Dissertations / Theses on the topic 'Biotic and abiotc'

With the predicted climate change and an ever-growing population there is increasing pressure to develop crop plants with improved stress responses, increased yield and high nutritive value. We have explored transcriptomic changes in the leaves and roots of rice plants (Oryza sativa japonica cv Nipponbare) in response to drought and the root-knot nematode Meloidogyne graminicola. A glasshouse model was developed to mimic conditions experienced by rice plants in the field. The plant responses under simultaneous biotic and abiotic stress were dominated by the drought element accompanied by a unique set of genes that were only responsive to the simultaneous stress. Highlighted within this group were novel members of stress-responsive gene families for example cytochrome P450, wall-associated kinases, lipid transfer proteinlike proteins and new candidate genes that may play important roles in the response of rice to multiple stresses. The genes that were differentially regulated between the multiple and the drought stress treatment were explored using loss-of-function mutants. The loss-of-function mutant for peroxidase precursor gene (per) showed improved growth and yield compared to the wildtype Nipponbare plants. The experiments conducted in growth rooms were validated in a field study. Both Nipponbare rice plants, and the popular lowland indica rice cv IR64 were grown under prolonged vegetative drought stress accompanied by cyst nematode or root-knot nematode infection. Reduction of phytate, an anti-nutrient, has been adopted as a major strategy to improve the nutritional value of crop plants. Nematode susceptibility of low phytate Arabidopsis plants was studied to determine the effect of reduced phytate content on the plant’s defence response. The study has provided insight into the genome-wide transcriptional changes in rice under a combined biotic and abiotic stress. It has led to better understanding of the stress responses in plants that will be advantageous in developing crop varieties with improved yield and nutritive value.

Roots and their associated mycorrhizal fungi have long been recognised as major determinants of nutrient cycling. Their measurement has been limited because soil limits accessibility. The use of in-situ camera techniques in conjunction with minirhizotrons and image analysis software now make the acquisition of accurate root longevity data possible. The current literature was reviewed in relation to root longevity - both measurement techniques and available data. Four main experiments were employed to study the root longevity of a number of tree species, grass and clover subject to differing environmental conditions and grass and clover and poplar roots with and without colonisation by Arbuscular Mycorrhizal fungi. The data was analysed in a number of different ways including the use of the powerful statistical technique for censored data - survival analysis. This technique proved to be very useful for analysing temporal changes to root longevity. The data indicate that root longevity can be extremely short but is dependent upon environment and for some species, colonisation by Arbuscular Mycorrhizal fungi. Preliminary calculations were completed to determine the role of root death in nutrient cycling and these predict that large quantities of nitrogen, phosphorus and carbon are flowing from the live to the dead root pool on an annual basis.

Many ecological communities show variation from place to place; understanding the causes of this variation is the goal of community ecology. Differences in community composition will be the result of both stochastic and deterministic processes. However, it is difficult to know to what degree deterministic processes will shape community composition. In this thesis I combined observational and experimental approaches to quantify deterministic processes within a particular ecological community -- they phytotelmata of bromeliad plants. In my thesis I describe three studies at different scales of organization: 1) do organisms of different size respond equally to changes in their environment 2) how do predators interact to influence prey survival 3) what mechanisms underly the response of similar species to the same environmental gradient, bromeliad size. In Chapter 1, I tested an hypothesis developed from previous observational data -- that smaller organisms respond less than larger ones to the same environmental gradient -- different bromeliad species that occur under different forest canopies. After removing variation caused by dispersal, I found that environmental variation explained little variation for bacteria, more for zooplankton and most of all for macroinvertebrates. In my second chapter, I examined ecological determinism on a smaller scale -- within a single trophic level (macroinvertebrate predators). I found that predators may interfere with each other, reducing predation rates and increasing prey survival. In Chapter 3, I examine macroinvertebrate responses to bromeliad volume. I use both null models and a field experiment to show that for at least one such pair, a difference in abiotic tolerances may be the plausible mechanism. Together these results illustrate when, and to what degree, bromeliad communities respond to deterministic factors. All three chapters first demonstrate a pattern, testing it against a suitable null distribution, before attempting to quantify possible mechanisms with a field experiment. This combination of observation and experiment is an approach which can contribute to our understanding of how ecological systems work.
Science, Faculty of
Graduate

One central question in ecology is why some areas have many species and others have few. Many explanations have been proposed and often the forces that drive species richness are context-dependent. These forces are divided into two general categories: biotic drivers and abiotic drivers. Biotic drivers are most commonly described in terms as top-down and bottom-up effects while abiotic drivers are commonly described in terms of climate and habitat disturbance. The objective of this thesis is to determine how these drivers affect species richness in terrestrial ecosystems. To test this I examine an insect herbivore assemblage in a disturbed forest fragment landscape in southern Canada. I use geographic information systems techniques to determine the impact of a natural episodic disturbance (i.e. an abiotic natural driver) and a chronic human disturbance (i.e. an abiotic human driver) on forest habitat quality (Chapter 1) and on a forest-dwelling caterpillar assemblage (Chapter 2). I show that ice storms result in a heterogeneous pattern of spatial damage across a forest landscape, differing depending on the type of coarse woody debris examined. These different types of coarse woody debris provide habitat for a diversity of taxa. In contrast with natural disturbance, I found that human-based disturbance do not have a positive impact on caterpillar assemblages. Pursuant to this, I explore the concept of habitat quality from the perspective of host plant identity (Chapter 3) and host plant quality (Chapter 4). I found that caterpillar assemblages have strong host plant preferences and that these preferences may depend on quadrat-scale foliar qualities (i.e. a biotic bottom-up driver) and parasitoid densities (i.e. a biotic top-down driver) at different times in the growing season. This thesis adds to a growing body of literature aimed to better understand the drivers of insect species richness across disturbed landscapes. In addition, this thesis develops several management-specific tools for measuring forest disturbance and provides valuable insight into how the selection of different tree species for planting initiatives can have important impacts on forest communities.
Les communautés forestières qui habitent les parcelles de forêts qui subsistent aujourd'hui sont affectées par les perturbations ainsi que par la qualité de l'habitat que leur procure les plantes-hôtes. Ces deux phénomènes ont un impact particulièrement important dans les paysages modifiés par l'activité humaine. Développer une meilleure compréhension de ces phénomènes va faciliter la prise de décision et les efforts de conservations visant à préserver et protéger la biodiversité des forêts. L'objectif global de cette thèse est d'étudier les divers aspects reliés à la qualité de l'habitat dans les parcelles forestières des collines montérégiennes du sud-est du Québec, Canada. J'utilise des techniques en système d'information géographique pour déterminer l'impact d'une perturbation naturelle épisodique (tempête de verglas) ainsi qu'une perturbation anthropogénique chronique (sentiers récréationnels) sur la qualité des habitats forestiers (Chapitre 1) et un assemblage de chenilles vivant en forêt (Chapitre 2). J'ai démontré que les dégâts engendrés par les tempêtes de verglas sont distribués de façon hétérogène à travers le paysage forestier, différant selon le type de débris ligneux grossiers examiné. Ces différents types de débris ligneux grossiers servent d'habitat à divers groupes taxonomiques. J'ai découvert que les perturbations anthropogéniques, au contraire des perturbations naturelles, n'ont pas eu d'impacts positifs sur les assemblages de chenilles vivants en forêt. J'ai également exploré le concept de qualité d'habitat en considérant l'identité de la plante hôte (Chapitre 3) et la qualité foliaire à l'échelle du quadrat (Chapitre 4). J'ai découvert que l'assemblage de chenille démontre des préférences marquées pour certaines plantes hôtes et que ces préférences peuvent dépendre de différentes qualités foliaires à l'échelle du quadrat à différentes périodes durant la saison de croissance. Cette thèse contribue à la documentation croissante sur les facteurs qui affectent la richesse spécifique des communautés d'insectes vivant dans les forêts des paysages perturbés. De plus, cette thèse propose plusieurs outils spécifiques à la gestion pour évaluer les perturbations en milieu forestier et donne un aperçu de l'impact que peut avoir la sélection de différentes espèces d'arbres sur les communautés forestières lors de l'élaboration d'initiatives de plantation d'arbres.

Over half of the carbon (C) taking part in the global C cycle is held in terrestrial systems. Because of the sensitivity of the C cycle to changes in such soil-based pools of carbon, it is important to understand the basic mechanisms by which soil C is stored and cycled between the range of di erent pools which occur belowground. In the context of climate change mitigation, it is considered that increasing soil-based stocks of C, either by reducing losses from soils, or by actively sequestering new carbon, is a potentially important strategy . Organic carbon is the main form of carbon in soil and as such has received most focus. Cont/d.

Plants are continuously exposed to different abiotic and biotic stresses in their natural environment. Their capacity to survive depends on the capacity to perceive external signal and quality amount a defence response for protection from the stress perceived. The purpose of this project was to study the impact of combined abiotic stress and biotic stress on the outcome of the disease inducing Arabidopsis thaliana – Pseudomonas syringae interaction. This study included a focus on the role of ABA in these interactions and also whether 3´-O-β D- ribofuranosyl adenosine (hereafter it called ‘400’ compound), a novel adenosine derived compound induced during compatible interactions, was involved. The later involved the targetted disruption of a putative 400 biosynthetic pathway involving analysis of knockout mutants of enzymes; APD-ribose diphosphatase NAD binding / hydrolases of the NUDIX class, glucosyl transferases, ribosyltransferases, a ribose-phosphate pyrophosphokinase3 and galactosyltransferases. Unfortunately, none of these targeted interventions modified the host response to Pseudomonas infection, nor altered levels of 400 in challenged leaves. The primary research investigated the interaction between abiotic and biotic stresses in Arabidopsis plants focussing on the modulation of plant defence against multiple, and possibly antagonistic, stress responses and the role plant hormones play in this process. We showed that high light caused enhanced susceptibility to the already virulent Pseudomonas syringae DC3000pvsp61. The pathways contributing to this enhanced susceptibility were largely ABA independent. Subsequent characterization of transgenic lines expressing the soluble Arabidopsis abscisic acid receptors, PYRABACTIN RESISTANCE1-LIKE4-6 provided compelling evidence for a role for these receptors in DC3000 virulence strategies, but they contribute to a lesser extent to the enhanced susceptibility under high light. This was corroborated genetically by using mutants of the immediately downstream targets of PYLs, the type two protein phosphatase, specifically the triple mutant hab1-1/abi2-1/abi1-2. A number of epitope and fluorescent constructs were generated to facilitate future studies of the role of ABA signaling. Targetted profiling suggested that SA dynamics were altered under DC3000 challenged Arabidopsis grown under high light. Furthermore, differential accumulation of flavonoids suggested these may also play a role in attenuating host defences under high light. Finally we provide evidence based on comparative analysis of that the photoreceptors phytochrome double mutant phyA-211/phyB-9 and cry1/cry2 behave antagonistically in Arabidopsis response to DC3000. Overall our studies support the conclusion that plants abiotic stress (HL) response takes precedence over biotic stress (DC3000) responses and that abiotic stress is detrimental to plant immunity. The luciferase transgenic PYL lines showed high level of expression of ClucP::PYL5 plant tissues challenged 2hpi of DC3000 (OD600: 0.15) in comparison with C1lucP::PYL6. This result opposes to what RT-PCR reported; which was that three PYLs genes display similar expression level at 6hpi of hrpA or 18hpi of DC3000. The epitope tags of CaMV::HA transgenic plants showed HA-tagged signal with stunted phenotype in a range of PYL4, 5 and 6 plants but none of the plants displayed any differences in susceptibility to DC3000. Although, RT-PCR assay showed high levels of expression in the three PYLs, 6hpi of hrpA but no signal was detected in B8eGFP::PYL5 transgenic line either followed the DC3000 and hrpA infection or by examined plant seedlings at early stages under confocal microscopy.

When active venting has ceased, reduced minerals in hydrothermal mounds and sediments continue to provide an inorganic energy source for chemolithotrophic microbes. This research focuses on the nature of microbially-mediated metal transformations in hydrothermal sediments during sulphide alteration and their impact on the ultimate fate of hydrothermal sulphides on the seafloor. The core studied is more seawater altered than other cores studied at TAG and provides an insight into the bacterial and archaeal communities as well as the geochemical processes taking place in highly altered metalliferous sediments. This study combines geochemical approaches with microbiological and organic biomarker measurements within the suboxic transition zone of sulphidic sediments to characterise the reactions and microbial communities present. This integrated approach demonstrates that (a) there is biogeochemical zonation within the sediment sequence with distinct microbial communities present at the sulphide-oxic seawater transition, (b) the microbes identified are associated with Fe and S redox cycling, (c) Marinobacter sp. are dominant at the sulphide interface. There is a significant shift in the microbiological community across the redox transition zone in these sulphidic sediments. The microbial assemblage of the suboxic transition zone is dominated by Bacillus sp. which are microaerophilic whereas the sulphide layer assemblage is dominated by Marinobacter sp. which are Fe oxidisers. Based on biomarker assemblages and genetic analyses, archaeal (and to a certain degree bacterial) communities are comparable to other hydrothermal settings despite the low biomass present. Processes inferred to be important in this sediment include the S, Fe and N cycle, all potentially coupled to the release and uptake of a range of transition metals. Significant recycling of redox active species occurs in the suboxic transition zones present in the sediment core. Uranium concentrations are low compared with other less altered sulphidic hydrothermal sediments, and U is associated with the upper regions of the suboxic transition zone and is associated with enrichment of a suite of other transition metals (e.g. Cu, Mo, As and V). Massive electrodes were constructed from CuFeS2 (from Ireland and TAG) and FeS2 (from TAG) and studied in oxygenated artificial seawater under circumneutral conditions using electrochemical methods. The results can be explained by existing hypotheses about pyrite and chalcopyrite oxidation and their oxidation products. The oxidation status of Cu in covellite could be identified as Cu+1. Impurities found (as expected because natural samples were used) have no effect on the electrochemical behaviour of the electrodes. The impact of Marinobacter sp. on sulphide alteration was studied in detail using an electrochemical approach. The results demonstrate that Marinobacter aquaeolei enhances the rates of oxidation. Marinobacter species seem to be of special importance for weathering reactions on the seafloor and in hydrothermal settings like the TAG area.

In Arabidopsis thaliana, eight histidine kinases (HKs) have been identified which function in hormone signalling, stimuli perception, and plant development. To better elucidate HK roles in signalling, the function of the least characterised HK, AHK5, in stress tolerance was investigated using a T-DNA insertion knockout line (ahk5-1). Reduced inhibition of seedling root growth was seen in ahk5-1 in response to salinity when compared to wild-type Col-0 in tissue culture assays. In mature plants, ahk5-1 showed greater fresh weight gain under either salinity or drought stress. Loss of AHK5 function did not alter cold stress tolerance, nor basal and acquired heat stress tolerance in terms of seedling root elongation. Infection with the biotrophic pathogen Pseudomonas syringae pv. tomato DC3000 revealed ahk5-1 is compromised in disease resistance, exhibiting increased chlorosis and in planta bacterial growth. Levels of the plant hormones salicylic acid, jasmonic acid, and abscisic acid, alongside the bacterial phytotoxin coronatine, were lower in pathogen challenged ahk5-1 mutants compared to wild-type plants. The ahk5-1 mutant was also more susceptible to the necrotrophic pathogen Botrytis cinerea, supporting more fungal growth and displaying accelerated symptom development. Hydrogen peroxide production has been linked with both resistance and susceptibility towards B. cinerea; in ahk5-1, 3,3-diaminobenzidene (DAB) staining suggested reduced hydrogen peroxide production in response to infection. Complementation and expression of AHK5 with either full-length genomic AHK5 under the 35S CaMV promoter or full-length AHK5 cDNA under the native promoter rescued the ahk5-1 mutant stress response phenotypes. In summary, AHK5 was found to negatively regulate abiotic stress tolerance whilst positively contributing towards resistance against pathogens employing different lifestyles. To begin to establish an AHK5 signalling network, tandem affinity purification coupled with LC-MS/MS was employed for identification of possible AHK5 interacting proteins. Suggestions for further optimisation of the purification method are presented. The role of AHK5 in regulation of plant stress responses through modulation of reactive oxygen species and hormone signalling and through protein-protein interactions are reviewed. Suggestions for further investigation are also discussed.

Biological invasions are a major component of global environmental change and are increasing in frequency. Most community-level impact studies of invasions are concerned with interactions between exotic and native species. However, interactions among exotic species are becoming increasingly common, potentially altering their respective impacts on invaded ecosystems. This research identifies one possible outcome of such interactions: the growing phenomenon of 'exotic species replacement', whereby a newly arriving exotic species surpasses the abundance of a functionally similar incumbent exotic species. This phenomenon is explored here using two Eurasian dreissenid bivalves that invaded the St. Lawrence River in the early 1990s, the zebra mussel (Dreissena polymorpha) and quagga mussel (D. bugensis). I review the general replacement pattern of the zebra mussel by its congener, and examine environmental factors and life history traits that mediate this replacement in a navigational canal connected to the river. Since the 1990s, quagga mussels have replaced the zebra mussel as the dominant dreissenid mussel, but the contemporary adult distribution and abundance is spatially structured: quagga mussels dominate the deep zone, while zebra mussels remain common in the shallow margins of the canal. Field surveys and in situ field experiments are used to examine the relative importance of pre-settlement, settlement and post-settlement processes, in the context of life history trade-offs and environmental gradients, in determining patterns of adult mussel distribution and abundance. Despite the potential importance of larval supply and behavior, including substrate selection at settlement, none of these processes determined adult dreissenid distribution and abundance. Rather, the main determinants were post-recruitment processes involving condition-specific competition. Adult zebra mussels generally had lower body condition, growth, shell length, and survivorship than quagga mussels, and these differences were most pronounced in the deep zone of the canal. This case highlights the importance of subtle differences in life history and abiotic tolerances among closely-related species in understanding changing patterns of distribution and abundance in an invaded community.
Les invasions biologiques sont une composante majeure des changements environnementaux au niveau mondiale et leurs fréquences continuent à augmenter. La plupart des études sur l'impact des invasions à l'échelle communautaire s'intéressent principalement aux interactions entre les espèces exotiques et indigènes. Par contre, on observe de plus en plus des interactions entre des espèces exotiques, ce qui pourrait modifier leurs impacts respectifs sur les écosystèmes envahis. Cette recherche a pour but d'examiner le 'remplacement d'espèces exotiques', un phénomène par lequel l'abondance d'une espèce exotique nouvellement arrivée surpasse l'abondance d'une espèce exotique déjà présente et dominante, qui possède également une similarité fonctionnelle. Ce phénomène est exploré ici à l'aide de deux bivalves Eurasiennes de la famille des Dreissenidés qui ont envahi le fleuve Saint-Laurent au début des années 1990, la moule zébrée (Dreissena polymorpha) et la moule quagga (D. bugensis). J'examine le schéma général de remplacement de la moule zébrée par son congénère dans un canal de navigation relié au fleuve. J'examine également les facteurs environnementaux et les traits d'histoire de vie de ces moules qui peuvent influencer se remplacement. Depuis les années 1990, la moule quagga a remplacé la moule zébrée en tant que le dreissenidé dominant. Par contre, la distribution et l'abondance contemporaines des adultes sont structurées de façon spatiale: les moules quagga dominent la zone profonde, tandis que les moules zébrées demeurent communes dans la région peu profonde du canal. Des études sur le terrain et des expériences in situ ont été utilisées pour examiner l'importance relative des processus de pré-établissement, d'établissement et de post-établissement, sur la distribution et l'abondance des moules adultes. Malgré l'importance potentielle de l'approvisionnement et du comportement larvaire, y compris la sélection du substrat durant l'établissement, aucun de ces processus ne joue un rôle important dans la détermination de l'abondance et la distribution des dreissenidés adultes. Plutôt, les principaux facteurs déterminants étaient les processus de post-recrutement impliquant la compétition mediée par l'environnement. En générale, la condition, la croissance, la longueur de coquille et la survie des moules zébrées adultes étaient inférieures à celles des moules quagga, et ces différences étaient plus prononcées dans la zone profonde du canal. Cette étude met en valeur l'importance des différences subtiles des traits d'histoire de vie et des tolérances abiotiques d'espèces étroitement liées dans la compréhension des schémas changeants de distribution et d'abondance d'individus dans les communautés envahies.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1995.
Includes bibliographical references (leaves 63-65).
by Henry Matthew Spliethoff.
M.S.

Tomato (Lycopersicon esculentum Mill., Solanum lycopersicon L.) is one of the most popular vegetable throughout the world, and the importance of its cultivation is threatened by a wide array of pathogens. In the last twenty years this plant has been successfully used as a model plant to investigate the induction of defense pathways after exposure to fungal, bacterial and abiotic molecules, showing triggering of different mechanisms of resistance. Understanding these mechanisms in order to improve crop protection is a main goal for Plant Pathology. The aim of this study was to search for general or race-specific molecules able to determine in Solanum lycopersicon immune responses attributable to the main systems of plant defense: non-host, host-specific and induced resistance. Exopolysaccharides extracted by three fungal species (Aureobasidium pullulans, Cryphonectria parasitica and Epicoccum purpurascens), were able to induce transcription of pathogenesis-related (PR) proteins and accumulation of enzymes related to defense in tomato plants cv Money Maker,using the chemical inducer Bion® as a positive control. During the thesis, several Pseudomonas spp. strains were also isolated and tested for their antimicrobial activity and ability to produce antibiotics. Using as a positive control jasmonic acid, one of the selected strain was shown to induce a form of systemic resistance in tomato. Transcription of PRs and reduction of disease severity against the leaf pathogen Pseduomonas syringae pv. tomato was determined in tomato plants cv Money Maker and cv Perfect Peel, ensuring no direct contact between the selected rhizobacteria and the aerial part of the plant. To conclude this work, race-specific resistance of tomato against the leaf mold Cladosporium fulvum is also deepened, describing the project followed at the Phytopathology Laboratory of Wageningen (NL) in 2007, dealing with localization of a specific R-Avr interaction in transfected tomato protoplast cultures through fluorescence microscopy.

Methane (CH4) plays an important role in regulating Earth’s climate. Its atmospheric concentrations are related to both biotic and abiotic processes. The biotic one can be formed either by chemoautotrophic or heterotrophic pathways by methanogens. Abiotic CH4 formation can occur from several sequential reactions starting with H2 production by serpentinization of Fe-bearing minerals followed by Fischer-Tropsch Type reactions or thermogenic reactions from hydrocarbons. In the presence of suitable electron acceptors, microbial oxidation utilizes CH4 and contributes to regulating its emission.  From the perspectives of astrobiology and Earth climate regulation, this thesis focuses on: (1) Dynamics of CH4 formation and oxidation in lake sediments (Paper I), (2) Constructing an automatic flux chamber to facilitate its emission measurements (Paper II), (3) dynamics of both abiotic and biotic CH4 formation processes related to olivine water interaction in temperature range 30 - 70°C (Paper III and IV). Paper I showed that potential CH4 oxidation strongly correlated to in situ its formation rates across a wide variety of lake sediments. This means that the oxidation rates could be enhanced in environments having the high formation rates. Thereby, the oxidation would likely be able to keep up with potentially increasing the formation rates, as a result diffusive CH4 release from freshwater sediments might not necessarily increase due to global warming. Paper II presented a new automated approach to assess temporal variability of its aquatic fluxes. Paper III and IV together revealed that H2 can be formed via olivine-water interaction. Abiotic CH4 formation was formed likely by Fischer-Tropsch Type reactions at low inorganic carbon concentration but by thermogenic processes at high inorganic carbon concentration. Paper IV showed that biotic methanogenic metabolism could harvest H2 and produce CH4. The dynamics of these processes seemed strongly affected by carbonate chemistry.
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 4: Submitted.

Todo en la tierra es química. Esta afirmación tiene profundas implicaciones para las interacciones ecológicas. Los organismos vivos promueven y controlan flujos de materia y energía entre la atmosfera, hidrosfera y litosfera; modificando la composición química de la tierra de muchas maneras diferentes. La estequiometría ecológica estudia el balance y el papel de múltiples elementos químicos en las interacciones ecológicas y nos ayuda a entender patrones y procesos en la naturaleza. Representa el enlace entre la biogeoquímica y el funcionamiento de los ecosistemas, permitiéndonos describir procesos a todos los niveles de organización biológica, desde estructuras sub-celulares a ecosistemas. En esta Tesis he usado la estequiometría ecológica para describir procesos a nivel de organismo y ecosistema en tres condiciones ambientales terrestres diferentes. La estequiometría de los autótrofos se establece cuando estos usan luz para fijar carbono (C) y simultáneamente asimilan nutrientes. Las plantas son capaces de almacenar nutrientes en la vacuola intracelular y en diferentes órganos, lo que hace que su estequiometría sea muy flexible (baja homeostasis) y se adapten a diferentes ambientes, incluyendo condiciones del suelo limitantes para el desarrollo de las plantas. También, la interacción planta suelo se puede explorar a través de la estequiometría foliar, ya que se ha demostrado en todos los ecosistemas terrestres que el N:P foliar esta correlacionado positivamente con el N:P del suelo, sugiriendo que es un buen indicador de la disponibilidad de nutrientes. Las adaptaciones de las plantas a condiciones limitantes de nutrientes en el suelo son comunes en todos los ecosistemas terrestres, como es la fijación de nitrógeno, la asociación con micorrizas, producción de fosfatasas o la reabsorción de nutrientes desde las hojas senescentes para el reciclado interno de nutrientes. La composición elemental de las especies es afectada por esas interacciones abióticas y bióticas, y el intercambio de elementos químicos entre las especies y el espacio abiótico determinaran la composición elemental de las diferentes partes del ecosistema. En el Capítulo 2 exploramos el efecto biótico de la composición de las comunidades sobre la composición química foliar de distintas especies vegetales, a través del nicho biogeoquímico de cada especie. Encontramos que cada especie presenta su propio nicho biogeoquímico y fueron capaces de reajustar su composición química foliar en respuesta a las diferentes condiciones bióticas. Concluimos que las plantas pueden reajustar su composición elemental foliar cuando crecen en comunidades con diferente composición de plantas, a través del desplazamiento del nicho biogeoquímico, sugiriendo un uso diferencial de los recursos cuando los patrones de coexistencia cambian. En el Capítulo 3 hemos explorado el cambio en la composición química del sistema planta-suelo debido a la expansión de arbustos en los pastizales subalpinos del Pirineo. Esta expansión representa la transición desde pastizales puros a matorrales. Los pastizales son un ecosistema dominado por especies de ciclo de vida corto, rápido intercambio de nutrientes entre los compartimientos planta-suelo, altas concentraciones de nitrógeno (N), fósforo (P) y potasio (K) en el sistema planta-suelo, con alta productividad pero capacidad limitada de acumulación de biomasa. En cambio, los matorrales se caracterizan por ser un ecosistema dominado por especies de ciclo de vida largo, con estrategias más conservativas, con un intercambio de nutrientes más lento (relación de C:nutrientes altos en la biomasa aérea y baja concentración de N y P en el sistema planta-suelo) y mayor almacenamiento de nutrientes en la biomasa aérea de las plantas. La matorralización incrementa la dependencia de la adquisición de nutrientes como el N a través de micorrizas desde los pastizales puros a matorrales. Todos los cambios en el almacenamiento y composición elemental del sistema planta-suelo a lo largo de la sucesión desde pastizales a matorrales sugiere una desaceleración del ciclo biogeoquímico en las áreas montañosas donde la expansión de arbustos está presente. En el Capítulo 4, describimos la distribución de C y los nutrientes más importantes para el desarrollo de las plantas (N, P, K) en el sistema planta-suelo de bosques tropicales maduros en suelos pobres de la Guyana Francesa. También estudiamos el proceso de reabsorción de nutrientes desde las hojas senescentes, un mecanismo de nutrición de las plantas para evitar la perdida de nutrientes poco estudiado en este ecosistema. Nuestros resultados muestran que el P es el elemento más escaso presente en hojas, hojarasca y suelo. Las eficiencias de reabsorción de K y P fueron más altas que la de N y la estacionalidad solo afecto la reabsorción de K. La reabsorción de P fue la única que mostró una correlación, aunque débil, con el P en el suelo (total y disponible). Las relaciones entre la reabsorción de nutrientes y los rasgos funcionales de las especies (tasa de crecimiento, densidad de madera, diámetro a la altura del pecho y el área foliar específica) fueron débiles y variaron dependiendo del nutriente, en tanto que la relación filogenética no explica la variabilidad en las eficiencias de reabsorción de nutrientes de las especies. Nuestros resultados sugieren que la alta reabsorción de K y P desde las hojas senescentes es una estrategia adaptativa de las especies que les permite lidiar con la escasez de estos nutrientes en el suelo. Asimismo, el nivel de inmovilización de los nutrientes en los compuestos foliares (N > P > K) parece determinar significativamente el proceso de reabsorción. Concluimos que la reabsorción de nutrientes desde las hojas senescentes es un proceso clave de las plantas para la conservación de nutrientes en los bosques tropicales de la Guyana Francesa, especialmente para K y P, elementos que presentan una disponibilidad baja en el suelo, y esta depende principalmente del material parental y del proceso de lixiviación. En resumen, en esta Tesis hemos demostrado como la composición elemental del sistema planta-suelo refleja procesos e interacciones ecológicas, como son las interacciones intra e inter específica entre plantas (Capítulo 2), procesos fisiológicos poco estudiados en las plantas como la reabsorción de nutrientes (Capítulo 4) y la importancia de los estudios de estequiometría para describir cambios a nivel de ecosistema y predecir escenarios futuros (Capítulo 3). Estos estudios aportan nuevos conocimientos en el campo de la estequiometría ecológica y resaltan la importancia de este enfoque en los estudios ecológicos.
Everything on Earth is based on chemistry. This statement has profound implications for ecological interactions. Living organisms generate and control fluxes of energy and matter among the atmosphere, lithosphere and the hydrosphere, shaping the chemistry of the Earth in many different ways. Ecological stoichiometry aims to explore the balance and role of multiple chemical elements in ecological interactions and help us to understand patterns and processes in nature. It represents the link between the biogeochemistry and the ecosystems’ function and allows to describe processes across different levels of biological organization, from cellular structures to ecosystems. In this Thesis I use ecological stoichiometry to describe processes at organism and ecosystem levels in three contrasting terrestrial environment conditions. Autotrophs’ stoichiometry is established when these organism use light to fix carbon (C) and simultaneously assimilate nutrients. Plants are able to store nutrients in the cells’ vacuole and in different organs, which make them highly flexible (less homeostatic) in terms of their elemental composition. This feature explains the high adaptability of plants to different environments, including soil nutrient limitation conditions. Furthermore, plant-soil interaction could be explored through the foliar stoichiometry, because it has been shown that the foliar N:P is positive correlated with the N:P of soil in all terrestrial ecosystem, suggesting that foliar stoichiometry is a good indicator of the resource availability. Plant adaptations to soil nutrient limiting conditions are quite common in all terrestrial ecosystems, such as nitrogen fixation, mycorrhiza association, production of phosphatases and nutrient resorption before leave abscission. The species’ chemical composition is affected by all these abiotic and biotic interactions, and these exchange of chemical elements between the species and the abiotic part of the system determine the elemental composition of different components of the ecosystems. In Chapter 2, we explore the biotic effect of the community composition on the species foliar stoichiometry, taken as a proxy of the species’ biogeochemical niche. We found that each species has its own biogeochemical niche and is able to readjust its chemical composition in response to different biotic conditions. We conclude that plants can readjust their foliar element composition when they grow in communities with contrasting plant composition through the biogeochemical niche displacement, suggesting a differential use of the resources when the patterns of species coexistence change. In Chapter 3 we explore the plant-soil stoichiometry changes due the shrub expansion into the subalpine grassland in the Pyrenees. Shrub expansion had a clear impact on the plant-soil stoichiometry spectrum. This expansion represents the transition from pure grassland to shrubland. The grassland is an ecosystem dominated by short-lived species, fast nutrient turnover between the plant-soil compartments, high nitrogen (N), phosphorus (P) and potassium (K) concentrations in the plant-soil system, high productivity but low biomass stocks. The shrubland is an ecosystem characterized by long-lived species with more conservative strategy, slow nutrient turnover (low N and P concentrations in the plant-soil compartments, high C:nutrient ratios in the aboveground biomass) and high stocks of C and nutrients in the plant aboveground biomass. Shrub encroachment increase the acquisition of N through mycorrhizal associations. The changes in storage and elemental composition of the plant soil system along the succession from grassland to shrubland suggests that there is a slowdown of the biogeochemical cycle in the subalpine mountain areas where shrub encroachment occurred. In the Chapter 4, we describe the distribution of C and the most important nutrients for the plant development (N, P, K) in the plant and soil compartments in old-growth tropical forests growing in nutrient-poor soil in French Guiana. We also studied the nutrient resorption from senescent leaves, a poorly explored mechanism that plants use to avoid losing nutrients in this ecosystem. Our results showed that P was the scarcest nutrient in the leaf, leaf-litter and soil. Resorption efficiencies were higher for K and P than for N, and only K resorption efficiency was affected by seasonality. P resorption showed a negative and weak correlation with P in soil (total and available). Relationships between nutrient resorption and species functional characteristics (growth rate, wood density, diameter at breast height and specific leaf area) were weak and varied among the nutrients, and phylogenetic relatedness did not account for the variability in resorption efficiencies. Our results suggest that high K and P resorption from senescent leaves is an adaptive strategy allowing species to cope with soil nutrient scarcity. Furthermore, the level of nutrient immobilization in foliar compounds (N > P > K) seem to significantly determine the resorption process. We conclude that nutrient resorption from senescent leaves is a key process for plants to conserve nutrients in tropical forests of French Guiana, especially for K and P, where soil availabilities are low and depend mainly on soil parent material and leaching process. To sum up, in this Thesis we have demostrated how the elemental composition of the plant-soil system reflects ecological interactions and processes, such as intra and inter specific plant interactions (Chapter 2), poorly explored physiological processes such as nutrient resorption (Chapter 4) and the importance of stoichiometry studies for describing changes at ecosystem level and predicting future scenarios (Chapter 3). These studies add new knowledge to the ecological stoichiometry field and highlights the importance of this approach in the ecological studies.

The triumvirate of tectonics, lithology, and climate control landscape evolution. This study quantifies how lithologic variation and climate-mediated changes in ecosystems perturb steady state processes in the unglaciated, soil-mantled Oregon Coast Range (OCR). I first demonstrate that minor grain-scale differences in rock properties in a seemingly uniform sandstone control differences in rock strength, biotic bedrock-to-soil production efficacy, and erosion rates and influence relief at the watershed scale. I then build on sedimentology, paleoecology, and isotopic-derived paleoerosion data I collected from a new 50 ka sediment archive at Little Lake, OR to explore climate controls on soil production and erosion rates 21 ka across the OCR and spanning 50 ky within a single watershed. In Chapter III, I combine a mechanistic frost weathering model with a regional Last Glacial Maximum (LGM) climate reconstruction and paleovegetation data to demonstrate that accelerated frost-driven erosion was pervasive across the OCR during the LGM. My findings provide a new framework to quantify how the late Pleistocene affects modern erosion and soil formation rates in unglaciated environments and implies that most landscapes reside in a transient state. In Chapter IV, I document climate-mediated ecosystem influence on erosion rates over 3 climatic intervals. 10Be-derived erosion rates increase 3x (from 0.6 mm/yr to 0.21 mm/yr) as the OCR transitioned from the open forest-dominated marine isotope stage (MIS) climate interval (50-26 ka) into the periglacial subalpine MIS 2 glacial interval (26-13 ka). Measured erosion rates fell by more than half as the subalpine ecosystem gave way to the modern MIS 1 closed canopy Douglas-fir forest. Coupling paleovegetation-derived climate information with core observations I model frost weathering intensity from ~ 43 ka to 21 ka and establish a correspondence with increasing frost weathering intensity and increasing 10Be-derived erosion rates. Utilizing a transient mixing depth and erosion rate model, I am able to broadly replicate measured erosion rates at Little Lake through time. My findings contradict previous work that suggests climate has only weak control on erosion rates. This dissertation includes previously published and unpublished co-authored material.

Aquatic insects are the most numerically abundant and diverse group of organisms found in lotic ecosystems in South Africa and the world over. They play vital roles in freshwater ecosystem functioning, processing nutrients and in turn forming integral links in stream food-webs. This thesis focussed on examining the macroinvertebrate fauna within three reaches of headwater streams of the Keiskamma River system: reaches that were considered to be fishless; reaches that were invaded by non-native salmonid species; and reaches that were dominated by native fish. I described the effects of predatory fish presence through detailed examination of macroinvertebrate assemblage composition; macroinvertebrate drift timing and density; and through niche utilisation determined from stable isotope data. Patterns in the macroinvertebrate assemblages of the headwaters of the Keiskamma River appear to be driven more strongly by flow rate and seasonal influences, but fish presence and biotope availability were also significant drivers. Niche shifts due to predator presence were not easy to detect and, while patterns of influence may have been evident, they were not found to be significant. However, I demonstrated that salmonids selectively feed on native fish species when the opportunity is presented, occupying significantly higher trophic levels when co-occurring with native fish than in invaded reaches where native fish are absent. Drift timing and density were demonstrated to be significantly different between reach for specific macroinvertebrate species from the Ephemeroptera and Plecoptera, under differing fish predation regimes, in agreement with what has been observed from studies in rivers elsewhere. In freshwater ecosystems of South Africa and worldwide, mitigation of negative effects of alien fishes through their removal using piscicides may also affect non-target organisms. To better understand the effects of just such a removal operation, employed for the first time in the history of freshwater conservation in South Africa, macroinvertebrate communities were assessed for non-target effects of rotenone. The fish eradication operations were demonstrated to have a short-term negative effect on the macroinvertebrate assemblage, through water quality index measurements and alteration of densities of macroinvertebrate taxa collected from stone surfaces. However, no long-term detrimental impact was observed as macroinvertebrate faunas returned to a comparable pre-treatment state within a year of each rotenone application.

This study evaluated the applicability of remote sensing instrumentation for site- specific management of abiotic and biotic stress on cotton grown under a center pivot. Three different irrigation regimes (100%, 75%, and 50% ETc) were imposed on a cotton field to 1) monitor canopy temperatures of cotton with infrared thermometers (IRTs) in order to pinpoint areas of biotic and abiotic stress, 2) compare aerial infrared photography to IRTs mounted on center pivots to correlate areas of biotic and abiotic stress, and 3) relate yield to canopy temperatures. Pivot-mounted IRTs and IR camera were able to differentiate water stress between the irrigation regimes, however, only the IR camera was effectively able to distinguish between biotic (cotton root rot) and abiotic (drought) stress with the assistance of groundtruthing. The 50% ETc regime had significantly higher canopy temperatures, which were reflected in significantly lower lint yields when compared to the 75% and 100% ETc regimes. Deficit irrigation up to 75% ETc had no impact on yield, indicating that water savings were possible without yield depletion.

In contrast to documented increases in woody plant dominance of former savannas and grasslands of North America, oak (Quercus L.) savannas that form lower treelines in the southwestern United States and northwestern Mexico have been relatively stable over the past millennium. This research identified potential biotic and abiotic constraints on seedling recruitment of Quercus emoryi Torr. (Emory oak) within the context of potential shifts in lower treeline. Field surveys were used to describe seedling distribution at and below lower treeline, and to determine the potential for acorn dispersal from lower treeline into adjacent grassland. Field and greenhouse experiments designed to determine constraints on seedling establishment included reciprocal soil transfers, nutrient amendment studies, provision of artificial shade, and manipulation of seasonal precipitation inputs. Results indicate that rates of Q. emoryi recruitment within grasslands below treeline are relatively low, and are constrained by low rates of seed dispersal coupled with a low probability of seedling emergence. Seedling recruitment rates were directly correlated with quantity of summer precipitation, but were independent of winter precipitation. Results of this and complementary research suggest that lower treeline in southern Arizona is stabilized by self-enhancing feedback mechanisms of overstory shade, seed dispersal, and seedling establishment coupled with strong abiotic constraints beyond the current ecotone. The observed shift in treeline in the last millennium was less likely the result of slow, spatial progression of autogenic safe sites than the result of episodic and infrequent allogenic processes that simulated, or negated the importance of, conspecific, biogenic safe sites. Increases in summer precipitation are one such process that would facilitate (historic or potential future) downslope shifts in lower treeline. This interpretation is consistent with observations that downslope shifts in lower treeline which occurred 700-1700 ybp coincided with a period of particularly high summer precipitation in the region (i.e., the "Medieval Warm" period, 645-1295 ybp).

Coexistence among ecologically similar species is often facilitated through temporal or spatial partitioning mechanisms that reduce or eliminate direct interaction. However, in many communities exhibiting guild structure, wherein potential competitors may also prey on one another, sympatric relationships persist despite species' similar life history strategies, spatial and temporal restrictions imposed by ephemeral habitats, and resource limitations that promote competition and predation. To identify the ecological roles of species-specific behavioral patterns within aquatic guilds, I quantified larval intraspecific agonistic behavior among two species of intraguild (IG) predators, Ambystoma opacum and A. tigrinum, and their shared intraguild prey, A. maculatum. All species exhibited similar ontogenetic patterns of aggression, characterized by peaks of aggression early in development and subsequent gradual decreases through metamorphosis. However, the intensity of aggression varied considerably among guild species through development, as did behavioral responses to varying levels of ambient water temperature, invertebrate prey density, and presence of predatory odonate naiads. The observed patterns suggest that guild species, despite morphological and physiological similarities, exhibit unique behavioral responses through ontogeny and in response to habitat variables, suggesting that temporally staggered breeding phenologies have contributed to behavioral divergence among these sympatric congeners. However, in situ observations of larval behavior, although largely in agreement with laboratory results on timing of increased aggression, indicated that IG predators exhibited pond-level species partitioning and do not necessarily co-occur despite being regarded as sympatric. These results, taken together with observed species-specific impacts of IG predators on IG prey, suggest that ecologically similar IG predators exert widely differing predatory pressure on shared prey, and that similarities among guild species may ultimately result in habitat partitioning across local scales.

Pharmaceuticals and personal care products found in the environment pose a significant hazard to human and ecosystem health. While there has been significant work on the fate and remediation of pharmaceuticals and personal care products in wastewater treatment, relatively little work has explored the fate, transport and remediation of these compounds in non-point source input. This is concerning given the increasing use of pharmaceuticals in livestock production and wastewater treatment derived biosolids frequently applied to land. These experiments aimed to quantify the abiotic adsorption and biotic transformation and uptake potential of woodchips and biochar-amended woodchips as a potential sorbent strategy for diffuse acetaminophen (ACT) pollution. Batch reactions were created in triplicate, supplied with 5 mM ACT, and analyzed over an eight hr period using ultraviolet spectrophotometry (298 nm). Ultraviolet absorbance readings for each time step then were compared to standard curves and solution ACT concentration was determined. Decreases in ACT from initial concentrations were the result of either abiotic and/or biotic. Overall, the woodchips and biochar-amended woodchips showed similar removal efficiency (16-21% of initial concentration). Whole model ANOVA analysis showed biologic activity having no significant effect on ACT solution concentration. However, within group ANOVA comparison showed significant differences between abiotic and biotic WC and abiotic and biotic WC treatments (controlling for media). Thus, the media effect could have masked the effect of biology on ACT removal. Species capable of degrading ACT exist and further study into their ability to grow and survive on these sorbents requires further work.
Master of Science

The Sardinilla plantation is a long-term facility for studying the links between tree species diversity and ecosystem function. Six native tree species were planted in 2001 in plots containing 1, 3 or 6 species. Soil respiration (SR) measurements were conducted from March to December 2004 on tree pairs. ANOVAs with repeated measure on days were used to test the main effects of species (monocultures), pair (single and two-species pairs), plot (pairs in monoculture, three-, and six-species plots), and season (dry vs. early wet season). ANCOVAs were run for each effect to determine possible biotic and abiotic covariates, including root, tree, and microbial biomass, soil moisture, surface temperature, and bulk density. Significant season and pair effects accounted for 89% and 2% of the variability in SR. Driven by soil moisture, SR increased seven fold during the seasonal transition. In the dry and wet season monocultures had significantly higher SR than two-species pairs.

Les flors emeten compostos orgànics volàtils (VOCs) per tal d’atreure pol·linitzadors i estimular la fecundació creuada. Alguns volàtils florals però juguen altres funcions, com ara la defensa contra els herbívors. Aquesta dualitat de rols que tenen les olors florals les converteix en complexes mescles de compostos amb múltiples efectes sobre diferents organismes. La complexitat de comprendre i caracteritzar les emissions florals augmenta quan considerem que són variables en el temps i l’espai. A aquestes fonts de variabilitat cal afegir diversos factors ambientals biòtics i abiòtics que modifiquen les emissions de COVs florals de diverses maneres. L’objectiu principal d’aquesta tesi és esclarir quins són els factors que determinen les emissions florals de volàtils, i veure de quina manera les afecten a elles i a les seves funcions ecològiques. En el primer capítol de la tesi hem revisat el coneixement actual sobre les emissions florals de VOCs i hem identificat les qüestions que necessitaven ser investigades en aquest camp de recerca. Les emissions florals estan determinades en primer lloc per la diversitat de compostos que les espècies són capaces de produir, els seu potencial biosintètic i la seva capacitat d’emissió, que estan fortament lligades a la biologia de l’espècie. Hem testat i demostrat que les plantes pol·linitzades per insectes solen presentar major diversitat de volàtils florals i emeten una major quantitat d’aquests que les plantes pol·linitzades pel vent, que no necessiten volàtils florals per funcions d’atracció. Hem testat si els patrons estacionals de disminució de la competència que ocorren cada any entre plantes d’una mateixa comunitat vegetal han donat lloc a la selecció d’un patró de disminució de les emissions i les recompenses florals al llarg del període de floració de cada espècie. També hem observat que les plantes adapten la seva fisiologia per optimitzar les seves emissions florals sota les condicions climàtiques de la seva època de floració. Les emissions florals de COVs es veuen afectades per factors ambientals al nivell d’organisme o de teixit. Hi ha diversos estats fisiològics de la planta que poden modificar substancialment la composició i la quantitat de les emissions florals de COVs. Els nostres experiments han demostrat que la microbiota floral pot jugar un rol crucial sobre la quantitat i composició de les emissions florals de COVs. També hem mostrat que l’herbivoria de flors per part d’erugues de Pieris brassicae sobre plantes de Diplotaxis erucoides indueixen augments immediats de les emissions de compostos amb funcions defensives. A més, l’herbivoria de flors i fulles combinada va mostrar un efecte sinèrgic que augmenta la resposta defensiva. La recerca sobre els canvis que poden experimentar les emissions florals en resposta a diversos agents del Canvi Global són de gran interès degut als diversos efectes que aquests canvis poden tenir sobre les interaccions que s’estableixen mitjançant els COVs florals. Els nostres resultats revelen que els augments de temperatura previstos per al segle següent deguts a l’Escalfament Global poden conduir a augments significatius de les emissions totals de COVs i també a canvis importants en la composició relativa de les olors florals. També hem observat que l’ozó causa una degradació significativa dels compostos florals i provoca canvis en la composició relativa de les olors. Els testos de resposta indiquen que els canvis observats en les olors florals exposades a ozó resulten en la pèrdua de l’atracció de pol·linitzadors. Aquesta tesi proporciona una nova visió sobre els factors que determinen les emissions florals de volàtils i les seves repercussions sobre les interaccions planta-pol·linitzador, i garanteix una major consideració dels factors biòtics i abiòtics que afecten la química i l’ecologia de les olors florals en un ambient contínuament canviant.
Flowers emit volatile organic compounds (VOCs) to attract pollinators and stimulate reproductive outcrossing. Some floral volatiles can play roles other than attraction, such as defense against herbivores. This duality of roles of flower emissions converts floral scents into complex mixtures of compounds with multiple effects on different organisms. The complexity of understanding and characterising floral emissions increases when considering that they are variable in time and space. To all these sources of variability we can add diverse biotic and abiotic environmental factors that modify floral VOC emissions in many different ways. The main objective of this thesis was to shed light on which are the factors that determine floral volatile emissions, and how do they affect these emissions and their ecological functions. In the first chapter of this thesis we reviewed the current knowledge on floral VOC emissions. We identified the open questions that still needed to be addressed or investigated in more detail in the research field of floral VOC emissions. Floral emissions are first determined by the array of compounds that the species are able to produce and their potential biosynthetic and emission capacities, which are strongly related to the species biology. We tested and demonstrated that flowering plants pollinated by insects usually present higher diversities of floral volatiles and emit higher amounts of them, than do plants pollinated by wind which do not need floral volatiles for attractive purposes. We tested whether well-known seasonal patterns of decreasing competition occurring every year in a community among co-flowering plants for pollinators led to the selection of a pattern of decreasing emission of floral volatiles and decreasing production of floral rewards along the flowering period of each species. We also observed that plants adapt their physiology to optimize their floral emissions under the climatic conditions of the flowering period. Floral VOC emissions of the species are affected by environmental factors at the individual (organism) or tissular level. There are diverse physiological states of the plant that can substantially modify the emission profiles and amounts of floral VOCs. Our experiments demonstrated that floral microbiota can play a crucial role in the quantity and quality of floral VOC emissions. We also showed that flower herbivory by Pieris brassicae caterpillars on Diplotaxis erucoides plants induced immediate increases in floral emission rates of few compounds with known defensive functions. Leaf herbivory caused no changes in the emissions of intact flowers, but the combination of leaf herbivory with flower herbivory showed a synergistic effect with enhanced defensive response. The research on the potential changes that floral emissions could experience in response to diverse drivers of Global Change are of critical interest because of the diverse effects that such changes can have on the interactions that floral VOCs mediate. Our results revealed that temperature increases as those predicted for the next century as a result of Global Warming can lead to significant total increases in floral VOC emissions and also to important changes in floral scent relative composition. We also detected that ozone caused significant degradation of floral compounds and changes in their relative composition. Behavioural tests indicated that all the changes observed in floral chemical cues when exposed to ozone resulted in the loss of attraction effect on pollinators. This thesis thus provides new insights on the factors that determine floral volatile emissions and their repercussions on plant-pollinator interactions and warrant deep consideration of both biotic and abiotic factors driving floral scent chemistry and floral scent ecology in a continuously changing environment.

Thesis (Ph.D.)--Kent State University, 2009.
Title from PDF t.p. (viewed Nov. 16, 2009). Advisor: Mark Kershner. Keywords: crayfish; stream; predation; current velocity; water depth; grain size; resource competition. Includes bibliographical references.

Streams are integrative systems spanning multiple spatial and temporal scales. Stream researchers, land-use managers, and policy decision makers must consider the downstream displacement of streams when approaching questions about stream ecosystems. The study of how anthropogenic land-use influences streams demands an ecosystem perspective, and this dissertation is an example of applying large scale analyses of stream reach responses, and linking the activity of humans in the landscape to stream structure and function. I investigate whether rural development and agriculture land-cover types influence abiotic and biotic stream responses. I establish a method for considering land-cover as an independent variable at multiple scales throughout a streamsâ watershed using hydraulic modeling. The travel time required for water to drain from the watershed to a stream reach provided a continuous index to delimit watershed sub portions along a spatial continuum. Within travel time zones (TTZs), I consider land-use at increasingly larger scales relative to a stream reach within which biotic responses are typically measured. By partitioning land-cover in TTZs, I was able to determine the spatial scale at which land-cover was most likely to influence in-stream responses. I quantified a suite of physical and biotic responses typical to the aquatic ecology literature, and found that streams did not respond much to rural development. Rural development influenced suspended and depositional sediments, and likely altered watershed hydrology though I was unable to find significant evidence supporting a hydrologic effect. Subtle differences in assemblages suggest that differences in sediment dynamics influenced macroinvertebrates and fish. Using the Land Cover Cascade (LCC) design, I link the influence of land-cover to biotic responses through a suite of multivariate models, focusing on sediment dynamics in an attempt to capture the subtle influence of hydrology and sediment dynamics. My dissertation provides future researchers with improved methods for considering land-cover as an independent variable, as well as introduces multivariate models that link land-cover to sediment dynamics and biota. My dissertation will assist future research projects in identifying specific mechanisms associated with stream responses to disturbance.
Ph. D.

Dissertation presented to obtain the Ph.D degree in Plant Sciences
"Common bean (Phaseolus vulgaris L.) is among the most important grain legumes for human consumption worldwide. Portugal has a promising common bean germplasm that resulted from more than five centuries of natural adaptation and farmers’ selection. Nevertheless, limited characterization of this resource hampers its exploitation by breeding programs. To support a more efficient conservation of the national bean germplasm and promote its use in crop improvement, we performed, for the first time, a simultaneous molecular marker and seed and plant morphological characterization of 175 accessions collected from Portuguese mainland and islands traditional bean-growing regions. Most of the Portuguese accessions grouped with the race representatives and wild relatives from the Andean region."
N/A

Carbon tetrachloride (CT) and chloroform (CF) are chlorinated methanes (CMs) which have been released to the environment for decades owing to scarce waste management. Since they are dense non-aqueous phase liquids (DNAPLs), CMs migrate downwards and reach groundwater constituting a contamination source. Thus, this pollution requires a thoughtful monitoring and treatment since CT and CF are toxic and predicted to be carcinogenic substances (IARC, 2017). Although CT and CF are considered quite persistent in aquifers, they undergo abiotic and biotic natural attenuation. This degradation occurs mainly through reductive pathways under anoxic conditions, but CF oxidative microbial cometabolism could be also plausible (Cappelletti et al., 2012; Penny et al., 2010). Hence, CMs transformation processes are expected under field conditions. Òdena field site (Barcelona, Spain) is polluted by CMs among other volatile organic compounds (VOCs) due to industrial activity during the 70s and 80s. Chlorinated ethenes (CEs) degradation was detected in the fractured aquifer by carbon isotope (δ13C) enrichment over time (Palau et al., 2014b). CF alkaline hydrolysis (AH) was also revealed by δ13C monitoring in the interception trenches filled with construction wastes (pH ~12) built in the unsaturated zone after 2005 source removal, whereas the cause of CT δ13C enrichment over time in these trenches remains unknown (Torrentó et al., 2014). Induced reactions bear potential to overcome the challenges derived from the slow degradation rates of CMs natural attenuation. Biostimulation, zero valent iron permeable reactive barriers (Fe(0)-PRB) or those made of other reducing agents are receiving increasing attention as alternative remediation strategies. However, in situ chemical oxidation (ISCO) and alkaline hydrolysis are techniques of interest only for CF as a result of the high oxidation state of carbon in CT. Compound specific isotopic analysis (CSIA) is a useful tool to evaluate the efficiency of both CMs natural attenuation and induced strategies in the field. CSIA not only verifies that the concentration decrease is due to reactive processes (instead of dispersion or dilution) but also permits quantification. Moreover, dual isotope plots in which shifts in isotope values of one element are plotted against those of a second element, allow distinction between different CMs reaction mechanisms by means of specific slopes (Λ). Thus, laboratory CMs degradation experiments under controlled conditions are required to gain understanding of the expected isotopic changes in the field and to evaluate whether it is feasible to quantitatively detect degradation. Although relatively new, Cl-CSIA for CEs and chlorinated ethanes has been gradually incorporated in the last 6 years in combination with consolidated C-CSIA. However, Cl-CSIA was only used in few laboratory experiments for CF and the method was not validated for any CMs prior to this thesis. The main aims of this thesis have been to better understand CMs natural attenuation together with potential CMs remediation strategies to improve the assessment of CMs fate in Òdena site and, by extension, in other polluted sites all over the world. These goals were addressed primarily by C-CSIA and Cl-CSIA, among other techniques. Prior to their use in laboratory or field samples, Cl-CSIA method has been developed and evaluated for CT and CF by both, gas chromatography-isotope ratio mass spectrometry (GC-IRMS) and by gas chromatography-quadrupole mass spectrometry (GC-qMS validated in an interlaboratory comparison) through an international collaboration (Helmholtz Zentrum München and Université de Neuchâtel) during different thesis stays. Three relevant abiotic CF transformation mechanisms were studied in batch experiments: oxidation by heat-activated persulfate (abbreviated as PS); AH and reductive dechlorination by Fe(0), obtaining similar Λ values for PS and AH (17±2, 13.0±0.8) which are distinguishable from reductive dechlorination (8±2). CT and CF degradation by Fe(0) and Fe-bearing minerals (pyrite (Py, FeS2) and magnetite (Mag, Fe3O4) in the presence of FeCl2 were carried out in laboratory experiments at pH 7 and 12 simulating groundwater in the saturated zone and in alkaline interception trenches in the unsaturated zone of Òdena site, respectively. CF hydrogenolysis to dichloromethane (DCM) by milli-sized Fe(0) was characterized at both pHs, whereas CF degradation by Fe- bearing minerals was only identified at pH 12. In this case, AH was hypothesized since no VOCs by-products were detected except for DCM only with Py, evidencing CF hydrogenolysis. CT degradation by both Fe(0) and Fe-bearing minerals was confirmed at pH 12, whereas at pH 7, CT degradation was only obtained by nano-sized Fe(0) and Py. pH did not affect Λ values of CT and CF degradation by Fe(0) nor CT degradation by Py. CT thiolytic reduction to carbon disulphide (CS2) occurred in parallel to CT hydrogenolysis in experiments with Py at both pH values, showing different Λ values to net CT hydrogenolysis by Fe(0), but similar Λ values to CT reduction by Mag at pH 12. These differences provide good chances to detect these pathways in the field. Additionally, CT and CF microcosm experiments were performed separately for each compound by using slurry from one of the most polluted wells in Òdena site (S3). Biotically- mediated CT hydrogenolysis was confirmed in the microscoms. Biostimulation with vitamin B12 catalyzed CT biodegradation and stimulates CF biodegradation, the latter not observed without B12. For both target compounds, no relevant accumulation of other chlorinated compounds neither CS2 was detected with B12. CT experiments with B12 might be linked to a major activity of Pseudomonas stutzeri able to reduce CT to CO2. Acidovorax, Ancylobacter and Pseudomonas were the most metabolically active genera observed in the experiments, whereas commonly found organo-halide respiring bacteria, Dehalobacter and Desulfitobacterium, were below 0.1% of relative abundance. The Λ of CF biodegradation by B12 (7±1) was similar to that reported for CF reductive dechlorination by Fe(0) (hydrogenolysis plus reductive elimination) (8±2). Λ of CT biodegradation without B12 showed no difference to CT hydrogenolysis by Fe(0) which indicates the same pathway. Furthermore, Λ of CT degradation was statistically different despite their 95% of confidence interval (CI) with and without B12 (5±1 vs. 6.1±0.5, respectively), indicating possible influence of other reduction processes different from CT hydrogenolysis. δ13C enrichment of CEs, once CMs were completely degraded by B12-catalyzed biotic reactions, confirmed CMs inhibition of CEs degradation. The obtained laboratory data improved the knowledge on CMs degradation processes and established the basis applicable in multi-contaminant polluted sites like Òdena. A long-term monitoring to study 2005 source’s removal effects on groundwater CMs has been performed from 2002 to 2014. Through by-products and C-CSIA monitoring, CMs transformation processes over time have been confirmed. The source’s removal was inefficient since active CMs leaching was proved in the outskirts of the dismantled wastewater pipe and in the wastewater tank. Nevertheless, by-products and Λ studies disclosed CT and CF reduction processes precisely in those areas. In contrast, in former disposal pit source, where removal was more efficient, isotopic values unveiled a migration of the focus downstream as well as an influence of hydrolysed CF coming from the alkaline trench and/or CF oxidation processes in the saturated zone of this area. To sum up, this thesis has provided progress in Cl-CSIA methodology for CMs and new compelling C and Cl-isotope laboratory data related with CT and CF degradation processes. These data combined with other microbial and geochemical tools have allowed the discrimination of CMs degradation processes at field scale and are promising for monitoring the efficiency of remediation strategies in other polluted sites. The routine use of Cl-CSIA analyses are worthwhile for further research together with well-stablished C-CSIA. Moreover, the up-scale application and evaluation of studied CMs remediation techniques such as biostimulation by economical B12 sources in combination or not with Fe(0) or Fe-bearing minerals (which implies mining wastes revalorization) are challenges ahead.
El tetracloruro de carbono (CT) y el cloroformo (CF) son compuestos orgánicos que pertenecen al grupo de los metanos clorados (CMs) los cuales han sido vertidos descontroladamente al medio ambiente durante décadas debido a la escasa gestión y tratamiento de residuos. Puesto que son disolventes más densos que el agua, una vez vertidos, estos contaminantes migran en profundidad hasta las aguas subterráneas creando frecuentes fuentes de contaminación ambiental que, por su persistencia, constituyen un riesgo para la salud pública. Por lo tanto, este tipo de contaminación requiere de un seguimiento exhaustivo, así como de hallar tratamientos específicos debido a que el CT y el CF son consideradas substancias tóxicas y carcinogénicas (IARC, 2017). Aunque el CT y el CF son persistentes en acuíferos, estos compuestos experimentan atenuación natural tanto biótica como abiótica. Los CMs se degradan principalmente a través de mecanismos de reducción bajo condiciones anóxicas, aunque la oxidación microbiana del CF por cometabolismo también es un proceso de degradación potencial (Cappelletti et al., 2012; Penny et al., 2010). Por consiguiente, se esperan procesos de transformación de los CMs en emplazamientos contaminados. El enclave contaminado de Òdena (Barcelona) se encuentra afectado tanto por CMs como por otros compuestos orgánicos volátiles (VOCs, por sus siglas en inglés) debido a actividad industrial en los años 70 y 80. La degradación de etenos clorados (CEs por sus siglas en inglés) en este acuífero fracturado fue detectada ya que se observó un enriquecimiento isotópico del carbono (δ13C) a lo largo del tiempo (Palau et al., 2014b). La presencia de hidrólisis alcalina (AH, por sus siglas en inglés) del CF fue también revelada mediante el seguimiento de la δ13C del CF en las rasas de intercepción de agua de lluvia creadas con residuos de la construcción (pH~12) en la zona no saturada, una vez que se extrajeron las fuentes de contaminación en 2005. Sin embargo, aún se desconoce el motivo del enriquecimiento de la δ13C del CT a lo largo del tiempo en estas rasas (Torrentó et al., 2014). Para mejorar las limitaciones de los potenciales procesos de atenuación natural de los CMs y hacerlos más eficientes, se pueden usar diferentes técnicas de remediación inducida. La bioestimulación y el uso barreras reactivas permeables de Fe(0) o construidas con otros agentes reductores son de creciente interés. La oxidación química in situ (ISCO) y la AH son técnicas de remediación abiótica pertinentes únicamente para el CF, debido al alto estado de oxidación del carbono en el CT. El análisis isotópico de compuesto específico (CSIA por sus siglas en inglés) es una herramienta muy útil para evaluar la eficiencia tanto de la atenuación natural de los CMs como la de las estrategias de remediación aplicadas en emplazamientos contaminados. El método de CSIA no solo verifica, mediante el seguimiento de la composición isotópica a lo largo del tiempo, que la disminución de la concentración de los CMs sea debida a procesos reactivos (vs. otros no destructivos, como por ejemplo la dispersión o la dilución), sino que también permite la cuantificación del alcance de la degradación del contaminante. Asimismo, los gráficos binarios de isótopos, en los que los cambios isotópicos de un elemento se grafican respecto al de un segundo elemento de la molécula estudiada, permiten la discriminación entre diferentes vías de degradación de los CMs, a través de la obtención de pendientes específicas de cada mecanismo (Λ). Para aplicar el CSIA con tales fines, deben realizarse previamente experimentos de laboratorio bajo condiciones controladas para estudiar las reacciones de degradación de los CMs. De este modo es posible evaluar de forma fiable los cambios isotópicos esperados en el campo y, por lo tanto, conocer si se puede detectar de forma cuantitativa la degradación, así como también, estudiar la viabilidad de los potenciales tratamientos. El CSIA del carbono (C-CSIA) está ampliamente consolidado para el análisis de VOCs. El CSIA del Cl (Cl-CSIA) ha sido extensamente usado en los últimos años para los CEs y los etanos clorados. Sin embargo, el Cl-CSIA solamente ha sido aplicado en algún experimento para el CF y no ha sido utilizado previamente para el CT. Por consiguiente, el método de Cl-CSIA no había sido evaluado ni validado pormenorizadamente para ningún CMs antes de la presente tesis. Los principales objetivos de esta tesis son la adquisición de un mejor conocimiento de los procesos de atenuación natural de los CMs a través de experimentos de laboratorio, así como también de las potenciales estrategias de remediación de éstos, con el fin de aplicar dichos avances en emplazamientos tales como el de Òdena. El C-CSIA y el Cl-CSIA han sido las herramientas de seguimiento principales de los estudios realizados, aunque se han utilizado otras técnicas geoquímicas y microbiólogas dando un carácter pluridisciplinar a la tesis. Previamente al uso del método de Cl-CSIA en los CMs de las muestras de laboratorio y campo, se ha desarrollado y validado el método para el CT y CF con un cromatógrafo de gases acoplado a un espectrómetro de relación isotópica (GC-IRMS) y con un cromatógrafo de gases acoplado a un espectrómetro de masas cuadrupolo (GC-qMS, siendo la metodología para este último comparada en un interlaboratorio). Este desarrollo se ha llevado a cabo en colaboración con grupos de investigación internacionales (Helmholtz Zentrum Müenchen y Université de Neuchâtel) durante las tres estancias del doctorado. Han sido estudiados tres mecanismos diferentes de transformación abiótica del CF en experimentos batch: oxidación por persulfato activado térmicamente (abreviado como PS); AH y decloración reductiva del CF con Fe(0). Se han obtenido valores similares de Λ del CF para PS y AH (17±2 y 13.0±0.8, respectivamente) que se pueden distinguir de la decloración reductiva (8±2). Se han realizado experimentos de degradación de CT y CF con Fe(0) y minerales de hierro (pirita (Py, FeS2) y magnetita (Mag, Fe3O4)), estos últimos con la presencia de FeCl2 a pH 7 y pH 12, simulando el agua subterránea de la zona saturada y la de las rasas de intercepción alcalinas de la zona no saturada de Òdena, respectivamente. Se detectó hidrogenólisis del CF a diclorometano (DCM) mediante Fe(0) de tamaño milimétrico para ambos valores de pH, mientras que la degradación del CF por minerales de hierro solo fue identificada a pH 12. En este último caso, se hipotetiza la existencia de AH ya que no se detectan VOCs como productos, salvo cierta acumulación de DCM con Py, lo que evidenciaría hidrogenólisis solo en el experimento con Py. La degradación del CT, mediante Fe(0) o minerales de hierro, ha sido confirmada a pH 12. Sin embargo, a pH 7 la degradación del CT solo ha sido confirmada con Fe(0) nanométrico y Py. Se ha observado la existenia paralela de reducción tiolítica del CT a CS2 e hidrogenólisis del CT a CF en ambos valores de pH, dando lugar ambos procesos a un valor de Λ diferente al obtenido para la hidrogenólisis neta del CT con Fe(0) y similar al de la reducción del CT con Mag a pH 12. De esta manera, se evidencia el potencial para detectar y diferenciar estos procesos en el campo mediante gráficos binarios de isótopos C-Cl. Así mismo, se deduce que el pH no afecta al valor de Λ de la degradación del CT ni del CF mediada por el Fe(0), ni a la degradación del CT por acción de la Py o del Fe(0). Adicionalmente, se han realizado experimentos de microcosmos con CT y CF, separadamente, con lodo del fondo de uno de los pozos más contaminados de Òdena (S3). Se ha confirmado una biodegradación natural de CT siguiendo la vía de hidrogenólisis a CF. La bioestimulación con vitamina B12 ha catalizado la degradación de CT y estimulado la biodegradación del CF, siendo la última inexistente sin la presencia de B12. Para ambos compuestos, no se detecta una acumulación de compuestos clorados ni de CS2 en los tratamientos con B12. La ausencia de acumulación de CF con la adicción de B12 durante la degradación de CT puede estar relacionada con una mayor actividad de la especie Pseudomonas stutzeri detectada más activa en esos tratamientos y capaz de reducir el CT a CO2. Los géneros más metabólicamente activos en los tratamientos del microcosmos son Acidovorax, Ancylobacter and Pseudomonas son, mientras que bacterias ampliamente conocidas como decloradoras (como Dehalobacter y Desulfitobacterium), se encuentran por debajo de un 0.1% de abundancia relativa. El valor de Λ para la biodegradación del CF (solo detectada con la adicción de B12, 7±1) es similar al registrado para la decloración reductiva del CF con Fe(0) (8±2), el cual incluye hidrogenólisis y eliminación reductiva. El valor de Λ de la biodegradación del CT sin la vitamina B12 y el de la hidrogenólisis neta del CT por Fe(0) no muestran diferencia estadística, lo cual confirma la misma vía para ambos experimentos. También cabe destacar que los valores de Λ de la degradación del CT con y sin B12 son estadísticamente diferentes (5±1 vs. 6.1±0.5), respectivamente, a pesar de su similitud a juzgar por su intervalo de confianza del 95%. Este hecho indicaría una posible influencia de otros procesos de reducción del CT diferentes a la hidrogenólisis cuando la vitamina B12 está presente. Por último, añadir que este estudio de microcosmos revela un enriquecimiento en 13C de los CEs, una vez los CMs son totalmente degradados mediante reacciones bióticas catalizadas por la B12, lo cual confirma la inhibición que ejercen los CMs en la degradación de los CEs. Considerando todo lo anteriormente mencionado, el conjunto de datos obtenido en los experimentos sienta las bases para un mejor conocimiento de la atenuación natural e inducida de los CMs aplicable a nivel práctico en acuíferos contaminados por múltiples contaminantes como el citado de Òdena. De esta forma, ha sido llevado a cabo un estudio a largo plazo (del 2002 al 2014) del efecto de la remoción de las fuentes de contaminación de CMs en 2005 en las aguas subterráneas del emplazamiento monitorizado de Òdena. A través del seguimiento de la concentración de los CMs y sus productos de degradación, así como del C-CSIA de los CMs, se han sido confirmado procesos de transformación de estos contaminantes a lo largo del tiempo. La remoción de las fuentes de contaminación se considera ineficiente dado que se han detectado procesos de lixiviado de CMs tanto en la zona no saturada alrededor del conducto de transporte de aguas residuales que fue desmantelado, como también entorno al tanque de almacenamiento subterráneo. No obstante, los productos de degradación y el estudio de los valores de Λ han evidenciado procesos de reducción del CT y del CF en ambas áreas. Por otro lado, en la zona donde se realizaron vertidos al aire libre sí se ha detectado una remoción eficiente de la fuente de contaminación y los valores isotópicos han revelado una migración del foco aguas abajo, así como también, cierta influencia de CF afectado por AH en las zanjas de intercepción y/o por procesos de oxidación del CF en la zona saturada de esta área. Para concluir, subrayar que esta tesis proporciona avances en la metodología de Cl- CSIA de los CMs, así como nuevos datos isotópicos de carbono y cloro para caracterizar procesos de degradación del CT y del CF. Estos datos combinados con otras técnicas geoquímicas y microbiológicas permiten discriminar y evaluar de forma pluridisciplinar procesos de atenuación natural en emplazamientos contaminados, así como realizar un asesoramiento y seguimiento de la eficiencia de las potenciales técnicas de remediación de CMs aquí descritas por parte de consultorías ambientales y administraciones. El uso rutinario del método de Cl- CSIA en los CMs es prometedor para futuras investigaciones y proyectos de remediación, paralelamente al ya consolidado C-CSIA. La implementación y evaluación de las técnicas de remediación de CMs a escala de campo, como la bioestimulación a través de fuentes económicas de B12, en combinación o no con el uso de Fe(0) o minerales de hierro a través de la puesta en valor de residuos mineros, son desafíos a corto plazo.

Bibliography: leaves 166-180. Determines the effect of chromium on the soil microbial community and its activity, the biotic-abiotic mechanisms involved in chromium oxidation, and phytostabilization of chromium using plants and organic amendment in tannery-waste contaminated soil.

After mineral exploitation the residual grinded and milled material, rich in sulphide minerals and heavy metals, is often left exposed to the atmospheric variables. This weathered mine waste material can lead to the formation of acid mine drainage (AMD) which has negative effects to the environment. The fractionation of stable isotope of metals such as Cu and Fe can be measured using innovative analytical techniques developed recently and could offer a detailed hindsight of the geochemical processes occurring in mine contaminated sites. Tailings profiles from Northern Sweden with high content of Cu and Fe sulphides and in different stages of weathering and/or remediation, along with plant and soil samples from a phytoremediation test site in Ronneburg, Germany were analysed using MC-ICP-MS to measure the isotope ratios of 65Cu/63Cu and 56Fe/54Fe. The analytical method used requires anion exchange chromatography to extract Cu and Fe from a complex matrix prior to the proper isotope ratio measurement. The samples from the tailings profile were useful to interpret the geochemical processes that can lead to a fractionation of Cu and Fe in the field, since redox-driven reactions such as rock oxidation and mineral precipitation are present in such environment. This study shows that precipitation of covellite in a redox-boundary zone in a mine tailings can cause a clear fractionation of Cu (Δ65Curock-covellite= -5.66±0.05‰) and a depletion of the lighter Cu isotope in the oxidised areas of the tailings due to dissolution of the remaining Cu-sulphides. Precipitation of Fe(oxy)hydroxides as a result of the oxidation process of sulphide-bearing rocks can also fractionate Fe, being the precipitated mineral slightly enriched in 56Fe.The influence of soil bacteria and plant uptake in the fractionation of Cu and Fe was investigated in pot and field experiments at the Ronneburg site, where organic amendments were used. The results showed that the plant material was enriched in the lighter Fe isotope compared to the substrate used in the pot and field experiments, in spite of the application of a bacterial consortium. Cu isotope fractionation is more susceptible to the changes in the amendments used, being those bacterial consortium, mychorriza or compost than Fe isotope fractionation. There are differences in the fractionation values in pot and field trials, regardless of the type of organic amendment applied. As an overall view, leaves are enriched in the heavier Cu isotope compared to the soils, regardless of the amendment usedThe application of the results obtained in this work would help not only to offer a view in the cycle of Fe and Cu in the surface environment, and the understanding of the (bio)geochemical processes occurring in sulphide soil surfaces. But also in the way that current remediation techniques of metal contaminated sites could be evaluated, having in mind that simplified systems show a different Cu and Fe fractionation compared to natural systems where more variables are needed to take into account.
Godkänd; 2012; 20120816 (natper); LICENTIATSEMINARIUM Ämnesområde: Tillämpad geologi/Applied Geology Uppsats: Fractionation of Cu and Fe Isotopes in Metal-Rich Mine sites: Biotic and Abiotic Processes Examinator: Professor Björn Öhlander, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Diskutant: Dr., Project Manager Magnus Land, Kungliga Vetenskapsakademien Tid: Tisdag den 25 september 2012 kl 10.00 Plats: F341, Luleå tekniska universitet

In der Entwicklung neuer Agrochemikalien ist es essentiell das weitere Schicksal im Bezug zum Abbau durch abiotische und biotische Einflüsse vorherzusagen. Pestizide gehören zu den Agrochemikalien und durch abiotischen und biotischen Stress werden Transformationsprodukte (TPs) gebildet. Daher ist es von Bedeutung, die TPs von Pestiziden und deren Entstehungsprozess zu untersuchen. Diese Dissertation beschäftigt sich mit biotischen und abiotischen Umwandlungsprozessen von zwei Modell-Pestiziden, nämlich Chlorpyrifos (ein Insektizid) und Fluopyram (ein Fungizid) unter Verwendung von Modellsystemen. Lebermikrosomeninkubation und elektrochemische Durchflusszellen, die an Online-Massenspektrometrie gekoppelt waren, wurden als experimenteller Modellansatz zu untersuchen um die Biotransformationsprozesse (phase I und phase II) der Ziel-Pestizide. Im zweiten Teil dieser Arbeit, wurden Photodegradationsprodukte der beiden Modellverbindungen durch Bestrahlung mit keimtötendem ultraviolettem Licht (200 - 280 nm) untersucht. Im letzten Teil dieser Arbeit wurde die Elektrochemie-Massenspektrometrie auf die Herstellung von Referenzstandards für Transformationsprodukte für das gezielte Screening in Lebensmittelproben ausgedehnt. Die strukturelle Aufklärung der Transformationsprodukte erfolgte mittels HPLC, gekoppelt an verschiedene Massenspektrometrietechniken (Single Quad, Triple Quad, FT-ICR HRMS, Triple TOF-MS, Orbitrap HRMS). Zusammenfassend konnte die Kopplung von EC/(LC)/MS als schnelle, zuverlässige, kostengünstige und matrix-unabhängige Methode genutzt werden, um den oxidativen Phase-I und II Metabolismus von Fluopyram und Chlorpyrifos zu simulieren. EC/MS könnte weiterhin zur Synthese von TP Referenzstandards und zur Messung von Realproben genutzt werden. Neue TPs und deren Bildungsmechanismen konnten im Rahmen dieser Dissertation für beide untersuchten Substanzen identifiziert werden.
One of the crucial steps of developing a new agrochemical product is predicting its fate following biotic or abiotic stress. In this regard, pesticides undergo transformation processes in response to biotic and abiotic stress. Therefore, it is important to investigate pesticides’ transformation products (TPs) and the formation processes they undergo. This dissertation deals on biotic and abiotic transformation processes of two model pesticides namely chlorpyrifos (an insecticide) and fluopyram (a fungicide) using model systems. Liver microsome incubation and electrochemical-flow-through cell coupled to online mass spectrometry were used as a model experimental approach to investigate phase I and phase II biotransformation processes of the targeted pesticides. In the second part of this thesis, photodegradation products of the two model compounds were investigated by irradiating with germicidal ultraviolet light (200 – 280 nm). In the last part of this work, electrochemistry-mass spectrometry was scaled-up to the production of transformation product reference standards for targeted screening in different food samples. Structural elucidations of transformation products were performed using HPLC coupled to different mass spectrometry techniques (single quad, triple quad, FT-ICR HRMS, TripleTOF-MS, Orbitrap HRMS). In summary, a fast, reliable, cost-effective and matrix-free simulation of oxidative metabolism (phase I and II) of fluopyram and chlorpyrifos was achieved here by EC/(LC)/MS. EC/MS could, therefore, be scaled up to synthesis TP reference standards for real sample investigation. Additionally, new TPs and their mechanisms were identified for both investigated compounds.