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Modelagem multi-hierárquica de distribuição potencial e seleção de filtros ambientais de espécies invasoras no Estado de São Paulo / Multi-hierarchical approach of potential species distribution modeling and selection of environmental filters of invasive species in the State of São PauloAugusto Hashimoto de Mendonça 13 July 2015 (has links)
Nas últimas décadas, em decorrência da globalização e do comércio internacional, o deslocamento de espécies para longe de suas regiões de origem tem crescido em frequência e extensão, aumentando o risco de invasões biológicas, que podem impactar significativamente a economia, o funcionamento dos ecossistemas e causar perdas de biodiversidade. A erradicação de espécies invasoras tem poucas chances de sucesso, de modo que prevenir a invasão constitui a melhor alternativa de manejo. Técnicas de modelagem preditiva de distribuição têm sido globalmente aplicadas para prever a distribuição potencial de espécies invasoras. No Brasil, são poucos e recentes os estudos sobre invasões biológicas. Visando ampliar o conhecimento sobre plantas consideradas invasoras e sua distribuição no estado de São Paulo, neste estudo aplicamos técnicas de modelagem preditiva a 10 espécies. Para cada uma delas buscamos caracterizar o padrão de invasão e identificar os fatores ambientais atuantes que limitam ou potencializam sua distribuição, por meio de modelos multi-hierárquicos de nicho ecológico. Para tanto, coletamos informações de ocorrência dessas espécies em todo o mundo e registramos coordenadas geográficas, características das populações e dos ambientes invadidos por essas espécies em todos os tipos de vegetação e em todas as regiões do estado de São Paulo. Com base nesses dados, caracterizamos o padrão de invasão de cada espécie e a invasibilidade de cada tipo vegetacional estudado. Aplicamos a metodologia de modelagem multi-hierárquica de nicho ecológico por meio do algoritmo MaxEnt em macro escala para todo o globo e em meso escala para o estado de São Paulo. Apesar das peculiaridades das espécies e dos tipos de vegetação, nossos resultados evidenciam a influência do estado de conservação do ecossistema e da posição na paisagem sobre a severidade da invasão e, também, sobre a invasibilidade dos tipos de vegetação em escala local. Mesmo os tipos de vegetação mais resistentes, como a restinga e a floresta ombrófila densa, podem se tornar suscetíveis à invasão em função de distúrbios e da pressão de propágulos. Em fragmentos conservados, porém, são raras as espécies exóticas capazes de se estabelecer e se tornar uma ameaça real à conservação. As fitofisionomias mais abertas do Cerrado mostraram-se como os tipos de vegetação suscetíveis à invasão pelo maior número de espécies, entre as estudadas. Em macro escala, os modelos de nicho ecológico identificaram as áreas potenciais de invasão e revelaram os limites fisiológicos de temperatura e precipitação para cada espécie, enquanto em meso escala, os modelos de nicho refinaram estas previsões e revelaram novos padrões associados com a distribuição das espécies na escala do estado de São Paulo. Este estudo gera contribuições importantes em termos de informação sobre as características e áreas potenciais de invasão para gestores e tomadores de decisão no processo de prevenção e controle de invasões, bem como identifica limites e fatores ambientais que contribuem para a melhor compreensão de invasões biológicas no Brasil. De forma geral, a abordagem multi-hierárquica se mostrou uma ferramenta poderosa para explorar padrões de distribuição em escalas apropriadas com os objetivos de conservação, prevenção e controle de espécies exóticas. / In recent decades, as a result of globalization and international trade, the movement of species away from their native regions has grown in frequency and extent, increasing the risk of biological invasions, which can significantly impact the economy, the functioning of ecosystems and cause biodiversity loss. The eradication of invasive species it is not an easy task, usually with little chance of success, so that prevent the invasion is still the best management alternative. Predictive species distribution modeling techniques have generally been applied to predict the potential distribution of invasive species. In Brazil, studies on biological invasions are recent and insufficient to understand the current invasive status. To enhance understanding about invasive plants and its distribution in the state of São Paulo, in this study we apply predictive modeling techniques to 10 species considered invasive. For each of the selected species we seek to characterize the invasion pattern and identify the active environmental factors that limit or leverage its distribution through multihierarchical ecological niche models. For this purpose, we collect information for these species occurring worldwide and recorded geographical coordinates characteristics of populations and environments invaded by these species in all vegetation types and in all regions of the state of São Paulo. Based on these data, we characterize the invasion pattern of each species and the invasiveness of each vegetation type studied. We applied the multihierarchical ecological niche modeling methodology through MaxEnt algorithm in macro scale for the entire globe and meso scale for the state of São Paulo. Despite the peculiarities of species and vegetation types, our results highlight the influence of ecosystem conservation status and position in the landscape on the severity of the invasion and on the invasiveness of vegetation types on a local scale. Even the most resistant types of vegetation, such as the restinga and the tropical rain forest, can become susceptible to invasion because of disturbances and seedlings pressure. In conserved fragments, however, exotic species were rarely able to settle down and become a real threat to conservation. The more open forms of the Cerrado vegetation types appeared as the most susceptible to invasion by most of the studied species. In macro scale, the ecological niche models identified the potential areas of invasion and revealed the physiological limits of temperature and precipitation for each species, while in meso scale, niche models refined these projections and revealed new patterns associated with the distribution of species on the scale of São Paulo. This study provides important contributions in terms of information about the characteristics and potential areas of invasion for managers and decision makers in prevention and control of invasions and identifies limitations and environmental factors that contribute to a better understanding of biological invasions in Brazil. In general, the multihierarchical approach proved to be a powerful tool to explore patterns of distribution at scales compatible with conservation objectives, prevention and control of alien species.
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O efeito da escala espacial no modelamento hidrológico / Effect of the spatial scale in the hydrological modelingSILVA, Claudio Rodrigues da 28 August 2009 (has links)
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Previous issue date: 2009-08-28 / This study presents the results of the analysis of the effect of the spatial scale in the hydrologic modeling. Nine watersheds were delimited in three different spatial scales:
small (Capão da Onça River Basin), middle (Areias River Basin) and large (Corrente River Basin). The physiographic characteristics, area, length of the main river and slope of the river were obtained from digital cartographic maps in the three available scales for Goiás, 1:1.000.000, 1:250.000 and 1:100.000, using tools of Geographic Information Systems. The physical data of the basins were used as input in the hydrologic model - HEC HMS version 3.3 - developed by Hydrologic Engineering Center of the U.S. Army Corps of Engineers, projected to simulate the precipitation-runoff process in a watershed. After the simulation procedures and calibration of the model, the study shows that data obtained from different cartographic scales little influence the final
result of the modeling in the three analyzed spatial scales. It was also evidenced that the modeling presented better results in the middle scale with a better adjustment between
the observed and calculated hydrographs. / Este estudo apresenta os resultados da análise do efeito da escala espacial na modelagem hidrológica. Para isto foram delimitadas bacias hidrográficas em três diferentes escalas espaciais: pequena (Bacia do Córrego Capão da Onça), média (Bacia do Rio Areias) e grande (Bacia do Rio Corrente), em Goiás e no Distrito Federal. As características fisiográficas, área, comprimento do rio principal e desnível do rio foram
obtidas a partir de bases cartográficas digitais nas três escalas disponíveis, 1:1.000.000, 1:250.000 e 1:100.000, utilizando-se ferramentas de Sistemas de Informações
Geográficas. Os dados físicos das bacias foram utilizados como dados de entrada no modelo hidrológico HEC HMS versão 3.3 - desenvolvido pelo Hydrologic Engineering Center of the U.S. Army Corps of Engineers, projetado para simular o processo chuva-vazão em bacias hidrográficas. Após os procedimentos de simulação e de calibração do modelo, o estudo mostra que dados obtidos a partir de diferentes
escalas cartográficas pouco influenciam o resultado final da modelagem nas três escalas espaciais analisadas. Foi evidenciado, também, que a modelagem apresentou melhores
resultados na média escala com um melhor ajuste entre as hidrógrafas observadas e calculadas
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Ecosystem services in agricultural landscapes : A study on farming and farmers in South Africa and SwedenMalinga, Rebecka January 2016 (has links)
Humanity is facing challenges of sustainably producing enough food for a growing population without further eroding the world’s ecosystems. Transformation of natural habitats into agriculture has resulted in opportunities for civilization, but has also led to land degradation and loss of biodiversity, threatening the generation of ecosystem services. A better understanding of interlinkages and trade-offs among ecosystem services, and the spatial scales at which services are generated, used and interact, is needed in order to successfully inform land use policies. This includes the need to develop transdisciplinary tools that can disentangle the relationships between the supply of and demand for ecosystem services. This thesis investigates agricultural landscapes as complex social-ecological systems, and uses a multi-method approach to assess ecosystem service generation from different types of agricultural landscapes and to examine the social-ecological nature of these services. More specifically, the thesis discusses the importance of appropriate spatial scales, explores landscape change, integrates stakeholder knowledge and develops tools to investigate supply and demand of multiple ecosystem services. Paper I reviews the literature on ecosystem service mapping, revealing that services were mostly mapped at intermediate spatial scales (municipality and province), and rarely at local scales (farm/village). Although most of the reviewed studies used a resolution of 1 hectare or less, more case-specific local scale mapping is required to unravel the fine-scale dynamics of ecosystem service generation that are needed to inform landscape planning. To explore future uncertainties and identify relevant ecosystem services in a study area, paper II builds alternative scenarios using participatory scenario planning in the Upper Thukela region, South Africa. The paper compares methods to select services for an ecosystem service assessment showing that scenario planning added limited value for identifying ecosystem services, although it improved knowledge of the study area and availed useful discussions with stakeholders. Papers III and IV combines social and biophysical data to study the supply and demand of ecosystem services at farm- and landscape level, through participatory mapping and expert assessments in the Upper Thukela region, South Africa (paper III), and through in-depth interviews and biophysical surveys in Uppsala County, Sweden (paper IV), including small-scale and large-scale farmers. Both papers find apparent differences between the farmer groups in terms of the supply and the demand of services, and also the capacity of the farmers to influence the generation of services (paper III). Paper IV further establishes the importance of using multiple indicators combining social and biophysical data to quantify and investigate the complex social-ecological nature of ecosystem services. A cross-case comparison of ecosystem service bundles, using data from papers III and IV, finds similarities in bundles generated in the large-scale systems, while the small-scale agriculture bundles varied. This thesis provides new insights into the social-ecological generation of ecosystem services at fine scales such as farm and landscape levels, and shows the importance of including the knowledge of various stakeholders, combining different methods and tools to increase the understanding of supply and demand of ecosystem services. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Manuscript.</p>
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A multi-spatial-scale characterization of Lark Sparrow habitat and the management implicationsCoulter, Melanie 29 July 2008 (has links)
No description available.
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Assessing plans that support urban adaptation to changing climate and extreme events across spatial scalesOmunga, Philip M. January 1900 (has links)
Doctor of Philosophy / Department of Environmental Design and Planning Program / Lee R. Skabelund / Despite the growing number of urban adaptation planning initiatives to climate change hazards, there exist significant barriers related to implementation uncertainties that hinder translation of adaptation plans into actions, resulting in a widely recognized ‘planning-implementation gap’ across scales and regions. Bridging the planning-implementation gap will require overcoming implementation uncertainties by better understanding the relationships between the primary factors driving adaptation planning initiatives and emerging adaptation options across spatial scales.
The modified Driver-Pressure-State-Impact-Response model published by Rounsevell, Dawson, and Harrison in 2010 provided a robust framework for identifying the primary factors driving adaptation planning initiatives and the emerging adaptation options related to risk of changing climate and flooding events in the urban context. Drawing on evidence from the systematic review of 121 adaptation planning case studies across North America, this research derived qualitative and quantitative data, which was subsequently analyzed using binary logistic regression to generate objective and generalizable findings.
The findings of binary logistic regression models suggest that the choice of specific adaptation options (namely enhancing adaptive capacity; management and conservation; and improving urban infrastructure, planning, and development) may be predicted based on the assessment of primary factors driving adaptation planning initiatives (namely, anticipation of economic benefits; perceived threats to management and conservation of urban natural resources; support of human and social systems; and improvement of policy and regulations) in relation to the risk of changing climate and urban flooding events. This does not imply that other primary factors (namely information and knowledge; perceived funding and economic opportunities; evidence of climate change effects; and general concerns) have no or insignificant relationships with the selection of adaptation options, only that the review did not find evidence to support such claims.
These study findings may offer useful guidance to the design and further development of planning and decision support tools that could be used for assessment of adaptation plans and selection of robust adaptation options that take account of uncertainties surrounding implementation of effective climate adaptation actions. Study findings can also inform evidence-based policy and investment decision making, especially in regions where urban adaptation plans are weak or absent.
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The role of microclimate for the performance and distribution of forest plantsDahlberg, C. Johan January 2016 (has links)
Microclimatic gradients may have large influence on individual vital rates and population growth rates of species, and limit their distributions. Therefore, I focused on the influence of microclimate on individual performance and distribution of species. Further, I examined differences in how microclimate affect species with contrasting distributions or different ecophysiological traits, and populations within species. More specifically, I investigated the performance of northern and southern distributed forest bryophytes that were transplanted across microclimatic gradients, and the timing of vegetative and reproductive development among northern, marginal and more southern populations of a forest herb in a common garden. Also, I compared the landscape and continental distributions across forest bryophytes and vascular plants and, thus, their distribution limiting factors at different spatial scales. Lastly, I examined the population dynamics across microclimatic gradients of transplants from northern and southern populations of a forest moss. The effects of microclimatic conditions on performance differed among bryophytes with contrasting distributions. There were no clear differences between northern and southern populations in the timing of development of a forest herb or in the population dynamics of a moss. However, within each region there was a differentiation of the forest herb populations, related to variation in local climatic conditions and in the south also to proportion of deciduous trees. The continental distributions of species were reflected in their landscape distributions and vice versa, in terms of their occurrence optima for climatic variables. The variation in landscape climatic optima was, however, larger than predicted, which limit the precision for predictions of microrefugia. Probably, the distributions of vascular plants were more affected by temperature than the distributions of bryophytes. Bryophytes are sensitive to moisture conditions, which was demonstrated by a correlation between evaporation and the population growth rate of a forest moss. We might be able to predict species’ landscape scale distributions by linking microclimatic conditions to their population growth rates, via their vital rates, and infer larger scale distribution patterns. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 4: Manuscript.</p> / EkoKlim
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Local management and landscape context effects on bee pollination, ant seed predation, and yield in Indonesian homegardens / Local management and landscape context effects on bee pollination, ant seed predation, and yield in Indonesian homegardensMotzke, Iris Cordula 15 May 2014 (has links)
No description available.
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"Vivre à l'ombre proche" du barrage de Manantali : les formes de représentations sociales des impacts dans les campements et les villages environnantsCisse, Coumba 09 June 2016 (has links)
En 1988, le Bassin du fleuve Sénégal au Mali a vu la mise en service d’un barrage par l’Organisation pour la Mise en Valeur du fleuve Sénégal (OMVS). L’objectif principale est la production d’énergie électrique partagée entre : le Mali (52%), le Sénégal (33%) et la Mauritanie (15%). Mais l’apparition de cet ouvrage constitue une perturbation profonde dans l’organisation et le fonctionnement des espaces riverains. Les territoires autour du Bafing, affluent où se localise le barrage, se trouvent ainsi cloisonnés en une partie amont et aval du lac de retenue. Ce dernier a insufflé une nouvelle dynamique spatiale avec l’installation récente de 25 campements de pêche.Cette nouvelle économie constitue un facteur d’attraction de pêcheurs professionnels venus des régions du Centre du Mali, particulièrement de Mopti et de Ségou. Le lac devient ainsi une immense réserve de poissons avec des tailles plus importantes par rapport à ceux capturés dans les affluents du Bafing, du Bakoye, ou même du fleuve Sénégal. En amont du barrage, la pêche devient la première activité économique poussant des jeunes agriculteurs et éleveurs «autochtones» à une reconversion professionnelle pas toujours aboutie. Les campements de pêcheurs occupent un ancien site des villages déplacés lors de la construction du barrage. Trente-trois villages sont actuellement réinstallés en aval du barrage dans le finage d’autres hameaux préexistants. Cette cohabitation bouleverse l’occupation de l’espace et entraine des tensions foncières. Certains sites comme Manantali à 5 km du barrage en sont les grands bénéficiaires. Ce village s’est transformé en un véritable « centre-rural », en accueillant les cadres et les ouvriers qualifiés et toute la main d’œuvre venus du Mali voire de l’étranger. Cet afflux d’habitants urbanisés a profondément changé la configuration du site et l’a surtout fortement ségrégué. Les bureaux de la société d’exploitation au pied du barrage, le vieux village de Manantali, les cités des ouvriers et celle des cadres sont autant de témoins d’un espace urbain en devenir, fonctionnel et très inégalitaire. Le principal objet de cette étude est l’étude des impacts du barrage de Manantali sur l’organisation socio-spatiale et physique des territoires riverains. L’entrée par une lecture des représentations sociales, consensuelles comme conflictuelles, par les habitants et les différents acteurs, est privilégiée. L’analyse des données quantitatives et des différents discours identifie les expressions tant des effets environnementaux physiques que socioéconomiques suscités par l’ouvrage. Le concept de représentations sociales est posé de la façon suivante: «les représentations forment des codes mémorisés par le cerveau, mobilisables de façon consciente et se prêtant à de multiples utilisations mentales. Ces codes servent en particulier à décrypter notre environnement géographique, mais aussi à communiquer avec autrui, à rêver, imaginer, planifier et orienter nos conduites ou nos pratiques les plus diverses» (DI MEO, 2008). Cette étude d’impact se positionne donc le domaine de la géographie sociale.Au cœur de cette étude se trouvent les acteurs, les responsables politiques à différentes échelles, et surtout l’habitant ordinaire qui vit à l’ombre du barrage de Manantali. Cette notion d’ombre doit être comprise dans la polysémie des impacts de l’ouvrage, tout autant néfastes que bénéfique, et par rapport à son aire d’influence. Les principales zones d’étude considérées se situent à « l’ombre proche » de l’ouvrage, ou à l’échelle locale, dans un rayon de 50 kilomètres autour du barrage. Il s’agit de 8 villages déplacés et anciens. Mais également des 25 campements de pêche autour du lac de retenue. / In 1988 the Senegal River basin in Mali has witnessed the building of a dam by the Organization for the Development of the Senegal River (OMVS) in French. The main objective is the production of electric power shared between: Mali (52%), Senegal (33%) and Mauritania (15%). But the birth of this dam has deeply disrupted the organization and functioning of all the waterside’s areas. The territories around the Bafing, the river where the dam is localized, are now strictlydivided by the reservoir between an upstream and downstream portions. This artificial lake has created new types of spatial organization with the recent settlements of 25 fishing camps.This new economy has created a pull factor for professional fishermen coming from the central regions of Mali, particularly Mopti and Segou. The lake hence becomes a huge fish reserve with larger sizes compared to those caught in the Bafing, the Bakoye or even in the Senegal River. In the upstream areas of the dam, fishing has become the first business activityencouraging local young farmers and herdsmen towards an unlikely professional retraining.Fishermen settlements occupy former site of displaced villages due to the dam construction. Thirty-three villages have been relocated downstream of the dam in the lands of existing hamlets. This cohabitation disruptstraditional land use and leads to social strains.
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An Object-Based Image Analysis of Treated and Untreated Pinyon and Juniper Woodlands Across the Great BasinHulet, April 07 March 2012 (has links) (PDF)
Land managers need to rapidly assess vegetation composition and bare ground to effectively evaluate, manage, and restore shrub steppe communities that have been encroached by pinyon and juniper (P-J) trees. A major part of this process is assessing where to apply mechanical and prescribed fire treatments to reduce fuel loads and maintain or restore sagebrush steppe rangelands. Geospatial technologies, particularly remote sensing, offers an efficient option to assess rangelands across multiple spatial scales while reducing the need for ground-based sampling measurements. High-spatial resolution color-infrared imagery (0.06-m pixels) was acquired for sagebrush steppe communities invaded by P-J trees at five sites in Oregon, California, Nevada, and Utah with a Vexcel Ultra CamX digital camera in June/July 2009. In addition to untreated P-J woodlands, imagery was acquired over P-J woodlands where fuels were reduced by either prescribed fire, tree cutting, or mastication treatments. Ground measurements were simultaneously collected at each site in 2009 on 0.1-hectare subplots as part of the Sagebrush Steppe Treatment Evaluation Project (SageSTEP). We used Trimble eCognition Developer to 1) develop efficient methods to estimate land cover classes found in P-J woodlands; 2) determine the relationship between ground measurements and object-based image analysis (OBIA) land cover measurements for the following classes: trees (live, burned, cut, and masticated), shrubs, perennial herbaceous vegetation, litter (including annual species), and bare ground; and 3) evaluate eCognition rule-sets (models) across four spatial scales (subplot, site, region, and network) using untreated P-J woodland imagery. At the site scale, the overall accuracy of our thematic maps for untreated P-J woodlands was 84% with a kappa statistic of 0.80. For treatments, the overall accuracy and kappa statistic for prescribed fire was 85% and 0.81; cut and fell 82% and 0.77, and mastication 84% and 0.80, respectively, each indicating strong agreement between OBIA classification and ground measured data. Differences between mean cover estimates using OBIA and ground-measurements were not consistently higher or lower for any land cover class and when evaluated for individual sites, were within 5% of each other; all regional and network OBIA mean cover estimates were within 10% of the ground measurements. The trade-off for decreased precision over a larger area (region and network scale) may be useful to prioritize fuel-management strategies but will unlikely capture subtle shifts in understory plant communities that site and subplot spatial scales often capture. Although cover assessments from OBIA differed somewhat from ground measurements, they were accurate enough for many landscape-assessment applications such as evaluating treatment success and assessing the spatial distribution of fuels following fuel-reduction treatments on a site scale.
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Reconstruction of fire and forest history on several investigation sites in Germany, based on long and short-term investigations - Multiproxy approaches contributing to naturalness assessment on a local scale / Reconstruction de l'histoire des feux et de la dynamique forestière d'un ensemble de sites d'étude en Allemagne, basée sur de longues et courtes échelles temporelles. Evaluation de la naturalité à l'échelle locale pour une approche pluridisciplinaireRobin, Vincent 04 November 2011 (has links)
Sur la base de constats globaux concernant l’importance d’appliquer des modes de gestion durable des zones forestières et le manque d’investigation concernant l’histoire passée des feux en Europe centrale, il a été entrepris de reconstruire l’histoire des événements de feux et de la dynamique forestière pour des sites d’étude en Allemagne. L’ensemble des données obtenues et analysées ont été utilisées pour l’évaluation du niveau de naturalité des sites étudiés, cette notion étant essentielle pour la mise en place d’une gestion durable, et/ou pour des projets de conservation et / ou de restauration des systèmes perturbés. Concernant les dynamiques des écosystèmes en Europe centrale, il a été souvent mis en évidence que l’homme joue un rôle essentiel depuis des millénaires. Par conséquent, l’approche historique des événements de feux et de la dynamique forestière à été réalisée sur de longues échelles temporelles. Neuf sites d’étude ont été sélectionnés incluant une large gamme de systèmes forestiers d’Europe centrale. Les sites d’études sont répartis dans deux zones générales d’étude : le nord de l’Allemagne (Schleswig-Holstein), qui comprend quatre sites d’étude, et le centre de l’Allemagne (le Harz), qui comprend cinq sites d’étude. Quatre disciplines ont été principalement utilisées. Pour définir l’état actuel des sites d’études ceux-ci ont été caractérisés, utilisant divers indicateurs dendrométriques concernant la structure et la composition des parcelles analysées. Pour obtenir des informations à propos de la dynamique forestière des peuplements forestiers en place des analyses dendroécologiques ont été utilisées. Pour analyser la dynamique forestière sur une longue échelle temporelle, à une échelle spatiale comparable, des analyses pédoanthracologiques ont été menées, combinées à des analyses de sols. De plus, des analyses anthracologiques de séquences de tourbes ont été réalisées, fournissant, combinées avec les données pedoanthracologiques, des enseignements à propos de l’histoire des incendies. L’état actuel et la dynamique forestière récente des sites étudiés indiquent divers niveaux de complexité des peuplements forestiers, correspondant souvent à divers niveaux postulés d’impact anthropique. Il a été obtenu huit chronologies moyennes, standardisées en haute et moyenne fréquences, âgées au maximum de 1744 et au minimum de 1923 ans. A partir de ces chronologies des changements dans les conditions de croissance de peuplements forestiers ont été mises en évidence. Basées sur un ensemble de 71 charbons de bois datés par radiocarbone, il a été mis en évidence, à l’échelle locale et globale, deux principales phases présentant plus d’événements de feux datés, une durant le Pléistocène supérieur/Holocène inférieur, une autre durant l’Holocène supérieur. Pour les deux phases identifiées des forçages climatique et anthropogénique ont été respectivement postulés comme déterminisme des occurrences de feux. Finalement, les différentes données collectées ont été utilisées de façon combinée pour reconstruire l’histoire des feux et des forêts des sites étudiés, afin de contribuer à l’évaluation de leur niveau de naturalité. / Considering two global observations in Central Europe of, firstly, the need for, and development of, sustainable and biological conservation practices for forest and/or woodland areas and, secondly, the lack of long-term fire history, an attempt has been made to reconstruct the fire and the forest history at several investigation sites in Germany. The overall data set gathered and analyzed has been used for on-site naturalness assessment. This latter notion is crucial for forest system conservation/restoration planning, considering the past human impact on forest dynamics. Also, in view of this past human impact on forest systems, which is well-documented for Central Europe, as occurring on a multi-millennium scale, an historical perspective perceptive that combined a long and short temporal scale of investigation was used.Nine investigation sites were selected, in order to include various and representative types of Central European forest. Therefore, the investigation sites were located in two main investigation areas. One is in Northern Germany (Schleswig-Holstein) and includes four investigation sites. The other is in Central Germany (Harz Mountains) and includes five investigation sites. Four main approaches were used. To assess the current state of the investigated site, forest stand characterization was undertaken (i.e. based on various forest attributes that concern stand structure and composition). Tree ring series were analyzed to provide insights about short-term forest tree population dynamics. Then, charcoal records from soil (combined with soil analysis) and peat sequences were qualitatively and quantitatively analyzed. These last two approaches also provide information about the past fire history. Forest current and short-term dynamics illustrated various levels of stand complexity, often corresponding to various levels of human impact that had been postulated. Eight mean site tree-ring chronologies, standardized in high and mid-frequency signal, spanning at a maximum of up to AD 1744 and at a minimum of up to AD 1923, were obtained. The insight, about the identification of events of growing changes and the correlated temporal and, if possible, spatial patterns, was discussed. Charcoal analysis provided a long-term insight about fire history. Based on 71 charcoal radiocarbon dates, it was shown on a macro-scale that there were two phases that had a greater frequency of fire - one during the transition from the late Pleistocene to the early Holocene, and one during the mid- and late Holocene. A strong human control during the most recent fire phase has been postulated. This is supported by on-site soil and peat charcoal record analysis, allowing one to point out the event of environmental changes (disturbances), at local scales. In the end, the on-site data from the various indicators were combined to assess the fire and forest history and the naturalness level of the investigated sites, based on past insights, thereby contributing to a better understanding of the present and helping to anticipate the future.
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