Soil organic carbon (SOC) concentrations and greenhouse gas (GHG) emissions are not uniform across the landscape, but assemble in "hotspots" in specific areas. These differences are mainly driven by human-induced activities such as agricultural management. 40-50% of the Earth's land surface is under agricultural land-use, for instance cropland, managed grassland and permanent crops including agro-forestry and bio-energy crops. Furthermore, 62% of the global soil C stock is SOC and the soil stores more than 3 times more C than the atmosphere. Thus, C sequestration in agricultural soil has a potentially important role in increasing SOC storage and GHG mitigation, and there is considerable interest in understanding the effects of agricultural management on SOC and GHG fluxes in both grasslands and croplands, in order to better assess the uncertainty and vulnerability of terrestrial SOC reservoirs. For the sake of discovering the agricultural management practices relating to the effective and sustainable C sequestration in agricultural lands in Europe, simulating future terrestrial C stocks and GHG budgets under varied agricultural management systems in major European ecosystems is essential. Using models is a useful method with the purpose of this and abundant studies have carried out. However, many model results have not been validated with reliable observed long-term data, while other studies have reported a strong impact of model initialisation on model result. Nevertheless, predictions of annual to decadal variability in the European terrestrial C and GHG ressources largely rely on model results. Consequently, finding the most appropriate and comprehensive model initialisation method for obtaining reliable model simulations became important, especially for process-based ecosystem models. In recent years, Zimmermann et al. (2007) have succeed in initialising the Rothamsted Carbon model (RothC) using a physical and chemical soil fractionation method. For that reason, we hypothesised that measured detailed SOC data would be useful to initialise ecosystem models, and this hypothesis should be tested for different process-based models and agricultural land-use and management. (...)

Proposed in this thesis is a methodology to enable yacht designers to develop innovative structural concepts, even when the loads experienced by the yacht are highly uncertain, and has been implemented in sufficient detail to confirm the feasibility of this new approach. The new approach is required because today??s yachts are generally lighter, getting larger and going faster. The question arises as to how far the design envelope can be pushed with the highly uncertain loads experienced by the structure? What are the effects of this uncertainty and what trade-offs in the structural design will best meet the overall design objectives? The new approach provides yacht designers with a means of developing innovative structural solutions that accommodate high levels of uncertainty, but still focus on best meeting design objectives constrained by trade-offs in weight, safety and cost. The designer??s preferences have a large, and not always intuitive, influence on the necessary design trade-offs. This in turn invites research into ways to formally integrate decision algorithms into knowledge-based design systems. A lean and robust design system has been achieved by developing a set of tools which are blanketed by a fuzzy decision algorithm. The underlying tool set includes costing, material optimisation and safety analysis. Central to this is the innovative way in which the system allows non-discrete variables to be utilized along with new subjective measures of structural reliability based on load path algorithms and topological (shape) optimisation. The originality in this work is the development of a knowledge-based framework and methodology that uses a fuzzy decision making tool to navigate through a design space and address trade-offs between high level objectives when faced with limited design detail and uncertainty. In so doing, this work introduces the use of topological optimisation and load path theory to the structural design of yachts as a means of overcoming the historical focus of knowledge-based systems and to ensure that innovative solutions can still evolve. A sensitivity analysis is also presented which can quantify a design??s robustness in a system that focuses on a global approach to the measurement of objectives such as cost, weight and safety. Results from the application of this system show new and innovative structural solutions evolving that take into account the designers preferences regarding cost, weight and safety while accommodating uncertain parameters such as the loading experienced by the hull.

Sugarcane crop is the main source of sugar and the second largest source of biofuel in the world. Since the 1980s, Brazil has been the largest sugarcane producing nation, producing half of the global amount. Ethanol and biomass from sugarcane account for more than 15% of the country´s energy source. Nevertheless, commercial Brazilian sugarcane yield has plateaued at 75 t ha-1, and to meet the increasing demand for sugar and ethanol, the crop has strongly expanded towards central-western regions, where irrigation is mandatory to offset water stress risks. To support decision making and scientific guidance towards where and how the crop should expand and/or to increase yields, a heuristic view of the crop system is needed, which can mathematically be translated into a crop model. In turn, the effects of crop management, land use change, climate variability and agro-economic change factors on crop production and associated quantities can and have been assessed by using crop process-based models (PBM). In contrast to other crops, however, sugarcane has only two PBMs available for end users (DSSAT-CANEGRO and APSIM-Sugar), and further modifications of these models are required to better assess and support sustainable sugarcane production in Brazil. Therefore, this study aimed to develop, calibrate and evaluate different crop modelling approaches for Brazilian sugarcane farming systems, water management strategies, climate change impacts and canopy structures to support improved decisions for private and public stakeholders in the sugarcane sector, provide scientific guidance and establish a Brazilian platform of crop simulations. A new version of the sugarcane process-based model (SAMUCA) was developed to operate at phytomer level, focusing on soil mulch effects on crop growth and development, tillering process under competition for light and sucrose accumulation based on source-sink relations. The model was embedded into a modular platform dedicated to simulating the soil-plant-atmosphere and the management of the sugarcane farm system. The previous version of SAMUCA was also re-structured and coupled to the SWAP (Soil, Water, Atmosphere and Plant) agrohydrological model platform, focusing on soil water relations to crop growth. Moreover, a Functional-Structural Plant Model (FSPM) for sugarcane was developed by integrating the main crop components at the organ level (phytomer), based on a relative source-sink approach and a robust light model embedded into a three-dimensional modelling platform (GroIMP). All approaches were evaluated, and the performance under experimental conditions for different Brazilian conditions was determined. The performance of the new version of SAMUCA in a long-term experiment and under different Brazilian conditions was satisfactory, with agreement indices close to those of other widely used sugarcane crop models (CANEGRO and APSIM-Sugar). In addition, the modulated crop simulation platform can be used to host more crop models and integrate new features of Brazilian farming systems. The coupling of the SWAP-SAMUCA model was accomplished, and although non-expressive improvements in model performance regarding crop yield were noticed (with an overall 6% lower RMSE), the ability of SWAP-SAMUCA to simulate soil water content was higher than that of the original \"tipping bucket\" approach (32% lower RMSE). The Functional-Structural Plant Model for sugarcane was able to satisfactorily simulate canopy development, tillering and sucrose accumulation at the organ level and its integration at the whole-plant level. Besides its ability to simulate competition for light, helping to understand intra-specific competition among tillers, the sugarcane FSPM framework can be used to support sucrose accumulation and translocation mechanism studies as well as intercropping studies for sugarcane, which has already successfully been done for other crops. / A cultura da cana-de-açúcar é a principal fonte de açúcar e a segunda maior fonte de biocombustíveis do mundo. O Brasil é o maior produtor mundial desde a década de 80 e atualmente representa metade da produção mundial, enquanto que ao mesmo tempo o etanol e a biomassa correspondem a mais de 15% da fonte de energia do país. Contudo, a produtividade comercial da cana-de-açúcar brasileira atingiu um limiar de cerca de 75 t ha-1 e para atender à crescente demanda de açúcar e etanol, a cultura expandiu-se fortemente para a região centro-oeste, onde a irrigação é obrigatória para manter os níveis de produção e diminuir riscos de quebra de safra. Para dar suporte a tomada de decisão e avanço científico sobre onde e como a cultura deve se expandir e/ou aumentar a produtividade, é necessária uma visão heurística do sistema agrícola brasileiro que pode ser traduzida matematicamente para um modelo de cultura. Desta forma, os efeitos do manejo e tipo de solo, variabilidade climática e fatores econômicos na produtividade de culturas agrícolas podem ser avaliados quantitativamente por meio de modelos de culturas baseados em processos (MBP). No entanto, em contraste a outras culturas, a cana-de-açúcar possui apenas dois MBPs disponíveis para usuários finais (DSSAT-CANEGRO e APSIM-Sugar) que requerem calibração e parametrização para melhor representar o sistema agrícola de cana-de-açúcar do Brasil. Portanto, este estudo teve como objetivo desenvolver, calibrar e avaliar diferentes abordagens de modelagem de culturas voltadas a produção de cana-de-açúcar no Brasil, para servir como ferramenta de tomada de decisão para o setor público e privado, auxilio no manejo da água e avaliação dos impactos nas mudanças climáticas. Portanto, uma nova versão do modelo baseado em processo de cana-de-açúcar (SAMUCA) foi desenvolvida para operar a nível de fitômeros, incluindo os efeitos no crescimento e desenvolvimento da cana com base na cobertura da palha no solo, competição por luz no processo de perfilhamento e acúmulo de sacarose com base nas relações fonte-dreno. O modelo foi incorporado em uma plataforma modular dedicada a simular o sistema solo-planta-atmosfera e manejo do sistema agrícola. Além disso, a versão anterior do SAMUCA também foi reestruturada e acoplada à plataforma agro-hidrológica SWAP (\"Soil, Water, Atmosphere and Plant\") com objetivo de aprimorar as simulações de balanço hídrico no solo e efeito no crescimento da cana-de-açúcar. Por fim, um Modelo Funcional-Estrutural de Plantas (MFEP) para a cana-de-açúcar foi desenvolvido integrando os principais componentes da cultura a nível de órgãos (fitômeros) com base em uma abordagem de fonte-dreno e um modelo robusto de radiação que foram introduzidos em uma plataforma de modelagem tridimensional (GroIMP). As três abordagens foram avaliadas e seu desempenho foi determinado com base em condições experimentais para diferentes regiões brasileiras. O desempenho da nova versão do modelo SAMUCA em experimento de longo prazo e em diferentes condições brasileiras foi satisfatório e os índices de concordância foram próximos de outros modelos de cana-de-açúcar amplamente utilizados (CANEGRO e APSIM-Sugar). Além disso, a plataforma de simulação de culturas modulada pode ser usada para hospedar mais modelos de culturas e integrar novas características do sistema de cultivo brasileiro. O acoplamento do modelo SWAP-SAMUCA foi realizado e apesar não apresentar melhorias expressivas no desempenho do modelo em simular os componentes da cultura (com erro médio quadrático [RMSE] 6% menor), a habilidade do modelo SWAP-SAMUCA em simular o teor de água no solo mostrou-se consideravelmente superior em comparação ao modelo original (RMSE 32% menor). O MFEP para cana-de-açúcar foi capaz de simular o desenvolvimento do dossel, o processo de perfilhamento e o acúmulo de sacarose ao nível de órgãos e planta de forma satisfatória. Além de sua capacidade em simular com precisão a interceptação da radiação por cada estrutura do dossel, podendo auxiliar na compreensão do processo de competição intraespecífica entre perfilhos, a estrutura do MFEP da cana-de-açúcar também pode ser usada no apoio à pesquisa focando os mecanismos de acúmulo de sacarose e translocação de açúcares bem como em estudos de consórcio em cana-de-açúcar, como têm sido realizado com sucesso para outras culturas nos últimos anos.

No description available.

The contamination of rivers with potentially pathogenic bacteria poses health risks for users. This is particularly true when the bacteria are carriers of antibiotic resistance genes (ARG). Pathogenic bacteria and ARG are primarily discharged into rivers from wastewater treatment plants (WWTP). There, ARG are subject to the processes of transport, retention, and degradation. Simultaneously, they can also propagate through the growth of the carrier bacteria and by horizontal gene transfer. According to the current state of knowledge, the horizontal transfer of ARG is mediated predominantly by plasmid transfer. While the transport of bacteria in rivers has been intensively investigated, the relationship between the location of the wastewater discharges and their impact on microbial (and ARG) loading in the receiving waters downstream remains largely unexplored. Process-based mathematical models have been designed in the past to specifically describe the plasmid-mediated transfer of ARG. However, these models are used with numerous pragmatic simplifications whose effects on the computational outcomes have not been systematically examined. The present work uses virtual experiments (VE) to answer crucial questions regarding the spread of ARG in rivers. On the one hand, VE are used to compare alternative configurations of WWTP (in terms of size and location) within a catchment with respect to the resulting microbial contamination in the river network. On the other hand, VE are used to quantify the biases that arise in the estimation of plasmid transfer rates from laboratory experiments when the mathematical models used for this purpose have structural deficiencies. The rates of plasmid transfer determined from laboratory experiments provide an initial basis for assessing the potential importance of the horizontal transfer of ARG occurring in the water column along rivers. The knowledge gained makes an important contribution to describing the spread of ARG in rivers in the future through mathematical models and to identifying possible mitigation measures.

Syftet med denna studie är att lämna förslag till Luossavaara-Kiirunavaara aktiebolags (LKAB i fortsättningen) arbetssätt för framtagning av hållbarhetsmål på koncernnivå. Två frågeställningar har konstruerats för att kunna besvara studiens syfte. Frågeställningarna undersöker hur LKAB arbetar idag med att ta fram hållbarhetsmål på koncernnivå och hur ett optimerat arbetssätt med framtagning av hållbarhetsmål skulle kunna se ut. Datainsamlingen består av intervjuer med olika medarbetare som på ett eller annat sätt har varit involverade i framtagning av förslag till hållbara mål. Resultatet visar att LKAB har arbetet med identifieringen av hållbarhetsmål utifrån ett projektbaserat arbetssätt. Detta är studiens första slutsats. Analysen visar att arbetssättet med framtagning av koncernmål skulle kunna genomföras utifrån ett processbaserat arbetssätt. Analysen och diskussionen i den här studien visar att ett optimerat arbetssätt skulle kunna uppnås genom att dela huvudprocessen till två och utveckla ett processbaserat arbetssätt för varje huvudprocess. Detta är studiens andra slutsats. / The purpose of this study is to submit proposals to the company Luossavaara-Kiirunavaara (LKAB) and its mythology of identifying sustainability goals at group level. two questions have been created in order to be able to answer the study´s purpose. The questions examine LKAB´s mythology of identifying sustainability goals at group level and how an optimized mythology of identifying sustainability goals could look like. The data collection consists of interviews with various employees who have been involved in the identifying of sustainability goals. The results shows that LKAB´s mythology of identifying sustainability goals has formed on a project-based approach. This is the first conclusion of this study. The analysis shows that the mythology of identifying sustainability goals could be implemented with a process-based mythology. The analysis and the discussion in this study show that an optimized mythology could be achieved by dividing the main process into two main processes and developing a process-based mythology for each main process. This is the second conclusion of this study.

This thesis presents a new stratigraphic forward numerical model to simulate the carbonate production of marine sedimentary basin through ecological model which is implemented in the SIMSAFADIM-CLASTIC program. This ecological model is based on the Generalized Lotka Voltera equations that model the population evolution of species. These populations are controlled by biological factors (growth rate, carrying capacity and interaction among species), and by the environmental conditions (light, energy of the medium, nutrients, bottom slope and concentration of clastic sediments in suspension) which are combined forming a unique environmental factor that downscale the intrinsic rate of growth. The algorithm to apply in the code uses an explicit Runge-Kutta numerical method of order (4)5 to solve the differential equations formulated in the ecological model. Finally, a 3D visualization output files for the interpretation and analysis are generated using the VTK format. The obtained code has been applied in three sample experiments in order to discuss the possibilities and the limitations of the code. The first example is the model of a theoretical basin. The results are compared with real cases. The second example is an actual basin sited in western Mediterranean Sea. The results are discussed to show the applicability and the limitations of the model. The third example applies several configurations to the Aptian Galve sub-basin (Maestrat Basin, E Iberia), allowing to define the environmental conditions.

The purpose of the thesis is to identify how a structure for a management system can be designed for a small industrial company based on the seven quality principles that are described in ISO 9000:2015 – fundamental concepts and principles of quality management. The aim of the thesis is to map the reference company's current situation and analyse the gap between the current situation and the quality principles. The thesis also aims to create a plan for the implementation, control and stabilisation of the proposed structure for a management system within the chosen industrial company. The theoretical selection is based on total quality management and the seven quality principles defined in ISO 9000. The case study is carried out via a qualitative strategy, where qualitative data contributes to formulating assumptions and hypotheses. Quantitative tools such as survey and self-assessment are used to identify the reference company's current situation. Qualitative tools such as document review, observations, a focus group and a group interview are used to investigate the studied phenomenon in the company more thoroughly. The study concludes that the company's current quality work is not based on any systematic working method or clear customer focus. The culture within the company is characterized by a commitment to work with quality, but the company lacks a structure to do this. The proposed structure for a corporate adapted management system is based on the process-based system model, which has been modified to include definitions of the company's risks and opportunities and the management's review. A plan for the implementation, control and stabilisation of the proposed structure is compiled and introduced in the company's reviewed strategy for work with quality. The plan's cyclical design reinforces the recurring improvement work based on the iterative four-step management method that is used for control and continuous improvement of processes and products. / Författarnas syfte med examensarbetet har varit att identifiera hur en struktur till ett företagsanpassat ledningssystem kan utformas i mindre industriföretag, utifrån de sju kvalitetsprinciperna som definieras i ISO 9000. Målet med examensarbetet har varit att kartlägga referensföretagets nuläge och analysera gapet mellan nuläget samt kvalitetsprinciperna. Målet har även varit att redovisa en plan för genomförande, uppföljning och säkring av den föreslagna strukturen för ledningssystemet inom det valda industriföretaget. Det teoretiska urvalet har sin utgångspunkt i det offensiva kvalitetsarbetet och de sju kvalitetsprinciperna som definieras inom ISO 9000. Fallstudien har genomförts via en kvalitativ strategi, där kvalitativa data har bidragit till formulering av antaganden och hypoteser. Författarna valde att använda kvalitativa verktyg såsom enkätundersökning och självskattning för att identifiera referensföretagets nuläge. Tillämpning av kvalitativa verktygen såsom dokumentgranskning, observationer, fokusgrupp och gruppintervju möjliggjorde en mer djupgående undersökningen av det studerade fenomenet. De slutsatser som författarna har kommit fram till är att företagets nuvarande kvalitetsarbete inte utgår ifrån något systematiskt arbetssätt eller ett tydligt kundfokus. Kulturen inom företaget kännetecknas dock av en vilja att jobba med kvalitet men det saknas en struktur för detta arbete. Författarnas föreslagna struktur för det företagsanpassade ledningssystemet bygger på den processbaserade systemmodellen (PBSM) som har modifierats till att omfatta definitioner av företagets risker och möjligheter samt ledningens genomgång. En plan för genomförande, uppföljning och säkring av den föreslagna strukturen har sammanställts och införts i företagets reviderade strategi för det interna kvalitetsarbetet. Planens cykliska utformning förstärker det återkommande förbättringsarbetet utifrån PDCA-cykeln.

La concentration de Carbone organique de sol (COS) et les émissions de gaz à effet de serre (GES) ne sont pas uniformes à travers l’espace, mais se regroupent en “hotspots” dans des endroits spécifiques. Ces différences s’expliquent principalement par les activités anthropiques telles que la gestion agricole. 40-50% de la surface de la Terre est utilisé par l’agriculture, par exemple les terres cultivées, les prairies gérées et cultures permanentes, y compris l’agro-foresterie et de bio-cultures énergétiques. En outre, 62% du carbone globale est COS, et le sol conserve plus que 3 fois plus de C que l’atmosphère. Ainsi, la séquestration du carbone dans les sols agricoles joue un rôle potentiellement important dans l’augmentation de stockage de COS et l’atténuation des GES, et il y a un intérêt considérable pour comprendre les effets de la gestion agricole sur le COS et les flux de GES aux prairies et terres cultivées, afin de mieux évaluer l’incertitude et la vulnérabilité des réservoirs de COS. Afin de découvrir les pratiques de gestion agricole qui contribuent à la séquestration efficace et durable du carbone aux terres agricoles en Europe, il est essentiel de simuler les stocks futurs de carbone terrestriel et les budgets de GES par rapport aux systèmes de gestion agricole variés sur les grands écosystèmes européens. Dans ce contexte, la modélisation est une méthode utile, et la modélisation a déjà été utilisée dans beaucoup d’études. Cependant beaucoup de résultats de la modélisation n’ont pas encore été validés avec les données mesurées sur l’horizon long-terme, et d’ailleurs d’autres études ont constaté un fort impact de l’initialisation du modèle sur le résultat du modèle. Néanmoins, la variabilité des prévisions annuelles et décennales concernant le C et le GES en Europe dépendent des résultats du modèle. Par conséquence, il est important de trouver la meilleure méthode d’initialisation des modèles pour obtenir des résultats des modèles fiables, notamment pour les modèles d’écosystèmes dits “process-based”. Au cours des dernières années, Zimmermann et al. (2007) a réussit à initialiser le modèle de Rothamsted carbone (RothC) en utilisant une méthode (physique et chimique) de fractionation des sols. Pour cette raison, j’ai fait l’hypothèse que les données COS détaillées seraient utiles pour initialiser des modèles d’écosystème, et que cette hypothèse doit être testée avec les modèles différents par rapport aux gestions agricoles différentes. Les buts de cette thèse sont les suivants: i) évaluation des influences des gestions agricoles sur le stockage de COS, en utilisant des approches expérimentales et des approches de modélisation; et ii) déterminer la meilleur méthode d’initialisation des modèles. (...) / Soil organic carbon (SOC) concentrations and greenhouse gas (GHG) emissions are not uniform across the landscape, but assemble in “hotspots” in specific areas. These differences are mainly driven by human-induced activities such as agricultural management. 40-50% of the Earth’s land surface is under agricultural land-use, for instance cropland, managed grassland and permanent crops including agro-forestry and bio-energy crops. Furthermore, 62% of the global soil C stock is SOC and the soil stores more than 3 times more C than the atmosphere. Thus, C sequestration in agricultural soil has a potentially important role in increasing SOC storage and GHG mitigation, and there is considerable interest in understanding the effects of agricultural management on SOC and GHG fluxes in both grasslands and croplands, in order to better assess the uncertainty and vulnerability of terrestrial SOC reservoirs. For the sake of discovering the agricultural management practices relating to the effective and sustainable C sequestration in agricultural lands in Europe, simulating future terrestrial C stocks and GHG budgets under varied agricultural management systems in major European ecosystems is essential. Using models is a useful method with the purpose of this and abundant studies have carried out. However, many model results have not been validated with reliable observed long-term data, while other studies have reported a strong impact of model initialisation on model result. Nevertheless, predictions of annual to decadal variability in the European terrestrial C and GHG ressources largely rely on model results. Consequently, finding the most appropriate and comprehensive model initialisation method for obtaining reliable model simulations became important, especially for process-based ecosystem models. In recent years, Zimmermann et al. (2007) have succeed in initialising the Rothamsted Carbon model (RothC) using a physical and chemical soil fractionation method. For that reason, we hypothesised that measured detailed SOC data would be useful to initialise ecosystem models, and this hypothesis should be tested for different process-based models and agricultural land-use and management. (...)

Uma questão que ainda instiga discussões na literatura ecológica é como explicar a coocorrência dinâmica e milenar de formações florestais e campestres sob um mesmo regime climático que tende a favorecer as primeiras, como ocorre atualmente com mosaicos florestacampo no sul do Brasil. A partir de meados do século XX, têm-se evidenciado um fenômeno mundial de avanço de elementos lenhosos sobre áreas abertas. Neste sentido, a modelagem dos processos ecológicos envolvidos na manutenção de ambas as formações numa escala de paisagem permite o esclarecimento dos mecanismos que atuam na manutenção dessa coexistência até o presente e permite prever estados futuros diante dos prognósticos de drásticas alterações climáticas globais já nas próximas décadas. Para tanto, desenvolveu-se um modelo espacialmente explícito (2D-aDGVM) que agrega um Modelo Adaptativo Global de Dinâmica de Vegetação (aDGVM) e ainda inclui heterogeneidades topográficas, propagação do fogo e dispersão de sementes. Este modelo busca satisfazer a necessidade de modelagem mais realista de processos biofísicos, fisiológicos e demográficos na escala de indivíduos e relacionados de forma adaptativa às variações ambientais e aos regimes de distúrbios, ao mesmo tempo que agrega importantes processos ecológicos espaciais, até então pouco ou nada abordados por esse grupo de modelos numa escala de paisagem. Com este modelo, avaliaram-se os efeitos das variações topográficas da radiação solar incidente e destas nos mecanismos de interação (feedbacks) positiva e negativa que surgem daqueles processos na escala de indivíduos e que definem localmente os limites da coexistência entre elementos arbóreos e herbáceos. Ainda, foram analisados os efeitos do aumento da temperatura, precipitação e CO2 atmosférico, desde o período pré-industrial até projeções futuras para as próximas décadas, na performance das diferentes fisiologias envolvidas, bem como no balanço daquelas interações entre as mesmas e, finalmente, na sensibilidade da dinâmica dos mosaicos floresta-campo. Os resultados evidenciaram que, sob o regime climático vigente, uma coexistência relativamente estável entre floresta e campo numa mesma paisagem é mantida por uma alta freqüência de distúrbios, que por sua vez, resulta do forte feedback positivo do acúmulo de biomassa inflamável da vegetação campestre na intensidade do fogo, proporcionado pela condição altamente produtiva do atual clima mesotérmico. Por outro lado, intensificadas pela declividade do terreno, as heterogeneidades espaciais afetaram o balanço dessas interações, interferindo nos padrões espaço-temporais relacionados ao comportamento do fogo e dependentes da densidade de elementos arbóreos. Ainda, tanto esses efeitos observados na escala das manchas de vegetação, como o arranjo espacial inicial das mesmas na paisagem, afetaram as taxas de expansão florestal. Em outras palavras, a manutenção da coexistência de duas formações vegetais constituídas por elementos de inerente assimetria competitiva é possível pela manutenção de uma maior conectividade daquela que propicia o distúrbio, superando a vantagem da outra, que por sua vez é dependente da densidade dos indivíduos. Numa escala de paisagem, isto causa a manutenção de uma baixa conectividade entre as manchas florestais, propiciando sua relativa estabilidade num contexto de dispersão predominante a curtas distâncias. Contudo, embora ambos os sistemas tenham apresentado incremento no crescimento, produtividade e fecundidade, observou-se uma sensibilidade maior no sentido de aumento das taxas de avanço florestal em resposta às projeções climáticas futuras, principalmente nos próximos 90 anos, mesmo na presença do fogo. Isto seria proporcionado pela vantagem fotossintética das árvores-C3 sobre gramíneas-C4 na presença do fogo sob altas concentrações de CO2 atmosférico. Por fim, uma abordagem mais sistêmica dos mosaicos como estados alternativos mostrou ser adequada para o entendimento dos mecanismos que propiciam essa coexistência dinâmica na paisagem. / A longstanding problem in ecology is how to explain the coexistence over thousands of years of forests and natural grasslands under the same climatic regime, which favors the first, such as in forest-grasslands mosaics in South Brazil. Since the middle of the 20th century, a worldwide bush encroachment phenomenon of woody invasion in open vegetation has been threatening this relatively stable coexistence. In this sense, modelling ecological processes that arbitrate the maintenance of both vegetation formations at the landscape scale allows a better understanding of the mechanisms behind the maintenance of this coexistence, as well as predictions of future states under projections of drastic climate change over the next decades. For this, we developed a bidimensional spatial explicit model (2D-aDGVM) that aggregates an adaptive Global Vegetation Model (aDGVM), which includes topographic heterogeneity, fire spread and seed dispersal. The model aims at fulfilling the need for a more realistic representation of biophysical, physiological and demographical processes using an individualbased approach as it adapts these processes to environmental variations and disturbance regimes. In addition, the model includes important spatial ecological processes that have gained less attention by such models adopting a landscape-scale approach. Therefore, we evaluated the effect of topographic variations in incoming solar radiation on positive and on negative feedbacks that rise from those individual-based processes, and which in turns define the limiting thresholds upon which woody and grassy forms coexist. Additionally, the effects of increasing temperature, rainfall and atmospheric CO2 levels on the performance of distinct physiologies (C3-tree and C4-grass) were analyzed, as well as the sensitivity of forestgrassland mosaics to changes in climate from the preindustrial period to the next decades. Results showed that a relatively stable coexistence of forests and grasslands in the same landscape was observed with more frequent fires under the present climatic conditions. This was due to strong positive feedbacks of the huge accumulation of flammable grass biomass on fire intensity promoted by the high productivity of the present mesic conditions. On the other hand, spatio-temporal density dependent processes linked to fire and enhanced by slope at the patch scale, as well as the initial spatial arrangement of vegetation patches affected the rate of forest expansion at the landscape scale. The persistence of coexisting vegetation formations with an inherent asymmetry of competitive interactions was possible when the higher connectivity of the fire-prone patches (grassland) affected negatively the performance of the entire fire-sensitive system (forest). This was possible by overcoming its local densitydependent advantage, or by maintaining it with a low connectivity, which is expected to reduce the rate of coalescence of forest patches in a scenario of predominantly short distance dispersal. Despite the increments in biomass production, stem growth and fecundity that were observed in both grassland and forest, climate change increased the rates of forest expansion over grasslands even in presence of fire, and mainly over the next 90 years. This was attributed to a high photosynthetic advantage of C3-trees over C4-grasses in presence of fire under higher atmospheric CO2 levels. Finally, in the face of the general observed tendency of forest expansion over grasslands, the ancient grasslands have persisted as alternative ecosystem states in forest-grassland mosaics. In this sense, exploring this dynamic coexistence under the concept of alternative stable states have showed to be the most appropriate approach, and the outcomes of this novel perspective may highlight the understanding of the mechanisms behind the long-term coexistence.