Changes in land use and water use can greatly impact the cycling of water and water-borne substances. Increased redistribution of river water to irrigated fields can cause enhanced evapotranspiration and decreased river discharge. Additionally, the water quality can be affected by the external input of fertilisers and pesticides, and by changed pollutant transport pathways in expansive irrigation canal systems. This thesis examines basin-scale changes in water use, river discharge, water quality and nitrogen (N) loading under conditions of intensified irrigated agriculture, using the Aral Sea drainage basin (ASDB) with its two large rivers Syr Darya and Amu Darya in Central Asia as study area. Results show that more efficient irrigation techniques could reduce outtake of river water to the cotton fields in the ASDB by about 10 km3/year, while the corresponding river water saving at the outlet would be 60% lower. The result illustrates the importance of accounting for return flows of irrigation water in basin-scale water saving assessments. Moreover, a decrease in riverine N concentrations at the outlet of the Amu Darya River Basin (ADRB) was observed during a 40-year period of increasing N fertiliser input. The decrease was identified to be primarily caused by increased recirculation of river water in the irrigation system, leading to increased flow-path lengths and enhanced N attenuation. Decreasing N loads were shown to be primarily related to reduced discharge. N export from the basin may further decrease due to projected discharge reductions related to climate change. Furthermore, nutrients and metals were occasionally found at concentrations above drinking water guideline values in surface waters in the ADRB. However, metal concentrations in groundwater in the lower ADRB were subject to orders of magnitude higher health hazards. Projected decrease in downstream surface water availability would thus imply decreased access to water suitable for drinking. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Submitted. Paper 5: Manuscript.</p>

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Wald weist gegenüber anderen Landnutzungen meist die günstigeren Wasserrückhalteigenschaften auf. Diese sind jedoch begrenzt. Ob zusätzlicher Wald in einem Einzugsgebiet zur Reduktion eines Hochwassers führt, hängt ab von der Vorwitterung, den Eigenschaften des Bodens, auf dem die Aufforstung etabliert wurde, Dauer und Intensität des hochwasserauslösenden Niederschlagsereignisses und Lage und Größe der Aufforstungsfläche im betrachteten Einzugsgebiet. Weiterhin spielt das Waldmanagement, welches in dieser Arbeit nur am Rande diskutiert wurde, eine bedeutende Rolle. Bei der Umwandlung einer anderen Landnutzung in Wald sind noch nicht alle Prozesse, die den Wasserrückhalt betreffen, ausreichend untersucht und beschrieben. Dies gilt besonders für die Änderungen in der hydraulischen Architektur der Böden. Es wurde dargestellt, dass aufwachsende Wälder schon nach wenigen Jahren die Porenverteilung besonders in den oberen Bodenhorizonten verändern. Obwohl experimentelle Felduntersuchungen besonders durch die Suche nach geeigneten Teststandorten schwierig sind, wären weitere Messergebnisse von anderen Böden mit anderen Baumarten hier wünschenswert. Eine modellhafte Beschreibung einer Landnutzungsänderung hin zu Wald in Bezug auf den Hochwasserrückhalt ist demnach mit hohen Unsicherheiten behaftet. Modelle bleiben dennoch die einzige Möglichkeit, Auswirkungen von Landnutzungsänderungen mit vertretbarem Aufwand quantifizierend abzuschätzen. Allgemein gilt bei der Anwendung hydrologischer Modelle zur Prognose von Auswirkungen veränderter Landnutzungen, dass bislang wenig quantitativ verwertbares Wissen über Änderungen im Boden besteht. Weder der Zielzustand noch der Verlauf der Transformation können hier sicher prognostiziert werden. Vernachlässigt man aber solche Prozesse, dürfen bei einer Ergebnisdiskussion auch nur die berücksichtigten Prozesse angeführt werden. Die Weiterentwicklung der Modelle mit gezielter paralleler Datenerhebung ist hier unabdingbar. Die zunehmenden Fragestellungen hinsichtlich veränderter Landnutzungssysteme erfordern auch innovative Formen der Parametrisierung und Kalibrierung der Modelle. Der zunehmende Grad an Prozessabbildungen in den Modellen darf die Parametrisierbarkeit nicht unmöglich machen. Eine adäquate Prozessabbildung ist jedoch der Schlüssel für die szenarienfähige Modellierung. Die Kommunikation der Ergebnisse muss deshalb eine hohe Transparenz mit der Benennung aller bekannten Unsicherheiten aufweisen, da Entscheidungen in der Landnutzung Konsequenzen über sehr lange Zeiträume hinweg nach sich ziehen. Die qualifizierte Prognose von Landnutzungsänderungen ist eine disziplinübergreifende Aufgabe. Hier wirken soziologische, ökonomische und ökologische Prozesse zusammen, deren Resultat die zukünftige Landnutzung ist. Eine weitere wichtige Schlussfolgerung der vorliegenden Arbeit ist daher, dass für die Umsetzung von Maßnahmen, zur Erhöhung des Wasserrückhaltes, wie hier der Aufforstung, ein breiter wissenschaftlicher und gesellschaftlicher Konsens herrschen muss. Es braucht integrierte Ansätze zur disziplinübergreifenden Beschreibung von Auswirkungen veränderter Landnutzung. Trotz aller Unsicherheiten bei der wissenschaftlichen Beweisführung wird erwartet, dass bis zur Umsetzung der Hochwasserrisiko-Managementpläne „nachhaltige Flächennutzungen“ zur „Verbesserung des Wasserrückhaltes“ definiert sind. Besonders für die politischen Entscheidungsträger ist zur Entwicklung geeigneter Steuerelemente festzuhalten, das Hochwasserschutzmaßnahmen in der Fläche ihre hauptsächliche Wirkung nicht am Punkt der Implementierung entfalten, sondern erst weiter flussabwärts. Daher sind die bisherigen Förderinstrumente der EU-Agrarflächenförderung für den Hochwasserschutz in der Fläche nahezu nicht anwendbar. Es gilt hier sektorales Denken zu überwinden. Unterschiedliche Ansprüche an Landnutzungssysteme sind durch Lösungsansätze auszubalancieren, die die unterschiedlichen Landschaftsfunktionen berücksichtigen, von denen Wasserrückhalt ein Teil sein kann. Andere Schutzziele wie Naturschutz, Bodenschutz, Ziele der Wasserrahmenrichtlinie, Fragen eines ästhetischen Landschaftsbildes und nicht zuletzt Fragen der wirtschaftlichen Ansprüche an die einzelnen Flächen spielen hier eine wichtige Rolle. Bei der Entwicklung begründeter Zukunftsszenarien ist diese transdisziplinäre Herangehensweise unbedingt zu empfehlen. Hochwasserschutz kann aber nicht die Aufgabe haben, Hochwasserereignisse vollkommen auszuschließen. Schon heute ist bekannt, dass das Ausbleiben kleiner und mittlerer Hochwässer ökologische Konsequenzen hat. Vielmehr könnte in Gebieten, wie dem hier untersuchten, eine Erhöhung des Waldanteils dazu beitragen, die anthropogenen Störungen zu reduzieren und den Wasserrückhalt dahingehend zu erhöhen, dass hochwasserverschärfende Eingriffe in den Einzugsgebieten zurückgebaut werden. / Forests show, compared to other land uses, in many cases good water retention potential. This is however limited. Whether additional forest area in a catchment leads to a reduction of flooding depends on the pre-event atmospheric conditions, the soil characteristics at the afforested site, the duration and intensity of the rain storm event, and location and size of the afforested area. Further, the forest management, which is only briefly discussed in this thesis, plays an important role. Many water retention related processes occurring during the transformation of a landuse into forest are not yet sufficiently investigated an described. This applies especially to the changes in the hydraulic architecture of the soil. It was shown that after a few years growing forests have already changed the pore distribution, especially in the upper soil horizons. However, further research under different soil and tree type would be desirable. Therefore, a model-based description of land use change towards forest with regard to flood retention comprises uncertainties which should be taken into consideration. Nevertheless, models are the only possibility to assess land use change effects with justifiable expenditure. In general, the application of hydrological models comprised sparse useful information about changes in the soil due to a changed land use. Neither the target state nor the progression of the transformation can be predicted with certainty. Further development of models with parallel observations and data gathering is essential. With increasing number of questions regarding modified land use systems, a need arises for innovative forms of parameterisation and model calibration. The increasing degree of process mapping in models may make parameterability difficult, however, adequate process mapping is the key to scenario capable modelling. The communication of results must therefore include a high degree of transparency in the definition of all known uncertainties, because decisions have long lasting consequences. A qualified prediction of land use changes is a cross-disciplinary task. Ecological, economical, and sociological processes together form the future land use distribution. An important conclusion from this thesis is that the implementation of measures targeting increased water retention requires must result in a consensus with society and economics. Integrated approaches and transdisciplinary assessment of impacts of land use modifications are needed. Although, the uncertainties in model-based land use change assessment are high, there is a need for the definition of “sustainable land use” and “increase of water retention” for the flood risk management plans. Adapted land use as a component of integrated flood risk management has a major constraint: the benefits of water retention in the landscape are mostly not directly noticeable at the place where a measure is implemented. This is highly important for stakeholders and decision makers. However, given that most of the land available for afforestation is a private property, it may be necessary to provide subsidies to encourage landowners to increase the percentage of forested land. Competitive land use system requirements need to be balanced with approaches dealing with different landscape functions. Water retention is part of this functioning. Other protection aims like nature protection, soil protection, aims of the Water Framework Directive, aesthetic land use pattern but also the agrar-economic production play an important role. Well-founded future land use scenarios should use this transdisciplinary view. Finally, it is also important to keep in mind that floods belong to a healthy river runoff regime. Floods are an important part of the natural hydrological cycle, and therefore the goal of watershed management should not be to eliminate them entirely. Additional forest can help to re-establish the natural water retention potential in anthropogenically disturbed river basins and to decrease the human-made contribution to flood generation.

A coastal lagoon is a landform that is influenced by natural processes and human activities. All human activities at the upstream, particularly agriculture and cultivation bring soil, waste, and other materials to the downstream area through the river drains into the lagoon. Even though its position is inland of water bodies, the lagoon is still affected by waves and winds from the sea. Additionally, coastal lagoon will be the depository place for sedimentation from the upland area. Segara Anakan (SA), which is located in Indonesia, is an example of a coastal lagoon area, which has a unique biophysical characteristic. The region has a great natural ability to ensure the sustainability of the interrelationships between terrestrial, estuarine and marine ecosystems in harmony and balance as a habitat for flora and fauna. The region is an area of migration of various types of protected animals and it is a place of breeding for diverse species of the shrimp and fish, which have a highly economical value. Segara Anakan lagoon (SAL), currently experiencing acceleration narrowed on its area due to a very intensive sedimentation from the mainland. The research aims to answer the question of how ecological dynamic occurs in the SAL area due to sedimentation. Achieving the objectives of this study required examining the morphology and land use changes with multitemporal remote sensing approaches. While, to assess the role of community participation and planning management strategies is using qualitative descriptive methods and SWOT analyze. The using of multitemporal remote sensing Landsat images is possible to analyze the morphological and land use changes with different time and sensors. These Landsat has image accuracy about 92.66%. It can be used for image interpretations resulting 13 classes of land use. The morphodynamics of SAL indicated by the changes of area of lagoon and accreted land and also the distance of coastlines during the periods 1979-2013. In addition, the land use or land cover also changes during that time. The bigger portions of land use changes are in the tropical and mangrove\'s forests. There are distinctive forms of participation in conservation efforts. The upstream community involvement in conservation tends to be different participating in the way of ideas, money, materials, properties, skills and expertise or social activities. In addition, the community at downstream area has a sufficiently high level of participation in environmental conservation. There are also strong relationships between the level of education and level of income and basic knowledge in conservation with the participation of SA conservation. The ecological dynamics of the SAL area are described with a historical time line. It is divided into three time periods: the 1970s - 1980s, the 1990s and from 2000 onwards. Each of these has occurrences that can lead to changes in the environment. The implementation of appropriate conservation technique can reduce the sedimentation rate. Hence, the synergic coordination measures between upstream and downstream regions are necessary in the future. Increasing community awareness and participation in the conservation by improving educational sector, providing information, and applying sustainable development land use are the ways to match human activities with the temporal and spatial dynamics of the coastal resources.

永續發展的概念現今已被運用於都市，其中，都市綠地在環境、生態、景觀、社會各層面之機能皆可提升都市永續性，在快速的都市化下，都市內綠地減少，土地利用變遷帶來之環境衝擊影響已自個體單元累積到全球。然而，過去研究中未有關注在綠地的變化趨勢與其他土地利用間的互動關係，以及在不同區域下的變化差異。因此，本研究採用GIS和景觀指數看在1995年至2006年間台北都會區綠地變遷趨勢，並分區探討土地利用間的互動關係，最後藉由二元羅吉斯迴歸分析綠地變化可能原因。 研究結果顯示，在1995年至2006年間，台北都會區整體發展是建地增加，林地也呈上升趨勢，而草地是土地利用轉移下被犧牲掉最多的土地，綠地轉移成其他土地利用情形以都會邊緣地區最嚴重。不同綠地型態在1995年至2006年間的變遷仍有差異，林地在整個台北都會區屬於景觀中的基質，主導性未受動搖，僅在都會中心減少並受破壞；而農地面積略微下降，呈破碎化發展，尤其以都會中心外圍區農地被破壞情形最明顯；草地面積亦下降，破碎化情形較農地更嚴重，在都會郊區、次中心之草地被破壞嚴重，草地各方面機能降低。透過二元羅吉斯迴歸分析發現自然環境、社會經濟與計畫環境皆影響台北都會區的綠地變遷。根據研究結果，建議未來政府於都市計畫上應將綠地空間納入考量，對於不同綠地型態應有不同管制措施，考量各區域綠地型態之差異性，以及自然環境、社會經濟和計畫環境對於綠地變遷的影響，以促進都市朝向永續發展。 / The concept of sustainable development has been applied in cities. Urban green space plays an important role in enhancing the sustainability of the city in regards to the environment, ecology, landscape and society aspects. Under rapid urbanization, green space has greatly declined in cities. Environmental impact resulting from land use change has grown from local to global proportions. However, researches did not pay attention to interactions between green spaces and other land-use change trends or different types of change in different areas. This research used GIS and landscape metrics to investigate the green space change trend and interactions among different land use types in the Taipei metropolitan area from 1995 to 2006. Furthermore, this research analyzed possible reasons that may have caused green space change through logistic regression. The results showed that, from 1995 to 2006, the built up area and the forest increased in Taipei Metropolitan Area; however, the grass decreased because of land use change. Urban fringe was the place that green space changed to other land-use most. There were differences of land use change for different types of green space. Forest was the matrix in the landscape of Taipei metropolitan area. It still kept the predominant role, only decreased and was destroyed in the center of metropolitan area. Farmland slightly decreased and became fragmented, especially in the periphery of the urban center. Grassland area decreased and became fragmented much more than farmland. In suburb and sub-center, grassland was destroyed seriously and became less functional. Through binary logistic regression, the study found that natural environment, socio-economic and government planning do have influence on green space changes in the Taipei metropolitan area. According to the result of the study, the recommendation was that government should take green space into consideration when doing urban planning. For different types of green space and different areas, the government needs to have different measures and needs to consider the impact factors of green space change in order to accelerate sustainable development in cities.

La végétation herbacée est un bon indicateur des conditions environnementales, et elle a pour cela été utilisée pour la mise en évidence des changements environnementaux causés par les actions humaines, tels qu'eutrophisation, dépôts atmosphériques acides, changements de l’usage des sols ou de la pression d'herbivorie. Depuis peu, on s’intéresse à la réponse de la végétation aux changements climatiques. Le choix des zones d'étude se porte naturellement sur la montagne, où le gradient thermique induit par le relief y est fort (-0,56°C pour 100 mètres d'altitude), et où l'urbanisation et la pression agricole sont moindres par rapport aux zones de plaine, favorisant ainsi une réponse migratoire des espèces précoce et non biaisée. Afin de s'affranchir des effets potentiels des changements d'usage du sol, une partie de cette thèse est consacrée aux milieux forestiers dans lesquels l'effet du pastoralisme est réduit. Par ailleurs, une méthode basée sur la modélisation des changements de la réponse de la végétation au gradient d'altitude est développée, permettant ainsi d'étendre l'utilisation de données anciennes à des séries de relevés non géolocalisés. En s'appuyant sur cette méthode, deux caractéristiques de la végétation ont été analysées : la position de l'optimum d'espèces prises individuellement d'une part, et les changements de la valeur indicatrice des communautés végétales d'autre part. Par ailleurs, on a étudié les déplacements à long terme de la limite inférieure des espèces, pour tester la réponse des espèces en limite inférieure de leur distribution. Enfin, on a étudié l'évolution de la flore d'une zone très localisée, protégée par une large barrière physique constituée de deux glaciers permettant de s'affranchir des effets potentiels d'autres perturbations anthropiques concomitantes. Chacun des cas étudiés montre une remontée des espèces en altitude. Cependant, d'autres phénomènes expliquant la réponse de la végétation sont clairement mis en cause : fermeture et maturation du couvert forestier, eutrophisation importante, probable fragmentation de l'habitat ou dispersion par les randonneurs. Ces perturbations anthropiques directes jouent à des échelles de temps et d'espace comparables à l'effet anthropique indirect du changement climatique. Il est donc primordial de les prendre en compte dans les changements de végétation observés, avant de conclure à un effet du réchauffement climatique seul / Herbaceous vegetation is a good bio-indicator of environmental conditions, and was often used to detect and to put in evidence environmental changes caused by anthropogenic activities, like eutrophication, acid atmospheric deposit, land-use change and herbivory pressure. More recently, the interest had focused on the response of vegetation to climatic change. Mountains were naturally chosen as study areas, since the thermal gradient induced by the relief is strong (-0.56°C for 100m a.s.l.) and urbanisation and agricultural pressure are weaker than in lowlands, thus promoting early and unbiased migratory response of species. To free oneself from potential effects of land use change, a part of this PhD is devoted to mountain forest habitat, where pastoralism effects are reduced. Moreover, a method is developed, based on the modelling of changes in vegetation response to elevation gradient, allowing extending the use of historical data to non-geolocalized dataset. With this method, two characteristics of vegetation were analysed: the optimum position of individual species on the one hand, and changes in the indicator value of plant communities on the other. Furthermore, the long-term shift of species’ lower limit is studied, to test the species response at their lower limit. The last part focuses on changes in the flora of a really localised area, protected by a broad physical barrier formed by two glaciers, allowing to free from potential effects of other parallel anthropogenic disturbances. Every studied case shows a shift of species toward higher elevations. However, other phenomena explaining vegetation response became also evident in our study: forest closure and maturation, important eutrophication, probable habitat fragmentation and dispersal by hikers. Those direct anthropogenic disturbances play a role comparable in space and time to the indirect anthropogenic impact of climate change. Thus, it is essential to consider them in the observation of vegetation changes, before assigning the effects to climate warming only

Transformações nas condições de vida da Terra fazem parte da nossa história evolutiva. Atualmente, as ações humanas provocam impactos tão intensos que já se considera que estamos marcando uma nova era geológica, o Antropoceno. As alterações globais de origem antropogênica estão relacionadas ao nosso modo de vida moderno e modelo de consumo, assim como ao crescimento demográfico, econômico, agropecuário, industrial que tem demanda crescente por recursos. Todos esses fatores apresentam potenciais efeitos comprometedores às funções ecossistêmicas e dos bens e serviços ambientais. Neste contexto, os sistemas aquáticos continentais, são significativamente impactados pela construção de barragens. As represas envolvem inúmeras transformações ambientais e ecológicas, sociais e econômicas. Já as regiões do seu entorno podem ser beneficiadas com a utilização das águas represadas. Entender a dinâmica da cobertura e uso do solo e analisar se há a abertura de oportunidade para o desenvolvimento de novas atividades econômicas, aproximam a compreensão dos seus impactos como base para a gestão desses ambientes. O objetivo geral desse trabalho foi analisar a influência das Usinas Hidrelétricas Canoas I e II nos municípios do seu entorno, a partir da analise espaço-temporal das mudanças no uso e cobertura do solo e das dinâmicas socioeconômicas relacionadas ao desenvolvimento das atividades de piscicultura. Os resultados obtidos caracterizam as atividades agropastoris da região como a maior força das dinâmicas ambientais e socioeconômicas. A extrema fragmentação da vegetação nativa é a mais importante consequência ecológica desse processo. Já em termos sociais e econômicos às mudanças no perfil da agricultura geraram a urbanização e o exôdo rural, marginalizando pequenos agricultores. A construção dos barramentos de Canoas I e II teve influência na composição da paisagem após a perda, principalmente de terras agrícolas e coincidiu com o aumento das áreas de urbanização, associada a um aumento da área dos fragmentos da cobertura vegetal nativa e um melhora no índice de proximidade, indicando maior conexão entre os mesmos. Para os entrevistados na pesquisa os reservatórios representam uma oportunidade de desenvolvimento da piscicultura, que já desperta interesse na população como a atividade econômica. Mas, há dificuldades a serem superadas para que se concretizem as expectativas de aproveitamento das águas represadas. / Transformations in Earth life conditions are part of our evolutionary history. Currently human activities result in impacts of such magnitude that it has been proposed and widely accepted that we are entering a new geologic era, the Anthropocene. Human induced global changes are related to our modern way of life and the consumption model, as well as to demographic, economic, agricultural and industrial growth, that have an increasing resources demand. All these factors have potential compromising effects on ecosystems functions and good and services that they provide. Furthermore, fresh water ecosystems are highly impacted by river dams. These impoundments involve innumerous environmental and ecological, social and economic transformations, while surrounding areas can benefit from its water use. Understand the land use and cover dynamic and analyze if there are opportunities for new economic activities level the comprehension of their impacts for further environmental management. The overall objective of this study was to analyze the Hydroelectric Power Canoas I and II influence on the watershed counties, by a couple analysis of the spatial and temporal land use changes and the related socio-economic dynamic related to fish farming activities development. Our results show that agriculture and cattle ragging are the main driver of environmental and socio-economic behavior. An extreme native vegetation fragmentation was the most important ecological consequence of this process. In term of social and economic aspects, changes in the agricultural profile lead to an urbanization and rural exodus, marginalizing small framers. The constructions of Canoas I and II dams resulted in losses of agricultural lands, which was associated with an urban sprawl and an area increase of native vegetation patches and proximity index, indicating that they became more connected. For the interviewed local people. The dams represent an opportunity for fish farm developing, since it arouses interest in the population as an economic activity. However, there are difficulties to be overcame to meet the expectation of the impounded waters use.

In spite tropical forests are the most important terrestrial global carbon sinks due to carbon storage in aboveground biomass, it is also the primary target of deforestation. The conversion of Tropical forests into anthropogenic areas might disrupt biological flux and also lead to severe microclimatic changes at forest edges. These combined effects can trigger profound changes in plant composition through both high mortality of fragmentation-sensitive species and proliferation of disturbed-adapted species which will ultimately impacts carbon storage. Thus, our main objective in this study was understand the role of human-induced disturbances in modulate the dimension of biomass loss at tropical forests. We applied a systematic literature review searching for empirical evidences that edge effects can drive biomass loss in tropical forests (Chapter 2). Our findings highlighted the gap of knowledge about the pattern and process related to biomass loss in tropical forests. To strengthen this understanding, we formulated a conceptual model linking landscape structure and patch-level attributes to severity of edge effects affecting aboveground biomass. Our model hypothesizes that habitat amount, isolation, time since edge creation, and the synergism between edge distance, patch size, and matrix type are the main drivers of biomass loss in anthropogenic tropical forests. We thus used a large plant dataset (18 503 trees &ge; 10 cm dbh) from 146 sites distributed across four Mexican and four Brazilian rainforest regions to test our conceptual model predictions, specifically the influence of forest cover, site isolation, edge distance, patch size and type of matrix on biomass (Chapter 3). We observed that carbon-rich sites presented species that are typical of old-growth forests (shade-tolerant, large-seeded, zoocoric) contrasting to carbon-poor sites composed by disturbed-adapted species (pioneer occupying the understory). Large shade-tolerant trees (&ge; 40 cm dbh) were impacted severely by the combination of forest loss and edge effects. Edge distance, patch size, and the amount of open-matrix strongly influence small shade-tolerant trees (&le; 20 cm dbh). Although our results do not fully corroborate the initial predictions of the conceptual model, they support the idea that landscape composition interact with patch structure and ultimately impacts biomass stocks in fragmented tropical forests. Finally, we further investigated if the disturbance level of the region influences plant-structure responses to forest loss (Chapter 4). Biomass, but not plant density, was affected by forest loss in regions with intermediate disturbance levels, i.e. regions showing a combination of moderate deforestation (20-40% of remaining forest cover) disturbed during the past 30-60 years, high defaunation but harboring relictual populations of large-mammals, and areas mostly composed by heterogeneous matrices. In general, our findings highlight that both landscape composition and patch structure are the main drivers of biomass loss in Neotropical forests, and that the landscape context must be considered to obtain more reliable estimations of carbon emissions due to forest degradation. Landscape planning (e.g. restoration of forest cover) should be included in conservation strategies in order to sustain carbon storage. Moreover, we advocate that conservation initiatives will be less costly and more effective if implemented in areas under intermediate disturbance levels / Apesar das florestas tropicais serem a mais importante fonte mundial de carbono da porção terrestre do globo devido ao armazenamento de carbono na biomassa acima do solo, elas são também o alvo primário do desmatamento. A conversão das florestas Tropicais em áreas antropogênicas pode interromper o fluxo biológico e também levar a severas mudanças microclimáticas na borda dos fragmentos. A combinação desses efeitos pode engatilhar profundas mudanças na composição da vegetação através tanto da mortalidade de espécies sensíveis à fragmentação como também pela proliferação de espécies adaptadas distúrbios, com impactos finais nos estoques de carbono. Assim, o maior objetivo desse estudo foi compreender o papel dos distúrbios induzidos pelo homem na modulação da dimensão da perda de biomassa em florestas Tropicais. Nós aplicamos uma revisão sistemática da literatura procurando por evidências empíricas de que o efeito de borda pode levar a perda de biomassa em florestas tropicais (Capítulo 2). Nossos resultados destacam a lacuna de conhecimento entre padrões e processos relacionados à perda de biomassa em florestas Tropicais. Para fortalecer esse conhecimento, nós formulamos um modelo conceitual conectando estrutura da paisagem e atributos na escala do fragmento à severidade do efeito de borda, e assim afetando a biomassa acima do solo. Nosso modelo hipotetiza que a quantidade de hábitat, o isolamento, o tempo desde a formação da borda e o sinergismo entre tamanho do fragmento, distância da borda e tipo de matriz são os principais condutores de perda de biomassa em florestas Tropicais antropogênicas. Utilizando um grande banco de dados (18 503 árvores &ge; 10 cm dap) provenientes de 146 locais distribuídos em quatro regiões de floresta úmida no México e quatro no Brasil, nós então testamos as predições do nosso modelo conceitual. Especificamente, a influência da cobertura florestal, isolamento, distância da borda, tamanho do fragmento e tipo de matriz sobre a biomassa (Capítulo 3). Nós observamos que áreas com muito carbono apresentaram espécies típicas de florestas maduras (tolerantes ao sombreamento, zoocóricas, com sementes grandes) contrastando com áreas com pouco carbono compostas por espécies adaptadas à distúrbio (pioneiras ocupando o sub-bosque). Árvores grandes tolerantes ao sombreamento (&ge; 40 cm dap) foram impactadas severamente pela combinação de perda de cobertura florestal e efeitos de borda. Distância da borda, tamanho do fragmento e a extensão da área de matriz aberta influenciaram fortemente as árvores pequenas tolerantes a sombreamento (&le; 20 cm dap). Apesar dos nossos resultados não corroborarem completamente as predições iniciais do nosso modelo conceitual, eles dão suporte à ideia de que a composição da paisagem interage com a estrutura do fragmento com impactos finais nos estoques de biomassa em florestas Neotropicais. Por fim, nós investigamos se o nível de distúrbio da região pode influenciar nas respostas da estrutura da vegetação à perda de cobertura florestal. Biomassa, mas não a densidade de indivíduos, foi afetada pela perda de cobertura florestal em regiões com nível intermediário de distúrbio, i.e. regiões apresentando uma combinação de níveis moderados de desmatamento (20-40% de cobertura florestal remanescente) em que a perturbação ocorreu ao longo dos últimos 30-60 anos, com alto grau de defaunação mas ainda abrigando populações relictuais de grandes mamíferos e, em sua maioria, compostos por uma matriz heterogênea. Em geral, nossos resultados destacaram que tanto a composição da paisagem como a estrutura do fragmento são os principais condutores de perda de biomassa em florestas Neotropicais e que o contexto da paisagem deve ser considerado para se obter estimativas mais confiáveis de emissão de carbono devido à degradação florestal. O planejamento da paisagem (e.g. restauração da cobertura florestal) deve ser incluído em estratégias de conservação em ordem de sustentar o armazenamento de carbono. Além disso, nós defendemos que iniciativas de conservação serão menos custosas e mais efetivas se implementadas em áreas sob níveis intermediários de distúrbio