Global ETD Search

51	The influence of hydrology and time on productivity and soil development of created and restored wetlands Anderson, Christopher John 02 December 2005 (has links) No description available. wetlands wetland creation and restoration flood pulsing soil development hydric soils sedimentation sediment and nutrient accumulation wetland productivity mesocosms bottomland hardwood forest riverine marshes
52	Silicon cycling in the Baltic Sea : Trends and budget of dissolved silica / Kisels kretslopp i Östersjön : Trender och budget av löst kisel Papush, Liana January 2011 (has links) The dissolved silicon (DSi) has a crucial role for growth of a large group of primary producers – diatoms and, hence, impact on functioning of the aquatic food web. This thesis contributes to an increased understanding of the modifications of the DSi cycling in the Baltic Sea. The results provide new information about spatial and temporal changes in DSi concentrations and nutrient ratios for the period 1970-2001 as well as during the 20th century. For the period 1970-2001, the declining DSi trends were found at the majority of monitoring stations all over the Baltic Sea. This decrease is assumed to be mainly due to the ongoing eutrophication. It is supported by the increasing trends of inorganic nitrogen and phosphorus. The trends have implications for the nutrient ratios, DSi:DIN and DSi:DIP, which are important indicators of the state of an ecosystem. The long-term retrospective DSi budget has shown that the DSi concentrations before major hydrological alterations and eutrophication were about twice the present ones. This decrease is related to both eutrophication and anthropogenic perturbations in the catchment. The occurrence of DSi concentrations close to the potentially limiting levels has been also analysed. While DSi concentrations are still high in the northern regions of the Baltic, other areas may be at risk of developing Si limitation if the decrease in DSi concentrations persists. The results depict the Baltic Sea journey from being water body with DSi levels sufficient to support diatom production to one that may experience Si limitation and its adverse ecological consequences. / Löst kisel (DSi) har en viktig roll för tillväxten av en stor grupp av primärproducenter – kiselalger, och därmed även påverkar hela den akvatiska näringskedjan. Denna avhandling bidrar till en ökad förståelse av förändringarna i DSi kretsloppet i Östersjön. Resultaten tillhandahåller ny information om rumsliga och tidsmässiga förändringar i DSi koncentrationer såväl för perioden 1970-2001 som för hela 1900-talet. För perioden 1970-2001 återfanns minskade DSi koncentrationer på mätstationer över hela Östersjön. Minskningen antas främst bero på den pågående övergödningen. Detta antagande stöds av stigande halter av oorganiskt kväve och fosfor. Sammantaget har dessa trender en inverkan på ekosystemets tillstånd och näringsämnenas kvoter, DSi: DIN och DSi: DIP. Ur ett längre tidsperspektiv kan man se att innan övergödningen och de stora hydrologiska ombildningar i Östersjöområdet var DSi koncentrationerna ungefär dubbelt så höga som idag. Dagens förekomst av DSi koncentrationer som ligger nära de potentiellt begränsande nivåerna har också analyserats. DSi koncentrationerna är fortfarande höga i norra delar av Östersjön, men är i andra områden i riskzonen för att utveckla Si begränsning om minskningen av DSi koncentrationer fortsätter. Resultaten skildrar Östersjöns resa från att vara ett havsområde med DSi halter som är tillräckliga för att understödja kiselalgernas produktion till ett sådant som kan uppleva Si begränsning och dess negativa ekologiska konsekvenser. Dissolved silica trends nutrient nutrient ratios diatoms Redfield limitation eutrophication riverine load budget fluxes accumulation retention optimisation Baltic Sea Löst kisel trender näringsämne näringsämnens kvoter kiselalger Redfield tillväxtbegränsning övergödning flodtillförsel budget flöden ackumulering retention optimering Östersjön NATURAL SCIENCES NATURVETENSKAP
53	Approaches to Empire: Hydrographic Knowledge and British State Activity in Northeastern North America, 1711-1783 Marsters, Roger Sidney 07 December 2012 (has links) This dissertation studies the intersection of knowledge, culture, and power in contested coastal and estuarine space in eighteenth-century northeastern North America. It examines the interdependence of vernacular pilot knowledge and directed hydrographic survey, their integration into practices of warfare and governance, and roles in assimilating American space to metropolitan scientific and aesthetic discourses. It argues that the embodied skill and local knowledge of colonial and Aboriginal peoples served vital and underappreciated roles in Great Britain’s extension of overseas activity and interest, of maritime empire. It examines the maritimicity of empire: empire as adaptation to marine environments through which it conducted political influence and commercial endeavour. The materiality of maritime empire—its reliance on patterns of wind and current, on climate and weather, on local relations of sea to land, on proximity of spaces and resources to oceanic circuits—framed and delimited transnational flows of commerce and state power. This was especially so in coastal and riverine littoral spaces of northeastern North America. In this local Atlantic, pilot knowledge—and its systematization in marine cartography through hydrographic survey—adapted processes of empire to the materiality of the maritime, and especially to the littoral, environment. Eighteenth-century British state agents acting in northeastern North America—in Mi’kmaqi/Acadia/Nova Scotia, Newfoundland and Labrador, Quebec, and New England—developed new means of adapting this knowledge to the tasks of maritime empire, creating potent tools with which to extend Britain’s imperial power and influence amphibiously in the eighteenth and nineteenth centuries. If the open Atlantic became a maritime highway in this period, traversed with increasing frequency and ease, inshore waters remained dangerous bypaths, subject to geographical and meteorological hazards that checked overseas commercial exchange and the military and administrative processes that constituted maritime empire. While patterns of oceanic circulation permitted extension of these activities globally in the early modern period, the complex interrelation of marine and terrestrial geography and climate in coastal and estuarine waters long set limits on maritime imperial activity. This dissertation examines the nature of these limits, and the means that eighteenth-century British commercial and imperial actors developed to overcome them.
54	Influence des flux anthropiques de nutriments et des caractéristiques du territoire sur la qualité de l'eau : une perspective historique du bassin du Saint-Laurent Goyette, Jean-Olivier 03 1900 (has links) No description available. azote phosphore eutrophisation anthropique charges fluviales qualité d'eau territoire lacs barrages climat bassin du Saint-Laurent historique Nitrogen Phosphorus Eutrophication Anthropogenic Riverine loads Water quality Land use Lakes Dams Climate St. Lawrence basin Historical
55	The Limits of Fire Support: American Finances and Firepower Restraint during the Vietnam War Hawkins, John Michael 16 December 2013 (has links) Excessive unobserved firepower expenditures by Allied forces during the Vietnam War defied the traditional counterinsurgency principle that population protection should be valued more than destruction of the enemy. Many historians have pointed to this discontinuity in their arguments, but none have examined the available firepower records in detail. This study compiles and analyzes available, artillery-related U.S. and Allied archival records to test historical assertions about the balance between conventional and counterinsurgent military strategy as it changed over time. It finds that, between 1965 and 1970, the commanders of the U.S. Military Assistance Command, Vietnam (MACV), Generals William Westmoreland and Creighton Abrams, shared significant continuity of strategic and tactical thought. Both commanders tolerated U.S. Army, Marine Corps, and Allied unobserved firepower at levels inappropriate for counterinsurgency and both reduced Army harassment and interdiction fire (H&I) as a response to increasing budgetary pressure. Before 1968, the Army expended nearly 40 percent of artillery ammunition as H&I – a form of unobserved fire that sought merely to hinder enemy movement and to lower enemy morale, rather than to inflict any appreciable enemy casualties. To save money, Westmoreland reduced H&I, or “interdiction” after a semantic name change in February 1968, to just over 29 percent of ammunition expended in July 1968, the first full month of Abrams’ command. Abrams likewise pursued dollar savings with his “Five-by-Five Plan” of August 1968 that reduced Army artillery interdiction expenditures to nearly ten percent of ammunition by January 1969. Yet Abrams allowed Army interdiction to stabilize near this level until early 1970, when recurring financial pressure prompted him to virtually eliminate the practice. Meanwhile, Marines fired H&I at historically high rates into the final months of 1970 and Australian “Harassing Fire” surpassed Army and Marine Corps totals during the same period. South Vietnamese artillery also fired high rates of H&I, but Filipino and Thai artillery eschewed H&I in quiet areas of operation and Republic of Korea [ROK] forces abandoned H&I in late 1968 as a direct response to MACV’s budgetary pressure. Financial pressure, rather than strategic change, drove MACV’s unobserved firepower reductions during the Vietnam War. 11th marines 12th marines abrams air force allied american way of war ammunition army artillery attrition arvn australian b-52 birtle budget cap cea classical clausewitz clifford coled-v collins communist congress constraints conventional counter-battery counterinsurgency dollar expenditures filipino finances fire support firepower five-by-five free world military fwmaf h&i haines harold harrassment hunt hybrid interdiction johnson kalergis komer korean krepinevich laird leonard taylor lewy lyndon macv marines mcnamara mekong nagl new zealand nixon nva observed operations philippine preemptive preparatory resor restraint riverine rok savings sensors sorley south vietnamese strategy summers tactics thai third country trinity unconventional unobserved usarv van fleet viet cong vietnam westmoreland wheeler wise men

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