Dissertations / Theses on the topic 'Plant biogeochemistry'
To see the other types of publications on this topic, follow the link: Plant biogeochemistry.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Plant biogeochemistry.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Arnold, Timothy. "Biogeochemistry of zinc and iron isotopes at the plant-soil interface." Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.501762.
Full text
2
Alfonso, Amanda. "Organic nitrogen use by different plant functional types in a boreal peatland." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=106594.
Full textAbstract:
Mineralization has long been thought to be the main driver in providing plant available nitrogen (N). However, slow mineralization rates of northern ecosystems cannot sustain total plant N accumulation and it is now recognized that plants can utilize organic forms of N. N is often a limited nutrient in ombrotrophic bogs and at Mer Bleue peatland nearly 80% of the N in the porewater is in the dissolved organic nitrogen (DON) form. This study determined whether peatland plants can take up organic forms of N and whether there are differences between plant functional types, which dominate bog vegetation. To determine if bog plants take up organic N, 16 plots were selected at Mer Bleue where half remained a control and half received a treatment of isotopically labeled glycine (13C2,15N, 98% atom). The labeled glycine was injected into the rhizosphere at a depth of 0-20cm. After 72 hours the leaves and roots of shrub (C. calyculata, V. myrtilloides, L. groenlandicum), sedge (E. vaginatum) and moss (S. magellanicum, S. capillifolium) in the plots were sampled and analyzed for plant δ13C and δ15N. Foliar samples showed a significant uptake of 15N across all species and no significant uptake of 13C. Root samples showed greater enrichment in 15N and 13C for both shrub and sedge species; however, sedge uptake of 13C was not found to be significant. Results showed that shrub species took up glycine intact while a significant uptake of glycine was not found for sedge and moss species. This suggests that the mycorrhizal associations of ericaceous shrubs may contribute to organic N uptake at Mer Bleue bog.La minéralisation a longtemps semblé être le conducteur principal fournissant l'azote aux plantes. Cependant, les faibles taux de minéralisation des écosystèmes nordiques ne peuvent pas pourvoir l'apport total d'azote des plantes et il est maintenant reconnu que les plantes peuvent utiliser les formes organiques de l'azote. L'azote est souvent un nutriment limitant dans les tourbières ombrotrophes et, à la tourbière Mer Bleue, près de 80% de l'azote dans l'eau interstitielle est sous forme d'azote organique dissous. Cette étude avait pour but de déterminer si les plantes des tourbières peuvent absorber l'azote sous formes organiques et s'il y a des différences entre les types fonctionnels de plantes qui dominent la végétation des tourbières. Pour déterminer si les plantes des tourbières absorbent l'azote organique, 16 parcelles ont été choisies à Mer Bleue, où une moitié a été utilisée comme contrôle et l'autre moitié a reçu un traitement de glycine marquée isotopiquement (13C2, 15N, 98% atomes). La glycine marquée a été injecté dans la rhizosphère à une profondeur de 0-20cm. Après 72 heures, les feuilles et les racines des arbustes (C.calyculata, V. myrtilloides, L.groenlandicum), laîches (E. vaginatum) et les mousses (S. magellanicum, S.capillifolium) dans les parcelles ont été recueillies et analysées pour les plantes δ13C et δ15N. Les échantillons foliaires ont montré une absorption importante de 15N pour toutes les espèces et aucune augmentation significative de signatures δ13C. Les échantillons de racines ont montré un enrichissement plus grand en δ15N et δ13C pour les deux espèces d'arbustes et celle de laîche. Cependant, l'absorption de δ13C pour espèces de laîche n'a pas été jugée significative. Les résultats ont montré que les espèces d'arbustes ont absorbé la glycine entièrement alors que l'absorption de glycine n'a pas été importante pour les espèces de carex et de mousse, ce qui suggère que les associations mycorhiziennes des arbustes éricacées peut être le facteur déterminant dans l'absorption de l'azote organique à la tourbière Mer Bleue.
3
Ker, Keomany. "AM fungal contribution to sunflower (Helianthus annuus L) in phytoremediation of nickel-treated soils." Thesis, University of Ottawa (Canada), 2006. http://hdl.handle.net/10393/27258.
Full textAbstract:
The main objective of this study was to examine the contribution of arbuscular mycorrhizal (AM) colonization on nickel (Ni) uptake and Ni tolerance in sunflower (Helianthus annuus L.) at a vegetative or reproductive stage of development. The combined effect of AM colonization, Ni input, and nitrogen (N) fertilization on N-assimilation in sunflower plants was also investigated. Furthermore, concerns over the transfer of heavy metals (HMs) to higher trophic levels led us to investigate whether the AM colonization and accumulation of Ni within plant tissues would induce synthesis of secondary defense compounds. It was hypothesized that AM colonization increases Ni content and plant Ni tolerance, the activities of N-assimilating enzymes (nitrate reductase, NR; glutamine synthetase, GS; and glutamine dehydrogenase, GDH), and induces the accumulation of sesquiterpene lactones (STLs), in sunflower grown under soil Ni conditions. It was also hypothesized that N-type fertilization affects ammonium assimilation as the activities of GS and GDH would be enhanced in plants supplied with an NH+4 as compared to a NO-3 fertilizer. To verify these hypotheses, three greenhouse experiments were performed with sunflower cv. "Lemon Queen", with or without the AM fungus, Glomus intraradices Schenck & Smith, and treated with (1) 0 or 100 mg Ni kg-1 dry soil (DS) at the reproductive stage, and supplied with NO-3 or NH+4 fertilizer; (2) 0, 100, 200 or 400 mg Ni kg-1, at the reproductive stage and supplied with a complete NH4NO 3 fertilization; and (3) 0, 200 or 400 mg Ni kg-1, at the vegetative stage and supplied with a complete NH4NO 3 fertilizer. The overall results indicated that AM colonization significantly enhances Ni content in sunflower plants, exposed to a moderate soil Ni level of 100 mg Ni kg-1, at the reproductive stage. Furthermore, at 100 mg Ni kg-1, the AM plants had a significantly higher shoot Ni extracted %, suggesting that the AM symbiosis contributed to Ni uptake and its translocation from roots to shoots. The AM contribution to plant Ni content and Ni extracted % were significantly higher in plants supplied with NO-3 than with NH+4 . Moreover, the plant biomass and shoot height were significantly higher in plants supplied with NO-3 than with NH+4 . In late Ni exposed sunflower, the AM colonization significantly increased the Ni extracted % at 400 mg Ni kg-1, yet also resulted in a biomass reduction of 45% as compared to only 14% at 100 mg Ni kg -1. Furthermore, a soil [Ni] of 400 mg Ni kg-1 was toxic to sunflower directly seeded in Ni treated soils, as all seedlings died within four weeks after sowing. The mineral concentrations were enhanced in AM plants, especially at lower soil Ni treatments. It is therefore concluded that the AM contribution to Ni uptake was optimal at 100 mg Ni kg-1 . The AM colonization also contributed to enhance the activities of N-assimilating enzymes, especially under NH+4 fertilization. Moreover, our results showed that the effects of HM stress and N fertilization were linked, as the activities of NR, GS, and GDH were significantly enhanced in plants under NH+4 and at 100 mg Ni kg-1. These results suggest that the combined treatments of soil Ni input and NH+4 nutrition enhance N assimilation via concurrent activities of the GS/GOGAT and GDH pathways. We also observed that both soil Ni input and AM colonization lead to an accumulation of STLs in sunflower leaves. In addition, the combination of AM colonization and soil Ni input would result in a synergistic effect to maximize defense properties while minimizing energy expenditure. These findings support the hypothesis that the AM symbiosis contributes to enhanced Ni uptake and Ni plant tolerance. It is therefore concluded that sunflower, especially in association with AM fungi, shows promise as a "candidate" species in phytoremediation strategies.
4
Hua, Yujie. "Changes of Soil Biogeochemistry under Native and Exotic Plants Species." FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/1912.
Full textAbstract:
Invasive plant species are major threats to the biodiversity and ecosystem stability. The purpose of this study is to understand the impacts of invasive plants on soil nutrient cycling and ecological functions. Soil samples were collected from rhizosphere and non-rhizosphere of both native and exotic plants from three genera, Lantana, Ficus and Schinus, at Tree Tops Park in South Florida, USA. Experimental results showed that the cultivable bacterial population in the soil under Brazilian pepper (invasive Schinus) was approximately ten times greater than all other plants. Also, Brazilian pepper lived under conditions of significantly lower available phosphorus but higher phosphatase activities than other sampled sites. Moreover, the respiration rates and soil macronutrients in rhizosphere soils of exotic plants were significantly higher than those of the natives (Phosphorus, p=0.034; Total Nitrogen, p=0.0067; Total Carbon, p=0.0243). Overall, the soil biogeochemical status under invasive plants was different from those of the natives.
5
Juice, Stephanie. "The Environmental Microbiome In A Changing World: Microbial Processes And Biogeochemistry." ScholarWorks @ UVM, 2020. https://scholarworks.uvm.edu/graddis/1181.
Full textAbstract:
Climate change can alter ecosystem processes and organismal phenology through both long-term, gradual changes and alteration of disturbance regimes. Because microbes mediate decomposition, and therefore the initial stages of nutrient cycling, soil biogeochemical responses to climate change will be driven by microbial responses to changes in temperature, precipitation, and pulsed climatic events. Improving projections of soil ecological and biogeochemical responses to climate change effects therefore requires greater knowledge of microbial contributions to decomposition. This dissertation examines soil microbial and biogeochemical responses to the long-term and punctuated effects of climate change, as well as improvement to decomposition models following addition of microbial parameters.
First, through a climate change mesocosm experiment on two soils, I determined that biogeochemical losses due to warming and snow reduction vary across soil types. Additionally, the length of time with soil microbial activity during plant dormancy increased under warming, and in some cases decreased following snow reduction. Asynchrony length was positively related to carbon and nitrogen loss. Next, I examined soil enzyme activity, carbon and nitrogen biodegradability, and fungal abundance in response to ice storms, an extreme event projected to occur more frequently under climate change in the northeastern United States. Enzyme activity response to ice storm treatments varied by both target nutrient and, for nitrogen, soil horizon. Soil horizons often experienced opposite response of enzyme activity to ice storm treatments, and increasing ice storm frequency also altered the direction of the microbial response. Mid-levels of ice storm treatment additionally increased fungal hyphal abundance. Finally, I added explicit microbial parameters to a global decomposition model that previously incorporated climate and litter quality. The best mass loss model simply added microbial flows between litter quality pools, and addition of a microbial biomass and products pool also improved model performance compared to the traditional implicit microbial model.
Collectively, these results illustrate the importance of soil characteristics to the biogeochemical and microbial response to both gradual climate change effects and extreme events. Furthermore, they show that large-scale decomposition models can be improved by adding microbial parameters. This information is relevant to the effects of climate change and microbial activity on biogeochemical cycles.
6
Montross, Scott Norman. "Geochemical evidence for microbially mediated subglacial mineral weathering." Thesis, Montana State University, 2007. http://etd.lib.montana.edu/etd/2007/montross/MontrossS0507.pdf.
Full textAbstract:
Interactions between dilute meltwater and fine-grained, freshly comminuted debris at the bed of temperate glaciers liberate significant solute. The proportions of solute produced in the subglacial environment via biotic and abiotic processes remains unknown, however, this work suggests the biotic contribution is substantial. Laboratory analyses of microbiological and geochemical properties of sediment and meltwater from the Haut Glacier d\'Arolla (HGA) indicates that a metabolically active microbial community exists in water-saturated sediments at the ice-bedrock interface. Basal sediment slurries and meltwater were incubated in the laboratory for 100 days under near in situ subglacial conditions. Relative proportions of solute produced via abiotic v. biotic mineral weathering were analyzed by comparing the evolved aqueous chemistry of biologically active (live) sediment slurries with sterilized controls. Aqueous chemical analyses indicate an increase in solute produced from mineral weathering coupled with nitrate depletion in the biologically active slurries compared with the killed controls. These results infer that microbial activity at HGA is likely an important contributor to chemical weathering associated solute fluxes from the glaciated catchment. Due to the magnitude of past glaciations throughout geologic time (e.g., Neoproterozoic and Late-Pleistocene), and evidence that subglacial microbial activity impacts mineral weathering, greater consideration needs to be given to cold temperature biogeochemical weathering and its impact on global geochemical cycles.
7
Gougherty, Steven W. "Exudation Rates and δ13C Signatures of Bottomland Tree Root Soluble Organic Carbon: Relationships to Plant and Environmental Characteristics." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1448818110.
Full text
8
Van, der Merwe Margaretha Johanna. "Influence of hexose-phosphates and carbon cycling on sucrose accumulation in sugarcane spp." Thesis, Link to the online version, 2005. http://hdl.handle.net/10019/1257.
Full text
9
Card, Marcella. "Interactions among soil, plants, and endocrine disrupting compounds in livestock agriculture." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1311287470.
Full text
10
Franklin, Oskar. "Plant and forest dynamics in response to nitrogen availability /." Uppsala : Swedish University of Agricultural Sciences, 2003. http://diss-epsilon.slu.se/archive/00000345/.
Full textAbstract:
Thesis (doctoral)--Swedish University of Agricultural Sciences, 2003.Appendix consists of reprints of three papers and a manuscript, three of which are co-authored with others. Includes bibliographical references. Also partially issued electronically via World Wide Web in PDF format; online version lacks appendix.
11
Navarrete, Gutiérrez Dulce Montserrat. "Plant Metal Hyperaccumulation in Mexico : Agromining Perspectives." Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0187.
Full textAbstract:
L’agromine concerne la récupération de métaux stratégiques dans les sols métallifères par la culture de plantes hyperaccumulatrices de métaux (et metalloïdes). Le moteur de cette recherche était d'évaluer le potentiel des ressources végétales mexicaines pour le développement de l'agromine. Les principaux objectifs étaient d'identifier et d'étudier quelques espèces de plantes hyperaccumulatrices de métaux au Mexique, et d'évaluer l'agronomie d'une de ces espèces avec des caractéristiques prometteuses pour l’agromine. Nous avons d'abord effectué des explorations dans trois régions ultramafiques riches en nickel (Ni) du centre et du sud du Mexique. Malgré la disponibilité du nickel dans le sol et les conditions climatiques, aucune hyperaccumulation de Ni n'a été trouvée dans ces régions. Une deuxième stratégie basée sur la phylogénie végétale comme outil de prédiction de l'hyperaccumulation des métaux a été suivie. Au total, dix espèces hyperaccumulatrices de métaux ont été identifiées au cours de cette recherche (Rubiaceae et Violaceae) dans des sols riches en Ni influencés par l'activité volcanique, dans le sud-est du Mexique ; la majorité d’entre elles n’était pas identifiée comme hyperaccumulatrices. Nos études ont révélé deux des hypernickelophores les plus puissants détectés jusqu'à présent (>4% wt Ni) et deux nouveaux genres hyperaccumulateurs de nickel (Orthion et Mayanaea). Une attention particulière a été accordée à l'hypernickelophore Blepharidium guatemalense. Le phloème des feuilles, des racines, des tiges et des pétioles de cette plante est très riche en Ni, ce qui suggère un mécanisme de redistribution via le phloème. Différentes pratiques agronomiques ont été testées pour cette plante. La fertilisation inorganique a fortement augmenté l'absorption du Ni sans modifier la croissance ou la biomasse de la plante, tandis que la fertilisation organique a augmenté la biomasse de la plante avec un effet négligeable sur les concentrations de Ni dans les parties aériennes. Une parcelle avec une culture de 5 ans, qui a ensuite été récolté deux fois par an, produit le rendement maximal en Ni de 142 kg ha⁻¹ an⁻¹. Blepharidium guatemalense est un candidat de choix pour l'agromine du Ni en raison de ses caractéristiques appréciables : absorption extrêmement efficace du Ni, production élevée de biomasse, taux de croissance rapide, et facilité de reproductionAgromining technology involves the recovery of strategic metals from metalliferous soils through the cultivation of metal(loid) hyperaccumulator plants. The impetus of this research was to evaluate the potential of Mexican plant resources for the future development of agromining. The main objectives were then to identify and to study some metal hyperaccumulator plant species in Mexico, and to assess the agronomy of one promising “metal crop” for agromining. We first undertook field explorations in three nickel-rich ultramafic regions of central and southern Mexico. Despite the availability of soil and climatic conditions, no nickel (Ni) hyperaccumulation was found in any of these regions. A second strategy based on plant phylogeny as a prediction tool for metal hyperaccumulation was followed. In total, ten plant metal hyperaccumulator species were identified during this research (Rubiaceae and Violaceae) in Ni-enriched soils influenced by volcanic activity in Southeastern Mexico; most of them were priorly unknown. Our studies revealed two of the strongest hypernickelophores reported so far (>4%wt Ni) and two new Ni hyperaccumulator genera (Orthion and Mayanaea). Special focus was given to the hypernickelophore tree Blepharidium guatemalense. The phloem on leaves, roots, stems and petioles of this plant are the richest in Ni suggesting an unusual re-distribution mechanism via the phloem. Different agronomic practices were tested for this plant. Synthetic fertilization strongly increased nickel uptake without any change in plant growth or biomass, whereas organic fertilization enhanced plant shoot biomass with a negligible effect on foliar Ni concentrations. A 5-year-old stand which was subsequently harvested twice per year produced the maximum Ni yield tree⁻¹ yr⁻¹, with an estimated total nickel yield of 142 kg ha⁻¹ yr⁻¹. Blepharidium guatemalense is a prime candidate for Ni agromining on the account of its valuable traits: extremely efficient Ni uptake, high biomass production, fast growth rate, and easy to reproduce
12
Branfireun, Marnie. "The role of decomposing plant litter in methylmercury cycling in a boreal poor fen /." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33382.
Full textAbstract:
Decomposition and MeHg concentration were measured for Sphagnum fuscum, Sphagnum angustifolium and Chamaedaphne calyculata in a poor fen in the low boreal forest zone of the Canadian Shield. Litter bags were transplanted reciprocally into hummocks, hollows and lawns and retrieved after 1, 2, 3,11 and 15 months.Mass losses follow the trend: Chamaedaphne calyculata >> S. angustifolium > S. fuscum. Between species differences were far more significant than differences between locations or depths, indicating that litter quality is the major control on decomposition.
McHg concentrations generally increased during decomposition, particularly near the water table: for C. calyculata up to 13000%, for the two Sphagnum mosses up to 500%, suggesting that decomposition stimulates mercury methylation or McHg scavenging.
The discovery of a high McHg substance on C. calyculata leaf surfaces (25 ng g-1) suggests that much plant MeHg data may by skewed by the presence of a biologically active 'film'.
13
Smith, Madelyn M. "Cometabolic Degradation of Halogenated Aliphatic Hydrocarbons by Aerobic Microorganisms Naturally Associated with Wetland Plant Roots." Wright State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=wright1341854406.
Full text
14
Mosher, Stella G. M. S. "Carbon Isotope Discrimination and Nitrogen Isotope Values Indicate that Increased Relative Humidity from Fog Decreases Plant Water Use Efficiency in a Subtropical Montane Cloud Forest." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1430750042.
Full text
15
Gormley, Mark D. "The Influence of Hydrogeomorphology, Soil Redox Conditions, and Salinity on the Spatial Zoning of Saltgrass, Salt Rush, and Cattails in Scotts Creek Marsh, Swanton Pacific Ranch, CA." DigitalCommons@CalPoly, 2013. https://digitalcommons.calpoly.edu/theses/1167.
Full textAbstract:
Scotts Creek Marsh (SCM) is a small coastal wetland ecosystem in Davenport, CA. The vegetation of SCM is dominated by three halophytic zones comprised of saltgrass, salt rush, cattails. The objectives of the study were (i) to investigate the variables that influence the zoning of the three dominant halophyte communities in SCM and (ii) to the test the effectiveness of Indicator of Reduction in Soil (IRIS) tubes to indicate the reduction of S. The study examined the following parameters from April 6 to July 21, 2013: (i) the HGM of Scotts Creek Marsh, (ii) soil oxidation and reduction (redox) conditions, (iii) salinity, and (iii) the effectiveness of Adobe Photoshop CS 5.1 (AP5) to analyze IRIS images. All three halophytes were well suited for anoxic, redox, and saline conditions by utilizing morphological adaptations (arenchyma, adventitious roots) to their root systems. The study concluded that the spatial zoning of the three dominate halophyte species within SCM was most likely due to slight differences in the water levels and salinity. The halophytes within SCM were zoned with saltgrass occupying the areas with the lowest water table and highest EC (26.98 dS/m). The cattails dominated the low average saline areas (9.60 dS/m) near the marsh channels with the highest water level. The salt rush zones had a mild EC level of 15.24 dS/m and intermediate water level. The IRIS tubes that were installed as indicators of both sulfur and iron reduction were effective. The tubes that were withdrawn after the closure of Scott’s Creek all had more than 30% reduction of the Fe3+ paint. The results from the IRIS study indicate that they are effective at recording the reduction of sulfur. The use of AP5 seemed to be an effective tool for analyzing IRIS images. The analyzed data from the study suggests that changes to the HGM of SCM could potentially alter the ecology of the marsh.
16
Matheny, Ashley Michelle. "Development of a Novel Plant-Hydrodynamic Approach for Modeling of Forest Transpiration during Drought and Disturbance." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1468595149.
Full text
17
Wilson, Benjamin J. "Drivers and Mechanisms of Peat Collapse in Coastal Wetlands." FIU Digital Commons, 2018. https://digitalcommons.fiu.edu/etd/3718.
Full textAbstract:
Coastal wetlands store immense amounts of carbon (C) in vegetation and sediments, but this store of C is under threat from climate change. Accelerated sea level rise (SLR), which leads to saltwater intrusion, and more frequent periods of droughts will both impact biogeochemical cycling in wetlands. Coastal peat marshes are especially susceptible to saltwater intrusion and changes in water depth, but little is known about how exposure to salinity affects organic matter accumulation and peat stability. I investigated freshwater and brackish marsh responses to elevated salinity, greater inundation, drought, and increased nutrient loading. Elevated salinity pulses in a brackish marsh increased CO2 release from the marsh but only during dry-down. Elevated salinity increased root mortality at both a freshwater and brackish marsh. Under continuously elevated salinity in mesocosms, net ecosystem productivity (NEP) was unaffected by elevated salinity in a freshwater marsh exposed to brackish conditions (0 à 8 ppt), but NEP significantly increased with P enrichment. Elevated salinity led to a higher turnover of live to dead roots, resulting in a ~2-cm loss in soil elevation within 1 year of exposure to elevated salinity. When exposing a brackish marsh to more saline conditions (10 à 20 ppt), NEP, aboveground biomass production, and root growth all significantly decreased with elevated salinity, shifting the marsh from a net C sink to a net C source to the atmosphere. Elevated salinity (10 à 20 ppt) did not increase soil elevation loss, which was already occurring under brackish conditions, but when coupled with a drought event, elevation loss doubled. My findings suggest these hypotheses for the drivers and mechanisms of peat collapse. When freshwater marshes are first exposed to elevated salinity, soil structure and integrity are negatively affected through loss of live roots within the soil profile, leaving the peat vulnerable to collapse even though aboveground productivity and NEP may be unaffected. Subsequent dry-down events where water falls below the soil surface further accelerate peat collapse. Although saltwater intrusion into freshwater wetlands may initially stimulate primary productivity through a P subsidy, the impact of elevated salinity on root and soil structure has a greater deleterious effect and may ultimately be the factors that lead to the collapse of these marshes.
18
Zhao, Hongwei. "A Proteomic Study of Plant Messenger RNA Cleavage and Polyadenylation Specificity Factors and the Establishment of an In Vitro Cleavage Assay System." Oxford, Ohio : Miami University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=miami1218547019.
Full text
19
Guigues, Stéphanie. "Caractérisation des interactions physico-chimiques entre le cuivre et les racines comme base de développement d'un modèle d'évaluation de la phytodisponibilité des éléments traces." Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4307.
Full textAbstract:
Cette étude a été dédiée au développement d’une nouvelle approche de modélisation de la phytodisponibilité des éléments traces. Cette approche a été employée pour prédire l’adsorption du cuivre (Cu) sur des racines de blé et de tomate. Plusieurs techniques analytiques (titrages acido-basiques, résonance magnétique nucléaire, spectroscopie d’absorption X) ont été employées et croisées avec des résultats de modélisation. Dans un premier temps, la réactivité des racines a été caractérisée. Les racines étant constituées de parois apoplasmiques et de membranes plasmiques, la contribution respective de ces deux compartiments végétaux aux propriétés de complexation des racines a été évaluée. L’étude a ensuite été focalisée sur la complexation du Cu au sein des racines et sur l’évolution de cette complexation en fonction des conditions physico-chimiques du milieu. Grâce aux résultats obtenus sur la caractérisation des racines et à l’acquisition d’un jeu varié de données expérimentales sur la complexation du Cu, le modèle a pu être paramétré. Il a été montré que les propriétés de complexation des racines de blé et de tomate proviennent conjointement des membranes plasmiques et des parois apoplasmiques. La spéciation du Cu au sein des racines était partagée entre les composés pectiques des parois apoplasmiques et les protéines enchâssées à la fois dans les parois apoplasmiques et les membranes plasmiques. Un modèle propre aux racines a pu être développé sur la base d’un modèle existant dédié à la réactivité des substances humiques. Le modèle WHAM-THP, présenté dans cette étude, est un premier pas vers un nouvel outil d’évaluation de la phytodisponibilité des éléments tracesThis study has been dedicated to the development of a new modeling approach of trace element phytoavailability, focusing on binding reactions between trace element and plant roots. This approach was used to predict copper (Cu) adsorption on wheat and tomato roots. Several analytical techniques (acid-base titrations, nuclear magnetic resonance of carbon 13, X-ray absorption spectroscopy) were used and crossed with modeling results. At first, plant root reactivity was characterized. Because plant roots are consist of cell walls and plasma membranes, the relative contribution of these two compartments in root binding properties was evaluated. The study was then focused on Cu binding reactions on roots and the effects of physico-chemical conditions (pH, ionic strength, presence of cations) on copper binding. The model has been set thanks to results on root characterization obtained and the acquisition of a set of experimental data on Cu binding. It has been shown that binding properties of wheat and tomato roots came from both cell walls and plasma membranes. Copper speciation in roots was shared, almost evenly, between cell wall pectic compounds and proteins embedded in cell walls and plasma membranes. A model, specific to plant roots, has been developed on the basis of a current model dedicated to the humic substances reactivity. The WHAM-Terrestrial Higher Plants model presented in this study is a first step towards a new tool for assessing the availability of trace elements for plants
20
Tang, Guoping. "An examination of vegetation modeling-related issues and the variation and climate sensitivity of vegetation and hydrology in China." Thesis, Connect to title online (Scholars' Bank) Connect to title online (ProQuest), 2008. http://hdl.handle.net/1794/8543.
Full textAbstract:
Thesis (Ph. D.)--University of Oregon, 2008.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 128-156). Also available online in Scholars' Bank; and in ProQuest, free to University of Oregon users.
21
Van, de Water Peter Kent. "δ¹³C and stomatal density variability in modern and fossil leaves of key plants in the western United States." Diss., The University of Arizona, 1999. http://hdl.handle.net/10150/289058.
Full textAbstract:
During the last deglaciation, 15,000 to 12,000 calendar years ago, global warming and wholesale shifts in regional precipitation patterns produced dramatic changes in vegetation worldwide. Paleobotanical records, namely pollen and macrofossils, have been used not only to reconstruct shifts in plant distributions and abundances, but also to quantify changes in temperature and precipitation amounts or seasonality. In addition to climatic change, during the full glacial period atmospheric CO₂ values had dropped 30% to 200 ppmv compared to the Holocene, preindustrial value of 280 ppmv. Hypothetically, variations in atmospheric CO₂ affect plant water-use efficiency (carbon gained to plant-water transpired) and thus may have modulated vegetation response as climates change. The studies incorporated in this dissertation focused upon carbon isotope and morphological changes in leaves of key functional groups. The studies concentrated on plant species that are abundant in the fossil record and comprise major floral components of past and present vegetation. Key findings include: (1) that shifts in δ¹³C in modern populations along steep environmental gradients seldom exceeds inter-plant variability at a given site, (2) inter-plant and intra-site variability in modern and historic herbarium collections of the C₄ halophytes Altriplex canescens and A. confertilfolia and packrat midden macrofossils of A. canescens excludes their use as a reliable proxy for atmospheric δ¹³C, (3) calcium-oxalate crystals are common component in plant tissue and can have a significantly different δ¹³C value that increases inter-plant variability, especially in C₄ plants such as Atriplex canescens and A. confertifolia, (4) carbon isotope and stomatal density/index measurements of macrofossils from packrat middens show species specific adaptation in ecophysiological processes as atmospheric CO₂ rose from the full glacial, and (5) the greatest adaptation to low atmospheric CO₂ during the last ice age was in the C₃ species and that C₄ and CAM plants showed few changes in their discrimination against ¹³C or in the number of stomata on their leaf surfaces.
22
Naude, Minette. "Fynbos riparian biogeochemistry and invasive Australian acacias." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/20325.
Full textAbstract:
Thesis (MScConEcol)--Stellenbosch University, 2012.ENGLISH ABSTRACT: Riparian ecotones, transitional areas between upland terrestrial communities and aquatic ecosystems, are very dynamic and complex ecosystems with intrinsic ecological properties differing in spatial structure, function and temporal dynamics. Riparian habitats along rivers of the Mediterranean south-western Cape are sensitive to environmental change and particularly vulnerable to invasion by invasive alien plants (IAPs), especially nitrogen-fixing Acacia spp., and yet relatively little work has focused on how riparian ecosystems in this region respond to such stressors. The important roles that intact riparian vegetation play in maintaining ecosystem integrity and services have been increasingly highlighted as we acknowledge the degradation of these habitats. While the Working for Water (WfW) programme has been shown to be very successful in eradicating IAPs in riparian zones in the short-term, the extent to which riparian ecosystems recover following alien clearing activities remains poorly understood. The results presented in this study addressed several different aspects of riparian structure and function and acts as a steppingstone for guiding future research and management in riparian zones by adding to the evaluation of the success of clearing initiatives and restoration thereof. The aim of this study was to assess plant functional type (PFT) cover, soil physical and chemical properties, and selected biogeochemical processes in natural, Acacia- invaded and cleared riparian ecotones and associated non-riparian upland fynbos. Fieldwork was performed in mountain and foothill sections of six perennial river systems within the south-western Cape. Eleven sites of three categories were chosen: four natural sites (uninvaded); four moderate to highly invaded sites (predominantly A. mearnsii); and three cleared sites (a formerly invaded site that had been cleared more than 7 years prior to the study). Within each site, four to five replicate plots were established along each of three geomorphological zones (wet bank, dry bank, and upland fynbos). Seasonal soil samples were collected for a period of one year. Results from this study showed that PFT cover and composition, soil physical and chemical properties and rates of nitrogen (N) and phosphorus (P) mineralization differed amongst invasion status, between geomorphological zones and across seasons. Regarding most soil physical and chemical properties and indices N and P cycling, river floodplains (dry banks) were very similar to terrestrial uplands. Acacia spp. changes soil properties and affects plant functional attributes by i) enriching the system with N; ii) enhancing litter inputs; iii) altering soil physical properties; iv) changing the composition and reducing the cover of PFT; and v) enhancing P mineralization rates. Although measured soil physical and chemical properties and N and P mineralization rates were reduced to levels that were similar to or resembled the situation at natural areas, available inorganic N remained two times higher after more than seven years of clearance. Furthermore, cleared areas were characterized by sparse woody cover and a high cover of alien grasses. Correlations between soil silt and clay content and several soil properties measured in this and other studies indicates important linkages between soil texture and resource availability. Clearing Acacia spp. may initiate restoration of invaded riparian ecosystems, but changes in ecosystem function (e.g. elevated soil N availability) as a result of invasion may necessitate active restoration following the removal of the alien species. Active restoration under such conditions would be required to facilitate the restoration of cleared riparian communities. However, we still lack the mechanistic understanding around fynbos riparian recovery after clearing, as the success of restoration may depend on complex interaction and feedback cycles between plants and their physical environment. A greater comprehensive understanding of fynbos riparian ecological processes will not only improve the effectiveness of restoration initiatives by integrating science and management, but also advance the field of riparian ecology.
AFRIKAANSE OPSOMMING: Rivier oewerwal-areas, oorgang gebiede tussen aangrensende terrestriële gemeenskappe en akwatiese ekosisteme, is baie dinamiese en komplekse ekosisteme met intrinsieke ekologiese eienskappe wat verskil in struktuur, funksie (bv. biogeochemie siklusse) en temporale dinamika. Oewerhabitatte langs riviere van die Mediterreense suid-wes Kaap is sensitief vir omgewingsveranderinge en kwesbaar vir indringing deur uitheemse plante (bekend as “invasive alien plants” (IAPs)), veral stikstof-fiksering Acacia spp., en relatief min werk het nog gefokus op hoe ekosisteme in die streek reageer op sulke veranderinge in die omgewing. Die belangrike rol wat gesonde oewerwal plantegroei speel in die handhawing van ekosisteemdienste- en integriteit, is al hoe meer uitgelig soos ons die agteruitgang van hierdie habitat in ag neem. Terwyl die Werk vir Water (WvW)-program al dat baie suksesvol was in die uitwissing van IAPs in oewersones in die kort termyn, is die mate waarin oewer-ekostelsels herstel na skoonmaakaksies swak verstaan. Fynbos oewerwal-areas is grootliks ingeneem deur houtagtige IAPs, veral stikstof fiksering Acacia spp. (soos Acacia mearnsii). Die resultate wat in hierdie studie aangebied is, het verskillende aspekte van oewer- struktuur en funksie aangespreek en dien as middel vir toekomstige navorsing en bestuur van oewerwal ekosisteme deur by te dra tot die evaluering van die sukses van skoonmaak inisiatiewe en die herstelproses daarvan. Die doel van hierdie projek was om die moontlikhede vir herstel van fynbos owerwal-ekostelsels te evalueer deur middel van verskeie grond- fisiese en chemiese eienskappe; plant funksionele groep dekking (genoem ‘plant functional types’ (PFT)); en geselekteerde grond biogeochemie prosesse in natuurlike, Acacia- aangetaste, en skoongemaakte rivierstelsels en nabygeleë terrestriese areas te vergelyk. Veldwerk is gedoen in bergstroom en voetheuwel rivierseksies van ses standhoudende rivierstelsels in Suid-wes Kaap, Suid Afrika. Van uit hierdie geselekteerde rivierstelsels is elf studie areas van drie kategorieë (of indringing status) gekies: vier natuurlike areas (nie aangetas); vier gematig- tot hoogs aangetaste areas (hoofsaaklik A. meanrsii); en drie skoongemaakte areas (rivieroewers wat meer as sewe jaar van te vore skoongemaak is). Binne elke studie area was vier tot vyf soortgelyke persele gevestig by elke van drie breë geomorfologiese sones: naamlik nat-, droë en hoogliggende terrestriese fynbos. Seisoenale grondmonsters vir 'n tydperk van een jaar is geneem. Resultate van hierdie studie het getoon dat PFT dekking en samestelling, grond fisiese- en chemiese eienskappe en N-mineralisasie en suur fosfatase aktiwiteit verskil tussen indringing status, geomorfologiese sones en oor seisoene. Ten opsigte van meeste grond fisiese en chemiese eienskappe en indekse van stikstof (N) en fosfor (P) siklusse kom die rivier vogregimes (droë oewersones) baie ooreen met die terrestriële gebiede. Aan die anderkant is die natbanksones gekenmerk deur grondeienskappe wat baie verskil van die ander twee geomorfologiese gebiede. Die gegewens ondersteun die hipotese dat indringing deur Acacia spp. verskeie grondeienskappe verander en plante se funksionele kenmerke beïnvloed deur i) die sisteem met voedingstowwe te verryk (veral N); ii) verhoog die toevoeging van plantmateriaal; iii) verander grond fisiese eienskappe; iv) verander die samestelling en verminder die dekking van PFT; v) en verhoog P biogeochemie. Hoewel grond fisiese -en chemiese eienskappe, en indekse van N en P mineralisasie verminder is tot vlakke wat soortgelyk aan natuurlike areas, het beskikbare anorganiese N twee keer hoër gebly by skoongemaakte gebiede. Nietemin, voorheen skoongemaakte gebiede is weer-binnegeval deur eksotiese grasse en die regenerasie of hertelling van inheemse fynbos gemeenskappe is taamlik beperk, veral houtagtige oewer struike en bome. Korrelasies tussen grond slik-en klei-inhoud en verskeie grondeienskappe gemeet in hierdie en ander studies dui op belangrike skakeling tussen die grondtekstuur en voedingstof beskikbaarheid. Die opruiming van Acacia spp. mag as aansporing dien vir die herstellingsproses van rivieroewerstelsels, maar veranderinge in die funksie van ekosisteme (bv. verhoogte grond N beskikbaarheid), as gevolg van indringing, mag aktiewe herstel noodsaak nadat die indringer spesies verwyder is. Aktiewe herstel onder sulke omstandighede sal verwag word om die herstel van skoongemaak oewer gemeenskappe te fasiliteer. Ons het wel egter nog 'n gebrek aan die meganistiese begrip in verband met die herstel van fynbos oewerwal areas na opruimings-inisiatiewe, sedert die sukses van herstel kan afhang van komplekse interaksie en terugvoer siklusse tussen die plante en hul fisiese omgewing. ʼn Meer omvattende begrip van fynbos rivieroewer ekologiese prosesse sal nie net die doeltreffendheid van opruimings-inisiatiewe deur die integrasie van wetenskaplike navorsing en bestuur verbeter nie, maar ook vooraf die gebied van rivieroewer-ekologie.
23
Bruckner, Monica Zanzola. "Biogeochemistry and hydrology of three alpine proglacial environments resulting from glacier retreat." Thesis, Montana State University, 2008. http://etd.lib.montana.edu/etd/2008/bruckner/BrucknerM1208.pdf.
Full textAbstract:
Proglacial environments, formed by glacier retreat, exhibit distinct characteristics in discharge, water temperature, water residence time, and dissolved ion, carbon, and suspended sediment concentrations. The unnamed alpine glacier at the headwaters of the Wheaton River, Yukon, Canada, provides an ideal setting to compare deglaciation processes that result in three different proglacial environments. The glacier has evolved from occupying one large catchment (~4 km 2) to two smaller catchments (each ~2 km 2) via glacier thinning and net mass loss, forming two lobes separated by a medial moraine. Field observations revealed neither crevasses nor evidence of subglacial drainage outlets and suggested this glacier had a non-temperate thermal regime with meltwater predominantly flowing from supraglacial and ice marginal sources. Climate and bedrock geology were similar for the subcatchments, providing a natural laboratory to compare deglaciation processes. This study compared the hydrology and biogeochemistry of three outlet streams from this glacier: one stream drained a proglacial lake which is fed by meltwater from the lower west lobe, a second stream drained the upper west lobe, and a third stream was the major drainage outlet for the east lobe. Hydrologic monitoring over the 2006 melt season (June-August) and analyses of water samples for dissolved ion content and carbon indicated that the meltwaters are dominated by Ca 2+ and HCO 3-, which are derived from biogeochemical weathering of crustal materials. The study demonstrated that the presence of the proglacial lake, which acted as a meltwater reservoir, measurably modified meltwater residence time, water temperature, water chemistry, and bacterial biomass relative to the proglacial streams. Rock:water interaction between meltwater and medial morainal sediment and fine-grained, reactive glacial flour suspended in the streams and the lake water column also enhanced biogeochemical weathering within the catchment. Thus, this study provided a small-scale example for how differences in proglacial environments and water flow paths affect headwater hydrology and biogeochemistry. This study was the first of its kind in the Coast Mountains, Yukon, Canada, and results presented here aid in the understanding of how proglacial environments created by climate-induced glacier retreat affect hydrochemistry, hydrology, and carbon dynamics in remote high elevation environments.
24
Pedicino, Lisa Christine 1973. "Carbon isotopic variations in 7 southwestern United States plants from herbarium collections of the last 150 years." Thesis, The University of Arizona, 1997. http://hdl.handle.net/10150/291639.
Full textAbstract:
Since industrialization atmospheric CO₂ concentrations have increased from 280 to 365 ppmv and δ¹³Cₐᵢᵣ has decreased from -6.5 to -8.2‰. These two trends have consequences for plant physiology. I examine δ¹³C plant and physiological parameters in herbarium specimens of Atriplex confertifolia, Atriplex canescens, Ephedra viridis, Pinus edulis, Pinus flexilis , Juniperus scopulorum, and Quercus turbinella. For all species, I found relatively high and unsystematic variability. δ¹³C values for A. confertifolia and A. canescens varied by up to 7.9 and 9.5‰ respectively; δ¹³C values of these C₄ shrubs are unsuitable for reconstructing δ¹³Cₐᵢᵣ, as previously claimed. δ¹³C(plant) generally becomes more depleted except in P. edulis. Other calculated parameters such as Δ, Cᵢ/Cₐ, Cᵢ, and A/g have varying responses even among similar functional groups. Because much of the isotopic variability caused by interplant, intertree, intersite, and interannual differences is implicit, herbarium specimens are inadequate for precise detection of direct CO₂ effects on plant physiology.
25
Kocha, Jahnavi. "A Spatial and Temporal Analysis of Uranium Concentrations at the Abandoned New Hope Method Mine in the Mojave Desert." Scholarship @ Claremont, 2019. https://scholarship.claremont.edu/cmc_theses/2237.
Full textAbstract:
The impacts of mining are easily observable in the way they alter the terrain of landscapes, displace animals, and increase waste accumulation in an area. An unobservable impact and one that lasts a long time is by radioactive exposure in the environment. Specifically, this is a risk at uranium (U) mine sites which are expanding in number to accommodate the world’s growing energy needs, and even to accommodate weapons manufacturing. This paper analyses the impacts of an abandoned uranium mine on the local environment through measurements of Uranium concentration in soil, plants, and rocks. Transect sampling was used to collect 22 soil samples and 17 plant samples between 5 and 100m of the mine shaft. Uranium concentrations in soil and plant samples, digested with nitric acid, were measured with an Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES), and an X-ray Powder Diffraction (XRD) analysis was used to find the mineral contents of the rock samples. Satellite positions were associated with each sample, which allowed an effective spatial analysis of the Uranium concentration values. U values in soil ranged from 0 to 5.291ppm, with mean concentrations of 0.710 ppm, and U values in plants ranged from 0.0323 to 0.1121ppm with mean concentrations of 0.0558 ppm. A paired t-test determined that there was no spatial autocorrelation in U concentrations of plants and adjacent soils. The highest U concentration was found closest to the mine, peaking at ~7.3 meters from the mine, and low spatial variability occurs in U concentrations at greater than 10 meters from the mine. In comparison with other mines internationally, U concentrations at this study site were low, which may be indicative of a small operating mine, efficient clean-up, and transport mechanisms of U in desert environments.
26
Öquist, Mats. "Northern peatland carbon biogeochemistry : the influence of vascular plants and edaphic factors on carbon dioxide and methane exchange /." Linköping : Univ, 2001. http://www.bibl.liu.se/liupubl/disp/disp2001/tek729s.pdf.
Full text
27
Khatiwada, Raju. "Speciation of phosphorus in reduced tillage systems: placement and source effect." Thesis, Kansas State University, 2011. http://hdl.handle.net/2097/9973.
Full textAbstract:
Master of ScienceDepartment of Agronomy
Ganga M. Hettiarachchi
Phosphorus (P) management in reduced tillage systems has been a great concern for farmers. Conclusive results for benefits of deep banding of P fertilizers for plant yield in reduced tillage system are still lacking. Knowledge of the dominant solid P species present in soil following application of P fertilizers and linking that to potential P availability would help us to design better P management practices. The objectives of this research were to understand the influence of placement (broadcast- vs. deep band-P or deep placed-P), fertilizer source (granular- versus liquid-P), and time on reaction products of P. Greenhouse and field based experiments were conducted to study P behavior in soils. Soil pH, resin extractable P, total P, and speciation of P were determined at different distances from the point of fertilizer application at 5 weeks (greenhouse and field) and 6 months (field) after P application (at rate 75 kg/ha) to a soil system that was under long-term reduced tillage. X-ray absorption near edge structure spectroscopy technique was used to speciate reaction products of fertilizer P in the soil. The reaction products of P formed upon addition of P fertilizers to soils were found to be influenced by soil pH, P placement methods, and P sources. Acidic pH (below~5.8) tended to favor formation of Fe-P and Al-P like forms whereas slightly acidic near neutral pH soils favored formation of Ca-P like forms. Scanning electron microscope with energy dispersive X-ray analysis of applied fertilizer granules at 5-wk showed enrichment of Al, Fe and Ca in granule- indicating these elements begin to react with applied P even before granules dissolve completely. The availability of an applied P fertilizer was found to be enhanced as a result of the deep banding as compared to the surface broadcasting or deep placed methods. Deep banded liquid MAP was found to be in more adsorbed P like forms and resulted greater resin extractable P both at 5 wk and 6 month after application. Deep banding of liquid MAP would most likely result both agronomically and environmentally efficient solution for no-till farmers.
28
Jackson, Leland J. (Leland Joseph). "Rooted aquatic macrophytes and the cycling of littoral zone metals." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=39449.
Full textAbstract:
The general goal of this thesis was to examine and quantify the role of rooted submerged aquatic macrophytes in the cycling of metals in the littoral zone. An empirical study using data from an extensive literature survey showed that aquatic plants do not differ markedly in element composition from the sediments in which they grow, and that during uptake the plant's roots do not discriminate between elements essential and not essential for growth. The organic content, pH and redox potential of the sediments were shown to affect the bioavailability of metals to the plants. Biomass density was used to categorize species to assess broad patterns in plant-sediment metal relationships. It was found that the presence/absence of an understory contributed variation to the plant-sediment metal relationships. The role of rooted macrophytes as vectors for various elements between the sediments and attached epiphyte was quantified by growing Myriophyllum spicatum in radio-labelled sediments. This species was found to be a link between the sediments and attached epiphytes for the 4 elements studied (Co, Cs, Eu and Mn). Finally, the export of dissolved metals from weedbeds during plant senescence was quantified using a mass balance approach. It was found that approximately 15% to 30% (depending on the metal) of the metal inventory of the plants at maximum seasonal biomass was lost as dissolved compounds during senescence. During the growing season the macrophyte beds were net sources of metals to the lake, but were net sinks annually.
29
Vetter, Alexandra [Verfasser], and Brian [Akademischer Betreuer] Horsfield. "The influence of geothermal plants on the biogeochemistry of the microbial ecosystems in aquifers / Alexandra Vetter. Betreuer: Brian Horsfield." Berlin : Universitätsbibliothek der Technischen Universität Berlin, 2012. http://d-nb.info/1028912900/34.
Full text
30
Perlatti, Fabio. "Trace metals biogeochemistry in soils and plants affected by mining waste rocks: consequences to ecosystem and options for restoration." Universidade Federal do CearÃ, 2015. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=14753.
Full textAbstract:
CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel SuperiorA extraÃÃo e beneficiamento de minerais metÃlicos geram grandes quantidades de rejeitos que se nÃo dispostos adequadamente, podem ser fontes de contaminaÃÃo e drenagem Ãcida; pelo contato de sulfetos com Ãgua e oxigÃnio; ocasionando diminuiÃÃo no pH e aumento na mobilidade dos metais no solo. O diagnÃstico do comportamento biogeoquÃmico de rejeitos pode fornecer informaÃÃes valiosas para que se possa dispor e controlar adequadamente os efeitos adversos causados por esse tipo de material, bem como subsidiar a adoÃÃo de medidas de controle e mitigaÃÃo mais eficientes. Esse estudo teve como objetivo geral, diagnosticar os impactos causados pela disposiÃÃo de rejeitos em uma mina de cobre (Cu) abandonada, bem como propor alternativas para mitigar os impactos e restaurar a qualidade ambiental do local, baseado na hipÃtese de que esses rejeitos podem contaminar o solo da regiÃo com os elementos traÃo presentes nos minerais, alÃm de gerar drenagem Ãcida, dada a presenÃa de sulfetos expostos Ãs condiÃÃes atmosfÃricas, impedindo a regeneraÃÃo natural do ecossistema. O capÃtulo 1 traz uma introduÃÃo ao tema, bem como uma revisÃo bibliogrÃfica sobre o assunto. O capÃtulo 2 faz um diagnÃstico geral da Ãrea, avaliando-se os teores de diversos elementos traÃo nos rejeitos, solos e plantas. No capÃtulo 3 foram aprofundados os estudos sobre o comportamento geoquÃmico dos rejeitos com foco na geraÃÃo de drenagem Ãcida, alÃm de um estudo detalhado do comportamento do Cu no solo, atravÃs da extraÃÃo sequencial. O capÃtulo 4 detalha os teores de metais nos tecidos vegetais das plantas, avalia a aptidÃo do uso dessas espÃcies para a fitoremediaÃÃo, bem como apresenta dados das alteraÃÃes que ocorrem na rizosfera. O capÃtulo 5 aprofunda-se nas alteraÃÃes que ocorrem na rizosfera das plantas e as consequÃncias na mobilidade e ecotoxicidade do Cu, via extraÃÃo sequencial, e por fim, o capÃtulo 6 apresenta um estudo experimental com a utilizaÃÃo de tecnosolos, para imobilizar o excesso de Cu lÃbil no solo. Os resultados indicam que o principal impacto à causado pelo excesso de Cu que ainda persiste nos rejeitos e que, por processos de oxidaÃÃo e dissoluÃÃo, translocam grandes quantidade do metal para o solo. A geraÃÃo de drenagem Ãcida foi descartada; dada a aÃÃo tamponante gerada pela dissoluÃÃo dos carbonatos, minimizando os efeitos negativos da oxidaÃÃo dos sulfetos. A extraÃÃo sequencial mostrou que o Cu no solo està associado principalmente aos carbonatos e Ãxidos de Fe amorfos. O ciclo geoquÃmico entre a dissoluÃÃo dos carbonatos e oxidaÃÃo dos sulfetos parece ser o principal mecanismo de liberaÃÃo e adsorÃÃo do Cu no solo. Jà as plantas estudadas, nÃo foram consideradas hiperacumuladoras, entretanto, foram observados elevados teores de metal em suas raÃzes, indicando que a estratÃgia de sobrevivÃncia dessas plantas consiste na imobilizaÃÃo do metal nas raÃzes/rizosfera. A extraÃÃo sequencial na rizosfera mostrou que a presenÃa das plantas altera as caracterÃsticas do solo sob sua influÃncia, e consequentemente o comportamento biogeoquÃmico do Cu. Jà os tecnosolos demostraram grande capacidade em imobilizar Cu. Os quatro tecnosolos elaborados imobilizaram mais de 85% do Cu, sendo a maior parte retida na fraÃÃo residual, que representa a fraÃÃo onde o cobre fica adsorvido mais fortemente, demostrando que os tecnosolos despontam como uma excelente alternativa na remediaÃÃo de solos contaminados por metais.
The extraction and processing of metallic minerals generate large amounts of waste which, if not disposed of properly, may be sources of contamination and acid mine drainage; by contact of sulphides with water and oxygen; causing a decrease in pH and an increase in the mobility of metals in the soil. The diagnosis of biogeochemical behaviour of wastes can provide valuable information to discard and control the adverse effects of this kind of material, as well to support the adoption of more efficient measures of control and mitigation. This study had as general objective diagnose the impacts of waste disposal in an abandoned copper mine (Cu), as well to propose alternatives to mitigate the impacts and restore the environmental quality of the site, based on the hypothesis that such wastes can contaminate the soil with trace elements contained in minerals, and generate acid mine drainage, given the presence of sulphides exposed to weather conditions, hindering the natural regeneration of the ecosystem. The Chapter 1 provides an introduction to the theme, as well as a literature review. Chapter 2 presents a general diagnosis from the area, assessing the levels of several trace elements in rock wastes, soils and native plant species. In chapter 3, a thorough study on the geochemical behaviour of wastes, with focus on the generation of acid drainage were done, plus a detailed study about Cu behaviour in soils, through a chemical sequential extraction. Chapter 4 details the content of metals in above-ground tissues from plants that naturally grow on the wastes, assess the ability of these plants to be used in phytoremediation and show data about the changes that occur in the rhizosphere. Chapter 5 provides through a comparative study by sequential extraction in the rhizosphere and bulk soils; details about the changes that occur in the rhizosphere of plants and their consequences for Cu mobility and ecotoxicity, and finally, the chapter 6 presents an experimental study with the use of technosols, as way to immobilize the excess of labile copper in soil solution. Based on the results, can be concluded that the major impact is caused by the excess of Cu which still persists in the waste rocks and, through oxidation and dissolution processes, translocate large amount of metal into soil. The acid mine drainage was discarded given the buffering action generated by dissolution of carbonates, minimizing the negative effects of the oxidation of sulphides. The sequential extraction showed that the Cu concentration in soil is associated mainly with carbonates and amorphous iron oxides. The geochemical cycle between the dissolution of carbonates and oxidation of sulphides appears to be the main control mechanism of release and adsorption of Cu in soil. Regarding the plants, was concluded that they cannot be considered as Cu hyperaccumulators, however, high levels of metal were observed in roots, indicating that the survival strategy of these plants consists in immobilize metal in roots/rhizosphere. The sequential extraction in the rhizosphere showed that the presence of plants alter various soil characteristics under its influence, and also the geochemical behaviour of Cu. The technosols showed great ability to immobilize Cu. The four technosols elaborated in this study can immobilize more than 85% of Cu in solution, with the largest portion retained in the residual fraction, where Cu is adsorbed strongly, demonstrating that technosols emerge as an excellent alternative to remediate soils contaminated by metals.
31
Biggs, Thomas Howard 1949. "Fire frequency, nutrient concentrations and distributions, and δ¹³C of soil organic matter and plants in a southeastern Arizona grassland." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/282517.
Full textAbstract:
Over the past century, woody plants and shrubs have increased in abundance at the expense of grasslands in many semiarid regions. The availability and concentrations of nutrients influence the relative success of plants, but the effects of fire frequency on soil nutrients is unknown for semiarid grasslands. On the gunnery ranges of Fort Huachuca in southeastern Arizona, study sites were established to examine the effects of fire frequency on soil biogeochemistry, plant biochemistry, and δ¹³C values in soil organic matter (SOM). The sites were on homogeneous granitic alluvium where wildfire frequency history is known from 1973 to present and no cattle grazing has occurred in recent decades. Subplots represent fire frequencies of no burns, 3 fires per decade, and 5 fires per decade. The "no burn" plot has abundant C3 Prosopis velentina (mesquite) trees, whereas the burned plots are open C4-dominated grasslands with scattered mesquite trees. Prosopis trees have altered SOM pools by the concentration of plant nutrients and the addition of isotopically light shrub litter. Frequent fires have altered the basic geochemistry and nutrient availabilities of the soil, and the changes appear to be significant enough to affect plant growth. Soil pH increases with burning frequency, and TOC, total nitrogen, and plant-available phosphorus show significant increases on the infrequently burned plot. Burning is advantageous for preservation or restoration of grasslands, as total living grass biomass is greater on the two burned plots. Root biomass 11 is significantly lower on the "frequently burned" plot. Concentrations of the key nutrients nitrogen and phosphorus are reduced in plants on the burned sites compared to plants on the unburned site. Fires help re-distribute nutrients but evidence of nutrient concentrations and δ¹³C values are retained in SOM for many decades. Estimates of bulk carbon turnover rates range from 112 to 504 years. Evidence for modern C3 shrub expansion is found in the shift of SOM δ¹³C values from values characteristic of C4 grasses to C3 shrubs in surface soil layers. δ¹³CSOM values indicate that the Holocene and Late Pleistocene were dominated by C4 grasslands, and the pre-Late Pleistocene vegetation was a C4-grass savanna with abundant C3 plants.
32
Laubscher, Sydney. "MANGANESE UPTAKE IN RED MAPLE TREES IN RESPONSE TO MINERAL DISSOLUTION RATES IN SOIL." Kent State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=kent1574431912056187.
Full text
33
Royer, Sarah-Jeanne. "Links Between Dimethylated Sulfur and Phytoplankton Photophysiology in the Surface Ocean Geographical Paterns and Short-Term Variability = Relación entre el Dimetilsulfuro y la Fotofsiología del Fitoplancton en la Superfcie del Océano. Patrones Geográfcos y Variabilidad a Corto Plazo." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/336378.
Full textAbstract:
Dimethylsulfide (DMS) and its algal metabolite precursor, dimethylsulfoproprionate (DMSP), are major players in the oceanic and atmospheric sulfur cycle. DMS is the most abundant volatile organic sulfur compound in the upper ocean and its global emission accounts ca. 28 Tg S per year, thus representing the main natural source of sulfur to the troposphere and about 30% of the global (including anthropogenic) sulfur emissions. DMS cycle has been the subject of hundreds of studies over the last 27 years because of its hypothesized role in climate regulation (CLAW hypothesis), where it has been postulated to regulate the number of cloud condensation nuclei over the oceans and hence reduce the total amount of solar radiation reaching the Earth's surface. However, this simplistic view has not been proven so far as the relationship between oceanic DMS concentrations and solar radiation is complex and involves several different actors. Both DMS and DMSP (hereafter referred together as DMS(P)) concentrations are variable in the surface ocean and physics, chemistry and biology in the photic upper layer all play important roles in their cycling, from DMSP biosynthesis to DMS ventilation, with their relative importance varying amongst the diversity of biomes and pelagic ecosystem settings encountered in the world's oceans. Hence, predicting DMS at a global scale needs an intricate understanding of processes affecting its cycle at all temporal and spatial scales. The premise of the thesis is to contribute to a better understanding of the different physical, chemical and biological drivers that shape the DMS(P) cycle in polar, tropical and sub- tropical oceanic environments from very short to longer term temporal scales. This work combines an extensive database of DMS measured at low and high frequency, in different regions and across environmental gradients, and at temporal scales that span from minutes to seasons. In the short term (minutes to hours) , exposure to UVR seems to play an important role in the physiological response of phytoplankton cells and DMS(P) production. Solar radiation also dictates the pace of variability in DMS concentration over diel (day-night) cycles, where DMS seems to be surprisingly coupled to photobiological clocks. However, while gross biological DMS production generally increases with light exposure, concentration depends on the net effect of production and losses by photolysis, microbial consumption and ventilation. As a result, no single pattern for diel DMS oscillations is valid for the global oceans. Extensive data gathering across many biogeographical provinces in the tropical and subtropical oceans confirmed that DMS distribution is better explained by abiotic factors (solar radiation, vertical mixing, light absorption by organic matter) and phytoplankton physiology (efficiency of photosystem II) than by indicators of plankton abundance and general activity. Our work also shows that inferences about the causes of the variability of DMS depend on the frequency of the data collection. During a circumnavigation cruise, data collected at low frequency translated into relatively low variation factor (5.1) within individual biogeochemical provinces. In contrast, high frequency data revealed much higher variation factor (96) because of the capture of sub-mesoscale variability. Statistical work on high frequency data showed that critical variability distances for DMS average 15 and 50 km for coastal and open ocean marine provinces, respectively. DMS distribution patchiness increases with productivity and latitude, with important implication for designing fieldwork and computational mapping of DMS concentration and emissions. Overall, this thesis sheds light on the complex interplay of physical, chemical and biological variables in the DMS cycle and emphasizes the difficulty of finding simple environmental drivers of quantitative applicability at global scales.El dimetilsulfur (DMS) i el seu precursor algal dimetilsulfoniopropionat (DMSP) són part fonamental del cicle del sofre als oceans i l’atmosfera. El DMS és el compost volàtil de sofre més abundant a l’oceà superficial, que n’emet a l’atmosfera una quantitat aproximada de 28 Tg S l’any. Això representa la principal font natural de sofre a la troposfera, i aproximadament un terç de l’emissió global de sofre, incloent-hi l’antropogènica. El cicle del DMS ha estat objecte de centenars d’estudis en els darrers 27 anys, motivats sobretot per la hipòtesi CLAW que proposava que el DMS és la principal font de nuclis de condensació de núvols sobre els oceans i, d’aquesta manera, ajuda a regular la quantitat de radiació solar que arriba a la superfície de la Terra i, de retruc, el clima. Aquesta hipòtesi, avui vista com a simplista, no s’ha arribat a provar totalment, sobretot perquè la relació entre radiació solar i concentració i emissió de DMS és complexa i hi intervenen múltiples factors. Tant la concentració del DMS com la del DMSP (que referim conjuntament com a DMS(P)) varien força en l’oceà superficial com a resultat de processos que van de la biosíntesi del DMSP a la ventilació del DMS. Aquests processos, a la vegada, responen a factors i actors físics, químics i biològics, la importància relativa dels quals varia entre biomes i configuracions de l’ecosistema pelàgic. Com a conseqüència, predir la distribució del DMS a escala global demana un coneixement profund de tots els processos implicats, a totes les escales temporals i espacials. L’objectiu general de la tesi és contribuir a conèixer millor els factors físics, químics i biològics que governen el cicle dels DMS(P) en aigües polars, subtropicals i tropicals a escales temporals molt diverses. El treball combina una base de dades extensa de mesures de DMS obtingudes a baixa i alta freqüència, en regions diverses, a través de gradients ambientals, i d’escales de temps que van des dels minuts fins a les estacions de l’any. A més curt termini (minuts a hores), l’exposició a la llum UV sembla jugar un paper important en la resposta fisiològica del fitoplàncton i la subseqüent producció de DMS(P). La radiació solar també dicta el ritme de variació de la concentració de DMS en cicles dia-nit, en què el DMS es mostra sorprenentment acoblat amb els rellotges fotobiològics. Tanmateix, malgrat que la producció biològical bruta de DMS generalment augmenta amb l’exposició a la llum, la concentració depèn de l’efecte net d’aquesta producció amb les pèrdues per fotòlisi, consum microbià i ventilació. Al capdavall, no sembla que hom pugui definir un patró d’oscil·lació dia-nit únic per al DMS a l’oceà global. L’obtenció de dades en moltes províncies oceàniques tropicals i subtropicals va confirmar que la distribució del DMS s’explica millor amb factors abiòtics tals com la radiació solar, la barreja vertical, l’absorció de la llum per la matèria orgànica, i també per factors de fisiologia de fitoplàncton, com l’eficiència del fotosistema II, més que amb els indicadors d’abundància i activitat general del plàncton. El treball mostra també que les inferències que hom pugui fer sobre les causes de variabilitat de la concentració del DMS depenen força de la freqüència d’observació. En una campanya de circumnavegació, les mesures fetes a baixa freqüència mostraven, per a una província donada, una amplitud de variació d’un factor de 5. En la mateixa província, les mesures d’alta freqüència mostraven una amplitud d’un factor de 96, perquè capturaven la variabilitat de mesoescala i submesoescala. L’anàlisi estadística de les dades d’alta freqüència va mostrar que les distàncies de variabilitat crítiques per al DMS eren de 15 i 50 km per aigües més costaneres i més oceàniques, respectivament. Les distàncies d’heterogeneïtat en la distribució del DMS es fan més curtes amb la latitud i com més productives són les aigües. Això té implicacions importants en el disseny de treball de camp i en els esforços de ‘mapejat’ computacional. En conjunt, la tesi aporta llum a la complexitat de les interaccions que intervenen en el cicle del DMS, i ressalta la dificultat de trobar una relació simple que permeti predir la concentració i emissió del DMS en qualsevol punt de l’oceà global a partir de variables ambientals conegudes.
34
Frederick, Hannah E. "A GEOCHEMICAL EVALUATION OF WEATHERING PROCESSES AND METAL UPTAKE BY VEGETATION IN COAL MINE SPOIL." Kent State University Honors College / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ksuhonors1494443548705579.
Full text
35
Chaudhry, Tariq M. "Biogeochemical characterization of metalliferous wastes and potential role of arbuscular mycorrhizae in their phytoremediation /." Campbelltown, N.S.W. : University of Western Sydney, Macarthur, Faculty of Informatics, Science and Technology, 1999. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030811.122338/index.html.
Full text
36
Bottoms, Richard M. "Grass-knapweed interference involves allelopathic factors associated with ecosystem mineral cycling /." free to MU campus, to others for purchase, 2001. http://wwwlib.umi.com/cr/mo/fullcit?p3036807.
Full text
37
Conley, Gary D. "Examining the Cover and Composition of the Successional Vegetation Mosaic of Pre-SMCRA Mined Landscapes in Southeast Ohio." Ohio University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1357751096.
Full text
38
Reimer, Adam. "The role of bog plants in the exchange of carbon dioxide and water between the atmosphere and the Mer Bleue peatland /." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33829.
Full textAbstract:
The exchange of carbon and water between a temperate peatland and the atmosphere was studied directly for the vascular plants; Chamaedaphne calyculata, Kalmia angustifolia, Vaccinium myrtilloides, and Maianthemum trifolium and indirectly for the bryophytes; Sphagnum rubellum and S. magellanicum. In vascular plants, carbon and water fluxes were well coupled (∼2.27 mumol CO 2 mmol-1 H2O) except in the post-deciduous period where temperature constrained water flux more than carbon flux. The seasonal cycle of Sphagnum water content was driven by water table depth; rain depth, rain frequency and atmospheric vapor pressure deficit. In 2000, these factors combined to cause primarily over saturation with regard to optimal net photosynthesis in Sphagnum. Carbon and water exchange at the community scale was also studied and related to the leaf level patterns observed. Few leaf level patterns were observable at the community scale although the effects of species composition and leaf area index were well represented in the community signal.
39
Powell, Christina Lynn. "Biodegradation of Groundwater Pollutants (Chlorinated Hydrocarbons) in Vegetated Wetlands: Role of Aerobic Microbes Naturally Associated with Roots of Common Plants." Wright State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=wright1289918991.
Full text
40
Lardy-Fontan, Sophie. "Les substances émergentes dans les écosystèmes aquatiques français : une application aux alkylphénol-polyéthoxylés et aux substances pharmaceutiques." Thesis, Bordeaux 1, 2008. http://www.theses.fr/2008BOR13702/document.
Full textAbstract:
Les alkylphénol-polyéthoxylés et les substances pharmaceutiques appartiennent à la classe des contaminants émergents qui sont depuis peu étudiés dans les milieux naturels. Ces composés d’usage très répandu (aussi bien en termes d’applications qu’en termes de quantité) sont introduits dans le milieu aquatique, via les stations d’épuration, principalement et sont susceptibles d’engendrer des effets toxiques sur les organismes vivants dans ces milieux. La première partie de ce travail de thèse a consisté en le développement et la validation de différentes méthodologies d’échantillonnage (ponctuel et intégratif (POCIS)), de différents protocoles d’extraction (SPE, extraction assistée par micro-ondes) et d’analyse (CL/SM, CL/SM/SM), nécessaires pour un dosage fiable des alkylphénol-polyéthoxylés et des substances pharmaceutiques dans les différents compartiments des systèmes aquatiques (phases dissoute, particulaire et sédimentaire, organismes biologiques). Ensuite, un bilan de la contamination de différents systèmes aquatiques (le bassin de d’estuaire de Seine, la Garonne et la Gironde, la baie de la Vilaine, la baie de l’Authie, l’Adour, la rade de Marseille) a été dressé. Une contamination généralisée par ces composés a été mise en évidence pour l’ensemble des sites étudiés. Les concentrations mesurées apparaissent extrêmement variables selon la classe de molécule considérée, les sites et le temps avec des concentrations comprises entre le ng.l-1 et la dizaine de µg.l-1 pour les phases dissoutes et de la dizaine de ng.g-1 et la dizaine de µg.g-1 pour les phases solides (plusieurs centaines de µg.g-1 dans les boues d’épuration). Ces études ont également permis de documenter la présence et le devenir des molécules ciblées dans les stations d’épuration et ont permis d’en évaluer l’efficacité quant l’abattement des substances incriminées. Enfin, ces travaux ont également permis de mettre en évidence des phénomènes de partition entre les phases dissoutes et les phases solides ainsi que des phénomènes de transferts vers les organismes du milieuAlkylphenol-polyethoxylates and pharmaceutical substances belong to the class of the emerging contaminants which have been recently studied in natural environments. These compounds of very widespread use (in terms of applications as well as in terms of quantity) are introduced into the aquatic environment, via the wastewater treatment plants, mainly, and are likely to generate toxic effects on the living organisms in these systems. The first part of this work consisted in the development and validation of various methodologies of sampling (grab sampling and integrative sampling (POCIS)), of various protocols of extraction (SPE, microwaves assisted extraction) and of analysis (LC/MS, LC/MS/MS), necessary for a reliable quantification of alkylphenol-polyethoxylates and pharmaceutical substances in the various compartments of aquatic systems (phases dissolved, particulate and sedimentary, biological organisms). Then, an assessment of the contamination of numerous aquatic systems (the catchment area of the Seine estuary, the Garonne and the Gironde, the bay of Vilaine, the bay of Authie, the Adour, the Mediterranean coast of Marseilles) was undertaken. A generalized contamination by these compounds was highlighted for all the studied sites. The measured concentrations appear to be extremely variable according to the class of molecule considered, the sites and time with concentrations ranging from the ng.l-1 to tens of µg.l-1 for the dissolved phases and from tens of ng.g-1 to tens of µg.g-1 for the solid phases (several hundreds of µg.g-1 in the clarification sludge). These studies also made it possible to document the presence and the fate of these molecules in the French wastewater treatment plant and made it possible to evaluate their effectiveness to remove the studied compounds. Lastly, this work also made it possible to highlight phenomena of partition between the dissolved phases and the solid phases as well as phenomena of transfers through the biological organisms
41
Harlay, Jérôme. "Biogeochemical study of coccolithophorid blooms in the context of climate change." Doctoral thesis, Universite Libre de Bruxelles, 2009. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210352.
Full textAbstract:
Coccolithophores are unicellular microscopic algae (Haptophyta) surrounded by calcium carbonate plates that are produced during their life cycle. These species, whose contemporary contributor is Emiliania huxleyi, are mainly found in the sub-polar and temperate oceans, where they produce huge blooms visible from space. Coccolithophores are sensitive to ocean acidification that results from the ongoing accumulation of anthropogenic carbon dioxide (CO2) in the atmosphere. The response of these organisms to global change appears to be related to the reduction of their ability to produce calcium carbonate at the cellular level. At the community levels, one anticipates changes in the carbon fluxes associated to their blooms as calcification is reduced. However, the consequences of such environmental changes on this species are speculative and require improvements in the description of the mechanisms controlling the organic and inorganic carbon production and export.The first aspect of this work was to study the response of these organisms to artificially modified CO2 concentrations representative of the conditions occurring in the past (glacial) and those expected by the end of the century (2100). Two different levels were examined: the continuous monospecific cultures (chemostats) allowed us to work at the cellular level while the mesocosms gave light to the mechanisms taking place in an isolated fraction of the natural community. The second aspect of this work consisted of field studies carried out during four cruises (2002, 2003, 2004 and 2006) in the northern Bay of Biscay, where the occurrence of E. huxleyi blooms were observed in late spring and early summer. We describe the vertical profiles of biogeochemical variables (nutrients, chlorophyll-a, dissolved inorganic chemistry, particulate carbon, transparent exopolymer particles (TEP)) and study processes such as primary production, calcification and bacterial production. The properties of these blooms are compared with those reported in the literature and enriched with original measurements such as the abundance and concentration of TEP that could play an important role in carbon export to the deep ocean, modifying the properties of the settling ballasted aggregates.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
42
Wang, Lixin. "Soil biogeochemistry, aridity and plant adaptation responses in southern Africa savannas." 2008. http://wwwlib.umi.com/dissertations/fullcit/3362902.
Full text
43
Kantola, Ilsa Beth. "Biogeochemistry of Woody Plant Invasion: Phosphorus Cycling and Microbial Community Composition." Thesis, 2012. http://hdl.handle.net/1969.1/ETD-TAMU-2012-05-11030.
Full textAbstract:
Woody plant encroachment is a globally-prevalent vegetation change phenomenon that has shifted grass-dominated ecosystems to mixed grass and woody plant matrices over the last century. In the Rio Grande Plains of Texas, the introduction of N-fixing woody legumes has increased above- and belowground primary productivity and changed the litter chemistry of the system, accelerating rates of belowground biogeochemical processes. The purpose of this study was to assess the impact of grassland to woodland transition on i) P concentrations in soil physical fractions that differ in their organic matter turnover rates, ii) P availability within the soil over the course of woody encroachment and across the landscape, and iii) microbial community composition and diversity. Soil samples were collected in remnant grasslands and four woody landscape elements (clusters, groves, drainage woodlands, and playas) along a 135-yr chronosequence of woody plant encroachment. P was fractionated by the Hedley method and P concentrations were determined by alkaline oxidation and lithium fusion coupled with ascorbic acid colorimetry. Bacterial and fungal communities were characterized by molecular methods. Whole soil P concentrations were 2-5X greater in woody landscape elements than in grasslands, and nutrient concentrations increased linearly with time following woody plant invasion in all but the slowest-cycling physical fractions. Plant-available P and organic P increased dramatically with time following encroachment. Changes in P availability were more pronounced in drainages and playas than in upland clusters and groves. Analysis of the bacterial and fungal communities demonstrated that microbial communities in grasslands differ at both phylum and genus level from the flora of the wooded landscape elements. This study demonstrates that woody encroachment strongly influences the distribution and availability of soil P and indicates that nutrient cycles in the soil are closely linked and similarly affected by increased woody plant abundance. Microbial communities under woody species differ in composition from those of the grasslands, and are likely contributing to the observed changes in nutrient availability. Since N and P are generally the most limiting nutrients in terrestrial ecosystems, increased stores of P are likely to alter rates of microbial processes, plant-microbe and plant-plant interactions, and successional dynamics in this ecosystem and similar landscapes around the world.
44
"Denitrification in Accidental Urban Wetlands: Exploring the Roles of Water Flows and Plant Patches." Doctoral diss., 2016. http://hdl.handle.net/2286/R.I.40731.
Full textAbstract:
abstract: Cities can be sources of nitrate to downstream ecosystems resulting in eutrophication, harmful algal blooms, and hypoxia that can have negative impacts on economies and human health. One potential solution to this problem is to increase nitrate removal in cities by providing locations where denitrification¬— a microbial process in which nitrate is reduced to N2 gas permanently removing nitrate from systems— can occur. Accidental urban wetlands– wetlands that results from human activities, but are not designed or managed for any specific outcome¬– are one such feature in the urban landscape that could help mitigate nitrate pollution through denitrification.
The overarching question of this dissertation is: how do hydrology, soil conditions, and plant patches affect patterns of denitrification in accidental urban wetlands? To answer this question, I took a three-pronged approach using a combination of field and greenhouse studies. First, I examined drivers of broad patterns of denitrification in accidental urban wetlands. Second, I used a field study to test if plant traits influence denitrification indirectly by modifying soil resources. Finally, I examined how species richness and interactions between species influence nitrate retention and patterns of denitrification using both a field study and greenhouse experiment.
Hydroperiod of accidental urban wetlands mediated patterns of denitrification in response to monsoon floods and plant patches. Specifically, ephemeral wetlands had patterns of denitrification that were largely unexplained by monsoon floods or plant patches, which are common drivers of patterns of denitrification in non-urban wetlands. Several plant traits including belowground biomass, above- and belowground tissue chemistry and rooting depth influenced denitrification indirectly by changing soil organic matter or soil nitrate. However, several other plant traits also had significant direct relationships with denitrification, (i.e. not through the hypothesized indirect relationships through soil organic matter or soil nitrate). This means these plant traits were affecting another aspect of soil conditions not included in the analysis, highlighting the need to improve our understanding of how plant traits influence denitrification. Finally, increasing species richness did not increase nitrate retention or denitrification, but rather individual species had the greatest effects on nitrate retention and denitrification.Dissertation/Thesis
Doctoral Dissertation Biology 2016
45
Prater, Margaret Rose. "Ecosystem consequences of post-fire invasive species in the Great Basin Desert /." 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3223695.
Full textAbstract:
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006.Source: Dissertation Abstracts International, Volume: 67-07, Section: B, page: 3556. Adviser: Evan DeLucia. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.
46
Sutton-Grier, Ariana E. "The Role of Plant Functional Diversity and Soil Amendments in Regulating Plant Biomass and Soil Biogeochemistry in Restored Wetland Ecosystems in the North Carolina Piedmont." Diss., 2008. http://hdl.handle.net/10161/620.
Full text
47
Willis, Cylette Raucene. "Intervarietal differences of methane emission related to plant parameters in irrigated rice cultivation." Thesis, 1995. http://hdl.handle.net/1911/16898.
Full textAbstract:
Field and laboratory experiments were conducted with the following ten cultivars of rice: Lebonnet, Lemont, Dawn, Katy, Della, IR36, Mars, Brazos, Labelle and Jasmine. For each variety, components of biomass, root porosity and methane emission were observed throughout the entire growing season and yield was determined at harvest. Methane emission differed among cultivars by as much as a factor of 2.4 and resulted in two distinct emission groups. Significant differences were also found for biomass among cultivars, although these differences did not coincide with the differences that were observed for emission among cultivars. Methane emission correlated strongly with aboveground live vegetative biomass within most varieties until heading and among cultivars within emission groups to heading. Emissions showed less correlation with biomass during ripening and may have been affected by other factors within the system at this time. Methane emission appeared to be consistently proportional to grain production among cultivars, when determined per gram biomass, and may be related through processes of carbohydrate partitioning. Root porosity did not appear to be associated with observed differences or trends in methane emission.
48
Prager, Case Mahone. "Plant diversity, physiology, and function in the face of global change." Thesis, 2017. https://doi.org/10.7916/D8K361M3.
Full textAbstract:
One central goal in ecology is to understand how biodiversity, and key organismal traits, interact with ecosystem properties and processes, and ultimately to understand and predict how these interactions will be affected by rapid environmental change. Thus, global change experiments and observational gradients in diversity provide the opportunity to examine and test hypotheses about how organismal traits, multiple dimensions of biodiversity, and ecosystem function will respond to environmental change. In Arctic tundra, increased nitrogen (N) and phosphorus (P) availability accompanying rapid warming is thought to significantly alter plant community composition and ecosystem function. The following four chapters examine hypotheses about the responses of species’ traits, multiple dimensions of biodiversity, and ecosystem function to the effects Arctic warming. Chapter 1 examines plant community composition and the capacity for ecosystem function (net ecosystem exchange, ecosystem respiration, and gross primary production) across a gradient of experimental N and P addition expected to more closely approximate warming-induced fertilization, demonstrating declines in plant diversity and an increase in the capacity for ecosystem carbon uptake at the highest level of fertilization. Chapter 2 examines a set of physiological and functional leaf traits across the same N and P gradient in order to evaluate the possible physiological mechanisms underlying community and ecosystem responses, highlighting the effects of increasing nutrient availability for deciduous shrub species. Chapter 3 found that single-dose, long-term nutrient addition (i.e., > 20 years) led to significant declines in multiple dimensions of diversity (taxonomic, functional and phylogenetic), and that these effects persist through time, increasing for dimensions that capture organismal traits (functional and phylogenetic). Finally, Chapter 4 examined the relationship between multidimensional diversity and ecosystem function across a natural gradient of diversity, and found that taxonomic diversity and functional diversity were significantly and positively related to whole ecosystem productivity, and, conversely, functional evenness and dispersion were significantly and negatively related to ecosystem productivity. Cumulatively, these four chapters advance our understanding of the connections between communities and ecosystems in a rapidly changing ecosystem.
49
Sorensen, Patrick. "Effects of winter snowpack on microbial activity, community composition, and plant-microbe interactions in mixed-hardwood temperate forests." Thesis, 2016. https://hdl.handle.net/2144/19576.
Full textAbstract:
Mean winter air temperatures have risen by 2.5˚C over the last 50 years in the northeastern U.S., reducing mean annual winter snowpack depth by 26 cm and the duration of winter snow cover by four days per decade. Because snow cover insulates soil from below-freezing air temperatures, continued declines in snowpack depth are projected to be accompanied by colder winter soil temperatures and more frequent soil freeze-thaw events. Soil bacteria and fungi will play a significant role in the forest ecosystem response to snowpack loss because they are the primary agents that carry out soil organic matter decomposition and soil nutrient cycling. Additionally, the effect of winter snowpack decline on soil bacterial and fungal communities may act indirectly via winter climate change effects on plant roots. The objectives of my dissertation research were to first determine the effect that reductions in winter snow cover has on microbial exoenzyme activity, microbial respiration, net nitrogen (N) mineralization, and net nitrification rates in two mixed-hardwood forests (Harvard Forest, MA and Hubbard Brook Experimental Forest, NH). Additionally, I sought to determine the relative role that abiotic factors (i.e., winter snow cover or soil frost) versus biotic factors (i.e., altered root-microbe interactions) contribute to overall changes in soil biogeochemical processes as winter snow cover declines. I found that winter snow depth and duration are related positively to microbial exoenzyme activity and microbial respiration following snowmelt in spring, but this relationship is transient and attenuates into the growing season. By contrast, soil freeze-thaw events during winter result in persistent declines in microbial oxidative enzyme activity that are not compensated for by warming soils during the growing season. Together, these results suggest that loss of winter snow cover will result in lower rates of nutrient cycling in northeastern U.S. hardwood forests. Tree roots interact with winter snow depth to affect net mineralization and nitrification rates, as well as bacterial and fungal community composition. Thus, winter climate change portends a reorganization of root-microbe interactions with important consequences for soil biogeochemical cycling in mixed hardwood forests of the northeastern U.S.
50
DeMeester, Julie E. "FEEDBACKS of NITROGEN CYCLING and INVASION with the NON-NATIVE PLANT, MICROSTEGIUM VIMINEUM, in RIPARIAN WETLANDS." Diss., 2009. http://hdl.handle.net/10161/1129.
Full textAbstract:
Invasive species are rapidly expanding in riparian wetlands while concurrently anthropogenic causes are increasing nitrogen (N) into these ecosystems.
To learn how
Last, we disturbed a floodplain similar to wetland restoration disturbance and tracked available N. We also established a native community of plants with and without
Dissertation