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  • 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.
31

Regional–local coordination of non-motorized transportation : an exploration of two regions

Dohm, Diane Annette 13 July 2011 (has links)
This research report explores two regions, Denver and Minneapolis, by describing and analyzing their regional and local coordination efforts with respect to non-motorized transportation. The report is comprised of a literature review on the MPO institutional framework and governance, description and analysis of each region including levels of relationships between the MPO, State DOT, local governments and advocacy groups, as well as a comparison of both regions leading to the findings, lessons learned, and research implications. Specifically, this research seeks to understand how different levels of government work together, how the regional relationships assist in creating and implementing plans, how relationships with advocacy groups affect planning, and how climate change goals are integrated into non-motorized transportation planning. / text
32

Paleolimnological assessment of environmental changes occurring on Pim Island, Nunavut, High Arctic Canada

ROUILLARD, ALEXANDRA 23 December 2010 (has links)
Despite the documented sensitivity of polar environments, long-term monitoring data are especially sparse in these regions. Diatom-based paleolimnology has contributed significantly to understanding the response of Arctic lakes to climate change, but most studies have been conducted in regions with relatively high lakewater buffering capacity. As such, Pim Island (Nunavut, Canada) is a region of limnological interest because, due to the local geology, its surface waters are of relatively lower pH and previous research suggests that such softwater lakes may be especially responsive to climate fluctuations and therefore provide the best paleoclimate records. This thesis has two separate but related chapters, as well as an exploratory study included in appendix. First, a novel approach using visible-near-infrared spectroscopy (VNIRS) was used to infer lakewater dissolved organic carbon (DOC), from a 160-lake calibration set from the Canadian Arctic. Historically sound and similar trends were reconstructed when compared against a Canadian diatom-based DOC and Swedish VNIRS-based total organic carbon (TOC) model on Arctic Holocene sediment records. Second, a diatom and spectroscopically-based multi-proxy approach was utilized on Holocene sedimentary records from two lakes on Pim Island to assess long-term environmental change from this region. Benthic and epiphytic diatom taxa dominated the pre-19th century assemblages, although marked shifts in dominant species were recorded during the mid-Holocene. The mid-Holocene diatom assemblages underwent an abrupt ecological shift from alkaliphilous Fragilaria sensu lato to slightly acidophilous Achnanthes and Navicula. The post-19th century was characterized by an increase in the planktonic species (Cyclotella radiosa), indicating marked lakeice reductions. Third, the limnological properties and modern diatom assemblages of ponds and lakes surveyed from 1979 to 2009 on Pim Island were examined as part of an exploratory study. The ponds and lakes displayed typical characteristics observed in high Arctic lacustrine environments (i.e. oligotrophic, very dilute) but with overall relatively low alkalinity. Poorly-buffered sites had diatom assemblages that were distinct from well-buffered lakes elsewhere in the High Arctic. Our findings contribute to an improved understanding of the interactions between local environments and limnological changes, and also provide insight on the biological responses of lakes to Holocene environmental change and allow us to compare responses to those in more alkaline sites. / Thesis (Master, Biology) -- Queen's University, 2010-12-22 19:53:45.03
33

Sub-orbital scale variations in the intensity of the Arabian Sea Monsoon

Ivanochko, Tara S. January 2005 (has links)
A high-resolution multi-proxy reconstruction of the Arabian Sea Summer Monsoon (ASSM) intensity over the past 90,000 years has been determined using two marine sediment cores: one from the Somali margin and one from the Indian margin. This reconstruction indicates that changes in monsoon- induced upwelling, primary productivity and denitrification have varied in synchrony with Dansgaard-Oeschger (D-O) cycles. Increased monsoon intensity correlates with warm climate events (interstadials) and decreased monsoon intensity, which coincides with stadials and Heinrich Events, is confirmed by elevated dust concentrations in the marine cores. A comparison of the Somali and Indian margin cores with previously reported studies from the Northern and Western Basin allows the identification of discrete sediment signals from the Indus River, the Arabian Peninsula and from local riverine runoff. Sedimentary deposition on the Indian margin during interglacials is dominated by local terrestrial runoff, whereas during glacial periods increased dust input from the Arabian Peninsula is evident. Both signals are related to changes in the intensity of the ASSM. Monsoon intensity has decreased during the Holocene as the Intertropical Convergence Zone (ITCZ) has moved to a more southerly position. The ASSM-ITCZ relationship (increased ASSM intensity and a northern ITCZ, decreased ASSM intensity and a southern ITCZ) has remained consistent over the last glacial cycle suggesting that global millennial scale climatic variability is in part driven by modulations in tropical hydrological cycle. This ASSM reconstruction provides evidence that rearrangements in the tropical convection system affected atmospheric dust concentrations as well as the concentration and location of atmospheric water vapour. In addition to modulating terrestrial and marine emissions of greenhouse gases, variation in the tropical hydrological cycle provides a mechanism of amplifying and perpetuating millennial-scale climatic changes.
34

Climate information from tree rings /

Kalela-Brundin, Maarit, January 1900 (has links) (PDF)
Diss. (sammanfattning) Umeå : Sveriges lantbruksuniv. / Härtill 4 uppsatser.
35

Impact of climate change on soil fauna diversity : effects of experimental drought, irrigation, soil warming and nutrient addition /

Lindberg, Niklas. January 2001 (has links) (PDF)
Lic.-avh. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 2 uppsatser.
36

Impact of elevated temperature and [CO₂] on spring phenology and photosynthetic recovery of boreal Norway spruce /

Slaney, Michelle, January 2006 (has links) (PDF)
Diss. (sammanfattning) Alnarp : Sveriges lantbruksuniv. / Härtill 5 uppsatser.
37

Supporting management of the risk of wind damage in south Swedish forestry /

Olofsson, Erika, January 2006 (has links) (PDF)
Diss. (sammanfattning) Alnarp : Sveriges lantbruksuniversitet, 2006. / Härtill 4 uppsatser.
38

The Geomorphic Map of Metropolitan Lima and its Hidrographic Basins, a Tool to the Sustainable Land Management / El mapa geomorfológico de Lima Metropolitana y sus cuencas hidrográficas, una herramienta para la gestión sostenible del territorio

Villacorta, Sandra, Ubeda, José 10 April 2018 (has links)
In this paper we present a joint initiative of the Instituto Geológico Minero y Metalúrgico (Ingemmet) and the Research Group of Physical Geography in High Mountains of the Universidad Complutense de Madrid (GFAM-UCM), to promote at Peru the research on geomorphology and climate change. The plan is to elaborate geomorphological maps of Lima Metropolitana and header watersheds (Chillón, Rímac and Lurín), to generating analytical instruments to achieve the following objectives: 1) Decoding the record of climatic changes in landforms. 2) Delimit water reserves stored as ice masses (cryosphere). 3) Recognize the relationship between the geomorphology and the geological hazards which may affect to people and their economic activities. 4) Design a methodology that can be extrapolated to other Peruvian regions. To this end, geomorphological mapping will be integrated into geographic information systems (GIS): will be identified the morphoclimatic units and the related genetic processes. Also, their relative chronologies will be proposed. Then, the absolute dating of key units will be established to confirm or correct the relative chronologies. The information will be compiled in databases to be contrasted with other evidences and paleoclimatic proxies. This is intended to produce models of climate evolution, to contribute to the assessment of geological hazards, and the knowledge of current state of cryosphere, including recent trends and future forecasts. / En este trabajo se presenta una iniciativa conjunta del Instituto Geológico Minero y Metalúrgico (Ingemmet) y el Grupo de Investigación en Geografía Física de Alta Montaña de la Univeridad Complutense de Madrid (GFAM-UCM) para promover en el Perú las investigaciones sobre geomorfología y cambio climático. El plan consiste en elaborar mapas geomorfológicos de la región de Lima Metropolitana y las cabeceras de sus cuencas hidrográficas (Chillón, Luríny Rímac) generando instrumentos de análisis para: 1) Decodificar el registro de los cambios climáticos en las formas del relieve. 2) Delimitar las reservas hídricas almacenadas en forma de masas de hielo (criosfera), conocer sus tendencias y elaborar pronósticos de futuro. 3) Identificar las relaciones entre las geoformas del relieve y los peligros geológicos que afectan a la población y sus actividades económicas. 4) Diseñar una metodología que pueda extrapolarse a otras regiones peruanas. Con el fin de lograr esos objetivos, en primer lugar se van a elaborar mapas geomorfológicos integrados en sistemas de información geográfica (SIG): se diferenciarán las unidades morfoclimáticas, se identificarán los procesos que las generaron y se propondrán sus cronologías relativas. A continuación, se establecerán las cronologías absolutas de unidades clave, que permitirán confirmar o corregir la anterior secuencia de edades. De este modo se desea contribuir a desarrollar modelos de la evolución del clima, colaborar con la evaluación de los peligros geológicos y conocer el estado de la criosfera, incluyendo tendencias pasadas y previsiones futuras.
39

La sélection naturelle : contraintes méthodologiques et déterminants climatiques chez la mésange bleue (Cyanistes caeruleus) / The natural selection : methodological constraints and climatic drivers in the Blue Tit (Cyanistes caeruleus)

Marrot, Pascal 30 November 2016 (has links)
Depuis plusieurs décennies, les populations font face à des changements environnementaux sans précédent. Afin de répondre à ces changements les espèces peuvent se déplacer vers un autre endroit (c’est la dispersion), répondre aux changements par plasticité phénotypique, ou encore s’adapter par sélection naturelle (c’est la réponse évolutive). Si la dispersion et la plasticité phénotypique permettent une réponse rapide face à un changement environnemental tel que le réchauffement climatique, seule la réponse évolutive permet une adaptation durable. Une réponse évolutive au changement climatique peut être attendue seulement si l'augmentation des températures occasionne une pression de sélection sur un et / ou des traits. Cependant, quantifier les pressions de sélection qui agissent sur les populations naturelles reste difficile, en particulier celles qui accompagnent le changement climatique.Au cours de cette thèse, j'ai cherché à quantifier les pressions de sélection reliées au changement climatique agissant sur une population sauvage de mésange bleue (Cyanistes caeruleus) suivie depuis 26 ans près de Montpellier. Dans un premier temps, j'ai exploré le biais induit par l'autocorrélation spatiale sur l'estimation de la sélection naturelle lorsqu'elle n'est pas prise en compte dans une population sauvage. Dans un deuxième temps, j'ai quantifier l'impact du réchauffement climatique sur la force de sélection agissant sur la date de ponte, un trait fortement relié au succès reproducteur chez la mésange bleue. Cependant, si le changement climatique est caractérisé par une augmentation des températures, il s'accompagne aussi d'une augmentation de la fréquence d'évènements extrêmes climatique (EEC). Dans un troisième temps, je me suis donc attaché à estimer l'influence des températures et des pluies extrêmes sur la force de la sélection naturelle. Concernant l'autocorrélation spatiale, nos résultats ont permit de mettre en avant un biais majeur sur l'estimation de la sélection naturelle lorsqu'elle n'est pas prise en compte. En effet, lorsque la valeur sélective est positivement spatialement autocorrélée, un modèle de sélection non-spatialisé surestimera la force de la sélection naturelle agissant sur les traits. Nous avons donc développé 4 modèles de sélection spatialisés, et nous les avons comparé entre eux sur la base de plusieurs paramètres. De plus, nous avons détecté un fort réchauffement dans notre population qui s'accompagnait d'une augmentation de la force de sélection naturelle agissant sur la date de ponte. En effet, nous avons quantifié une augmentation de 46% de la force de sélection naturelle tout les +1°C de la température maximum du mois d'Avril. Au delà des températures moyennes, nous avons mis en évidence un fort impact négatif de la présence / absence de journées extrêmement chaudes durant l'élevage des oisillons au nid sur le succès d'envol. Plus intéressant encore, ces EECs augmentaient significativement la force de sélection naturelle agissant sur la date de ponte, indépendamment de l'augmentation des températures moyennes.Ainsi, ma thèse a contribué à une meilleure compréhension méthodologique de la sélection naturelle, ainsi que de l'impact sélectif du changement climatique. Le premier chapitre a permit de mettre en évidence un problème méthodologique majeur lorsque on estime la sélection naturelle dans les populations sauvages, ainsi que de proposer des solutions concrètes. Le second chapitre a permit de confirmer l'impact sélectif du changement climatique, laissant entrevoir une possibilité de réponse évolutive au réchauffement. Enfin, le troisième chapitre démontrait la sélection naturelle reliée à l'apparition d'EEC, et en quantifiait les effets, un résultats encore jamais montré. Nous espérons que cette thèse ouvrira la voie à plus d'études explorant l'impact du changement climatique sur la sélection naturelle, permettant peut être de prévoir les réponses évolutives futures. / Global change results in an increase in temperature mean and variability and generates new environmental conditions for wild populations. In order to respond to this new treat, wild populations can move to another place (dispersion), change their behaviour or their phenology (phenotypic plasticity) or respond by evolutionary change (involving changes in alleles frequency). However, phenotypic plasticity or dispersion are unlikely to sustain population responses to climate change over the long term, contrary to the evolutionary response. Wild populations could evolutionary respond to climate change only if the increase in temperature represents a selective pressure on fitness-related traits. Yet, quantifying the selective pressures acting on wild populations remains challenging, especially in response to climate change.During this PhD, I focused on the selection pressures related to climate warming during a 26-year monitoring of blue tits (Cyanistes caeruleus) in southern France. First, I explored the bias inducted by spatial autocorrelation on estimation of natural selection in the wild when it is not taken into account. Second, I quantified the impact of climate warming on natural selection acting on laying date. Along with a rise in mean temperatures, climate change is also characterized by an increase in the frequency of extreme climatic events (ECE). Hence, I finally explored the impact of multiple ECEs such heavy rainfalls and extremes temperatures on the strength of natural selection acting on laying date.Our results showed that spatial autocorrelation is severely biasing our estimation of natural selection in the wild if it is not taken into account. In fact, natural selection is continuously overestimated by a non-explicit spatial model when the fitness is spatially autocorrelated. Hence, we developed 4 spatially-explicit models of selection, and we compared them in order to assess their reliability. Also, we detected a strong warming in our study site, which was correlated with an increase in natural selection strength. In fact, our results indicated an increase in the strength of selection by 46% every +1°C anomalies in maximum April temperature. Beyond this selective impact of the warming trend, we detected an impact of the extreme hot days occurrence during the nestlings stage on the fledglings success. More interesting, these ECEs significantly increased the strength of selection acting on laying date, independently form the mean temperatures.To conclude, my PhD helped to a better understanding of natural selection estimation in the wild, and the selective impact of climate warming. The first part allowed to develop specific models of selection in order to take into account spatial autocorrelation, a universal phenomenon present at any scale. The second part confirmed the selective impact of warming, pointing out a potential evolutionary response to climate change in the future. The last part demonstrated and quantified the selective impact of multiple ECEs, which has not been demonstrated before. We call now for more studies assessing the selective impact of climate warming, which could allow to predict the evolutionary responses in the future.
40

Influencia del cambio climático en la evolución de la vegetación nival de las montañas mediterráneas. sierra de guadarrama, españa / Influencia del cambio climático en la evolución de la vegetación nival de las montañas mediterráneas. Sierra de Guadarrama, España

García-Romero, Antonio, Muñoz, Julio, Andrés, Nuria, Palacios Estremera, David 10 April 2018 (has links)
It studies recent climate variation and its consequences on the nival vegetation distributionin two basins of the Sierra de Guadarrama, Spain. The climate change was documented from eighteen different variables related to temperature, pluvial and snow precipitation, snow du ration within the period 1951-2000. To evaluate vegetation response to climate variation we determined the nival correlation of the distinct vegetation classes. To do this, we considered their spatial and / or temporal relation with distinct variables of climate, snow variation, and nival geoforms. Nival vegetation maps were made of five dates (1956 to 1998) and to quan tify and explain tendencies it was necessary to calculate surfaces and percentages of change, annual mean transformation index (ITMA’s) and transition matrixes. The results show that in the area studied there are 14 vegetation classes belonging to four groups of high, medium, low and negative nival correlation. Evolution of the last fifty years is summarized in a notable spatial reduction of vegetation with high nival correlation, moderate vegetation reduction with medium nival correlation and significant vegetation expansion with negative nival correlation. Change processes leave a main succession that consists on the herbal formation substitution highly correlated with snow duration and the abundance of fusion water, by leguminous shrubsapart from the nival influence, which slowly densify. / Se estudia la variación reciente del clima y sus consecuencias sobre la distribución de la vegetación nival en dos cuencas de la Sierra de Guadarrama, España. El cambio climático se documentó a partir de dieciocho variables referentes a temperatura, precipitación pluvial y nival, y duración de la nieve, durante el período 1951-2000. Para evaluar la respuesta de la vegetación a la variación del clima se partió de determinar la correlación nival de las distintas clases de vegetación, para lo cual, se consideró su relación espacial y/o temporal con distintas variables del clima, la duración de la nieve y las geoformas nivales. Se generaron mapas de la vegetación nival en cinco fechas (1956 a 1998) y para cuantificar y explicar las tendencias se calcularon superficies y porcentajes de cambio, índices de transformación media anual (ITMA) y matrices de transición. Los resultados muestran que el área de estudio incluye catorce clases de vegetación pertenecientes a cuatro grupos de alta, media, baja y negativa correlación nival. La evolución de los últimos cincuenta años se resume en una notable reducción espacial de la vegetación con correlación nival alta, moderada reducción de la vegetación con correlación nival media y significativa expansión de la vegetación con correlación nival negativa. Los procesosde cambio dejan ver una línea principal de sucesión que consiste en la sustitución de las formaciones herbáceas altamente correlacionadas con alta duración de la nieve y abundancia de las aguas de fusión, por matorrales de leguminosas alejados de la influencia nival, que se densifican paulatinamente.

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