Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniversitet, 2005. / Härtill 5 uppsatser.

Thesis (Ph. D.)--Oregon State University, 2009. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Thesis (Ph. D.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 183-197). Also available on the World Wide Web.

Thesis (M.S.)--University of North Carolina Wilmington, 2009. / Title from PDF title page (January 15, 2010) Includes bibliographical references (p. 66-70)

Thesis (M.S.)--Florida State University, 2006. / Advisor: Joel Kostka, Florida State University, College of Arts and Sciences, Dept. of Oceanography. Title and description from dissertation home page (viewed Oct. 24, 2006). Document formatted into pages; contains viii, 101 pages. Includes bibliographical references.

Thesis (doctoral)--Swedish University of Agricultural Sciences, 2003. / Appendix consists of reprints of three papers and a manuscript, three of which are co-authored with others. Includes bibliographical references. Also partially issued electronically via World Wide Web in PDF format; online version lacks appendix.

With a burgeoning population, increasing land area, and the emergence of new megacities, urban areas have the ability to alter biogeochemical cycles across great scales. Though cities are hotspots of pollution, these concentrated population centers present an opportunity to reduce the human footprint and provide a model of sustainability. Creating sustainable cities requires an understanding of urban biogeochemical cycles of nutrients, such as carbon (C), nitrogen (N), and phosphorus (P). Studies in urban areas, however, often include measurements at only a few sites, either in an urban-rural comparison or as an anchor along an urban-rural gradient. In my dissertation work, I deployed a network of sites across the greater Boston area to measure several key biogeochemical processes: 1) rates of carbon dioxide (CO2) efflux through soil respiration, 2) atmospheric inputs and soil solution concentrations of N, P, and organic C, and 3) rates of N mineralization and nitrification in soils. I found that urban soil respiration is driven by landowner management and that respiration from urban residential soils produces almost 75% of the CO2 as fossil fuel emissions in these areas during the growing season. I also found that mean fluxes of inorganic N in throughfall are double rural rates and vary more than threefold throughout the urban area, exhibiting rates at some urban sites which are as low as rural rates. These rates are driven by vehicular N emissions and local fertilizer inputs, and are decoupled from rates of soil biogeochemical cycling of C and N. Finally, I found atmospheric fluxes of organic N equaling almost 40% of total atmospheric N inputs, atmospheric inputs of organic C on par with rural rates, atmospheric inputs of P similar to rates of P in parking lot runoff, and an enhancement of nutrient inputs to urban ecosystems by the urban tree canopy. My dissertation work highlights the need for a more thorough understanding of biogeochemical fluxes in cities, provides further impetus for the development of a more holistic, multifaceted understanding of urbanization, and suggests that urban areas should be studied as systems unto themselves, rather than strictly in comparison to rural areas.

This study observes an influence of two-year application of NPK fertilizer on the amount of soluble nitrogen, microbial N transformations, and microbial biomass and the composition of microbial community in mineral and organic soils of two wet meadows. This study is the first version of manuscript, supplemented with a wider literature review, which will be submitted in 2010.

O ciclo do nitrogênio vem sendo alterado pelas atividades antropogênicas, em função do incremento de culturas, como as leguminosas, a queima de combustíveis fósseis e o desmatamento de florestas para uso agrícola e pecuário. Em regiões de climas temperados, existem muitas informações sobre o ciclo biogeoquímico deste elemento e sobre o papel das alterações antropogênicas no mesmo. Entretanto, em regiões tropicais, onde o ritmo do desmatamento ainda é intenso, poucas são as informações sobre este elemento. Em função disto, o presente trabalho visa fornecer informações sobre possíveis alterações nas formas de nitrogênio transportadas por pequenos igarapés, após a conversão de florestas em pastagens de regiões tropicais. Para tal, selecionaram-se duas microbacias, uma coberta com floresta primária e outra com pastagem, no estado de Rondônia (Cacaulândia). Em ambas foram realizados balanços, por eventos de chuva, das formas e quantidades de nitrogênio transportadas desde a precipitação até a água dos rios. As coletas foram realizadas durante a estação chuvosa, de 21 de janeiro a 27 de fevereiro de 2004. Como resultado, observou-se: (1) um maior fluxo de água na microbacia da pastagem, e como conseqüência, uma maior exportação de nitrogênio na mesma; (2) diferenças nas formas de nitrogênio predominantes em cada compartimento estudado. O nitrogênio orgânico dissolvido predominou na precipitação interna, no escoamento superficial e nos igarapés, enquanto que, o amônio predominou na água subsuperficial e na água subterrânea; (3) diferenças nas formas de nitrogênio inorgânico dissolvido presentes nos igarapés de cada microbacia, sendo o nitrato a principal forma observada na floresta, e o amônio na pastagem; (4) o nitrogênio orgânico dissolvido no igarapé da pastagem provem principalmente do escoamento superficial, enquanto que, no igarapé da floresta não foi possível identificar a principal fonte desta forma de nitrogênio. Este estudo mostra mudanças significativas no ciclo do nitrogênio como conseqüência do desmatamento e da implantação de pastagens. / The nitrogen cycle has been altered by anthropogenic activities, in response to the increment of cultures such, as the leguminous, fossil fuel use, and deforestation for agricultural uses and cattle raising. In temperate regions, there is considerable information about the biogeochemical cycle of nitrogen and the role of anthropogenic alterations on this cycle. However, in tropical regions, where deforestation rates are significant, there is little available information about these processes. The objective of the present work was to provide information on possible alterations in nitrogen forms transported in small catchments (igarapés) of tropical regions, after the conversion of forests into pastures. Two small catchments, one covered by primary forest, and another one covered by pasture, were selected in Rondonia State (Cacaulândia). At both catchments, balances of nitrogen forms and of quantities transported from the rain water to the rivers were calculated, employing a rain event approach. Sampling was done during the wet season, from January 21 to February 27, 2004. We observed: (1) higher discharges at pasture catchment, which resulted in larger nitrogen fluxes; (2) differences in the predominant nitrogen forms at each studied compartment. Dissolved organic nitrogen predominated in the internal precipitation, overland flow, and stream water, while ammonium predominated in the subsurface water and groundwater; (3) differences in the predominat dissolved inorganic nitrogen forms in stream waters of each catchment, nitrate in the forest, and ammonium in the pasture; (4) Dissolved organic nitrogen in the pasture stream comes primarily from overland flow but, for the forest stream, it was not possible to clearly identify the main source of this nitrogen form. This study shows significant changes in nitrogen cycling in small tropical catchments, as a result of deforestation for pasture.

Submitted by (lucia.rodrigues@ufrpe.br) on 2016-11-03T12:49:59Z No. of bitstreams: 1 Elba Ninfa de Lima.pdf: 1640154 bytes, checksum: 5c17b22e2ef92ae560f8626c810470d3 (MD5) / Made available in DSpace on 2016-11-03T12:52:05Z (GMT). No. of bitstreams: 1 Elba Ninfa de Lima.pdf: 1640154 bytes, checksum: 5c17b22e2ef92ae560f8626c810470d3 (MD5) Previous issue date: 2006-02-03 / The science curriculum has undergone great changes in the past decades due to the constant transformations of the society and its consequent scientific advance. It is possible to perceive, in this current panorama, that as to ideas there is an evergrowing evolution, however, as to actions much remains to be done. This study focuses as a topic on the existing teacher`s dependence on the textbook to approach a certain subject matter in the classroom, being the focus of this paper on the Nitrogen Cycle. Its main purpose is to know if science textbooks have an adequate approach to the aforementioned cycle, so that it meets the teacher`s needs. This subject matter was select based on the uderstanding that its study is of the utmost importance, since the energetic balance in nature, the maintenance of nutrients in the soil and the formation of nitrogenous compounds vital to the organic structure of living beings depend on such a cycle. In the classroom, the study makes understanding such phenomena possible, but the teacher should above all, identify the relations between different scientific concepts of diferrente areas involved in this cycle. The research work was carried out at first, through the analysis of the science textbooks recommended by the Textbooks Guide 2005, considering that, supposedly, upon being apprived and suggested by the National Textbooks Program, they are already qualified to be adopted by teachers. Finally, teachers thoughts were analyzed through written comments on statements related to the subject. From this research we reached the conclusion that there are different limits to approach the Nitrogen Cycle, both in textbooks and in teachers presentation. However, this conclusion is not enough to solve a real problem; it is believed, however, that becoming aware of the existence of this set of problems and understanding what brought it about tend to make a possible solution to this question less distant and less conflictive. / O currículo de Ciências tem sofrido intensas mudanças nas últimas décadas, devido às constantes transformações da sociedade e a seu conseqüente avanço científico. É possível perceber, nessa panorâmica atual, que no plano das idéias existe uma evolução crescente, entretanto, no campo das ações, ainda há muito por fazer. Este estudo apresenta como tema a dependência que tem existido do professor em relação ao livro didático para a abordagem de determinado conteúdo em sala de aula, no caso específico deste trabalho, o Ciclo do Nitrogênio. O objetivo está em identificar se os livros didáticos de Ciências apresentam uma abordagem adequada sobre o referido ciclo, de modo que atenda às necessidades do professor. Esse conteúdo foi definido por se entender que seu estudo é de fundamental importância, pois desse ciclo depende o equilíbrio energético na natureza, a manutenção da riqueza do solo em nutrientes e a formação dos compostos nitrogenados vitais para o organismo de todos os seres vivos. Em sala de aula, o estudo possibilita a compreensão desses, mas o professor deve, sobretudo, estabelecer as relações entre os diferentes conceitos científicos das diferentes áreas envolvidas nesse ciclo. O trabalho de pesquisa foi realizado, primeiramente, por meio de análise dos livros didáticos de Ciências indicados pelo Guia do Livro Didático 2005, considerando-se que, supostamente, ao serem aprovados e sugeridos pelo PNLD, já se apresentam qualificados para serem adotados pelos professores. Por fim, analisou-se o pensamento do professor através dos comentários escritos sobre afirmativas relacionados ao tema. Com a presente pesquisa, constatou-se que existem diferentes limites na abordagem do Ciclo do Nitrogênio, tanto por parte dos livros didáticos quanto do professor. Entretanto, essa constatação não é suficiente para resolução de um problema real; acredita-se, contudo, que perceber a existência dessa problemática e entender os motivos que a originam tende a tornar menos distante e conflituosa uma possível solução para essa questão.