• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 36
  • 13
  • 3
  • 1
  • 1
  • 1
  • Tagged with
  • 81
  • 9
  • 8
  • 8
  • 8
  • 7
  • 7
  • 7
  • 6
  • 6
  • 6
  • 6
  • 6
  • 6
  • 6
  • 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

Characteristics and Management Implications of Mollic Soils in Forest Versus Grassland Settings in Central California

Clark, Brian Charles 01 March 2021 (has links) (PDF)
Efforts to sequester soil carbon (C) should consider soils intrinsically capable at C retention. Of the mineral soil orders, Mollisols have minimum requirements for soil organic C (SOC; over 0.06 %) and basic saturation (over 50 %). In the U.S., grasslands comprise 93% of the vegetation mapped above Mollisols. Soils beneath the southern extent of Sequoia sempervirens (redwood) forests in central California are mapped as Molliols. It widely accepted that redwood forests harbor considerable biomass C, but the extent to which aboveground C is retained in the soil is not well understood. This study aimed to: (i) to gather baseline soils data (bulk density, pH, basic saturation, cation exchange capacity, SOC, total nitrogen, structure, depth) for an iconic and understudied ecosystem, the southern extent of coast redwood forests and to compare said properties to those in adjacent grasslands, (ii) to identify taxonomic classifications of said soils, (iii) to investigate the influence of vegetative gradation on soil properties between these ecosystems using auger sampling, (iv) to compare levels of basic cations between the forest floor and mineral horizons and, (v) to characterize the total C and active C pools within these ecosystems and to explore interpretations of these pools. In sites randomly selected across two regions, Swanton Pacific Ranch (SPR) and Landels-Hill Big Creek Reserve (LHBCR), soil was collected and described in 24 profiles beneath redwoods and compared to 19 profiles in nearby grasslands. Auger samples at fixed depths were collected in a complimentary study from 5 randomized transects that transitioned through mixed-evergreen forest (and across ecotones) between redwoods and coastal grasslands at SPR. Mineral soil samples were analyzed for SOC, permanganate oxidizable C (POXC), C/N ratio, pH, extractable basic cations, and cation exchange capacity. Samples of forest litter were analyzed for basic cation composition. Multivariate regression models of profile data found higher values of pH, C/N, and CEC in redwoods than in grasslands, and lower values of bulk density in redwoods than in grasslands. Redwood soils were conducive to mollic epipedon formation (21 of 24 profiles in the redwoods as Mollisols) and generally had high base levels, for which extractable calcium from the forest floor was the main driver. Along the transects, multivariate regression returned generally consistent and graded patterns for C/N ratios, POXC/SOC ratios, and pH; these variables were generally highest in the redwood forest and decreased sequentially across mixed-evergreen forest and into the grassland Our look at soil C pools focused on the fraction of SOC that was POXC. Observed higher ratios of POXC/SOC in redwoods than in the grasslands at SPR was corroborated by the transect study; at LHBCR, the regression model provided no evidence for a significant difference in POXC/SOC ratios between communities. Differences in POXC fractions across plant communities and localities were postulated as the result (and combination) of contrasting ecologies, and different management strategies and disturbance histories. The data collected in this study does not provide clear mechanisms to explain these discrepancies, and further research is needed; disharmonious interpretations of POXC across the literature suggested that the replacement of operationally defined C fractions with pools tied to a particular stabilization mechanism would provide clearer insights across ecosystems to land managers. Our estimates of SOC in the top 1 m of soil showed redwood soils stored as much or more C than soils in the neighboring grasslands, at SPR, 144 (± 21) and 123 (± 25) tons SOC per ha in the top 1 m of redwoods and grasslands, respectively, and at LHBCR, 221 (± 23) and 126 (± 24) tons SOC per ha in the top 1 m of redwoods and grasslands, respectively. The carbon densities provided in this study can be used as a baseline to measure changes to SOC and POXC pools in response to future activities to sequester C in our study regions and/or to assess losses from recent 2020 wildfires. We are curious to see how the breadth of information gathered in this study can provide refinement for following questions that will hopefully one day, direct considerate and conscientious management in response to the environmental challenges ahead.
72

Vers une redéfinition de la nature américaine : trois études de cas dans la région de Los Angeles / Towards a Redefinition of Nature in the United States : three Case Studies in the Los Angeles Area

Schmutz, Hélène 08 November 2013 (has links)
Les historiens de l’environnement s’attachent à déchiffrer les modes de relation entre l’homme et la nature aux Etats-Unis. La manière dont elle est définie conditionne les politiques environnementales, et donc contribue à la transformation matérielle du continent. Cinq traditions de la pensée environnementale américaine sont décrites : la nature comme ressource transformée par le travail ; le préservationnisme ; le conservationnisme ; l’écologie ; et la justice environnementale. Ces idées perdurent au XXIème siècle dans les discours construits au sujet de la nature : elles se juxtaposent ou se confrontent. L’objectif de ce travail est de savoir si elles se transforment, en évoluant vers une définition de la relation homme/nature comme hybride socionaturel. À cette fin, trois cas sont étudiés, tous situés dans la région de Los Angeles au début des années 2000. Le premier concerne le ranch Tejon, dont l’accord passé en 2008 entre associations de protection de la nature et propriétaires pose la question du sens donné à une préservation qui veut prendre en compte les aspects à la fois écologiques, mythiques et économiques de ce territoire, vestige du passé de l’Ouest. Le second se rapporte à la décision prise en 2007 par la ville de Los Angeles de revitaliser son fleuve et fournit un exemple de l’élargissement de la définition de la nature : celle-ci peut être urbaine. Enfin, troisième cas, la justice environnementale appliquée à la ferme communautaire de South Central Los Angeles, entretenue de 1994 à 2006, est signe de la transition de la pensée de la nature américaine d’un objet délimité dans l’espace vers une problématique mondiale. / Environmental historians have worked at redefining the modes of relationship between man and nature in the United States. The way this relation is defined conditions environmental politics, and therefore contributes to the material transformation of the continent. Five major trends of thought about nature are described: nature as a resource transformed by work ; preservationism ; conservationism ; ecology ; and environmental justice. Those ideas endure to this very day in the discourses constructed about nature: they either juxtapose or confront each other. The goal of this thesis is to understand whether they undergo a transformation, evolving towards a definition of the man/nature relationship as a socionatural hybrid. To this end, three cases are examined here, all of which are connected with the Los Angeles area in the early 2000s. The first concerns Tejon Ranch and the agreement passed in 2008 about Tejon Ranch between environmental associations and the owners : it poses the question of the meaning given to a preservation that would incorporate ecological, mythical and economic aspects of that territory, a remain of the Western past. The second deals with the decision that was made in 2007 by the City of Los Angeles to revitalize its river and offers a good example of the broadening of the definition of nature: it can also be urban. The ecological and cultural preoccupations about the river complicate the conservation problematic in Southern California. Finally, South Central Farm’s environmental justice case (1994-2006) is the sign of a transition in American environmental ideas from a clearly spatially limited object to a world issue.
73

Cattle Capitalists: The XIT Empire in Texas and Montana

Miller, Michael M. 12 1900 (has links)
The Texas Constitution of 1876 set aside three million acres of Texas public land in exchange for construction of the monumental red granite Capitol that continues to house Texas state government today. The Capitol project and the land went to an Illinois syndicate led by men influential in business and politics. Austin's statehouse is a recognizable symbol of Texas around the world. So too, the massive Panhandle tract given in exchange -- what became the "fabulous" XIT Ranch -- has come to, for many, symbolize Texas and its role in the nineteenth century cattle boom. After finding sales prospects for the land, known as the Capitol Reservation, weak at the time, backed by British capital, the Illinois group, often called the Capitol Syndicate, turned their efforts to cattle ranching to satisfy investors until demand for the land increased. The operation included a satellite ranch in Montana to which two-year-old steers from Texas were sent for fattening, often "over the trail" on a route increasingly blocked by people and settlement. Rather than a study focused on ranching operations on the ground -- the roundups, the cattle drives, the cowboys -- this instead uncovers the business and political side of the Syndicate's ranching operation, headquartered in Chicago. The operation of the XIT Ranch looked more like other Gilded Age businesses employing armies of clerks, bookkeepers, and secretaries instead of how great western ranches have been portrayed for years in popular literature and media. The XIT Ranch existed from 1885 to 1912, yet from Texas to Montana the operation left a deep imprint on community culture and historical memory.
74

Thickwood

2015 September 1900 (has links)
My thesis is a novel-length work of historical fiction entitled Thickwood. The novel can be situated within the context of great/interior plains literature, given its substantial focus on the Thickwood Hills, the northern remnant of the Missouri Coteau. This transition zone between the plains and the mixed boreal forest is an area of geographical and cultural tension. Within this drainage system of the Saskatchewan Rivers, Europeans traded for food and furs with First Nations and Métis peoples, leading to the signing of Treaty 6 and the formation of First Nations Reserves. In Thickwood characters travel across the rugged landscape but also travel into their interior landscape to struggle with questions about belonging and place. During formative years of development, certain landscapes become places of significant attachment, laden with emotional connection and sentiment. This historical work, set in Saskatchewan in 1950, takes place during intense changes after World War Two. Many rural communities without power, good roads, and even telephone services struggled to keep up with post-war development. The cooperative movement, encouraged by Premier Tommy Douglas, was a means for rural people to pool resources to improve their communities. Beef prices were climbing to an all-time high, increasing demand for pastureland. Using close third-person point of view, the novel follows a young female character skilled in ranching, horses, and the sport of baseball. Willomena Swift struggles to find a future for herself after returning from two seasons pitching in the All-American Girls Professional Baseball League. The lease to her family ranch is about to end and her father sells the remaining land to the growing community pasture. After a rogue stallion kills Willo’s purebred foal, she begins a quest to control the stallion and avoid its villainous owner, who is also the pasture committee chairman. Willo uses wit and skill to survive the perils of the landscape and gains confidence to confront Nesteroff about taking over her home as the new pasture headquarters after her father’s death. The novel Thickwood explores personal connections to rugged homeland, spirited horses, and love.
75

A comparative study of recidivism rates between graduates of Twin Pines Ranch and juveniles in Riverside County who completed probation

Smith, Djuan Maria 01 January 1998 (has links)
The purpose of this study is to determine the role of a military style counseling and vocational program in reducing recidivism.
76

Avian Community Response to Riverby Ranch Restoration Reconstruction

Boucher, Tessa Katrish 12 1900 (has links)
Anthropogenic activities have caused many wildlife spices to decline in populations worldwide. The grassland bird communities are especially being impacted by these land use changes. Breeding success is closely tied to functional habitats for most grassland bird species in North Texas. Restoring these degraded habitats is an important component to aid in conserving wildlife biodiversity. We surveyed the bird population at Riverby Ranch Mitigation site by conducting point count sampling. This site consists of recently restored grassland, wetland, and forested habitat. This research was focused on conducting post restoration monitoring of the bird community in the early succession of the restored habitats. We set out to use the bird community as biomonitors to help assess if the restoration practices could be considered successful. We found that density estimates were more than double at the restored site when comparing to three different references sites under different management practices. This included an unrestored working ranch, a wildlife management area, and a conservation managed prairie site. We found that biodiversity metrics were as high or higher than the reference sites. In addition, we also found that there were more observations of species of high conservation concern present at the restored stie. This research supports that the reconstructive restoration that took place at Riverby Ranch was highly effective at restoring a diverse and abundant grassland and wetland bird community.
77

Los hijos sin nombre: el silencio del olvido. Sábato y el claroscuro gnóstico argentino.

Hermosilla Sánchez, Alejandro 21 March 2006 (has links)
La tesis estudia la historia de Argentina en relación con la obra de Ernesto Sábato. El trabajo intenta a través de la historia del país sudamericano y la lectura de la obra de Sábato llegar a conclusiones que permitan explicar los hechos sucedidos en diciembre del 2001 en Argentina. Para ello, la tesis lleva a cabo un estudio mítico de la historia de Argentina en el que destaca el realizado sobre la figura del emigrante, héroe de las novelas de Sábato, a quien se compara con Caín. Por tanto, Caín, Abel y el Dios judío, Yahvé, serán los personajes fundamentales estudiados en esta tesis para comprender el destino de la Argentina y de la obra de Sábato desde un punto de vista mítico, místico, simbólico y religioso. / The thesis studies the history of Argentina in relation to the work of Ernesto Sábato. The work tries, though the history of the south american country and the reading of the work of Sábato, to search conclusions that allow to explain the facts happened in December of 2001 in Argentina. For it, the thesis carries out a mythical study of the history of Argentina in which it emphasizes the made one on the figure of the emigrant, hero of novels of Sábato, to that it compares with Caín. Therefore, Caín, Abel and the Jewish God Yahvé, will be the fundamental personages studied in this one thesis to understand the destiny of the Argentina and the work of Sábato from a mythical, symbolic and religious point of view.
78

Identifying Potential Patterns of Wildfires in California in Relation to Soil Moisture using Remote Sensing

Link, Adam John 01 May 2020 (has links)
No description available.
79

Ecology of a Myth: Landscape, Vernacular, and Settler Colonialism at the Sea Ranch

Jennings, Michele Lee January 2022 (has links)
No description available.
80

Geology of the Palo Verde Ranch Area, Owl Head Mining District, Pinal County, Arizona

Applebaum, Steven January 1975 (has links)
A quartz diorite intrusion of probable early Tertiary age that crops out over at least 6 square miles in the Palo Verde Ranch area in Pinal County, Arizona was mapped as a distinct intrusion. The quartz diorite intrudes an area comprising Pinal Schist, Oracle granite, andesitic flows, granoaplite, and dike rocks including both pegmatite and diabase. Two major physical features, the Owl Head Buttes and Chief Buttes volcanic areas, both remnants of an extensive early Tertiary series of flows of intermediate composition that covered the area, now remain as lava-capped buttes above the pediment. Weak but persistent fracture-controlled copper mineralization is found in the quartz diorite and the Pinal Schist at or near their mutual contacts in the form of chrysocolla, malachite, black copper oxides, chalcocite, chalcopyrite, and bornite, in decreasing order. Pyrite is rare. Alteration related to northeast and northwest-trending fractures increases in intensity from the common propylitic to argillic to the northeast toward the San Juan claims area. A barely discernible increase in copper sulfides mirrors the alteration zoning, although geochemical sampling showed background copper in the quartz diorite to be more uniform away from fractures.

Page generated in 0.0437 seconds