• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 77
  • 48
  • 6
  • 5
  • 4
  • 3
  • 2
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 161
  • 161
  • 77
  • 48
  • 34
  • 33
  • 29
  • 26
  • 23
  • 23
  • 21
  • 21
  • 20
  • 15
  • 13
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Mikroregion Kamenice-Velké Popovice - příklad dynamiky kulturní krajiny v novověku / Microregion Kamenice-Velké Popovice - an example of cultural landscape development in the modern period

Korbelíková, Daniela January 2011 (has links)
This thesis is a part of the Faculty of Humanities project which investigates the development of the countryside in Bohemia during the age of industrialization. It focuses on the micro- region Kamenice-Velké Popovice. In the 19th century the Ringhoffer family established here the so-called United Dominion Kamenice-Štiřín. Following their commercial, cultural, representative and recreational activities, they gently and with consideration transformed the countryside step by step. The thesis is based on archival research, field research of the landscape traces of the Ringhoffers' activities in both XIX and XX centuries and on the study of literature and maps. Keywords Ringhoffer, land-use, landscape, dominion, land, business
72

An Agroecological Study on Land-use and Land-cover Changes in a Cyclone-affected Village of the Ayeyarwady Delta, Myanmar / ミャンマー・イラワジデルタのサイクロン被災村落における土地利用・土地被覆変化に関する農業生態学的研究

Thinn, Thinn 23 March 2017 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(地域研究) / 甲第20494号 / 地博第213号 / 未着(附属図書館) / 京都大学大学院アジア・アフリカ地域研究研究科東南アジア地域研究専攻 / (主査)教授 竹田 晋也, 教授 岩田 明久, 准教授 安藤 和雄, 准教授 鈴木 玲冶 / 学位規則第4条第1項該当 / Doctor of Area Studies / Kyoto University / DGAM
73

Influence of Land Use, Land Cover, and Hydrology on the Spatial and Temporal Characteristics of Dissolved Organic Matter (DOM) in Multiple Aquatic Ecosystems

Singh, Shatrughan 11 August 2017 (has links)
Spatial and temporal patterns of dissolved organic matter (DOM) were characterized using a combination of spectroluorometric measurements and multivariate analysis techniques. The study was conducted over a four-year (2012-2016) period in multiple watersheds located in the Gulf-Atlantic Coastal Plain Physiographic region of the southeast USA as well as in the Indo-Gangetic Plain of India. Surface water samples were collected from five major lakes in the Mississippi, an estuarine region in the southeastern Louisiana, and from the coastal region in the eastern Mississippi Sound in the USA, and a large river (Ganges River) in India. Absorption and fluorescence measurements were performed to generate absorption spectra and excitation-emission matrices (EEMs). Using parallel factor analyses (PARAFAC), EEM models were developed to characterize the biogeochemistry of DOM in three studies in this project. Principal component analysis and regression analyses of DOM data indicated that the northern Mississippi lakes were majorly influenced by agricultural land use, estuarine region was affected by natural DOM export from forests and wetlands, while the coastal waters were affected by a mix of anthropogenic and natural inputs of DOM. Spatial analyses indicated that DOM derived from watershed with increased wetland coverage was humic and aromatic while the DOM derived from agricultural watersheds was bioavailable. Temporal patterns of DOM in the estuary indicated the influence of hydrologic conditions and summer temperatures, and revealed strong seasonality in DOM evolution in the watershed. During high discharge periods (spring), aromatic and humic DOM was exported from the watershed while strong photochemical degradation during summer resulted bioavailable DOM. Comparison between two river systems, a highly urbanized large river and a small pristine river, indicated the influence of anthropogenic inputs of DOM in the large river system. DOM was bioavailable during summer due to anthropogenic activities in the large river system while it varied with hydrological connectivity in a small river system during summer and winter. In conclusion, this study has improved my understandings of the DOM properties, which are critical for a comprehensive assessment of biogeochemical processes undergoing in important water bodies on which our society is heavily dependent upon.
74

The Post-frontier: Land use and social change in the Brazilian Amazon (1992 - 2002)

Summers, Percy M. 21 July 2008 (has links)
Deforestation of tropical forests is one of the most pressing environmental problems of the twenty-first century, leading to the loss of environmental services such as climate regulation and biodiversity. The expansion of the agricultural frontier by small landholder farmers continues to be one of the major drivers of land use change in the Amazon region. Much of the recent research in the Brazilian Amazon has been focused on modeling their behavior in order to prescribe policies that can curb current deforestation rates and promote more sustainable land use practices. The availability of more sophisticated remote sensing and economic modeling tools has led to the proliferation of agricultural household level models that attempt to explain land use change processes at the farm level. This dissertation tests the household life cycle theory in one of the oldest colonization fronts in the Brazilian Amazon: Rondônia, now a post-frontier. The study examines household and farm level changes over time for specific aspects of the frontier process that can be tested using the household life cycle theory. This study introduces important additions to the life cycle theory in order to consider the more dynamic and complex set of factors that characterize modern frontier processes. Specifically the study examines: (1) property fragmentation and expansion processes, (2) property ownership, turnover and change, and (3) land use change processes at the property level. These are linked to changes in the social and economic features of the smallholder farmer as it moves along its life cycle. The central hypothesis is that these changes in property and land use dynamics can be explained by the corresponding changes in the life cycle of the household as the frontier evolves over time into a post-frontier. It was found that the household life cycle theory did not adequately explain land use change processes over time. As the frontier evolved into the modern post-frontier, the labor and drudgery constraints associated with the initial frontier processes, as exemplified in the household life cycle theory, became less relevant. The Sauerian concept of cultural successions and the concept of scale from hierarchical ecology are used in order to explain the apparent inconsistencies found between the household life cycle theory and land use change processes over time and at different scales of analysis. The household life cycle theory is a useful theoretical framework from which to examine the effects of household level factors on land use; however, this must be embedded within concepts of time and scale that determine their differentiated impact and behavior. Existing plans to expand road infrastructure into the Amazon region will open-up previously inaccessible rainforest regions to agricultural frontier expansion at a scale unprecedented since the mid-eighties. Findings from this study reveal that policies based on household life cycle postulates will have limited impacts in reducing deforestation rates and promoting sustainable land use practices. Appropriate accounting of the social and environmental costs of future infrastructure development projects should consider associated frontier agricultural expansion costs to discourage further deforestation. / Ph. D.
75

Assessment of nutrient sources at watershed scale in agro-ecosystem of Mississippi

Risal, Avay 25 November 2020 (has links)
Excessive nutrient concentrations from a different point and non-point sources are the main cause of water impairment in the United States. Appropriate management practices, according to the source and quantity of pollutions, need to be implemented to control excessive nutrient influx in the water body. Various types of hydrological and water quality models with diverse function, capability and degree of complexity are employed to quantify watershed hydrologic processes and nutrient pollution. Multiple models can be applied to a watershed but the suitable model must be selected based on watershed type and simulation need. Two watershed-scale models, Soil and Water Assessment Tool (SWAT) and Hydrologic Simulation Program-Fortran (HSPF) were chosen for this study to simulate runoff, sediment yield, and nutrient load from the Big Sunflower River Watershed (BSRW) of Mississippi. The objectives of this study are to access the nutrient sources within the watershed, determine the appropriate model to quantify them, develop and evaluate model considering spatial and temporal variations in input data, and evaluate the effectiveness of different Best Management Practices (BMPs) on surface runoff, sediment yield and nutrient load at watershed scale. This study has identified a potential source of nutrients in BSRW and provided a suitable BMP for its management. Similarly, the study found both SWAT and HSPF were efficient in the simulation of streamflow, sediment yield and nutrient load, where SWAT was more efficient during simulation streamflow and sediment yield. Likewise, the study established that both water-quantity and water-quality are sensitive to the change in LULC data layers and thus, seasonal LULC data applied to SWAT will better explain variation in hydrology and water quality as compared to the annual cropland data layer. Moreover, the study showed that well managed vegetative filter strip was very efficient in reducing sediment yield, TN, and TP at both field and watershed scale among different BMPs evaluated at field and watershed scale. This study will be beneficial in developing efficient nutrient management strategy at field and watershed scale, selecting appropriate model and input according to the need and type of watershed, and providing further research opportunities to the scientific community.
76

How Local and Landscape Factors Affect Anuran Species Distributions in Agricultural Landscapes

Youngquist, Melissa Betty 24 July 2015 (has links)
No description available.
77

Impacts of Land Use and Land Cover Changes, and Climate Variability on Hydrology and Soil Erosion in the Upper Ruvu Watershed, Tanzania

Mbungu, Winfred Baptist 10 January 2017 (has links)
Land alterations including deforestation, unsustainable land management practices and an increase in cultivated areas have occurred in the Upper Ruvu watershed in recent decades threatening water and natural resources. This study, which used a combination of remote sensing techniques, field experiments, watershed monitoring, and modeling was designed to investigate impacts of environmental changes on hydrology and soil erosion. The objectives were to: map the extent of land use and land cover change and its influence on soil erosion; correlate the contribution of climate variability and human activities to the changes in hydrology at headwater and watershed scales; estimate surface runoff, sediments and Curve Number at plot scale, and model streamflow responses to changes in land use and land cover using the SWAT watershed model. Results indicate that areas covered by forest decreased from 17% in 1991 to 4% of the total watershed area in 2015. However, areas covered by cropland increased from 14% to 30% of the total watershed area from 1991 to 2015, respectively. Further, results indicate that site characteristics affect runoff and sediment yield as higher soil loss was estimated from cropland with a mean of 28.4 tha-1 in 2015 from 19.8 tha-1 in 1991. Results from monitoring show high sediment loads were from the most disturbed watersheds, compared to Mbezi. Analysis of trends for the long term records at the watershed showed that rainfall had significant decreasing trends. At annual scale, climate variability contributed 46% and human activities contributed 54% of the changes in streamflow. Results from the rainfall simulation experiments show upland rice had higher runoff (48 mmh-1) and soil loss (94 gm-2) compared to grassland and forest. Results from the model outputs showed that average streamflow decreased by 13% between 1991 and 2015. Average peak flows increased by 5% and 12% for 2000 and 2015, respectively compared to the baseline. Land alterations had impacts on surface runoff which increased by 75% and baseflow decreased by 66% in 2015 from the baseline. These results highlight the main areas of changes and provide quantitative information to decision makers for sustainable land and water resources planning and management. / Ph. D.
78

Terrestrial ecosystem impacts on air quality

Wong, Yik Hong 16 July 2024 (has links)
The terrestrial ecosystem is an integral component of the Earth System. Constant atmosphere-biosphere exchanges of energy and material affect both the physics and chemistry of the atmosphere. While the general roles of terrestrial ecosystems in regulating ozone and particulate matter air pollution have long been acknowledged, our understanding at both individual process and system level are far from perfect. Also, new process-level discoveries about terrestrial atmosphere-biosphere exchanges are not timely incorporated in numerical models routinely used to study and forecast air quality. These hinder our ability to understand how air quality respond to environmental changes and variabilities. Chapter 1 of this dissertation provides a brief overview on these topics. In Chapter 2 of this dissertation (Wong et al., 2019), we conduct global long-term simulations of ozone dry deposition velocity with four different types of dry deposition parameterizations. We find that none of the tested parameterizations universally stands out in terms of matching observed ozone deposition velocity over different land cover types. Combining this with sensitivity simulations from a global 3-D atmospheric chemistry model (GEOS-Chem), we find that the choice of dry deposition parameterizations can affect the mean, trend and variability of simulated surface O3 level. In Chapter 3 of this dissertation (Wong et al., 2022), we analyze long-term ozone flux observation from three field sites to examine the effects of extreme heat and dryness on ozone deposition. We find that non-stomatal ozone uptake tends to increase during hot days, which either partially offsets or dominates over the reduction in stomatal ozone uptake anticipated by ecophysiological theory. While the response of ozone deposition to dryness is more varied, changes in non-stomatal deposition are usually important. Current dry deposition parameterizations often fail to capture such changes in non-stomatal ozone uptake, resulting in considerable potential error in simulated surface ozone level during hot and dry days. In Chapter 4 of this dissertation (Wong and Geddes, 2021), we conduct global GEOS-Chem numerical experiments with anthropogenic emission inventories and land surface remote sensing products to compare the effects land cover versus land management changes on O3 and fine particulate matter air quality over 1992 – 2014. We find that land cover has stronger effects on O3, while land management has stronger effects on fine particulate matter pollution. We also find that land management has significantly altered regional and global nitrogen deposition, and therefore the risk of critical load exceedance. Chapter 5 of this dissertation includes the concluding remarks and suggestions for future work. In addition, I outline and present the preliminary result from a project examining the future of soil reactive nitrogen emissions and their impacts on air quality.
79

Analyse de la détérioration de la forêt de la Cordillère de la Costa dans le sud chilien : géomatique et modélisation prospective appliquée sur une forêt patrimoniale de la province d'Osorno (41º 15’ - 41º 00’ latitude Sud) / Analysis of the deterioration of forest in the Cordillera de la Costa in southern Chile : geomatics and prospective modeling applied to a national forest in the province of Osorno (41°15' - 41°00' south latitude)

Toro Balbontin, Darío 08 September 2014 (has links)
On étudie une zone de la Cordillère de la Costa au sud du Chili (41°15'S-41°00'S), habitée par l'ethnie Mapuche. Là, il y a encore des précieuses forêts tempérées, qui ont une haute priorité de conservation au plan mondial. Mais, il est constaté, un processus continu de transformation lié à l'extraction de bois de chauffe, l'élevage extensif, la perturbation de l'habitat du conifère Fitzroya cupressoides, et le déploiement des plantations forestières. Sur la base d'une classification multi-temporelle d'images satellite, une modélisation spatio-temporelle a été mise en œuvre pour comprendre et anticiper la dynamique de la détérioration de la forêt. L'analyse rétrospective révèle qu'entre 1976 et 2008, la forêt a été réduite 12400 ha, soit un taux de déforestation 0,25% par an. 20 modèles de déforestation sont calibrés, 4 d'entre eux sont sélectionnés pour construire des scénarios prospectifs. La simulation prévoit que la diminution de forêt entre 2008 et 2040 pourrait atteindre 13000 ha. Deux autres modèles mis en œuvre simulent l'évolution de la qualité de l'habitat de F. cupressoides. Les scénarios prévoient une augmentation de la surface détériorée ; l’extrapolation à partir de la période d’apprentissage 2001-2008 pendant laquelle la plus grande part de terres indigènes a été légalisée, par rapport à la période précédente à 2001, prédit une augmentation plus significative de la surface détériorée. On fournit un outil pour amplifier la gestion territoriale des systèmes environnementaux toujours non incorporée dans la planification chilienne. Enfin, la thèse met également d'intéressantes comparaisons entre modèles qui diffèrent par rapport aux paramètres de calibration. / SAn area of the Cordillera de la Costa is studied in southern Chile (41°15'S - 41°00'S), inhabited by ethnic Mapuche. There are still valuable temperate forests that have high conservation priority worldwide. But it is found, a continuous process of transformation related to the extraction of firewood, ranching, disruption of habitat conifer Fitzroya cupressoides, and deployment of forest plantations. Based on a multi-temporal satellite images classification, a spatial-temporal modeling was implemented to understand and predict the dynamics of the deterioration of the forest. Retrospective analysis revealed that between 1976 and 2008, the forest has been reduced 12,400 ha, a deforestation rate of 0.25% per annum. 20 models of deforestation are calibrated, 4 of them are selected to construct scenarios. The simulation predicted that reductions of forest between 2008 and 2040 could reach 13,000 ha. Two other models implemented simulate changes in habitat quality F. cupressoides. Scenarios predict an increase in the damaged surface; extrapolating from the learning period 2001-2008 during which the largest share of indigenous lands was legalized, compared with the previous period to 2001, predicts a significant increase in the damaged surface. In this way, it provides a tool to enhance the local management of environmental systems still not incorporated into the Chilean planning. Finally, the thesis also makes interesting comparisons between models that differ with respect to the calibration parameters.
80

Impactos das atualizações do uso e cobertura da terra e das características físico-químicas da vegetação na América do Sul em modelos climáticos / Impacts caused by updating the land use and land cover and the physical-chemical properties of vegetation to South America in climatic models

Pereira, Gabriel 09 November 2012 (has links)
As mudanças de uso e cobertura da terra ocasionam alterações no balanço de energia, na temperatura do ar, na precipitação, na umidade do ar e na circulação regional e global. Consequentemente, mapas de uso e cobertura da terra e suas respectivas características físico-químicas e biológicas constituem-se em uma importante variável na modelagem numérica de sistemas terrestres. Entretanto, na maioria dos modelos regionais de previsão do tempo e clima, o mapa de uso e cobertura da terra não é atualizado com frequência e encontra-se defasado, o que influencia os resultados das simulações. Desta forma, o presente trabalho tem como objetivo principal verificar o impacto nas simulações numéricas do RegCM4 oriundas da atualização do mapa de uso e cobertura da terra e dos parâmetros físicos como, por exemplo, o índice de área foliar (IAF), a reflectância no visível ( 0,7m) e no infravermelho próximo e médio (>0,7m) utilizados pelo Biosphere Atmosphere Transfer Scheme (BATS), além da validação dos dados provenientes do Tropical Rainfall Measuring Mission (TRMM). Consequentemente, a comparação entre os dados de precipitação mensal estimada pelo TRMM e 183 estações meteorológicas espalhadas por todo o Brasil apresentam uma concordância de aproximadamente 97%. Ainda, em relação à precipitação, temperatura máxima e temperatura mínima, obtém-se um melhor ajuste do modelo RegCM4 quando os dados de entrada do modelo são compostos pelas reanálises do SST-ERA-Interim e ERA-Interim e com a parametrização cúmulos proposta por Emmanuel. A partir da atualização do uso e cobertura da terra utilizado no modelo de superfície BATS para o ano 2007 obteve-se uma melhora de 10% na simulação da precipitação, aumentando de 0,84 para 0,92 o coeficiente de correlação (significante a p<0,05, teste t-student). Do mesmo modo, a simulação realizada com a alteração dos valores de fração máxima de cobertura vegetal apresentou valores de precipitação 18% acima dos observados. Ainda, as alterações da reflectância no visível e no infravermelho próximo e do índice de área foliar superestimaram a precipitação em 19% e 23%. Ressalta-se que todas as simulações apresentaram boa concordância no que diz respeito à temperatura máxima e mínima, apresentando valores muito próximos ao esperado. A variação trimestral dos parâmetros físicos utilizados pelo modelo de superfície BATS reduziram para 3% as superestimativas de precipitação, provendo uma correlação de 92% (significante a p<0,05, teste t-student). Em relação às variáveis meteorológicas, as principais diferenças encontradas na evapotranspiração, precipitação, umidade relativa do ar e temperatura a 2 metros concentram-se na região noroeste do Estado do Mato Grosso, nas divisas dos Estados de Mato Grosso do Sul e Mato Grosso com a Bolívia (áreas alagadas do Pantanal brasileiro), região noroeste do Paraguai e para a região da Bacia do Rio da Prata na Argentina, Região Nordeste do Brasil entre outras, devido principalmente à alteração da classe Floresta Ombrófila Densa para áreas de pastagem e agricultura e à substituição de áreas de agricultura por áreas de gramíneas, pastagem, vegetação arbustiva e Floresta Estacional Decidual. / The land use and land cover changes modify the air temperature, precipitation, air moisture, energy balance and regional and global circulations. Consequently, the land use and land cover maps and its physical-chemical and biological properties are important variables for numerical modeling of terrestrial systems. However, in most of regional weather and climate models the land use and land cover maps are not frequently updated, being out-of-date and, influencing the results of simulations. Therefore, this work has as main objective to analyze the impacts in numerical simulations by RegCM4 of land use and land cover maps updating, as well as the alteration of physical parameters, such as the leaf area index (LAI), the visible (<0.7 m) and near infrared and medium (> 0.7 m) reflectance used by the Biosphere Atmosphere Transfer Scheme (BATS). The validation of simulated precipitation by comparison to the Tropical Rainfall Measuring Mission (TRMM) data is also an objective. The comparison between monthly precipitation data estimated by TRMM and the 183 weather stations distributed throughout Brazil presented a concordance of approximately 97%. Also related to rainfall, maximum and minimum temperature simulations, better assessments of RegCM4 were found when SST-ERA-Interim, ERA-Interim reanalysis and cumulus parameterization proposed by Emmanuel were used. In addition, the update of the South America 2007 land use and land cover map used by BATS has improved the simulation of precipitation in 10%, increasing the correlation coefficient from 0.84 to 0.92 (significant at p <0.05, t-test student). Moreover, the results show good agreement between simulated and observed maximum and minimum temperature, with correlation coefficients near to 0.95 for both variables. Correspondingly, the simulations performed with adjustments on maximum fractional of vegetation cover showed precipitation mean value 18% above the observed data. Changes in visible and infrared reflectance and in the leaf area index overestimated the precipitation in 19% and 23%, respectively. It is noteworthy that all simulations showed good agreement for maximum and minimum temperature, with values very close to those observed. The three-monthly (seasonal) change of the physical parameters, which characterize the surface model BATS, provided a reduction of 3% in the mean simulated precipitation if compared to the results obtained without seasonal variation of surface parameters. The linear correlation between simulated and observed monthly precipitation obtained by considering seasonal changes in the surface parameter was equal to 92% (significant at p <0.05, Student\'s t-test). Regarding to atmospheric variables, the more significant differences observed in evapotranspiration, precipitation, relative humidity and temperature above two meters from surface are located in the northwest of Mato Grosso state, at the Mato Grosso do Sul, Mato Grosso states and the Bolivia bordering (placed on the Brazilian Pantanal wetlands), over Northeastern Brazil region, northwestern Paraguay, and River Plate Basin, among others. These important differences are due to the substitution of Tropical Rain Forest by pasture and agriculture and, the replacement of agricultural areas by areas of grass pasture, shrub and Deciduous Forest.

Page generated in 0.0933 seconds