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114 Research products

  • Rural Digital Europe
  • 2013-2022
  • Doctoral thesis
  • European Commission

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  • Authors: Kounades-Bastian, Dionyssos;

    In this thesis we address the problem of multichannel audio source separa- tion (MASS) for underdetermined convolutive mixtures through probabilistic modeling. We focus on three aspects of the problem and make three contri- butions. Firstly, inspired from the empirically well validated representation of an audio signal, that is know as local Gaussian signal model (LGM) with non-negative matrix factorization (NMF), we propose a Bayesian extension to this, that overcomes some of the limitations of the NMF. We incorporate this representation in a MASS framework and compare it with the state of the art in MASS, yielding promising results. Secondly, we study how to separate mix- tures of moving sources and/or of moving microphones. Movements make the acoustic path between sources and microphones become time-varying. Ad- dressing time-varying audio mixtures appears is not so popular in the MASS literature. Thus, we begin from a state of the art LGM-with-NMF method designed for separating time-invariant audio mixtures and propose an exten- sion that uses a Kalman smoother to track the acoustic path across time. The proposed method is benchmarked against a block-wise adaptation of that state of the art (ran on time segments), and delivers competitive results on both simulated and real-world mixtures. Lastly, we investigate the link between MASS and the task of audio diarisation. Audio diarisation is the detection of the time intervals where each speaker/source is active or silent. Most state of the art MASS methods consider the sources to emit continuously; A hypothe- sis that can result in spurious signal estimates for a source, in intervals where that source was silent. Our aim is that diarisation can aid MASS by indicat- ing the emitting sources at each time frame. To that extent we design a joint framework for simultaneous diarisation and MASS, that incorporates a hidden Markov model (HMM) to track the temporal activity of the sources, within a state of the art LGM-with-NMF MASS framework. We compare the proposed method with the state of the art in MASS and audio diarisation tasks. We ob- tain performances comparable, with the state of the art, in terms of separation while winning in terms of diarisation.; Dans cette thèse nous abordons le problème de la séparation de sources audio dans des mélanges convolutifs multicanaux et sous-déterminés, en utilisant une modélisation probabiliste. Nous nous concentrons sur trois aspects, et nous apportons trois contributions. D’abord, nous nous inspirons du modèle Gaussien local par factorisation en matrices non-négatives (LGM-with-NMF), qui est un modèle empiriquement validé pour représenter un signal audio. Nous proposons une extension Bayésienne de ce modèle, qui permet de sur- passer certaines limitations du modèle NMF. Nous incorporons cette représentation dans un cadre de separation audio multicanaux, et le comparons avec l’état de l’art sur des tâches de séparation. Nous obtenons des résultats prometteurs. Deuxièment, nous étudions comment séparer des mélanges audio de sources et/ou des capteurs en mouvement. Ces déplacements rendent le chemin acoustique entre les sources et les microphones variant en cours du temps. L’adressage des mélanges convolutifs variant au cours du temps est peu exploré dans la littérature. Ainsi, nous partons d’une méthode de l’état de l’art développée pour la séparation de mélanges invariant (sources et microphones statiques) et utilisant LGM-with-NMF. Nous proposons à ceci une extension qui utilise un filtre de Kalman pour suivre le chemin acoustique au cours du temps. La technique proposée est comparée à une adaptation block-par-block d’une technique de l’état de l’art appliquée sur des intervalles de temps, et a donné des résultats exceptionels sur les mélanges simulés et les mélanges du monde réel. Enfin, nous investiguons les similitudes entre la séparation et la journalisation audio. La journalisation est le problème de détection des intervalles auxquels chaque locuteur/source est émettant. La plupart des méthodes de séparation supposent toutes les sources émettent continuellement. Cette hypothèe peut donner lieu à de fausses estimations durant les intervalles au cours desquels cette source n’a pas émis. Notre objectif est que la journalisation puisse aider à résoudre la séparation, en indiquant les sources qui émettent à chaque intervalle de temps. Dans cette mesure, nous concevons une cadre commun pour traiter simultanément la journalisation et la séparation du mélange audio. Ce cadre incorpore un modèle de Markov caché pour suivre les activités des sources au sein d’une technique de séparation LGM-with-NMF. Nous comparons l’algorithme proposé à l’état de l’art sur des tâches de séparation et de journalisation. Nous obtenons des performances comparables avec l’état de l’art pour la séparation, et supériures pour la journalisation.

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    Authors: Chugh, Tushar;

    Steering feedback is an important element that defines driver–vehicle interaction. It strongly affects driving performance and is primarily dependent on the steering actuator's control strategy. Typically, the control method is open loop, that is without any reference tracking; and its drawbacks are hardware dependent steering feedback response and attenuated driver–environment transparency. This thesis investigates a closed-loop control method for electric power assisted steering and steer-by-wire systems. The advantages of this method, compared to open loop, are better hardware impedance compensation, system independent response, explicit transparency control and direct interface to active safety functions. The closed-loop architecture, outlined in this thesis, includes a reference model, a feedback controller and a disturbance observer. The feedback controller forms the inner loop and it ensures: reference tracking, hardware impedance compensation and robustness against the coupling uncertainties. Two different causalities are studied: torque and position control. The two are objectively compared from the perspective of (uncoupled and coupled) stability, tracking performance, robustness, and transparency. The reference model forms the outer loop and defines a torque or position reference variable, depending on the causality. Different haptic feedback functions are implemented to control the following parameters: inertia, damping, Coulomb friction and transparency. Transparency control in this application is particularly novel, which is sequentially achieved. For non-transparent steering feedback, an environment model is developed such that the reference variable is a function of virtual dynamics. Consequently, the driver–steering interaction is independent from the actual environment. Whereas, for the driver–environment transparency, the environment interaction is estimated using an observer; and then the estimated signal is fed back to the reference model. Furthermore, an optimization-based transparency algorithm is proposed. This renders the closed-loop system transparent in case of environmental uncertainty, even if the initial condition is non-transparent. The steering related active safety functions can be directly realized using the closed-loop steering feedback controller. This implies, but is not limited to, an angle overlay from the vehicle motion control functions and a torque overlay from the haptic support functions. Throughout the thesis, both experimental and the theoretical findings are corroborated. This includes a real-time implementation of the torque and position control strategies. In general, it can be concluded that position control lacks performance and robustness due to high and/or varying system inertia. Though the problem is somewhat mitigated by a robust H-infinity controller, the high frequency haptic performance remains compromised. Whereas, the required objectives are simultaneously achieved using a torque controller.

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    Chalmers Research
    Doctoral thesis . 2021
    Data sources: Chalmers Research
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      Chalmers Research
      Doctoral thesis . 2021
      Data sources: Chalmers Research
  • Authors: Devaurs, Didier;

    Planning a path for a robot in a complex environment is a crucial issue in robotics. So-called probabilistic algorithms for path planning are very successful at solving dicult problems and are applied in various domains, such as aerospace, computer animation, and structural biology. However, these methods have traditionally focused on nding paths avoiding collisions, without considering the quality of these paths. In recent years, new approaches have been developed to generate high-quality paths: in robotics, this can mean nding paths maximizing safety or control; in biology, this means nding motions minimizing the energy variation of a molecule. In this thesis, we propose several extensions of these methods to improve their performance and allow them to solve ever more dicult problems. The applications we present stem from robotics (industrial inspection and aerial manipulation) and structural biology (simulation of molecular motions and exploration of energy landscapes).; Planifier le chemin d'un robot dans un environnement complexe est un problème crucial en robotique. Les méthodes de planification probabilistes peuvent résoudre des problèmes complexes aussi bien en robotique, qu'en animation graphique, ou en biologie structurale. En général, ces méthodes produisent un chemin évitant les collisions, sans considérer sa qualité. Récemment, de nouvelles approches ont été créées pour générer des chemins de bonne qualité : en robotique, cela peut être le chemin le plus court ou qui maximise la sécurité ; en biologie, il s'agit du mouvement minimisant la variation énergétique moléculaire. Dans cette thèse, nous proposons plusieurs extensions de ces méthodes, pour améliorer leurs performances et leur permettre de résoudre des problèmes toujours plus dificiles. Les applications que nous présentons viennent de la robotique (inspection industrielle et manipulation aérienne) et de la biologie structurale (mouvement moléculaire et conformations stables).

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    Authors: Beltrán-Abaunza, José M.;

    This PhD study focusses on the use of MEdium Resolution Imaging Spectrometer (MERIS) data for reliable and quantitative water-quality assessment of optically-complex waters (lake, brackish and coastal waters). The thesis is divided into two parts: A. intercalibration of reflectance measurements in different optically-complex water bodies (Paper I), and validation of various satellite processing algorithms for the coastal zone (Paper II). B. Applications: the use of MERIS data in integrated coastal zone management mostly using Himmerfjärden bay as an example. Himmerfjärden bay is one of the most frequently monitored coastal areas in the world and it is also the recipient of a large urban sewage treatment plant, where a number of full-scale nutrient management experiments have been conducted to evaluate the ecological changes due to changes in nutrient schemes in the sewage plant. Paper I describes the development and assessment of a new hyperspectral handheld radiometer for in situ sampling and validation of remote sensing reflectance. The instrument is assessed in comparison with readily available radiometers that are commonly used in validation. Paper II has a focus on the validation of level 2 reflectance and water products derived from MERIS data. It highlights the importance of calibration and validation activities, and the current accuracy and limitations of satellite products in the coastal zone. Bio-optical in situ data is highlighted as one of the key components for assessing the reliability of current and future satellite missions. Besides suspended particulate matter (SPM), the standard MERIS products have shown to be insufficient to assure data quality retrieval for Baltic Sea waters. Alternative processors and methods such as those assessed and developed in this thesis therefore will have to be put in place in order to secure the success of future operational missions, such as Sentinel-3. The two presented manuscripts in the applied part B of the thesis (paper III and IV), showed examples on the combined use of in situ measurements with optical remote sensing to support water quality monitoring programs by using turbidity and suspended particulate matter as coastal indicators (manuscript III). The article also provides a new turbidity algorithm for the Baltic Sea and a robust and cost-efficient method for research and management. A novel approach to improve the quality of the satellite-derived products in the coastal zone was demonstrated in manuscript IV. The analysis included, the correction for adjacency effects from land and an improved pixel quality screening. The thesis provides the first detailed spatio-temporal description of the evolution of phytoplankton blooms in Himmerfjärden bay using quality-assured MERIS data, thus forwarding our understanding of ecological processes in in Swedish coastal waters. It must be noted that monitoring from space is not a trivial matter in these optically-complex waters dominated by the absorption of coloured dissolved organic matter (CDOM). These types of coastal waters are especially challenging for quantitative assessment from space due to their low reflectance. Papers III and IV thus also provide tools for a more versatile use in other coastal waters that are not as optically-complex as the highly absorbing Baltic Sea waters. The benefits of the increased spatial-temporal data coverage by optical remote sensing were presented, and also compared to in situ sampling methods (using chlorophyll-a as indicator). Research funders:European Space Agency (ESA, contract no.21524/08/I-OL)NordForsk funding: Nord AquaRemS Ref. no. 80106NordForsk funding: NordBaltRemS Ref.no. 42041At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.

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    Authors: Férriz Núñez, Macarena;

    El aumento de la concentración de CO2 atmosférico [CO2] como consecuencia de las emisiones antropogénicas lleva asociado un aumento en la temperatura media del planeta. La cuenca mediterránea es particularmente sensible a perturbaciones más intensas debido a una mayor aridez y al legado de usos de suelo que ha modificado notablemente los paisajes actuales. En este contexto de cambio global, estudiamos el decaimiento y las dinámicas de regeneración de tres especies de coníferas mediterráneas con diferente tolerancia a la sequía Pinus pinaster < Pinus pinea < Juniperus oxycedrus (Capítulo 2). Comparamos los patrones de crecimiento y la respuesta al clima de individuos con diferente estado de salud: sanos (las tres especies), en decaimiento (sólo P. pinaster) y muertos (P. pinaster y P. pinea). La actual especie dominante, P. pinaster, muestra claros signos de decaimiento -definido por alta defoliación e infección de muérdago- y mortalidad, con escasa regeneración, siendo reemplazada por regeneración de otras especies más tolerantes a la sequía como Quercus ilex, P. pinea y J, oxycedrus. Desde los años 80, los eventos de sequía han sido más frecuentes y severos en la zona, habiendo incitado el decaimiento en P. pinaster pero no en las otras especies acompañantes. Los individuos no-sanos de P. pinaster mostraron una reducción en el crecimiento desde 1995, mientras que en los individuos muertos de P. pinea este declive comenzó en 2005. La supervivencia de P. pinaster en la zona estaba relacionada con una mayor sensibilidad a la precipitación de primavera y a sitios con mayor disponibilidad de agua, mientras que la supervivencia de P. pinea estaba principalmente relacionada con un mayor diámetro del árbol. En el Capítulo 3, seleccionamos 5 árboles de cada estado de salud y especie y estudiamos la anatomía del xilema y la discriminación isotópica de carbono (13C) en anillos de crecimiento. Las dos especies de pinos mostraron traqueidas más grandes y una mayor plasticidad del xilema en respuesta a la variabilidad climática que J. oxycedrus. Los caracteres anatómicos se diferenciaron entre estados de salud en P. pinaster y P. pinea. Los individuos sanos tenían mayor área de lumen en la madera temprana y paredes celulares más gruesas en la madera tardía que los individuos no-sanos, junto con mayor plasticidad en el xilema frente al clima, lo que les permitió ajustar sus caracteres anatómicos para aumentar la seguridad en el xilema durante eventos de sequía. La habilidad de mantener un xilema competitivo y plástico es crucial para conseguir ratios productivos en escenarios de cambio climático. Nuestro estudio reveló que los pinos muertos y en decaimiento tenían valores similares de 13C que los árboles sanos, lo que sugiere que los pinos no-sanos ejercen un menor control estomático que debería maximizar la tasa fotosintética y aumentar el transporte de agua hacia la copa para compensar por la pérdida excesiva de agua. Los resultados de los Capítulos 2 y 3 sugieren que a pesar del decaimiento general observado en P. pinaster en el área, los individuos sanos de esta especie pueden sobrevivir en áreas con mayor disponibilidad de agua, mientras que en el resto del paisaje serán eventualmente sustituidos por especies más tolerantes a la sequía como P. pinea y J. oxycedrus. Además, los patrones de regeneración en la zona revelaron que tanto el estrés hídrico como el legado de usos de suelo limitan el establecimiento de regenerado de P. pinaster en comparación con la más abundante regeneración que presentan P. pinea, J, oxycedrus y Q. ilex. Debido a que los cambios de distribución de las especies están determinados en última instancia por el regenerado, comprender el efecto combinado de altas concentraciones de [CO2] y el estrés hídrico es fundamental para pronosticar futuros cambios en el paisaje e identificar qué especies prevalecerán en estos nuevos escenarios. Por ello en el Capítulo 4, analizamos cómo el enriquecimiento con [CO2] puede mitigar los efectos negativos del estrés hídrico en plántulas de dos especies de pino mediterráneas P. pinaster y P. pinea. En cámaras de crecimiento, testamos los efectos de dos concentraciones de [CO2]: a[CO2] (380 ppm) y e[CO2] (800 ppm) y dos regímenes de riego. En condiciones de e[CO2], ambas especies aumentaron la biomasa total, WUE (el uso en la eficiencia del agua a nivel de toda la planta) y WUEi (uso en la eficiencia del agua intrínseco) en comparación con valores medidos en condiciones de a[CO2]. El aumento de WUEi bajo condiciones de alto [CO2] se debió a una reducción en la conductancia estomática y a un aumento de la tasa fotosintética. Sin embargo, encontramos diferencias en los ajustes funcionales al e[CO2] y estrés hídrico en las dos especies. P. pinea mostró una mayor tasa fotosintética y menores potenciales hídricos al amanecer (amanecer) y al mediodía (mediodía,) mostrando que esta especie tiene un comportamiento más anisohídrico que P. pinaster, el cual mantuvo una estrategia más isohídrica y de mayor ahorro de agua mediante un mayor control estomático, invirtiendo más en el desarrollo de la raíz que P. pinea. Además, en el Capítulo 5 estudiamos los ajustes en la anatomía del xilema y en el sistema hidráulico de las plántulas en estas condiciones de e[CO2] alto y estrés hídrico. El estrés hídrico indujo una menor producción de acículas en P. pinaster para minimizar la pérdida de agua. Por otro lado P. pinea mostró una mayor plasticidad en el xilema mediante la reducción del tamaño del lumen para aumentar la seguridad en el xilema ante estrés hídrico. Aunque ambas estrategias pueden ser efectivas a la hora de minimizar transpiración y mantener la seguridad en el xilema, reducir el área foliar puede comprometer la tasa fotosintética a largo plazo, perjudicando la habilidad del individuo para competir. Por el contrario, una mayor plasticidad en el xilema en P. pinea permitiría a los árboles adaptar su crecimiento y estructura a las condiciones ambientales y optimizar el uso de recursos disponibles manteniendo una mayor área foliar activa (es decir, el aparato fotosintético). Altas concentraciones de [CO2] redujeron la conductancia específica de la hoja en ambas especies de pino, probablemente mediante menor conductancia estomática. El aumento en el número de traqueidas en el xilema P. pinea le permite construir un xilema más seguro a la vez que compensa un menor tamaño de traqueidas bajo estrés hídrico. Por tanto, nuestros resultados sugieren que un aumento de [CO2] beneficiará de forma diferente a las dos especies estudiadas, aun asumiendo que ambas pertenecen al mismo grupo funcional. El enriquecimiento en [CO2] beneficiará más a P. pinea que a P. pinaster bajo condiciones de estrés hídrico, debido a que P. pinea puede mantener la conductividad hidráulica con un xilema más resistente a la cavitación. Si extrapolamos nuestros resultados a condiciones naturales y en particular a los escenarios climáticos esperados en el futuro, podemos concluir que la mayor tolerancia a la sequía expresada por P. pinea hará que esta especie prevalezca frente a P. pinaster en ambientes futuros con mayor aridez y mayor concentración de [CO2]. ----------ABSTRACT---------- Rising CO2 atmospheric concentration ([CO2]) as a consequence of anthropogenic emissions is driving an increase in the average temperature of the planet. The Mediterranean basin is particularly sensitive to more intense disturbances due to aridification and land-use legacies that have strongly shaped the current landscapes in the Region. In this context of global change, we studied the decline and regeneration dynamics of three co-occurring Mediterranean coniferous species of different drought tolerance: Pinus pinaster < Pinus pinea < Juniperus oxycedrus (Chapter 2). We compared the growth patterns and climatic response of trees with different health status: healthy (for the three species), declining (only P. pinaster) and dead (P. pinaster and P. pinea). The currently dominant species, P. pinaster, shows extensive signs of decline -assessed by high canopy defoliation and mistletoe infection- and mortality. In addition, the species presents scarce regeneration, whereas it is being replaced by Quercus ilex, P. pinea and J. oxycedrus, with more abundant regeneration and abundance in juvenile stages. Since the 1980s, more frequent and severe drought events have occurred, inciting tree growth decline in dead and non-healthy pine trees, but with differences between species. Non-healthy individuals of P. pinaster exhibited negative growth trends since 1995. In dead P. pinea trees, the growth decline started later since 2005. P. pinaster survival in the study area was linked to a higher sensitivity to spring precipitation and was concentrated in sites with higher moisture availability, while P. pinea survival was higher in trees with larger diameters. In Chapter 3, we selected 5 individuals from each status and species and studied the xylem anatomical traits and carbon isotopic discrimination (13C) in annual tree-rings. Pine trees exhibited larger tracheids and higher xylem plasticity to climate variability than J. oxycedrus. Xylem traits differed between different health status in Pinus pinaster and Pinus pinea. Healthy pine trees had bigger lumen sizes in the earlywood and thicker cell walls in the latewood than non-healthy trees, along with expressing a higher xylem plasticity to climate. This xylem plasticity allowed P. pinea to adjust their xylem characteristics to increase cell safety during drought events. The ability to maintain a competitive yet plastic xylem structure is crucial to sustain productivity rates under more xeric, climate change scenarios. Our study revealed that non-healthy pines (i.e. declining and dead pine trees) and healthy trees exhibited similar 13C, which suggests that non-healthy pine trees had low stomatal control to maximize photosynthesis and increase water transport to the crown to compensate for the excessive water loss. Results from Chapters 2 and 3 suggest that despite the general species decline (i.e. high mortality, canopy defoliation, mistletoe infection) observed in P. pinaster in the area, healthy individuals of this species are performing well in sites with higher moisture availability, while in soils with less moisture availability in the area it can be eventually replaced by more drought-tolerant P. pinea, J. oxycedrus and Q. ilex. Regeneration patterns in the area revealed that water stress along with land-use legacies are limiting P. pinaster establishment in comparison to more abundant regeneration of these three more drought-tolerant co-occurring taxa. Since species distribution shift is ultimately driven by regeneration success, understanding the combined effect of enriched [CO2] and water stress on seedlings is crucial to forecast future changes in the landscape and identify which species will prevail in these new scenarios. Therefore, in Chapter 4, we characterized how elevated [CO2] can mitigate the negative effects of water stress on seedlings of the two Mediterranean pine species P. pinaster and P. pinea. In growth chambers, we tested the effects of two [CO2] treatments: a[CO2] (380 ppm) and e[CO2] (800 ppm) and two water regimes. Under e[CO2], both species increased total biomass, WUE (whole-plant water use efficiency) and WUEi (intrinsic water use efficiency) in comparison to measured values in a[CO2]. Increases in WUEi under high [CO2] were both due to reduced stomatal conductance and increased photosynthetic rates. However, we also found differences in the functional adjustment to elevated [CO2] and water stress of the two species. P. pinea exhibited higher photosynthetic rates and lower water potential, both predawn and midday, suggesting that this species follows a more anisohydric behaviour than P. pinaster, which in contrast maintained a more isohydric, water-saving strategy and invested more in root development than P. pinea. In addition, in Chapter 5 we studied the xylem anatomical adjustments and hydraulic performance of seedlings under e[CO2] and water stress. Water shortage induced a reduction in P. pinaster leaf production to minimise water loss, while P. pinea exhibited a higher xylem plasticity, particularly by reducing lumen size to increase xylem safety. Although both strategies can be effective in minimising transpiration and maintaining xylem safety, reducing leaf area may compromise photosynthetic rates in the long-term, worsening plant ability to compete. In contrast, higher xylem plasticity in P. pinea would allow trees to adapt growth and structure to environmental conditions and to optimise the use of available resources by keeping a greater active leaf area (i.e., photosynthetic apparatus) under water stress. Elevated [CO2] reduced leaf specific conductivity in both pine species, which was probably linked to lower stomatal conductance. The increased in the number of tracheids in P. pinea xylem allowed it to develop a safer xylem that compensated for smaller tracheids under water stress. Thus, our results suggest that rising [CO2] will differently benefit the two studied species, even if they are assumed to belong to the same functional type. [CO2] enrichment will benefit more P. pinea under water stress than P. pinaster, since P. pinea can maintain hydraulic conductivity with a greater xylem resistance to cavitation. If our results hold for natural conditions, we can conclude that due to the higher drought tolerance expressed by P. pinea in comparison to P. pinaster, the former species will prevail under future more xeric and enriched [CO2] environments, particularly where these two species form mixed stands today.

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    https://doi.org/10.20868/upm.t...
    Thesis . 2022 . Peer-reviewed
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      https://doi.org/10.20868/upm.t...
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    Authors: Pereira Ramos, Eunice;

    The last decade has seen the emergence of a new research theme - the study of the resources Nexus. The “Nexus” refers to considering the functioning of several systems simultaneously, as opposed to one, as the object of research. This perspective reasons that coherent decision-making needs to consider systems' interconnectedness. Typical system-of-systems (Nexus) studied relate to the security of services, such as the Water-Energy and Food Nexus, and resources, i.e. the Climate, Land, Energy and Water systems (CLEWs) Nexus. The process of examining cross-systems dynamics and interactions is known as the Nexus approach. Implementing it requires understanding multiple systems, disciplinary integration, and multi-stakeholder engagement at various decision levels. Adequate planning of an assessment process is needed to ensure the successful implementation of the approach and its long-lasting presence in decision-making processes. Therefore, reviewing the application of Nexus approaches can inform essential aspects that clarify and streamline the entire process. Current gaps in Nexus research include the lack of clarity in systems representation, the lack of flexible and accessible tools and methods for Nexus analyses, and the need for transparency in modelling approaches. All of these hinder the integration of the approach in research and the incorporation into decision-making processes. The thesis aims to advance the science of integrated resource assessments, particularly the Nexus approach, and support its dissemination and implementation within and beyond academia. Insights from applying two Nexus approaches (CLEWs and SIM4NEXUS) are distilled from the comparison of case studies. Overarching aspects examined include the expertise engaged in assessments, practitioners' roles and transdisciplinarity. Also analysed are selected components in the Nexus approach, such as identifying systems' interactions, analytical approaches, and stakeholder engagement and participation. The transversal feature of knowledge transfer between experts, practitioners, and stakeholders is examined to understand its importance in the assessment process. Examples of quantitative analyses illustrate the representation of different Nexus contexts and the elaboration of relevant insights. This thesis presents two such quantitative examples. One example is an entry-level CLEWs modelling exercise, whose development is described from conceptualisation, model development, and interpretation of results. The other example is a quantitative analysis of the transboundary Syr Darya river basin, which investigates the role of model structure in exploring Nexus questions. The thesis highlights a list of principles to support the Nexus approach's operationalisation deriving from practice and considering current research gaps. Det senaste decenniet har sett uppkomsten av ett nytt forskningstema - studiet av resurserna Nexus. "Nexus" hänvisar till att betrakta funktionen hos flera system samtidigt, i motsats till ett, som föremål för forskning. Detta perspektiv motiverar att ett sammanhängande beslutsfattande måste beakta systemens sammanlänkning. Typiska system-of-systems, Nexus, som studeras relaterar till säkerheten för tjänster, såsom vatten-energi- och livsmedelsnexus, och resurser, dvs. Processen att undersöka dynamik och interaktioner mellan olika system är känd som Nexus-metoden. Att implementera det kräver förståelse för flera system, disciplinär integration och engagemang från flera intressenter på olika beslutsnivåer. Adekvat planering av en bedömningsprocess krävs för att säkerställa ett framgångsrikt genomförande av tillvägagångssättet och dess långvariga närvaro i beslutsprocesser. Därför kan en granskning av tillämpningen av Nexus tillvägagångssätt informera viktiga aspekter som förtydligar och effektiviserar hela processen. Aktuella luckor i Nexus-forskningen inkluderar bristen på tydlighet i systemrepresentationen, avsaknaden av flexibla och tillgängliga verktyg och metoder för Nexus-analyser och behovet av transparens i modelleringsmetoder. Allt detta hindrar integreringen av tillvägagångssättet i forskningen och införlivandet i beslutsprocesser. Avhandlingen syftar till att främja vetenskapen om integrerade resursbedömningar, särskilt Nexus-metoden, och stödja dess spridning och implementering inom och utanför akademin. Insikter från två Nexus-metoder (CLEWs och SIM4NEXUS) kommer från jämförelsen av fallstudier. Övergripande aspekter som granskas inkluderar expertis som är engagerad i bedömningar, utövarnas roller och transdisciplinaritet. Dessutom analyseras utvalda komponenter i Nexus-metoden, som att identifiera systemens interaktioner, analytiska tillvägagångssätt och engagemang och deltagande av intressenter. Det tvärgående inslaget i kunskapsöverföring mellan experter, praktiker och intressenter undersöks för att förstå dess betydelse i bedömningsprocessen. Exempel på kvantitativa analyser illustrerar representationen av olika Nexus-kontexter och utarbetandet av relevanta insikter. Denna avhandling presenterar två sådana kvantitativa exempel. Ett exempel är en CLEWs modelleringsövning på ingångsnivå, vars utveckling beskrivs från konceptualisering, modellutveckling och tolkning av resultat. Det andra exemplet är en kvantitativ analys av det gränsöverskridande flodområdet Syr Darya, som undersöker modellens strukturs roll för att utforska Nexus-frågor. Avhandlingen belyser en lista med principer för att stödja Nexus-metodens operationalisering som härrör från praktiken och med tanke på aktuella forskningsluckor.

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    Authors: Frey, Eva;

    Das Honigbienenvolk ist konfrontiert mit einer Vielzahl an Pathogenen, darunter Viren, Bakterien, Pilze und Milben. Der weltweit bedeutendste Parasit der westlichen Honigbiene ist dabei die ektoparasitische Bienenmilbe Varroa destructor. Entdeckt wurde die Milbe zu Beginn des 20. Jahrhunderts in Südostasien in Völkern der östlichen Honigbiene Apis cerana, ihrem ursprünglichen Wirt. Ab Mitte des letzten Jahrhunderts wurde die Milbe dann durch Transporte infizierter A. mellifera Völker weltweit verbreitet mit meist dramatischen Folgen für wildlebende und bewirtschaftete Honigbienenvölker. Mittlerweile stellt der Parasit das größte wirtschaftliche Problem für die globale Imkerei dar. So gibt es in den gemäßigten Breiten nahezu kein varroafreies Volk mehr und ohne regelmäßige Bekämpfung der Varroose durch den Imker gehen Bienenvölker innerhalb weniger Jahre ein. Dies bestätigt, dass sich bei A. mellifera nach wie vor kein stabiles Wirt-Parasit-Verhältnis entwickelt hat und die Bekämpfung von V. destructor nach wie vor die größte Herausforderung für die Imkerei darstellt. Die Hauptursache für die Wirtsschädigungen ist die enorme Zunahme der Varroapopulation im Jahresverlauf, die offensichtlich durch das Bienenvolk nicht ausreichend kontrolliert werden kann. Dieses Populationswachstum wird beeinflusst durch Reproduktionsrate der Varroaweibchen innerhalb der einzelnen Brutzellen, durch Parasit-Wirt-Wechselwirkungen auf der Ebene des Bienenvolkes und durch Wechselwirkungen zwischen den Bienenvölkern. Im Rahmen der vorliegenden Dissertation wurden Untersuchungen auf allen drei Ebenen durchgeführt. Zunächst konnte auf der individuellen Ebene erstmals nachgewiesen werden, dass Signale der Bienenlarve nicht nur die Reproduktion der Varroaweibchen aktivieren, sondern eine begonnene Oogenese sogar wieder stoppen können. Unter evolutiven Gesichtspunkten macht dies Sinn, da das Varroaweibchen nur dann Ressourcen in die Eibildung investiert, wenn die Bedingungen für eine erfolgreiche Reproduktion gegeben sind. Meine Ergebnisse lassen vermuten, dass kutikuläre altersabhängige Duftstoffe der Bienenlarve an der Steuerung der Varroareproduktion maßgeblich beteiligt sind. Als Wirtssignale kommen dabei bestimmte Fettsäureester in der polaren Fraktion des Kutikulaextraktes in Frage. Im Rahmen eines Kooperationsprojektes konnten wir darüber hinaus zeigen, dass die temporär auftretende Infertilität von Varroaweibchen signifikant mit drei QTL auf drei Chromosomen der Wirtslarve korreliert ist, es also offensichtlich eine genetische Basis für solche reproduktionshemmenden Resistenzfaktoren gibt. Hierfür machten wir uns die haplo-diploide Geschlechtsbestimmung bei Honigbienen zunutze, da potentielle Resistenzgene eher im haploiden Phänotyp sichtbar werden und sich das Genom leichter molekulargenetisch charakterisieren lässt. Für Untersuchungen von Varroaresistenz auf der Ebene des Bienenvolkes sowie für die Durchführung von Selektionsprogrammen ist ein weiterer Aspekt von enormer Bedeutung. In zwei Versuchsansätzen konnte ich nachweisen, dass der Eintrag von Varroamilben von benachbarten Völkern – oft als „Reinvasion“ bezeichnet - die Populationsentwicklung des Parasiten im Volk nachhaltig beeinflusst. Zunächst wurde unter den Bedingungen eines isolierten Truppenübungsplatzes der Eintrag von Milben in Abhängigkeit vom Invasionsdruck (= Anzahl und Entfernung infizierter Bienenvölker) quantifiziert. Hierfür wurden mit Akariziden dauerbehandelte Völker in unterschiedlichen Abständen zu stark parasitierten Völkern aufgestellt und der Milbeneintrag wöchentlich erfasst. In einem weiteren Versuch wurde der Ansatz erweitert: Neben der Varroainvasion wurde nun auch die Vermehrung der eingetragenen Milben quantifiziert. Unter praxisnahen Bedingungen konnte so nachgewiesen werden, dass horizontale Verbreitung plus anschließende Vermehrung der eingeschleppten Varroamilben zu einem exponentiellen Anstieg der Varroapopulation führen können, der innerhalb von drei Monaten die Schadensschwelle übersteigt und dadurch die Überwinterung der Bienenvölker gefährdet wird. Aus den Versuchsergebnissen werden Empfehlungen für eine flächendeckende und zeitlich koordinierte Varroabekämpfung sowie für die Selektion resistenter Bienenvölker abgeleitet. Mit meinen Versuchen konnte ich einige Mosaiksteine zum Verständnis der Varroa-Reproduktionssteuerung innerhalb der individuellen Brutzelle und zur Varroa-Populationsdynamik innerhalb des Bienenvolkes hinzufügen. Ein solches Verständnis der Populationsdynamik und der zugrunde liegenden Wirtsfaktoren ist meiner Meinung nach essentiell für die Selektion varroaresistenter Bienenvölker und darüber hinaus wichtig für die Entwicklung von Varroa-Bekämpfungskonzepten. The honey bee colony is faced with a huge number of pathogens, including bee viruses, bacteria, fungi and mites. Among these pathogens, the ectoparasitic mite Varroa destructor is considered the most important parasite of the honey bee worldwide. This mite was discovered at the beginning of the last century in South East Asia within colonies of the original host, the Eastern honey bee Apis cerana. From the middle of the last century the mite has been spread worldwide by transports of infested A. mellifera colonies with dramatic consequences for both, feral and managed honey bee colonies. In the meantime this parasite has become the most serious economic problem for global beekeeping. In temperate climates nearly all honey bee colonies are infested and without yearly Varroa treatments these colonies would collapse within a few years. This confirms that a stable host parasite relationship has not been established yet. Therefore the control of V. destructor still represents the main challenge for beekeeping. The main reason for host damages is the dramatic increase of the Varroa population during the season. Our honey bee colonies are obviously unable to control this population dynamic of the parasite. The increase of the mite population is influenced by the reproductive rate of Varroa females within individual brood cells, by host-parasite-interactions on the colony level and by interactions among honey bee colonies on the population level. The dissertation at hand presents experimental approaches and results at all three levels. On the individual level we were able to demonstrate that age-dependent signals of the honey bee larvae not only activate the oogenesis of the Varroa females but even trigger the further course of mite reproduction. Our studies on the activation of the Varroa reproduction revealed that exclusively larvae within 18 h (worker) and 36 h (drones), respectively, after cell capping were able to stimulate the mite’s oogenesis. Furthermore, we were able to confirm for the first time the presence of a signal in the host larvae allowing the reproducing mites to adjust their own reproductive cycle to the ontogenetic development of the host. Under certain conditions such host signals can even stop an oogenesis of the female mite that has already been started. From an adaptive point of view that sort of a stop signal enables the female mite to save resources for a next reproductive cycle if the own egg development is not sufficiently synchronized with the development of the host. My results indicate that age specific volatiles of the larval cuticle are involved in the regulation of mite reproduction. According to preliminary quantitative GC–MS analysis we suggest certain fatty acid ethyl esters as candidate compounds. These host signals – either involved in the activation or in the interruption of the Varroa reproduction – offer possibilities to influence the reproductive success of Varroa females and might therefore be used for biological control in the future. Within an EU cooperation project we could additionally demonstrate that the so called temporary infertility of Varroa females is significantly correlated with three QTL of the host larvae. This confirms a genetic basis for host resistance factors that inhibit the mite reproduction. For this study we made use of the fact that we had access to a honey bee population at the island of Gotland, Sweden that has survived mite infestation without any treatment for more than 10 years. We crossed a queen from this tolerant population with drones from susceptible colonies to rear hybrid queens and produced a mapping population of haploid drones from these hybrids. Because honey bees have a haplodiploid sex determination, the haploid drones provide an extremely simple and highly efficient model system for genetic studies. Subsequently, we mapped three candidate target regions on chromosomes 4, 7, and 9. Although the individual effect of these three QTL was found to be relatively small, the set of all three had significant impact on the suppression of V. destructor reproduction by epistasis. The detection of this epistatic interaction was only possible because we used the simple genetic make-up of haploid drones. For studies on Varroa resistance on the colony level and for selection programs the interactions among the colonies of the local honey bee population have to be considered. In two experimental approaches I was able to prove that the invasion of Varroa mites from neighboring colonies – often called “reinvasion” – significantly influences the population dynamic of the parasite within the colony. First, we quantified the number of mites invading individual colonies in relation to the invasion pressure (= number and distance of infested colonies). For this approach we made use of an isolated military training area near Münsingen at the Swabian Alb not accessible to other beekeepers. We established ten “mite receiver colonies” continuously treated against V. destructor and placed them at distances of 1m to 1.5 km from four heavily infested “mite donor colonies”. In the donor colonies, we estimated the population of bees, brood, and V. destructor at three week intervals. The invasion of mites into the receiver colonies was recorded every 7-12 days. During the measurement period of about two months, between 85 and 444 mites per colony were introduced into the receiver colonies. Surprisingly, there were no significant differences in the invasion rates in relation to the distance between donor and receiver colonies. The second approach was performed under more realistic field conditions of two experimental apiaries established in regions with high and low bee densities, respectively. Additionally, in this experiment we analyzed the multiplication of the invaded mites. Thereby we confirmed that horizontal transmission plus the reproduction of the invaded Varroa mites can cause an exponential increase of the mite population that may exceed the damage threshold within three months. We were further able to show that the invasion rates – and therefore the final infestation – differ significantly according to the number of honey bee colonies in the neighborhood of the apiary: At the site with a high bee density, the average invasion rate per colony over the entire three and a half months period was 462 mites per colony compared to only 126 mites per colony at the site with a low bee density. As a consequence, the colonies of the apiary at the high bee density site revealed an average final infestation in November of 2,082 mites per colony compared to 340 mites per colony at the low bee density site. The highly infested colonies lost about three times more bees compared to the lower infested colonies – obviously a result of Virus infections transmitted by Varroa mites. With my different approaches I was able to add further elements of knowledge for a better understanding of how host factors and ambient conditions influence the Varroa reproduction within individual brood cells and the population dynamic within a honey bee colony. A better knowledge of these host parasite interactions is essential for the selection of mite resistant colonies and further more important for the development of concepts for an effective Varroa treatment.

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    Authors: Emmi, Luis Alfredo;

    Precision Agriculture (PA) aims to the application of selective treatments as well as the use of agricultural inputs depending on the field and crop needs spatially localized. One of the most demanded agricultural work is the effective weed control, to increase productivity while decreasing the usage of polluting chemical products. The incorporation of new positioning technologies (GPS, Laser), acquisition and detection (computer vision) and automatic control adapted for vehicles (tractors) and for agricultural machinery (implements), has established the foundation for the development of PA. Although, only a few cases have achieved a configuration of a fully autonomous agricultural system, and with a minor dimension, a configuration of a fleet of robots for cooperation and for distribution of agricultural tasks. The study presented in this research includes three major contributions oriented to the aforementioned automation. More specifically, this research provides the foundation through the development of a control architecture for the integration of both an autonomous vehicle and an autonomous implement, endowed with the technology required to achieve such autonomy and efficient performance. The first contribution is the development of a simulation environment to study and evaluate the implementation of PA techniques that allows the performance, cooperation and interaction of a group of autonomous robots to be analyzed, while the execution of a specific task is simulated in a three-dimensional world. The second contribution is the development of a proposal of a control architecture to integrate a vehicle equipped with an implement, with the purpose to constitute a fully autonomous agricultural unit able to work cooperatively in a fleet of robots. The third contribution is the integration and validation, in a real crop field, of a perception system (based on computer vision and GPS location), an actuation system (consisting of an autonomous tractor and an autonomous implement for mechanical weed control) and a decision-making system (which is the core of the integration of these elements), all encompassed in the control architecture developed from the perspective of full autonomy. This integration was performed using the selection, management, configuration and synchronization of these systems, providing a model for a fully autonomous vehicle for agricultural applications. Successful results of several experiments conducted on real crop fields in differentseasons and under different crop conditions are presented, demonstrating the performance and validity of the integrated proposal in guidance and weed control tasks in a maize field, and its usefulness and effectiveness. This work is a major advance in the design of mobile units able to work in coordination as a fleet of robots in agricultural tasks, resulting in several publications in various scientific journals and prestigious international conferences in the area of PA. The developments obtained have been a fundamental part in the progress of the RHEA project, demonstrating the ability to configure a fleet of robots for PA applications, having been endorsed by members of the project consortium, as well as positive evaluations of the representatives of the European Union, both technical and management. Tesis Doctoral defendida para la obtención del Título de Grado de Doctor. xx, 213 p. : il., fot., diagr. Fecha de defensa de la Tesis Doctoral: 19 de diciembre de 2014. Calificación: Sobresaliente C. Laude Peer Reviewed

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    E-Prints Complutense
    Doctoral thesis . 2014 . Peer-reviewed
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    Tesis Doctorals en Xarxa
    Doctoral thesis . 2016 . Peer-reviewed
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      E-Prints Complutense
      Doctoral thesis . 2014 . Peer-reviewed
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      Tesis Doctorals en Xarxa
      Doctoral thesis . 2016 . Peer-reviewed
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    Authors: Roquette Tenreiro, Tomás;

    En campos en pendiente, los cultivos de secano experimentan diferentes grados de estrés hídrico causados por variaciones espaciales de la humedad en el suelo, y los rendimientos varían espacialmente dentro del mismo campo. Esta variabilidad supone una oportunidad para la agricultura de precisión a través del manejo espacialmente variable. Sin embargo, si bien se han logrado avances significativos en los aspectos de la ingeniería de la variación espacial, como el aumento de la resolución espacial de los sistemas de datos y la automatización, se ha avanzado mucho menos en relación a la simulación de las respuestas de los cultivos a las variaciones espaciales de la humedad y los flujos hídricos. La mayoría de los estudios sobre las brechas de rendimiento de secano ignoran la variabilidad dentro de la parcela. Sin embargo, el uso de modelos de simulación de cultivos como medida de apoyo a los sistemas de gestión espacialmente variable, requiere que los enfoques de modelación espacial del agua sean capaces de representar y simular con precisión la variación dentro del campo de los factores relacionados con el agua disponible y la respuesta de los cultivos. Esta tesis doctoral representa una nueva contribución a la agronomía de los sistemas agrícolas de secano, con énfasis en el papel que juegan los flujos de agua en zonas de topografía ondulada en la determinación de las variaciones espaciales del rendimiento del trigo. La tesis se ha desarrollado en capítulos que se complementan siguiendo un enfoque integrador. La presente tesis doctoral revisó algunos de los modelos hidrológicos y de cultivo más ampliamente adoptados y exploró nuevas oportunidades para simular variaciones espaciales del agua a nivel de campo mediante la incorporación del flujo lateral de escorrentía superficial y sub-superficial en las zonas de menor elevación del campo. Desde este punto de vista, se evaluaron las variaciones espaciales de las brechas de rendimiento en trigo de secano, en Córdoba, España, que son causadas por flujos laterales de los puntos altos a los bajos. Desde una perspectiva agronómica, las entradas laterales del agua contribuyen a las variaciones de rendimiento en los sistemas de producción de trigo de secano como el que se ha estudiado en el ámbito de esta tesis. La contribución neta de estos flujos a las variaciones espaciales de los rendimientos potenciales de secano se mostró relevante pero altamente irregular entre diferentes años. A pesar de la variabilidad interanual, típica de las condiciones mediterráneas, la existencia de dichos flujos hizo que los rendimientos de trigo simulados variaran un +16% desde las áreas más elevadas de un campo hacia abajo. El rendimiento medio observado osciló entre 1.3 y 5.4 Mg de rendimiento de grano (GY) ha−1. Las respuestas de rendimiento neto al flujo lateral, cuenca abajo, fueron en promedio 383 kg de rendimiento de grano (GY) ha−1, y la productividad marginal de agua de LIF alcanzó 24.6 (±13.2) kg GY ha−1 mm−1 en años de máxima capacidad de respuesta. Dichos años de máxima capacidad de respuesta se asociaron con bajas precipitaciones durante las etapas vegetativas del cultivo en combinación con flujos laterales en las etapas posteriores a la floración. En condiciones de campo, estas diferencias solo fueron visibles en uno de los dos años experimentales. Las implicaciones económicas asociadas con múltiples escenarios de tasa de aplicación variable de nitrógeno se exploraron a través de un caso de estudio y se propusieron varias recomendaciones. Tanto el tamaño de la finca (el área sembrada anual) como la estructura topográfica afectaron la dinámica de los rendimientos de la inversión. Bajo las condiciones actuales de política agrícola, y de precios, la adopción de la tasa de aplicación variable tendría una ventaja económica en fincas similares a la del caso de estudio con un área sembrada anual superior a 567 ha año−1. Sin embargo, las tendencias actuales en los precios de la energía, los costes de transporte y los impactos tanto en los precios de los cereales como en los costes de los fertilizantes mejoran la viabilidad de la adopción de esta tecnología para una población más amplia de tipos de fincas. La rentabilidad de la adopción de aplicación variable de nitrógeno mejora bajo dichos escenarios y, en ausencia de apoyos adicionales, el área mínima para la adopción de aplicación variable disminuye hasta un rango de 68-177 ha año−1 de área de siembra. La combinación de aumentos de precios con la introducción de un subsidio adicional asociado al área de cultivo podría reducir sustancialmente el umbral de adopción hasta 46 ha año−1, lo que hace que la tecnología sea económicamente viable para una población mucho más amplia de agricultores. In sloping fields, rainfed crops experience different degrees of water stress caused by spatial variations in water and, consequently, yields also vary spatially within a field. This offers opportunities for precision agriculture through site-specific management. However, while significant advances have been accomplished in the engineering aspects of precision agriculture, such as increasing spatial resolution of data systems and automation, much less effort has been dedicated to the simulation of within field crop responses to spatial variations. Most studies on rainfed yield gaps ignore intra-plot variability, but if crop models are to be used in assisting site-specific management, they may greatly benefit from spatial water modelling approaches capable of accurately representing and simulating within-field variation of water-related processes. This doctoral thesis represents a novel contribution to the agronomy of rainfed agricultural systems, evaluating the role played by water flows in areas of undulating topography in determining the spatial variations of wheat yield. The thesis has been carried out in chapters that are associated by following an integrative approach. The thesis first reviewed some of the most widely adopted crop and hydrologic models and explored new opportunities for simulating spatial water variations at crop field level through the incorporation of lateral inflow at lower elevation zones of the field. From this standpoint, the spatial variations of yield gaps in rainfed wheat, caused by lateral flows from high to low areas, were assessed in Córdoba, Spain. From an agronomic perspective, water lateral inflows (LIF) due to surface and subsurface runoff contribute to yield variations in rainfed wheat production systems such as the one studied here. The net contribution of these flows to spatial variations of rainfed potential yields showed to be relevant but highly irregular among years. Despite the inter-annual variability, typical of Mediterranean conditions, the occurrence of LIF caused simulated wheat yields to vary +16% from up to downslope areas of the field. Average crop yield ranged from 1.3 to 5.4 Mg grain yield (GY) ha−1. The net yield responses to LIF, in downslope areas were on average 383 kg grain yield (GY) ha−1, and the LIF marginal water productivity reached 24.6 (±13.2) kg GY ha−1 mm−1 in years of maximum responsiveness. Such years of maximum responsiveness were associated with low rainfall during the vegetative stages of the crop in combination with LIF occurring at post-flowering stages. However, under field conditions, these differences were only visible in one of the two experimental years. The economic implications associated with multiple scenarios of variable application rate of nitrogen were explored through a case study and several recommendations were proposed. Both farm size (i.e., annual sown area) and topographic structure impacted the dynamics of investment returns. Under current policy-prices conditions, the adoption of variable application rate would have an economic advantage in farms similar to that of the case study with an annual sown area greater than 567 ha year−1. Nevertheless, current trends on energy prices, transportation costs and impacts on both cereal prices and fertilizers costs enhance the viability of variable application rate adoption for a wider population of farm types. The profitability of adopting VAR improves under such scenarios and, in the absence of additional policy support, the minimum area for adoption of variable application rate decreases to a farm size range of 68-177 ha year−1. The combination of price increases with the introduction of an additional subsidy on crop area could substantially lower the adoption threshold down to 46 ha year−1, turning this technology economically viable for a much wider population of farmers.

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    Recolector de Ciencia Abierta, RECOLECTA
    Doctoral thesis . 2022
    License: CC BY NC ND
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      Recolector de Ciencia Abierta, RECOLECTA
      Doctoral thesis . 2022
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    Authors: Suárez de Puga García, Jara;

    [EN] Nowadays, the complexity of traditional network administration, together with the lack of scalability and flexibility, has been a challenge for the proper development and integration of new emerging technologies which make use of this network. As an example, we have the so-called Internet of Things (IoT). The principal IoT network requirement that enables the growth of this paradigm is the need to facilitate high data volume exchange and administration, from very heterogeneous sources. The IoT concept is defined as the digital interconnection of daily objects endowed with more "intelligence" (Smart devices) through a data communication network either public (Internet) or private. However, this technological trend does not only depend on the "smart devices", but on the whole infrastructure, platforms, frameworks, services, and applications that helps data to travel from the source devices to their different destinations. Also, the handling of the massive volumes of data extracted from those smart devices, their storage, processing, and analysis, known as Big Data, is a key part of this paradigm. This data is gathered from very different sources, and hence, it has diverse data structures and formats. Moreover, it is exchanged using various network protocols (LoRa, CoAp, etc.) which hinder its management and communication through conventional networks, that were not created for such data traffic. Given this problem, several technological approaches have emerged to solve it. Virtual software-defined networking is presented as a possible solution to provide flexibility, scalability, and simplicity of management to the networks that interconnect these devices, platforms, services, and other IoT elements. The virtualization of the network infrastructure, includes an extra layer of abstraction, thus providing a holistic vision of the network and centralizing the administration of its elements and the development of specific network services for IoT deployments. This project is presented as an approximation of these two technological paradigms and will have as the main objective the design of an architectural blueprint and testbed were testing the control tools of software-defined networks (SDN) and the virtualized network functions (NFV) applied to IoT deployments. Thereby, its advantages and implications can be evaluated, and new lines of development can be discovered on this base. [CA] La complexitat en la gestió de les xarxes de comunicació tradicionals, així com la seua poca escalabilitat i flexibilitat, suposa un obstacle per al desenvolupament i consolidació de noves tecnologies emergents com és el cas de la Internet de les Coses (Internet of Things), on la facilitat per a l'intercanvi i maneig de grans volums de dades heterogènies procedents de sensors és un requisit clau per al correcte funcionament del sistema. La Internet de les Coses es defineix com la interconnexió digital d'objectes quotidians dotats d'intel·ligència (Smart devices) a través de xarxes de comunicació de dades ja siguen públiques (Internet) o privades. No obstant això, la Internet de les Coses no sols està compost per aquests dispositius, tota la infraestructura, plataformes, aplicacions i serveis que ajuden les dades a viatjar des dels dispositius d'origen i cap a les seues diferents destinacions, i la gestió d'aquests també formen part de la denominada Internet de les Coses. L'emmagatzematge, anàlisi, processament i gestió massiva d'aquestes dades és el que es denomina Big Data, i està compost de grans quantitats de dades (massive data) estructurats en diferents formats, models de dades i protocols, la qual cosa dificulta el seu tractament i el seu intercanvi a través de les xarxes de dades convencionals. Davant aquesta problemàtica la implementació de xarxes virtuals definides per software es presenta com una possible solució per a dotar de flexibilitat, escalabilitat i senzillesa de gestió a les xarxes que interconnecten aquests dispositius, plataformes i altres elements IoT, permetent una visió global, una gestió centralitzada i un desenvolupament de serveis a nivell de xarxa específics per als entorns d'Internet de les Coses. Aquest projecte es presenta com una aproximació d'aquestes dues tecnologies i tindrà com a objectiu el disseny d'una solució on provar les eines de control de xarxes definides per software o programables (SDN) i les funcions virtuals de xarxes (NFV) aplicades a desplegaments d'Internet de les Coses (IoT) de manera que es puguen demostrar els seus avantatges i implicacions, i es puguen descobrir noves línies de desenvolupament sobre aquesta base. [ES] La complejidad en la gestión de las redes de comunicación tradicionales, así como su poca escalabilidad y flexibilidad, supone un obstáculo para el desarrollo y consolidación de nuevas tecnologías emergentes como es el caso del Internet de las Cosas (Internet of Things), dónde la facilidad para el intercambio y manejo de grandes volúmenes de datos heterogéneos procedentes de sensores es un requisito clave para el correcto funcionamiento del sistema. El Internet de las Cosas se define cómo la interconexión digital de objetos cotidianos dotados de inteligencia (Smart devices) a través de redes de comunicación de datos ya sean públicas (Internet) o privadas. Sin embargo, el Internet de las Cosas no sólo está compuesto por estos dispositivos, toda la infraestructura, plataformas, aplicaciones y servicios que ayudan a los datos a viajar desde los dispositivos origen y hacia sus diferentes destinos, y la gestión de estos también forman parte del denominado Internet de las Cosas. El almacenamiento, análisis, procesado y gestión masiva de dichos datos es lo que se denomina Big Data, y está compuesto de grandes cantidades de datos (massive data) estructurados en diferentes formatos, modelos de datos y protocolos, lo que dificulta su tratamiento y su intercambio a través de las redes de datos convencionales. Ante esta problemática la implementación de redes virtuales definidas por software se presenta como una posible solución para dotar de flexibilidad, escalabilidad y sencillez de gestión a las redes que interconectan estos dispositivos, plataformas y otros elementos IoT, permitiendo una visión global, una gestión centralizada y un desarrollo de servicios a nivel de red específicos para los entornos de Internet de las Cosas. Este proyecto se presenta como una aproximación de estas dos tecnologías y tendrá como objetivo el diseño de una solución donde probar las herramientas de control de redes definidas por software o programables (SDN) y las funciones virtuales de redes (NFV) aplicadas a despliegues de Internet de las Cosas (IoT) de forma que se puedan demostrar sus ventajas e implicaciones y se puedan descubrir nuevas líneas de desarrollo sobre esta base.

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    RiuNet
    Other literature type . Thesis . 2022 . Peer-reviewed
    Data sources: RiuNet; Crossref
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      RiuNet
      Other literature type . Thesis . 2022 . Peer-reviewed
      Data sources: RiuNet; Crossref
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  • Authors: Kounades-Bastian, Dionyssos;

    In this thesis we address the problem of multichannel audio source separa- tion (MASS) for underdetermined convolutive mixtures through probabilistic modeling. We focus on three aspects of the problem and make three contri- butions. Firstly, inspired from the empirically well validated representation of an audio signal, that is know as local Gaussian signal model (LGM) with non-negative matrix factorization (NMF), we propose a Bayesian extension to this, that overcomes some of the limitations of the NMF. We incorporate this representation in a MASS framework and compare it with the state of the art in MASS, yielding promising results. Secondly, we study how to separate mix- tures of moving sources and/or of moving microphones. Movements make the acoustic path between sources and microphones become time-varying. Ad- dressing time-varying audio mixtures appears is not so popular in the MASS literature. Thus, we begin from a state of the art LGM-with-NMF method designed for separating time-invariant audio mixtures and propose an exten- sion that uses a Kalman smoother to track the acoustic path across time. The proposed method is benchmarked against a block-wise adaptation of that state of the art (ran on time segments), and delivers competitive results on both simulated and real-world mixtures. Lastly, we investigate the link between MASS and the task of audio diarisation. Audio diarisation is the detection of the time intervals where each speaker/source is active or silent. Most state of the art MASS methods consider the sources to emit continuously; A hypothe- sis that can result in spurious signal estimates for a source, in intervals where that source was silent. Our aim is that diarisation can aid MASS by indicat- ing the emitting sources at each time frame. To that extent we design a joint framework for simultaneous diarisation and MASS, that incorporates a hidden Markov model (HMM) to track the temporal activity of the sources, within a state of the art LGM-with-NMF MASS framework. We compare the proposed method with the state of the art in MASS and audio diarisation tasks. We ob- tain performances comparable, with the state of the art, in terms of separation while winning in terms of diarisation.; Dans cette thèse nous abordons le problème de la séparation de sources audio dans des mélanges convolutifs multicanaux et sous-déterminés, en utilisant une modélisation probabiliste. Nous nous concentrons sur trois aspects, et nous apportons trois contributions. D’abord, nous nous inspirons du modèle Gaussien local par factorisation en matrices non-négatives (LGM-with-NMF), qui est un modèle empiriquement validé pour représenter un signal audio. Nous proposons une extension Bayésienne de ce modèle, qui permet de sur- passer certaines limitations du modèle NMF. Nous incorporons cette représentation dans un cadre de separation audio multicanaux, et le comparons avec l’état de l’art sur des tâches de séparation. Nous obtenons des résultats prometteurs. Deuxièment, nous étudions comment séparer des mélanges audio de sources et/ou des capteurs en mouvement. Ces déplacements rendent le chemin acoustique entre les sources et les microphones variant en cours du temps. L’adressage des mélanges convolutifs variant au cours du temps est peu exploré dans la littérature. Ainsi, nous partons d’une méthode de l’état de l’art développée pour la séparation de mélanges invariant (sources et microphones statiques) et utilisant LGM-with-NMF. Nous proposons à ceci une extension qui utilise un filtre de Kalman pour suivre le chemin acoustique au cours du temps. La technique proposée est comparée à une adaptation block-par-block d’une technique de l’état de l’art appliquée sur des intervalles de temps, et a donné des résultats exceptionels sur les mélanges simulés et les mélanges du monde réel. Enfin, nous investiguons les similitudes entre la séparation et la journalisation audio. La journalisation est le problème de détection des intervalles auxquels chaque locuteur/source est émettant. La plupart des méthodes de séparation supposent toutes les sources émettent continuellement. Cette hypothèe peut donner lieu à de fausses estimations durant les intervalles au cours desquels cette source n’a pas émis. Notre objectif est que la journalisation puisse aider à résoudre la séparation, en indiquant les sources qui émettent à chaque intervalle de temps. Dans cette mesure, nous concevons une cadre commun pour traiter simultanément la journalisation et la séparation du mélange audio. Ce cadre incorpore un modèle de Markov caché pour suivre les activités des sources au sein d’une technique de séparation LGM-with-NMF. Nous comparons l’algorithme proposé à l’état de l’art sur des tâches de séparation et de journalisation. Nous obtenons des performances comparables avec l’état de l’art pour la séparation, et supériures pour la journalisation.

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    Authors: Chugh, Tushar;

    Steering feedback is an important element that defines driver–vehicle interaction. It strongly affects driving performance and is primarily dependent on the steering actuator's control strategy. Typically, the control method is open loop, that is without any reference tracking; and its drawbacks are hardware dependent steering feedback response and attenuated driver–environment transparency. This thesis investigates a closed-loop control method for electric power assisted steering and steer-by-wire systems. The advantages of this method, compared to open loop, are better hardware impedance compensation, system independent response, explicit transparency control and direct interface to active safety functions. The closed-loop architecture, outlined in this thesis, includes a reference model, a feedback controller and a disturbance observer. The feedback controller forms the inner loop and it ensures: reference tracking, hardware impedance compensation and robustness against the coupling uncertainties. Two different causalities are studied: torque and position control. The two are objectively compared from the perspective of (uncoupled and coupled) stability, tracking performance, robustness, and transparency. The reference model forms the outer loop and defines a torque or position reference variable, depending on the causality. Different haptic feedback functions are implemented to control the following parameters: inertia, damping, Coulomb friction and transparency. Transparency control in this application is particularly novel, which is sequentially achieved. For non-transparent steering feedback, an environment model is developed such that the reference variable is a function of virtual dynamics. Consequently, the driver–steering interaction is independent from the actual environment. Whereas, for the driver–environment transparency, the environment interaction is estimated using an observer; and then the estimated signal is fed back to the reference model. Furthermore, an optimization-based transparency algorithm is proposed. This renders the closed-loop system transparent in case of environmental uncertainty, even if the initial condition is non-transparent. The steering related active safety functions can be directly realized using the closed-loop steering feedback controller. This implies, but is not limited to, an angle overlay from the vehicle motion control functions and a torque overlay from the haptic support functions. Throughout the thesis, both experimental and the theoretical findings are corroborated. This includes a real-time implementation of the torque and position control strategies. In general, it can be concluded that position control lacks performance and robustness due to high and/or varying system inertia. Though the problem is somewhat mitigated by a robust H-infinity controller, the high frequency haptic performance remains compromised. Whereas, the required objectives are simultaneously achieved using a torque controller.

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    Chalmers Research
    Doctoral thesis . 2021
    Data sources: Chalmers Research
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      Chalmers Research
      Doctoral thesis . 2021
      Data sources: Chalmers Research
  • Authors: Devaurs, Didier;

    Planning a path for a robot in a complex environment is a crucial issue in robotics. So-called probabilistic algorithms for path planning are very successful at solving dicult problems and are applied in various domains, such as aerospace, computer animation, and structural biology. However, these methods have traditionally focused on nding paths avoiding collisions, without considering the quality of these paths. In recent years, new approaches have been developed to generate high-quality paths: in robotics, this can mean nding paths maximizing safety or control; in biology, this means nding motions minimizing the energy variation of a molecule. In this thesis, we propose several extensions of these methods to improve their performance and allow them to solve ever more dicult problems. The applications we present stem from robotics (industrial inspection and aerial manipulation) and structural biology (simulation of molecular motions and exploration of energy landscapes).; Planifier le chemin d'un robot dans un environnement complexe est un problème crucial en robotique. Les méthodes de planification probabilistes peuvent résoudre des problèmes complexes aussi bien en robotique, qu'en animation graphique, ou en biologie structurale. En général, ces méthodes produisent un chemin évitant les collisions, sans considérer sa qualité. Récemment, de nouvelles approches ont été créées pour générer des chemins de bonne qualité : en robotique, cela peut être le chemin le plus court ou qui maximise la sécurité ; en biologie, il s'agit du mouvement minimisant la variation énergétique moléculaire. Dans cette thèse, nous proposons plusieurs extensions de ces méthodes, pour améliorer leurs performances et leur permettre de résoudre des problèmes toujours plus dificiles. Les applications que nous présentons viennent de la robotique (inspection industrielle et manipulation aérienne) et de la biologie structurale (mouvement moléculaire et conformations stables).

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    Authors: Beltrán-Abaunza, José M.;

    This PhD study focusses on the use of MEdium Resolution Imaging Spectrometer (MERIS) data for reliable and quantitative water-quality assessment of optically-complex waters (lake, brackish and coastal waters). The thesis is divided into two parts: A. intercalibration of reflectance measurements in different optically-complex water bodies (Paper I), and validation of various satellite processing algorithms for the coastal zone (Paper II). B. Applications: the use of MERIS data in integrated coastal zone management mostly using Himmerfjärden bay as an example. Himmerfjärden bay is one of the most frequently monitored coastal areas in the world and it is also the recipient of a large urban sewage treatment plant, where a number of full-scale nutrient management experiments have been conducted to evaluate the ecological changes due to changes in nutrient schemes in the sewage plant. Paper I describes the development and assessment of a new hyperspectral handheld radiometer for in situ sampling and validation of remote sensing reflectance. The instrument is assessed in comparison with readily available radiometers that are commonly used in validation. Paper II has a focus on the validation of level 2 reflectance and water products derived from MERIS data. It highlights the importance of calibration and validation activities, and the current accuracy and limitations of satellite products in the coastal zone. Bio-optical in situ data is highlighted as one of the key components for assessing the reliability of current and future satellite missions. Besides suspended particulate matter (SPM), the standard MERIS products have shown to be insufficient to assure data quality retrieval for Baltic Sea waters. Alternative processors and methods such as those assessed and developed in this thesis therefore will have to be put in place in order to secure the success of future operational missions, such as Sentinel-3. The two presented manuscripts in the applied part B of the thesis (paper III and IV), showed examples on the combined use of in situ measurements with optical remote sensing to support water quality monitoring programs by using turbidity and suspended particulate matter as coastal indicators (manuscript III). The article also provides a new turbidity algorithm for the Baltic Sea and a robust and cost-efficient method for research and management. A novel approach to improve the quality of the satellite-derived products in the coastal zone was demonstrated in manuscript IV. The analysis included, the correction for adjacency effects from land and an improved pixel quality screening. The thesis provides the first detailed spatio-temporal description of the evolution of phytoplankton blooms in Himmerfjärden bay using quality-assured MERIS data, thus forwarding our understanding of ecological processes in in Swedish coastal waters. It must be noted that monitoring from space is not a trivial matter in these optically-complex waters dominated by the absorption of coloured dissolved organic matter (CDOM). These types of coastal waters are especially challenging for quantitative assessment from space due to their low reflectance. Papers III and IV thus also provide tools for a more versatile use in other coastal waters that are not as optically-complex as the highly absorbing Baltic Sea waters. The benefits of the increased spatial-temporal data coverage by optical remote sensing were presented, and also compared to in situ sampling methods (using chlorophyll-a as indicator). Research funders:European Space Agency (ESA, contract no.21524/08/I-OL)NordForsk funding: Nord AquaRemS Ref. no. 80106NordForsk funding: NordBaltRemS Ref.no. 42041At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.

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    Authors: Férriz Núñez, Macarena;

    El aumento de la concentración de CO2 atmosférico [CO2] como consecuencia de las emisiones antropogénicas lleva asociado un aumento en la temperatura media del planeta. La cuenca mediterránea es particularmente sensible a perturbaciones más intensas debido a una mayor aridez y al legado de usos de suelo que ha modificado notablemente los paisajes actuales. En este contexto de cambio global, estudiamos el decaimiento y las dinámicas de regeneración de tres especies de coníferas mediterráneas con diferente tolerancia a la sequía Pinus pinaster < Pinus pinea < Juniperus oxycedrus (Capítulo 2). Comparamos los patrones de crecimiento y la respuesta al clima de individuos con diferente estado de salud: sanos (las tres especies), en decaimiento (sólo P. pinaster) y muertos (P. pinaster y P. pinea). La actual especie dominante, P. pinaster, muestra claros signos de decaimiento -definido por alta defoliación e infección de muérdago- y mortalidad, con escasa regeneración, siendo reemplazada por regeneración de otras especies más tolerantes a la sequía como Quercus ilex, P. pinea y J, oxycedrus. Desde los años 80, los eventos de sequía han sido más frecuentes y severos en la zona, habiendo incitado el decaimiento en P. pinaster pero no en las otras especies acompañantes. Los individuos no-sanos de P. pinaster mostraron una reducción en el crecimiento desde 1995, mientras que en los individuos muertos de P. pinea este declive comenzó en 2005. La supervivencia de P. pinaster en la zona estaba relacionada con una mayor sensibilidad a la precipitación de primavera y a sitios con mayor disponibilidad de agua, mientras que la supervivencia de P. pinea estaba principalmente relacionada con un mayor diámetro del árbol. En el Capítulo 3, seleccionamos 5 árboles de cada estado de salud y especie y estudiamos la anatomía del xilema y la discriminación isotópica de carbono (13C) en anillos de crecimiento. Las dos especies de pinos mostraron traqueidas más grandes y una mayor plasticidad del xilema en respuesta a la variabilidad climática que J. oxycedrus. Los caracteres anatómicos se diferenciaron entre estados de salud en P. pinaster y P. pinea. Los individuos sanos tenían mayor área de lumen en la madera temprana y paredes celulares más gruesas en la madera tardía que los individuos no-sanos, junto con mayor plasticidad en el xilema frente al clima, lo que les permitió ajustar sus caracteres anatómicos para aumentar la seguridad en el xilema durante eventos de sequía. La habilidad de mantener un xilema competitivo y plástico es crucial para conseguir ratios productivos en escenarios de cambio climático. Nuestro estudio reveló que los pinos muertos y en decaimiento tenían valores similares de 13C que los árboles sanos, lo que sugiere que los pinos no-sanos ejercen un menor control estomático que debería maximizar la tasa fotosintética y aumentar el transporte de agua hacia la copa para compensar por la pérdida excesiva de agua. Los resultados de los Capítulos 2 y 3 sugieren que a pesar del decaimiento general observado en P. pinaster en el área, los individuos sanos de esta especie pueden sobrevivir en áreas con mayor disponibilidad de agua, mientras que en el resto del paisaje serán eventualmente sustituidos por especies más tolerantes a la sequía como P. pinea y J. oxycedrus. Además, los patrones de regeneración en la zona revelaron que tanto el estrés hídrico como el legado de usos de suelo limitan el establecimiento de regenerado de P. pinaster en comparación con la más abundante regeneración que presentan P. pinea, J, oxycedrus y Q. ilex. Debido a que los cambios de distribución de las especies están determinados en última instancia por el regenerado, comprender el efecto combinado de altas concentraciones de [CO2] y el estrés hídrico es fundamental para pronosticar futuros cambios en el paisaje e identificar qué especies prevalecerán en estos nuevos escenarios. Por ello en el Capítulo 4, analizamos cómo el enriquecimiento con [CO2] puede mitigar los efectos negativos del estrés hídrico en plántulas de dos especies de pino mediterráneas P. pinaster y P. pinea. En cámaras de crecimiento, testamos los efectos de dos concentraciones de [CO2]: a[CO2] (380 ppm) y e[CO2] (800 ppm) y dos regímenes de riego. En condiciones de e[CO2], ambas especies aumentaron la biomasa total, WUE (el uso en la eficiencia del agua a nivel de toda la planta) y WUEi (uso en la eficiencia del agua intrínseco) en comparación con valores medidos en condiciones de a[CO2]. El aumento de WUEi bajo condiciones de alto [CO2] se debió a una reducción en la conductancia estomática y a un aumento de la tasa fotosintética. Sin embargo, encontramos diferencias en los ajustes funcionales al e[CO2] y estrés hídrico en las dos especies. P. pinea mostró una mayor tasa fotosintética y menores potenciales hídricos al amanecer (amanecer) y al mediodía (mediodía,) mostrando que esta especie tiene un comportamiento más anisohídrico que P. pinaster, el cual mantuvo una estrategia más isohídrica y de mayor ahorro de agua mediante un mayor control estomático, invirtiendo más en el desarrollo de la raíz que P. pinea. Además, en el Capítulo 5 estudiamos los ajustes en la anatomía del xilema y en el sistema hidráulico de las plántulas en estas condiciones de e[CO2] alto y estrés hídrico. El estrés hídrico indujo una menor producción de acículas en P. pinaster para minimizar la pérdida de agua. Por otro lado P. pinea mostró una mayor plasticidad en el xilema mediante la reducción del tamaño del lumen para aumentar la seguridad en el xilema ante estrés hídrico. Aunque ambas estrategias pueden ser efectivas a la hora de minimizar transpiración y mantener la seguridad en el xilema, reducir el área foliar puede comprometer la tasa fotosintética a largo plazo, perjudicando la habilidad del individuo para competir. Por el contrario, una mayor plasticidad en el xilema en P. pinea permitiría a los árboles adaptar su crecimiento y estructura a las condiciones ambientales y optimizar el uso de recursos disponibles manteniendo una mayor área foliar activa (es decir, el aparato fotosintético). Altas concentraciones de [CO2] redujeron la conductancia específica de la hoja en ambas especies de pino, probablemente mediante menor conductancia estomática. El aumento en el número de traqueidas en el xilema P. pinea le permite construir un xilema más seguro a la vez que compensa un menor tamaño de traqueidas bajo estrés hídrico. Por tanto, nuestros resultados sugieren que un aumento de [CO2] beneficiará de forma diferente a las dos especies estudiadas, aun asumiendo que ambas pertenecen al mismo grupo funcional. El enriquecimiento en [CO2] beneficiará más a P. pinea que a P. pinaster bajo condiciones de estrés hídrico, debido a que P. pinea puede mantener la conductividad hidráulica con un xilema más resistente a la cavitación. Si extrapolamos nuestros resultados a condiciones naturales y en particular a los escenarios climáticos esperados en el futuro, podemos concluir que la mayor tolerancia a la sequía expresada por P. pinea hará que esta especie prevalezca frente a P. pinaster en ambientes futuros con mayor aridez y mayor concentración de [CO2]. ----------ABSTRACT---------- Rising CO2 atmospheric concentration ([CO2]) as a consequence of anthropogenic emissions is driving an increase in the average temperature of the planet. The Mediterranean basin is particularly sensitive to more intense disturbances due to aridification and land-use legacies that have strongly shaped the current landscapes in the Region. In this context of global change, we studied the decline and regeneration dynamics of three co-occurring Mediterranean coniferous species of different drought tolerance: Pinus pinaster < Pinus pinea < Juniperus oxycedrus (Chapter 2). We compared the growth patterns and climatic response of trees with different health status: healthy (for the three species), declining (only P. pinaster) and dead (P. pinaster and P. pinea). The currently dominant species, P. pinaster, shows extensive signs of decline -assessed by high canopy defoliation and mistletoe infection- and mortality. In addition, the species presents scarce regeneration, whereas it is being replaced by Quercus ilex, P. pinea and J. oxycedrus, with more abundant regeneration and abundance in juvenile stages. Since the 1980s, more frequent and severe drought events have occurred, inciting tree growth decline in dead and non-healthy pine trees, but with differences between species. Non-healthy individuals of P. pinaster exhibited negative growth trends since 1995. In dead P. pinea trees, the growth decline started later since 2005. P. pinaster survival in the study area was linked to a higher sensitivity to spring precipitation and was concentrated in sites with higher moisture availability, while P. pinea survival was higher in trees with larger diameters. In Chapter 3, we selected 5 individuals from each status and species and studied the xylem anatomical traits and carbon isotopic discrimination (13C) in annual tree-rings. Pine trees exhibited larger tracheids and higher xylem plasticity to climate variability than J. oxycedrus. Xylem traits differed between different health status in Pinus pinaster and Pinus pinea. Healthy pine trees had bigger lumen sizes in the earlywood and thicker cell walls in the latewood than non-healthy trees, along with expressing a higher xylem plasticity to climate. This xylem plasticity allowed P. pinea to adjust their xylem characteristics to increase cell safety during drought events. The ability to maintain a competitive yet plastic xylem structure is crucial to sustain productivity rates under more xeric, climate change scenarios. Our study revealed that non-healthy pines (i.e. declining and dead pine trees) and healthy trees exhibited similar 13C, which suggests that non-healthy pine trees had low stomatal control to maximize photosynthesis and increase water transport to the crown to compensate for the excessive water loss. Results from Chapters 2 and 3 suggest that despite the general species decline (i.e. high mortality, canopy defoliation, mistletoe infection) observed in P. pinaster in the area, healthy individuals of this species are performing well in sites with higher moisture availability, while in soils with less moisture availability in the area it can be eventually replaced by more drought-tolerant P. pinea, J. oxycedrus and Q. ilex. Regeneration patterns in the area revealed that water stress along with land-use legacies are limiting P. pinaster establishment in comparison to more abundant regeneration of these three more drought-tolerant co-occurring taxa. Since species distribution shift is ultimately driven by regeneration success, understanding the combined effect of enriched [CO2] and water stress on seedlings is crucial to forecast future changes in the landscape and identify which species will prevail in these new scenarios. Therefore, in Chapter 4, we characterized how elevated [CO2] can mitigate the negative effects of water stress on seedlings of the two Mediterranean pine species P. pinaster and P. pinea. In growth chambers, we tested the effects of two [CO2] treatments: a[CO2] (380 ppm) and e[CO2] (800 ppm) and two water regimes. Under e[CO2], both species increased total biomass, WUE (whole-plant water use efficiency) and WUEi (intrinsic water use efficiency) in comparison to measured values in a[CO2]. Increases in WUEi under high [CO2] were both due to reduced stomatal conductance and increased photosynthetic rates. However, we also found differences in the functional adjustment to elevated [CO2] and water stress of the two species. P. pinea exhibited higher photosynthetic rates and lower water potential, both predawn and midday, suggesting that this species follows a more anisohydric behaviour than P. pinaster, which in contrast maintained a more isohydric, water-saving strategy and invested more in root development than P. pinea. In addition, in Chapter 5 we studied the xylem anatomical adjustments and hydraulic performance of seedlings under e[CO2] and water stress. Water shortage induced a reduction in P. pinaster leaf production to minimise water loss, while P. pinea exhibited a higher xylem plasticity, particularly by reducing lumen size to increase xylem safety. Although both strategies can be effective in minimising transpiration and maintaining xylem safety, reducing leaf area may compromise photosynthetic rates in the long-term, worsening plant ability to compete. In contrast, higher xylem plasticity in P. pinea would allow trees to adapt growth and structure to environmental conditions and to optimise the use of available resources by keeping a greater active leaf area (i.e., photosynthetic apparatus) under water stress. Elevated [CO2] reduced leaf specific conductivity in both pine species, which was probably linked to lower stomatal conductance. The increased in the number of tracheids in P. pinea xylem allowed it to develop a safer xylem that compensated for smaller tracheids under water stress. Thus, our results suggest that rising [CO2] will differently benefit the two studied species, even if they are assumed to belong to the same functional type. [CO2] enrichment will benefit more P. pinea under water stress than P. pinaster, since P. pinea can maintain hydraulic conductivity with a greater xylem resistance to cavitation. If our results hold for natural conditions, we can conclude that due to the higher drought tolerance expressed by P. pinea in comparison to P. pinaster, the former species will prevail under future more xeric and enriched [CO2] environments, particularly where these two species form mixed stands today.

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    https://doi.org/10.20868/upm.t...
    Thesis . 2022 . Peer-reviewed
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      https://doi.org/10.20868/upm.t...
      Thesis . 2022 . Peer-reviewed
      Data sources: Crossref
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    Authors: Pereira Ramos, Eunice;

    The last decade has seen the emergence of a new research theme - the study of the resources Nexus. The “Nexus” refers to considering the functioning of several systems simultaneously, as opposed to one, as the object of research. This perspective reasons that coherent decision-making needs to consider systems' interconnectedness. Typical system-of-systems (Nexus) studied relate to the security of services, such as the Water-Energy and Food Nexus, and resources, i.e. the Climate, Land, Energy and Water systems (CLEWs) Nexus. The process of examining cross-systems dynamics and interactions is known as the Nexus approach. Implementing it requires understanding multiple systems, disciplinary integration, and multi-stakeholder engagement at various decision levels. Adequate planning of an assessment process is needed to ensure the successful implementation of the approach and its long-lasting presence in decision-making processes. Therefore, reviewing the application of Nexus approaches can inform essential aspects that clarify and streamline the entire process. Current gaps in Nexus research include the lack of clarity in systems representation, the lack of flexible and accessible tools and methods for Nexus analyses, and the need for transparency in modelling approaches. All of these hinder the integration of the approach in research and the incorporation into decision-making processes. The thesis aims to advance the science of integrated resource assessments, particularly the Nexus approach, and support its dissemination and implementation within and beyond academia. Insights from applying two Nexus approaches (CLEWs and SIM4NEXUS) are distilled from the comparison of case studies. Overarching aspects examined include the expertise engaged in assessments, practitioners' roles and transdisciplinarity. Also analysed are selected components in the Nexus approach, such as identifying systems' interactions, analytical approaches, and stakeholder engagement and participation. The transversal feature of knowledge transfer between experts, practitioners, and stakeholders is examined to understand its importance in the assessment process. Examples of quantitative analyses illustrate the representation of different Nexus contexts and the elaboration of relevant insights. This thesis presents two such quantitative examples. One example is an entry-level CLEWs modelling exercise, whose development is described from conceptualisation, model development, and interpretation of results. The other example is a quantitative analysis of the transboundary Syr Darya river basin, which investigates the role of model structure in exploring Nexus questions. The thesis highlights a list of principles to support the Nexus approach's operationalisation deriving from practice and considering current research gaps. Det senaste decenniet har sett uppkomsten av ett nytt forskningstema - studiet av resurserna Nexus. "Nexus" hänvisar till att betrakta funktionen hos flera system samtidigt, i motsats till ett, som föremål för forskning. Detta perspektiv motiverar att ett sammanhängande beslutsfattande måste beakta systemens sammanlänkning. Typiska system-of-systems, Nexus, som studeras relaterar till säkerheten för tjänster, såsom vatten-energi- och livsmedelsnexus, och resurser, dvs. Processen att undersöka dynamik och interaktioner mellan olika system är känd som Nexus-metoden. Att implementera det kräver förståelse för flera system, disciplinär integration och engagemang från flera intressenter på olika beslutsnivåer. Adekvat planering av en bedömningsprocess krävs för att säkerställa ett framgångsrikt genomförande av tillvägagångssättet och dess långvariga närvaro i beslutsprocesser. Därför kan en granskning av tillämpningen av Nexus tillvägagångssätt informera viktiga aspekter som förtydligar och effektiviserar hela processen. Aktuella luckor i Nexus-forskningen inkluderar bristen på tydlighet i systemrepresentationen, avsaknaden av flexibla och tillgängliga verktyg och metoder för Nexus-analyser och behovet av transparens i modelleringsmetoder. Allt detta hindrar integreringen av tillvägagångssättet i forskningen och införlivandet i beslutsprocesser. Avhandlingen syftar till att främja vetenskapen om integrerade resursbedömningar, särskilt Nexus-metoden, och stödja dess spridning och implementering inom och utanför akademin. Insikter från två Nexus-metoder (CLEWs och SIM4NEXUS) kommer från jämförelsen av fallstudier. Övergripande aspekter som granskas inkluderar expertis som är engagerad i bedömningar, utövarnas roller och transdisciplinaritet. Dessutom analyseras utvalda komponenter i Nexus-metoden, som att identifiera systemens interaktioner, analytiska tillvägagångssätt och engagemang och deltagande av intressenter. Det tvärgående inslaget i kunskapsöverföring mellan experter, praktiker och intressenter undersöks för att förstå dess betydelse i bedömningsprocessen. Exempel på kvantitativa analyser illustrerar representationen av olika Nexus-kontexter och utarbetandet av relevanta insikter. Denna avhandling presenterar två sådana kvantitativa exempel. Ett exempel är en CLEWs modelleringsövning på ingångsnivå, vars utveckling beskrivs från konceptualisering, modellutveckling och tolkning av resultat. Det andra exemplet är en kvantitativ analys av det gränsöverskridande flodområdet Syr Darya, som undersöker modellens strukturs roll för att utforska Nexus-frågor. Avhandlingen belyser en lista med principer för att stödja Nexus-metodens operationalisering som härrör från praktiken och med tanke på aktuella forskningsluckor.

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