1,721,127 research outputs found
Nitrous oxide emissions from agricultural land use in Germany - a synthesis of available annual field data
No full textThe nations that have ratified the Kyoto Protocol must set up an appropriate national inventory on N2O emissions from agricultural land use, in order to report properly on the achievements made in reducing greenhouse-gas emissions. The search for the appropriate method is a controversial topic as it is subject to high uncertainty in particular associated to the upscaling from site measurements. In this study, all available data from Germany on annual N2O-emission rates derived from field experiments of at least an entire year are summarized. From each study, only differences in soil properties on N input qualified as an individual data set. Under these premises, 101 treatments from 27 sites were found equally spread across Germany. The annual N application ranged from 0 to 400 kg N ha(-1) and the annual emission rates from 0.04 to 17.1 kg ha(-1). Annual emission factors (EFs), uncorrected for background emission, varied considerably from 0.18% to 15.54% of N applied. There was no nationwide correlation found for the relationship between N2O losses and N application, soil C, soil N, soil texture, or soil pH. However, site-specific trends in the relationship between emission factor and mean soil aeration status, as expressed by the soil type and/or mean climatic conditions, were revealed. Regularly water-logged soils were characterized by low emission factors as were soils from the drier regions (2O emissions from agricultural land use on the national scale, there must be a biological adaptation to mean site conditions, i.e., different microbial communities react differently to similar actual conditions in terms of N2O dynamics. Regardless of the point of view, the chapter on N2O Soil dynamics cannot be closed yet, and new additional model concepts, process studies, and field measurements are needed. [References: 59
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Biodiversity in European agricultural landscapes: transformative societal changes needed
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Biogenic Greenhouse Gas Emissions from Agriculture in Europe - Quantification and Mitigation
Full text linkDie Dissertation analysiert Klimaschutzmaßnahmen in der europäischen Landwirtschaft im Hinblick auf Potentiale, Umweltwirkungen, Minderungskosten und damit verbundene Unsicherheiten im Hinblick auf die Umsetzung des Kyoto-Protokolls. Dazu werden Literaturstudien durchgeführt, Lebensweganalysen und Treibhausgasinventare methodisch weiterentwickelt und schließlich Treibhausgasemissionen und deren Minderungspotential auf europäischer Ebene berechnet und bewertet.
Die europäische Landwirtschaft emittierte im Jahr 1995 0.84 ± 0.29 Tg N2O, 8.1 ± 1.9 Tg Methan (CH4) und 39 Tg ± 25 Kohlendioxid (CO2), insgesamt 470 ± 80 Tg CO2-Äquivalente oder 11 % der gesamten anthropogenen Treibhausgase der EU. Die hier entwickelte Berechnungsmethodik bildet regionale Charakteristika der landwirtschaftlichen Produktion ab und halbiert die methodische Unsicherheit gegenüber den offiziellen nationalen Inventaren.
Landwirtschaftliche Böden Europas werden kurzfristig maximal etwa 200 Tg a-1 CO2 aufnehmen können, wobei entsprechende Maßnahmen auch andere positive Umweltwirkungen zeigen. Das biologische Substitutionspotential von Bioenergie in der EU liegt zwischen 400 und 800 Tg a-1 CO2-Äquivalente. Aus Umweltaspekten heraus sollten perenne, holzige Kulturen statt annuelle Intensivkulturen genutzt werden. Das Minderungspotential der technischen Maßnahmen zur direkten Treibhausgasminderung liegt zwischen 100 und 200 Tg a-1 CO2-Äquivalenten, z.B. durch eine Extensivierung der Pflanzenproduktion mit reduziertem Einsatz von Stickstoff bzw. technologische Innovation im Bereich der Tierhaltung, die möglichst von einem Abbau der Tierzahlen flankiert wird, sowie die Wiedervernässung von gedränten Moorböden. Eine Veränderung der sozioökonomischen und politischen Rahmenbedingungen kann das Minderungspotential erhöhen.This dissertation analyses relevant potential mitigation strategies of biogenic greenhouse gases (GHGs) in the agriculture of the European Union (EU) in light of the Kyoto Protocol. It identifies where important sources and mitigation potentials are located and what uncertainty, environmental ancillary effects and costs are associated with them. Literature reviews are performed and methodologies for environmental assessment and GHG accounting are further developed. On this basis, GHG emissions are quantified and reduction potentials are assessed at European level.
In 1995, European agriculture emitted 0.84 ± 0.29 Tg N2O, 8.1 ± 1.9 Tg methane (CH4) and 39 Tg ± 25 carbon dioxide (CO2), which adds up to 470 ± 80 Tg CO2-equivalents or 11% of the overall anthropogenic greenhouse gas emissions of the EU. The detailed methodology developed here adequately resolves regional specifics of agricultural conditions and reduces the methodological uncertainty in the estimates to half of the one in the official national inventories.
European agricultural soils will at maximum sequester carbon in the order of 100 Tg a-1 CO2 over the coming years, which may also provide other environmental benefits. The biological potential of bioenergy in the EU allows to substitute for 400 to 800 Tg a-1 CO2-equivalents. From an environmental perspective, the use of perennials, especially of residues and woody biomass, is preferable to intensively grown annual crops. The biological potential for technical GHG reduction measures in EU agriculture is between 100 and 200 Tg a-1 CO2-equivalents. Promising measures promote the extensivation of arable cropping by reducing nitrogen inputs, technological innovation in animal husbandry, which is best accompanied by a further decline in animal numbers, as well as rewetting drained organic soils. Most measures will provide ancillary environmental benefits. Changing the socio-economic and political frame conditions may enhance the GHG mitigation potential
Towards greenhouse gas management: can management intensity help identify priorities for greenhouse gas mitigation?
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