No description available.

While streams and rivers emit large quantities of CO2 to the atmosphere, both the mechanisms controlling CO2 evasion as well as the sources of CO2 are still uncertain. One potential source of stream CO2 is in-stream degradation of dissolved organic matter (DOM). Streams and rivers transport, stores and transform large quantities of DOM, which can be more or less biologically reactive (bioreactive) meaning how easily accessible the organic material is for biological degradation. Little is known about the dynamics controlling DOM bioreactvity in agricultural stream water. This project investigated potential physico-chemical and land-use controls of DOM bioreactivity and its link to CO2 evasion in ten Swedish agricultural streams by correlating estimated values of DOM bioreactivity as well as CO2 evasion rates with different parameters for physico-chemical and land-use controls measured during eleven field excursions. A direct positive correlation was found between DOM bioreactivity and CO2 evasion rates during spatial correlation but not when all measurements were used. DOM bioreactivity was found to correlate to parameters for DOM quality and quantity, concentrations of dissolved oxygen (D.O.) and total dissolved solids (TDS) as well as stream width, water depth, specific discharge, temperature and electric conductivity. Nutrients, fraction land-use, catchment size, vegetation cover and turbulence were not found to be potential controls of either DOM bioreactivity or CO2 evasion. CO2 evasion was found to have fewer significant correlations with parameters for DOM quality compared to DOM bioreactivity, indicating a weaker link between CO2 emissions and DOM quality in the stream water, and was not tied to variables affected by increased discharge. Spatial and temporal analysis indicated that while CO2 evasion rates were more site specific, bioreactivity was more influenced by temporal variations where periods of increased bioreactivity and increased variability between sites occurred during periods of increased specific discharge, supporting existence of a hydrological influence on DOM bioreactivity.

Natural hazards, paired with affected communities’ exposure and vulnerability, have caused numerousfatalities and great economic losses worldwide in recent decades. Floods represent about one-third ofall natural hazards, and together with storms they comprise 77% of economic losses caused byextreme weather events from 1980 to 2006 in Europe and have been the main natural hazards inEurope for more than a century. Survey data of public risk perception were collected in Sweden andItaly through online surveys several times during the COVID-19 pandemic, and the respondents wereasked questions about risk perception regarding nine threats: epidemics, floods, droughts, earthquakes,wildfires, terror attacks, domestic violence, economic crises, and climate change. The survey explorespublic perception on five factors: experience, likelihood, potential impact, as well as preparedness andknowledge of the phenomenon. The survey data were analysed by using ordinal logistic regression,were the variable of previous flood experience along with socioeconomic factors were used to explorehow/if previous experience has any statistical significance and potentially affects risk perception. Inaddition, this thesis also presents a spatial analysis of respondents’ previous flood experience andprevious flood events in Sweden, to explore whether this is reflected in the survey data. The resultsshow that the effect of experience on likelihood, knowledge and preparedness is high, and womenhave a higher perceived risk in all variables except preparedness. The results of the spatial analysisshow that the majority of respondents with experience live in North Middle Sweden which correlateswell with the analysis of past flood events during the recent decade. These findings could potentiallybe used in continuous research regarding disaster risk reduction and developing frameworks,specifically how impacts and perception influence other variables such as vulnerability, behaviour, andgovernance.

Strong tornadoes have impacted the central Appalachian Mountains multiple times in recent years. The topography of this region leads to unique spatial patterns of tornado damage as the tornado vortices pass over ridges in forested areas, and this damage can be detected with vegetation indices derived from remotely sensed imagery. The objectives of this study were to 1) Classify forest damage from the April 19, 2019 EF-3 tornado in Franklin County, VA using remotely-sensed images, 2) Quantify the spatial patterns of forest damage intensity across the path using derived vegetation indices and terrain variables (primarily slope, aspect, elevation, and exposure), and 3) Use regression models to determine if relationships exist among terrain variables along the and forest damage patterns. I generated EVI and NDII vegetation indices from Sentinel-2 imagery and compared the derived damage to the underlying terrain variables. Results revealed that the two vegetation indices were effective for classifying tornado damage, and discrete damage classes aligned well with NWS EF-scale tornado intensity estimations. ANOVA testing suggested that EF-3 equivalent damage was more likely to occur on downslope topography, leeward of the tornado's direction of travel. OLS and geographically weighted regression (GWR) modeling performed poorly, suggesting that an alternative method may be more suitable for modeling, the scale of assessment was inadequate, or that important predictor variables were not captured. Overall, the intensity of the tornado was clearly modified by terrain interactions, and the remote sensing methodology used was effective for reliably identifying and rating damage in forested areas. / Master of Science / Strong tornadoes have impacted the central Appalachian Mountains multiple times in recent years. The topography of this region leads to unique spatial patterns of tornado damage as the tornado vortices pass over ridges in forested areas, and this damage can be detected with vegetation indices derived from remotely sensed imagery. The objectives of this study were to 1) Classify forest damage from the April 19, 2019 EF-3 tornado in Franklin County, VA using remotely-sensed images, 2) Quantify the spatial patterns of forest damage intensity across the path using derived vegetation indices and terrain variables (primarily slope, aspect, elevation, and exposure), and 3) Use regression models to determine if relationships exist among terrain variables along the and forest damage patterns. I generated EVI and NDII vegetation indices from Sentinel-2 imagery and compared the derived damage to the underlying terrain variables. Results revealed that the two vegetation indices were effective for classifying tornado damage, and discrete damage classes aligned well with NWS EF-scale tornado intensity estimations. ANOVA testing suggested that EF-3 equivalent damage was more likely to occur on downslope topography, leeward of the tornado's direction of travel. OLS and geographically weighted regression (GWR) modeling performed poorly, suggesting that an alternative method may be more suitable for modeling, the scale of assessment was inadequate, or that important predictor variables were not captured. Overall, the intensity of the tornado was clearly modified by terrain interactions, and the remote sensing methodology used was effective for reliably identifying and rating damage in forested areas.

Glacier retreat is considered a clear sign of global climate change. Although a rich body of work has documented glacial response to climate warming trends, comparatively little research has assessed vegetation change in recently deglaciated areas. In this study, we assess vegetation change at two glacier forefronts in Glacier National Park, Montana, through remote sensing analysis, fieldwork validation, and statistical modelling. The research objectives were to: 1) quantify the spatial and temporal patterns of landcover change of five classes"ice, rock, tree, shrub, and herbaceous at the two glacier forefronts in Glacier National Park, and 2) determine the role of selected biophysical terrain factors (elevation, slope, aspect, solar radiation, flow accumulation, TWI, and geology) on vegetation change at the deglaciated areas. Landsat imagery of the study locations in 1991, 2003, and 2015 were classified and validated using ground truth points and visual interpretation for accuracy. Overall accuracies were above 75% for all classified images. To identify biophysical correlates of change, we used generalized linear mixed models with non-vegetated surfaces to vegetation (code=1) or stable non-vegetation class (code=0) as a binary response variable. Results revealed elevation, slope, TWI, geology, and aspect to be associated with increased vegetation over time at Jackson Glacier forefront, whereas elevation, slope, solar radiation, and geology were significant at Grinnell Glacier forefront. New case studies on vegetation change in recently deglaciated regions can deepen our knowledge about how glacier retreat at local scales results in recharged ecosystem dynamics. / Master of Science / Glacier retreat is considered a clear sign of global climate change. Although glaciers are retreating globally, comparatively little research has assessed how vegetation changes in recently deglaciated areas. The research objectives were to: 1) quantify patterns of landcover change of five classes—ice, rock, tree, shrub, and herbaceous at two glacier forefronts in Glacier National Park, and 2) determine the environmental and terrain factors that affect vegetation change at the deglaciated areas. Landsat imagery of the study locations in 1991, 2003, and 2015 were classified and validated using ground truth points and visual interpretation for accuracy. To identify terrain and environmental factors that influence change, we modeled change from nonvegetated surfaces to vegetation (code=1) and the stable non-vegetation class (code=0). Results revealed elevation, slope, topographic moisture, geology, and aspect to be associated with increased vegetation over time at Jackson Glacier forefront. Elevation, slope, solar radiation, and geology were significant at Grinnell Glacier forefront, indicating some geographic differences in important factors. New case studies on vegetation change in recently deglaciated regions can deepen our knowledge about how glacier retreat at local scales results in recharged ecosystem dynamics. This study provides further insight on the future of alpine ecosystems as they respond to global climate change and a compelling new perspective on the future of the Park. Additionally, we demonstrate the benefits of using remote sensing applications to study land cover change as a proxy for vegetation colonization, especially in remote mountainous environments.

No description available.

<p>The global carbon cycle is subject to intense research, where sources and sinks for greenhouse gases, carbon dioxide in particular, are estimated for various systems and biomes. Lakes have previously been neglected in carbon balance estimations, but have recently been recognized to be significant net sources of CO2.</p><p>This thesis estimates emission of carbon dioxide (CO2) from boreal lakes and factors regulating the CO2 saturation from field measurements of CO2 concentration along with a number of chemical, biological and physical parameters. Concentration of dissolved organic carbon (DOC) was found to be the most important factor for CO2 saturation in lake water, whereas climatic parameters such as precipitation, temperature and global radiation were less influential. All lakes were supersaturated with and, thus, sources of CO2. Sediment incubation experiments indicated that in-lake mineralization processes during summer stratification mainly occurred in the pelagial. Approximately 10% of the CO2 emitted from the lake surface was produced in epilimnetic sediments. </p><p>The mineralization of DOC and emission of CO2 from freshwaters was calculated on a catchment basis for almost 80,000 lakes and 21 major catchments in Sweden, together with rates of sedimentation in lakes and export of organic carbon to the sea. The total export of terrestrial organic carbon to freshwaters could thereby be estimated and consequently also the importance of lakes for the withdrawal of organic carbon export from terrestrial sources to the sea. Lakes removed 30-80% of imported terrestrial organic carbon, and mineralization and CO2 emission were much more important than sedimentation of carbon. The carbon loss was closely related to water retention time, where catchments with short residence times (<1 year) had low carbon retentions, whereas in catchments with long residence times (>3 years) a majority of the imported TOC was removed in the lake systems. </p><p>The Gulf of Bothnia was also studied in this thesis and found to be a net heterotrophic system, emitting large amounts of CO2 to the atmosphere on an annual basis. The rate of CO2 emission was depending on the balance between primary production and bacterial respiration, and the system was oscillating between being a source and a sink of CO2.</p>

No description available.

The global carbon cycle is subject to intense research, where sources and sinks for greenhouse gases, carbon dioxide in particular, are estimated for various systems and biomes. Lakes have previously been neglected in carbon balance estimations, but have recently been recognized to be significant net sources of CO2. This thesis estimates emission of carbon dioxide (CO2) from boreal lakes and factors regulating the CO2 saturation from field measurements of CO2 concentration along with a number of chemical, biological and physical parameters. Concentration of dissolved organic carbon (DOC) was found to be the most important factor for CO2 saturation in lake water, whereas climatic parameters such as precipitation, temperature and global radiation were less influential. All lakes were supersaturated with and, thus, sources of CO2. Sediment incubation experiments indicated that in-lake mineralization processes during summer stratification mainly occurred in the pelagial. Approximately 10% of the CO2 emitted from the lake surface was produced in epilimnetic sediments. The mineralization of DOC and emission of CO2 from freshwaters was calculated on a catchment basis for almost 80,000 lakes and 21 major catchments in Sweden, together with rates of sedimentation in lakes and export of organic carbon to the sea. The total export of terrestrial organic carbon to freshwaters could thereby be estimated and consequently also the importance of lakes for the withdrawal of organic carbon export from terrestrial sources to the sea. Lakes removed 30-80% of imported terrestrial organic carbon, and mineralization and CO2 emission were much more important than sedimentation of carbon. The carbon loss was closely related to water retention time, where catchments with short residence times (&lt;1 year) had low carbon retentions, whereas in catchments with long residence times (&gt;3 years) a majority of the imported TOC was removed in the lake systems. The Gulf of Bothnia was also studied in this thesis and found to be a net heterotrophic system, emitting large amounts of CO2 to the atmosphere on an annual basis. The rate of CO2 emission was depending on the balance between primary production and bacterial respiration, and the system was oscillating between being a source and a sink of CO2.

Orientador: Regina Célia de Oliveira / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Geociências / Made available in DSpace on 2018-08-18T07:13:22Z (GMT). No. of bitstreams: 1 Amorim_RaulReis_D.pdf: 119801790 bytes, checksum: 040d888f718cb48d6a1fd01d33281426 (MD5) Previous issue date: 2011 / Resumo: O estudo ambiental tem revelado sobretudo nas últimas décadas, um caráter interdisciplinar nas pesquisas pautadas sobre a dinâmica dos agentes naturais, frente à crescente pressão de uso do espaço, materializada por conflitos de diversas ordens, sejam esses, históricos, políticos, culturais, religiosos, enfim, relações humanas que se estruturam sobre o território e impõem a esse espaço níveis diversos de interferência no mecanismo natural preexistente. Nesse contexto, entender as relações das sociedades humanas com a natureza, dentro de uma perspectiva absolutamente dinâmica, que envolve os aspectos culturais, sociais, econômicos e naturais, exige adotar um procedimento analítico que leve em consideração a sociedade nos seus diversos estágios de desenvolvimento, e remeta a uma visão holística da organização do espaço. Sendo assim, a ciência geográfica, tendo como objeto de análise o espaço geográfico, possibilita, sob um olhar crítico, a realização de estudos ambientais integrados, de maneira a dar suporte técnico científico para a elaboração de estudos como aqueles relacionados ao zoneamento ambiental, que podem estar inseridos nas políticas públicas, contribuindo no planejamento e tomada de decisão. Considerando o exposto, esta tese se propõe à elaboração de um Zoneamento Ambiental, como subsidio ao planejamento do uso e ocupação das terras da zona costeira da região Costa do Descobrimento, situada na região Extremo Sul do Estado da Bahia. Tal proposta de estudo justifica-se por três fatores: (a) essa região é uma das áreas de povoamento pioneiro do território nacional, área em que o agente antrópico atua como ator na configuração da paisagem há mais de cinco séculos; (b) a área tem sofrido transformações no uso e ocupação das terras, não considerando os níveis de fragilidade ambiental da área em estudo, o que acentua os problemas ambientais; e (c) a inexistência de estudos que integrem os sistemas naturais aos sistemas antrópicos no planejamento no uso e ocupação da zona costeira da região Costa do Descobrimento. Nos últimos quarenta anos, ela se tornou uma das regiões mais dinâmicas economicamente do Estado da Bahia, e também é um dos principais destinos turísticos do Brasil. Para atingir tal meta, adotou-se a metodologia proposta por Rodriguez, Silva e Cavalcanti (2004), enfatizando a análise funcional da paisagem. As diferentes atividades econômicas implantadas na Região Costa do Descobrimento, nos últimos 40 anos possibilitaram a formação de diversos sistemas ambientais com fragilidades complexas e que sofrem há séculos pressões de uso, resultando em problemas ambientais que alteram a dinâmica dos sistemas naturais e também o modo de viver da população local / Abstract: The environmental study has revealed especially in recent decades in an interdisciplinary research guided on the dynamics of natural agents face the growing pressure of space usage, embodied by conflicts of various orders, are those, historical, political, cultural, religious, in order, human relations that are structured on the territory and impose on this space several levels of interference in the natural pre-existing mechanism. In this context, understanding the relationship of human societies and nature, within an absolutely dynamic perspective that involves cultural, social, economic and natural, requires adopting an analytical procedure that takes into account the society in their various stages of development, which refers to a holistic view of space organization. Thus, the geographical science as the object of the geographic analysis, allows a critical eye on the implementation of integrated environmental studies in order to provide technical support for the development of scientific studies such as those related to environmental zoning that can be inserted on policy contributing public in planning and decision taken. Considering the above, this thesis proposes the development of an environmental zoning as support for planning the use and occupation of the coastal region of the Discovery Coast, located in the extreme south of Bahia. This proposed study is justified by three factors: (a) this region is a pioneer of the populated areas of the country, an area in which the agent acts as man-made actor in shaping the landscape for more than five centuries, (b) area has undergone significant changes in the use and occupation of land, not considering the levels of environmental fragility of the study area, which emphasizes environmental issues, and (c) the lack of studies integrating natural systems to anthropogenic systems in use in planning and occupation of the coastal region of the Discovery Coast, that the last forty years has become one of the economically most dynamic regions of the state of Bahia, and is also one of the major tourist destinations in Brazil. To achieve this goal, we adopted the methodology proposed by Rodriguez, Cavalcanti, Silva and Cavalcanti (2004), emphasizing the functional analysis of the landscape. The different economic activities implemented in the Discovery Coast Region in the last 40 years has enabled the formation of different complex environmental systems with frailties and suffering centuries of use pressures resulting in environmental problems that affect the dynamics of natural systems and also the way of life of local population / Doutorado / Análise Ambiental e Dinâmica Territorial / Doutor em Ciências