une pression nutritive supplémentaire sur les forêts. Le but de ce travail est de combler les lacunes concernant le dépôt atmosphérique particulaire (taux de dépôt, composition minéralogique et chimique), ainsi que d'étudier son influence sur les cycles biogéochimiques forestiers. Pour ce faire, un échantillonnage de 2 ans a été mis en place dans 4 hêtraies de la moitié Nord de la France. Un développement métrologique a été nécessaire pour concevoir les capteurs hors et sous canopée et pour séparer les particules de la phase dissoute puis compartimenter le dépôt particulaire en fonction du modèle conceptuel organo-minéral établi dans cette étude. Les résultats obtenus valident ce modèle et montrent (i) un taux de dépôt annuel de 19±3 kg.ha-1.an-1 de minéraux peu solubles témoignant d'origines diverses, (ii) des flux de nutriments inférieurs à ceux des dépôts dissous et de l'altération des minéraux du sol mais qui contribuent à améliorer la fertilité des forêts, (iii) un captage supplémentaire induit par la canopée et (iv) une dissolution des particules minérales lors de leur transport atmosphérique qui enrichit les précipitations en nutriments. Un échantillonnage optimisé sur le long terme est indispensable pour confirmer et préciser les tendances observées, en particulier concernant les épisodes de très fort dépôt particulaire et le dépôt sous la canopéeQuantifying 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
35
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.
Testo completoAbstract (sommario):
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. Kelly N. Bringhurst Abstract This study is concerned with potential environmental degradation of soils, rivers and coastal regions of the Osa Peninsula, Costa Rica due to deforestation. A paired, small-catchment approach to the study of environmental pressures on nutrient transfer and aquatic enrichment was used with one catchment that had been cleared for pasture (CN9) and the second primarily undisturbed tropical wet forest (CS 1). Nutrients and related parameters in soils and transferred in normal hydrological discharge were investigated. Soils in the study area are oxisols with concentrations of organic matter, total and plant available P higher in the forested catchment. Indirect measures of suspended sediment by turbidity showed an increase in the deforested catchment stream. Water input via rainfall for the year June 2008-June 2009 was approximately 5000 mm. Stream discharge was approximately 3300 mm year" for each catchment as measured by continuous recorders and evapotranspiration was, on average, 1500 mm year". These data suggested a good resolution of the water balance from independent measurements. The effect of deforestation on stream discharge was a 59% increase in flow during the wet season and an increase in the Q5:Q95 ratio showing that the deforested stream was flashier. Loss of forest canopy and decreased organic matter in the soil resulted in a depletion of available N. The deforested catchment loss of dissolved inorganic nitrogen (DIN) increased 33% over the forested catchment. Soluble reactive phosphorus (SRP) showed a 47% increase in the deforested catchment compared with the forested catchment. The molar N:P ratios were lower than expected and both streams were well below the 0.06 mg L-1 level at which N- limitation has been reported. Effects of nutrient loading have been observed through increased algal growth on equipment surfaces in the deforested catchment stream and increased nutrient yields will likely lead to eutrophication of coastal waters. Key Words - eutrophication, phosphorus, nitrogen, suspended sediment, deforestation, tropical forest.
36
Panassa, Essowe [Verfasser], Judith [Akademischer Betreuer] Hauck, Dieter A. [Gutachter] Wolf-Gladrow e 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.
Testo completo
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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.
Testo completoAbstract (sommario):
[Truncated abstract] Globally, tropical rainforests are noted for their high biodiversity and key roles in carbon storage and influence on climate. Nevertheless, tropical deforestation in many parts of the world continues at an alarming rate. In Papua New Guinea (PNG), tropical rainforest is relatively well maintained, with about 70 % of the land area still covered by primary forest. However, PNG's native forests are coming under increasing pressure, particularly from selective logging for high quality timber. While the forests of PNG, and more broadly the entire New Guinea Island, are recognised as of high conservation and ecological significance, they remain grossly understudied with little knowledge of key ecosystem processes within lowland forests in particular. Such knowledge is urgently required if the impacts of logging and other land-use change are to be assessed and in order to develop sustainable management systems. This thesis investigated the impacts of logging on diversity and nutrient cycling in a lowland tropical rainforest growing on limestone soils in the area of the Mongi-Busiga Forest Management Agreement (FMA, which is a logging concession area), in northeastern PNG. These forests are on relatively young soils and provide a useful contrast to the majority of tropical forests. The research includes a four-year study of the recovery of diversity and structure after logging, and quantified forest structure, tree species diversity, forest biomass and productivity, and nutrient distribution and cycling. This thesis also examines the ecological sustainability of Eucalyptus deglupta plantations in Wasab, PNG as an alternative resource for timber and biomass energy. The thesis concludes with a discussion of long-term forest recovery and sustainable forest management in north-eastern PNG. Two adjacent one-hectare plots were established in lowland tropical rainforest at Mongi-Busiga FMA. One of these plots was subsequently selectively logged, one year after establishment. Before logging, the two one-hectare plots contained a total of 37 families, 70 genera and 110 tree species that were >5 cm in diameter at breast height. Mean basal area was 42.4 m2 ha-1. Two tree species, Madhuca leucodermis (Sapotaceae) and Pometia pinnata (Sapindaceae) accounted for ~60% of the total basal area. Gymnacranthera paniculata (Myristicaceae) was the most common species and accounted for 13% of individuals. ... This study concludes that the Mongi-Busiga forest has many unusual characteristics for a tropical forest, including relatively low diversity of tree species, high accumulation of P in the biomass, and N limitations, compared to other tropical rainforests. However, those extraordinary characteristics may be explained well by the underlying geology of young, marine-derived limestone. Sustainable management of the lowland tropical forests of PNG should consider the consequences of logging on nutrient cycling processes, with the possible significant removal of P from site with repeated logging, as well as the interactions between N and P in these systems. Establishment of Eucalyptus plantations on previously cleared land also has the potential to meet some of the timber and biomass energy requirements of northern PNG in ecologically sustainable manner.
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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.
Testo completoAbstract (sommario):
Bien que l’importance des eaux souterraines et des eaux porales (recirculation) en tant que voie d’apports de nutriments vers les systèmes côtiers soit de plus en plus reconnue, il y a encore peu d’information sur leur réel rôle écologique. Cette thèse vise à évaluer l’impact des flux d’eaux souterraines et du processus de recirculation au sein du sédiment sur le fonctionnement des écosystèmes lagunaires côtiers et sur leur vulnérabilité face aux impacts anthropiques et climatiques. Deux lagunes contrastées de la côte méditerranéenne française ont été étudiées (Etangs de La Palme et Salses-Leucate). Nos résultats montrent que la recirculation est la principale source d'azote inorganique dissous (DIN) et de phosphore inorganique dissous (DIP) dans la lagune de La Palme. Les signatures isotopiques d'azote (δ15N) chez les macrophytes et le phytoplancton reflètent principalement celles des formes inorganiques dissoutes des eaux souterraines et des eaux porales dans les lagunes de La Palme et de Salses-Leucate, démontrant ainsi le rôle significatif de ces sources dans le soutien de la production primaire. Les signatures isotopiques du carbone (δ13C) indiquent que les eaux souterraines sont également des sources importantes de carbone inorganique dissous pour les producteurs primaires. Cette étude montre aussi que les moules des sites influencés par les eaux souterraines ont un taux de croissance et un indice de condition (poids des tissus / poids de la coquille) plus élevés que ceux du site témoin hors influence des eaux souterraines probablement dues aux températures hivernales plus élevées et à l'apport permanent d'éléments nutritifs provenant des eaux souterrainesWhilst 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
39
Becker, Joscha Nico Verfasser], Yakov [Akademischer Betreuer] [Kuzyakov, Michaela [Gutachter] Dippold, Daniela [Gutachter] Sauer e 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.
Testo completo
40
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.
Testo completoAbstract (sommario):
The objective of this thesis was to validate the dynamic model SAFE (Soil Acidification in Forested Ecosystems) in a small deciduous watershed of southern Quebec. SAFE could then be used to: (1) identify which processes are governing acidification, and (2) assess the rates of acidification according to various forest conditions.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.)
41
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.
Testo completoAbstract (sommario):
Cell cycle control by trophic factors has a key role in regulation of cell proliferation in all organisms. Nutrients are one of these important factors needed by cells to reproduce, so very well regulated mechanisms must exist that connect nutrient availability to cell cycle. Hence the importance on studying how exactly nutrient-dependent signaling pathways work.
Cln3, the most upstream G1 cyclin in Saccharomyces cerevisiae, is one well demonstrated common effector of multiple nutrient-dependent signaling pathways. Moreover, its role in cell cycle is crucial. So it is a good candidate to regulate cell cycle progression in response to nutrient availability.
One important question is to find the protein that could directly modulate Cln3 levels in response to nutrient availability. This protein could play as a nutrient sensor and as a cell cycle regulator at the same time.
In the present thesis, Pho85 is founded to be the protein that could run these two highly different tasks, because of its well-characterized properties on sensing phosphate availability and the well-known functions on modulating cell cycle as CDK.
The results of the present work clearly demonstrate that when phosphate is present, Pho85 regulates Cln3 levels by increasing the stability of the cyclin through specific phosphorylations, promoting cell cycle progression. Contrary, under phosphate depletion conditions, Pho85 become inactive and Cln3 is rapidly degraded, leading to a cell cycle arrest in order to maintain cell chronological lifespan.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.
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Sergi, Sara. "Nutrient input from seamounts and hydrothermal vents in the Southern Ocean : impacts on the pelagic ecosystems and implications for conservation". Electronic Thesis or Diss., Sorbonne université, 2021. http://www.theses.fr/2021SORUS508.
Testo completoAbstract (sommario):
Les processus bottom-up contôlent une portion importante de la variabilité des écosystèmes marins. Dans l'océan Austral, des contrastes intenses dans la distribution des écosystèmes pélagiques sont génerés par la limitation de la production primaire par le fer et la Courant Circumpolaire Antarctique. Les efflorescences massives en phytoplancton en aval des îles entretiennent des vastes réseaux trophiques. En comparaison, l'impact des sources profondes de nutriments sur la production pélagique semble négligeable. Les programmes de conservation dans la Courant Circumpolaire Antarctique vont de pair avec cette description, avec des Aires Marines Protégées uniquement autour des îles. En combinant des données multi-satellites, des observations in-situ, des données de télémétrie animale et des sorties de modèles, cette thèse réévalue le rôle écologique des sources profondes de nutriments sur les écosystèmes pélagiques. L’analyse Lagrangienne des courants géostrophiques relie des vastes blooms phytoplanctoniques à des sources hydrothermaux ou des monts sous-marins. Les études contenues dans cette thèse démontrent que les forçages bottom-up induits par les sources profondes en nutriments façonnent le paysage marin pélagique à l'échelle du bassin, des producteurs primaires aux mégafaunes. Les résultats issus de cette thèse sont ainsi considérés dans le contexte des programmes de conservation. Il s’agit notamment des travaux de la CCAMLR visant à développer un système représentatif d’Aires Marines Protégées et dans le projet actuel d'extension de l’Aire Marine Protégée des îles françaises Saint-Paul et d'AmsterdamBottom-up forces control a large fraction of marine ecosystem variability. In the Southern Ocean, intense contrasts in the distribution of pelagic ecosystems are driven by the iron limitation of biological productivity and the vigorous Antarctic Circumpolar Current. Massive phytoplankton blooms stemming from islands support large trophic chains. By comparison, the impact of deep nutrient sources on the pelagic production appears negligible. Conservation efforts in the Antarctic Circumpolar Current are in line with this description, with Marine Protected Areas only occurring around islands. By combining multi-satellite data, in-situ observations, animal telemetry data and model outputs, this thesis revaluates the ecological role of deep nutrient sources. Lagrangian analyses of altimetry-derived velocity fields link vast phytoplankton blooms to hydrothermal vents or seamounts. The studies contained in this thesis demonstrate that bottom-up forcings driven by deep nutrient sources shape the pelagic seascape at basin scale (O(103 km)) from primary producers up to megafauna species. These findings underline the ecological importance of the open Southern Ocean waters and advocate for a connected vision of future conservation actions along the Antarctic Circumpolar Current. The analyses of bottom-up forcings are consequentially considered within the CCAMLR’s effort for developing a representative system of Marine Protected Areas and within the ongoing extension project of the French Saint Paul and Amsterdam islands’ Marine Protected Areas
43
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.
Testo completo
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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.
Testo completo
45
Liu, Shibin Verfasser], Yakov [Akademischer Betreuer] [Kuzyakov, Michaela [Gutachter] Dippold, Sandra [Gutachter] Spielvogel, Bruno [Gutachter] Glaser e 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.
Testo completo
46
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.
Testo completo
47
Le, Noë Julia. "Biogeochemical functioning and trajectories of French territorial agricultural systems : carbon, nitrogen and phosphorus fluxes (1852-2014)". Electronic Thesis or Diss., Sorbonne université, 2018. http://www.theses.fr/2018SORUS159.
Testo completoAbstract (sommario):
Cette thèse décrit les systèmes de production agricole en termes de flux biogéochimiques d’azote (N), de phosphore (P) et de carbone (C) dans les territoires français de 1852 à 2014 suivant une approche socio-écologique qui permet d’appréhender les logiques qui les gouvernent. Les résultats obtenus mettent en lumière à l’échelle des territoires français le lien systémique entre structures de production, bilans N et P et variations des stocks de C organique dans les sols agricoles. Les systèmes agricoles intensifs et spécialisés engendrent les pertes environnementales et les consommations de ressources par unité de surface agricole les plus considérables et accentuent l’ouverture des cycles d’N et de P. Cependant, c’est seulement après la seconde guerre mondiale que certaines régions françaises se sont spécialisées dans la grande culture ou, à partir des années 1980, dans l’élevage intensif. La période des années 1950 à 1980 est marquée par l’accélération des rendements des cultures végétales, de la densité de cheptel et de l’usage des fertilisants minéraux. Les conséquences en ont été une augmentation des bilans N et P et des apports de C aux sols agricoles, causant des pertes considérables d’N vers l’hydrosphère et l’atmosphère et l’augmentation des stocks de P et de C dans les sols. Néanmoins, l’accumulation du C n’a été rendue possible que par le recours aux fertilisants minéraux et au machinisme agricole consommant des énergies fossiles. Ainsi, le stockage du C dans les sols représente un effet secondaire du passage d’un métabolisme énergétique dépendant de l’énergie solaire à un métabolisme fondé sur la combustion d’énergie fossileThis 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
48
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.
Testo completoAbstract (sommario):
Cette thèse décrit les systèmes de production agricole en termes de flux biogéochimiques d’azote (N), de phosphore (P) et de carbone (C) dans les territoires français de 1852 à 2014 suivant une approche socio-écologique qui permet d’appréhender les logiques qui les gouvernent. Les résultats obtenus mettent en lumière à l’échelle des territoires français le lien systémique entre structures de production, bilans N et P et variations des stocks de C organique dans les sols agricoles. Les systèmes agricoles intensifs et spécialisés engendrent les pertes environnementales et les consommations de ressources par unité de surface agricole les plus considérables et accentuent l’ouverture des cycles d’N et de P. Cependant, c’est seulement après la seconde guerre mondiale que certaines régions françaises se sont spécialisées dans la grande culture ou, à partir des années 1980, dans l’élevage intensif. La période des années 1950 à 1980 est marquée par l’accélération des rendements des cultures végétales, de la densité de cheptel et de l’usage des fertilisants minéraux. Les conséquences en ont été une augmentation des bilans N et P et des apports de C aux sols agricoles, causant des pertes considérables d’N vers l’hydrosphère et l’atmosphère et l’augmentation des stocks de P et de C dans les sols. Néanmoins, l’accumulation du C n’a été rendue possible que par le recours aux fertilisants minéraux et au machinisme agricole consommant des énergies fossiles. Ainsi, le stockage du C dans les sols représente un effet secondaire du passage d’un métabolisme énergétique dépendant de l’énergie solaire à un métabolisme fondé sur la combustion d’énergie fossileThis 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
49
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.
Testo completo
50
Le, Van Khoi. "Nutrient cycle in an integrated recirculating aquaculture system". Thesis, Curtin University, 2012. http://hdl.handle.net/20.500.11937/1916.
Testo completoAbstract (sommario):
Intensive marine aquaculture may cause negative impacts on the aquatic environment by causing water pollution, algae bloom and reduction in biodiversity of the surrounding aquatic environment. The nutrient-rich effluents from aquaculture activities contain nitrogen and phosphate which serve as a nutrient source for bivalve, algae and invertebrates. Seaweed and mussels have been integrated with marine species in culture systems to remove the waste from aquaculture farms. The research has explored the nutrient uptake capacities of green seaweed (Ulva lactuca) and blue mussel (Mytilus edulis) integrated with western king prawn (Penaeus latisulcatus) in the integrated closed recirculating aquaculture systems (IRAS) and has evaluated the nutrient retention of seaweed and animals in the system.One experimental unit of an IRAS consisted of three tanks: a mussel tank, a prawn tank and a waste-collection tank. The mussel tank and the prawn tank were set on the top and lower tiers of a metal frame; the waste-collection tank was on the floor. Water was pumped from the waste-collection tank to the reservoir tank by a submersible pump, circulated to the prawn tank and then returned to the waste collection tank through gravity.A series of experiments were conducted under laboratory conditions to investigate the water quality; survival, growth of western king prawn and nutrient budget in the IRAS. The research results proved that the recirculating culture system could maintain acceptable water quality for western king prawn at stocking densities till 16 prawn m-2 and at feeding rate of 3.0% of wet weight biomass. Increasing the stocking densities results in decreasing the water quality in the culture media, the growth and survival of western king prawn reared in the recirculating aquaculture system. In contrast, increasing feeding rate did not improved growth and survival rate of western king prawn but feed utilization efficiency decreased significantly with increasing the feeding rates. Total phosphorus (TP) and orthophosphate (PO43-) concentrations increased linearly with increasing the feeding rates of western king prawn. High percentage of nutrient inputs accumulated into tank bottom at higher stocking densities whereas over 50% of nutrient inputs were in discharged water at harvest in lower stocking densities.Inclusion green seaweed into western king prawn culture system improved the water quality in the IRAS. Concentrations of total ammonia nitrogen (TAN), nitrate (NO3-) and PO43- in the integrated culture system were lower than those in the monoculture system. Green seaweed effectively removed 24.02-99.05% TAN and 13.80-96.40% PO43- in the culture media. Feed utilization efficiency in integrated culture was significantly enhanced by 24.90 % nitrogen (N) and 19.41% phosphorus (P). Nutrient budget revealed that western king prawn and green seaweed retained 28.00-31.90% and 6.53-29.71% N of total nitrogen (TN) inputs at harvest, respectively while P retention was 13.46-14.63% and 1.62-13.50% of TP inputs, respectively. The rest of total nutrient input was in discharged water and tank sediments.Integrated culture of blue mussel and western king prawn could improve the water quality in the IRAS though effectively removing of the total bacteria (TB), total suspended solids (TSS) and total nitrogen (TN) in the cultured media. However, concentrations of NO2-, NO3- and PO43- were increased due to the mussel excretion. Growth and survival of western king prawn were not affected by adding blue mussels into western king prawn culture in IRAS at stocking rate of 250 mussel m-2 and 16.07 prawn m-2. When stocking rates exceed density of 312.5 mussel m-2 and =21.36 prawn m-2, growth and survival of both western king prawn and blue mussel in the IRAS were declined significantly due to the low water quality and crowded effects in the culture media. Inclusion of blue mussels into western king prawn culture was enhanced the feed utilization efficiency further up to 10.63 % N and 4.89 % P and reduced the nutrient discharged through draining at harvest. N and P contents accumulated in mussel tanks increased linearly with the increasing mussel stocking densities in the IRAS. The results indicate that the use of integrated aquaculture system is a step forward to achieve sustainability in aquaculture.