342 research outputs found
Assessing the Equivalence of the Scientific Literacy tests at the Secondary Level I
Vor dem Hintergrund der verschiedenen nationalen und internationalen Tests, die in Deutschland zur Messung der naturwissenschaftlichen Kompetenz eingesetzt werden, stellt sich die Frage nach einer wechselseitigen Verbindung ihrer Ergebnisse. In der vorliegenden Dissertation wurde die Möglichkeit einer Übertragung der Kompetenzstufen des PISA-Tests zur Erfassung naturwissenschaftlicher Grundbildung und der Tests zur Überprüfung des Erreichens der Bildungsstandards in den Fächern Biologie, Chemie und Physik für den Mittleren Schulabschluss auf die Testergebnisse des NEPS-Naturwissenschaftstests für die neunte Klasse untersucht. Dazu wurde der Ansatz von Kolen und Brennan genutzt, dessen Fokus beim Vergleich der Testinstrumente auf den Schlussfolgerungen, Zielpopulationen, Messintentionen und Konstrukten liegt. Der letzte Aspekt kann im Rahmen des kulturvergleichenden Ansatzes von van de Vijver in Bezug auf die konzeptionelle Äquivalenz, dimensionale Äquivalenz und die Skalenäquivalenz der Testinstrumente beurteilt werden. Zur wechselseitigen Verbindung der NEPS-Skala mit den Skalen von PISA 2012 und dem Ländervergleich 2012 (LV) wurde eine Linking-Studie durchgeführt, in der Schülerinnen und Schüler die Aufgaben aus allen drei Studien bearbeitet haben. Die Analysen zeigten eine hohe Vergleichbarkeit des NEPS-Tests mit den PISA- und LV-Testinstrumenten hinsichtlich ihrer Rahmenkonzeption, der faktoriellen Struktur der Daten sowie der Verteilung von Kompetenzwerten. Das Linking erfolgte mittels Equipercentile Equating und zeigte eine hohe Übereinstimmung des NEPS-Testinstruments mit den PISA- und LV-Testinstrumenten in der Verteilung der Personen auf die PISA- und LV-Kompetenzstufen.Several national and international tests are used in Germany to assess the scientific literacy of 9th grade students. Hence the question arises whether the different tests can be conceptually linked and the results transferred into each other. The present dissertation examined the possibility of transferring the proficiency scales of the PISA scientific literacy test and the tests of the German National Assessment Study in Science (LV) to the Grade 9 NEPS scientific literacy. For this purpose we used the approach of Kolen and Brennan focusing on the comparison of the test instruments with regard to the inferences, target populations, measurement conditions and constructs. The last aspect can be assessed in terms of the conceptual equivalence, dimensional equivalence and scale equivalence of the test instruments in the context of van de Vijver's cross-cultural approach. A linking study was conducted in which students worked on the tasks from all three studies to link the NEPS scale with the scales of PISA 2012 and LV 2012. The analyses showed a high comparability of the NEPS test with the PISA and LV test instruments with regard to their framework, the factorial structure of the data and the distribution of competence scores. Linking was done using Equipercentile Equating and showed a high degree of agreement between the NEPS test instrument and the PISA and LV test instruments in the distribution of individuals to the PISA and LV competency levels
Modelling forest recolonization by an epiphytic lichen using a landscape genetic approach
The process of recolonization after disturbance is crucial for the persistence and dynamics of patch-tracking metapopulations. We developed a model to compare the spatial distribution and spatial genetic structure of the epiphytic lichen Lobaria pulmonaria within the perimeter of two reconstructed 19th century disturbances with a nearby reference area without stand-level disturbance. Population genetic data suggested that after stand-replacing disturbance, each plot was colonized by one or a few genotypes only, which subsequently spread clonally within a local neighborhood. The model (cellular automaton) aimed at testing the validity of this interpretation and at assessing the relative importance of local dispersal of clonal propagules vs. long-distance dispersal of clonal and/or sexual diaspores. A reasonable model fit was reached for the empirical data on host tree distribution, lichen distribution, and tree- and plot-level genotype diversity of the lichen in the reference area. Although model calibration suggested a predominance of local dispersal of clonal propagules, a substantial contribution of immigration of non-local genotypes by long-distance dispersal was needed to reach the observed levels of genotype diversity. The model could not fully explain the high degree of clonality after stand-replacing disturbance, suggesting that the dispersal process itself may not be stationary but depend on the ecological conditions related to disturbanc
An ecological connectivity network maintains genetic diversity of a flagship wildflower, Pulsatilla vulgaris
Ecological connectivity networks have been proposed as an efficient way to reconnect communities in fragmented landscapes. Yet few studies have evaluated if they are successful at enhancing actual functional connectivity (i.e. realized dispersal or gene flow) of focal species, or if this enhanced connectivity is enough to maintain genetic diversity and fitness of plant populations. Here we test the efficacy of an ecological connectivity network implemented in southern Germany since 1989 to reconnect calcareous grassland fragments through rotational shepherding. We genotyped 1449 individuals from 57 populations and measured fitness-related traits in 10 populations of Puisatilla vulgaris, a flagship species of calcareous grasslands in Europe. We tested if the shepherding network explained functional connectivity in P. vulgaris and if higher connectivity translated to higher genetic diversity and fitness of populations. We found that population-specific F-st was lowest in populations that had high connectivity within the shepherding network, and that well-connected populations within the network had significantly higher genetic diversity than ungrazed and more isolated grazed populations. Moreover, genetic diversity was significantly positively correlated with both seed set and seed mass. Together our results suggest that the implementation of an ecological shepherding network is an effective management measure to maintain functional connectivity and genetic diversity at the landscape scale for a calcareous grassland specialist. Populations with reduced genetic diversity would likely benefit from inclusion, or better integration into the ecological connectivity network. Our study demonstrates the often postulated but rarely tested sequence of positive associations between connectivity, genetic diversity, and fitness at the landscape scale, and provides a framework for testing the efficacy of ecological connectivity networks for focal species using molecular genetic tools.Peer reviewe
Validation study for the addition of Cicer arietinum (Desi type) as a species to which the conductivity test for seed vigour can be applied to support Rules proposal C.15.1
The conductivity test identified differences in field emergence of 11 seed lots of the Desi type of chickpea (Cicer arietinum). Six of these seed lots, all having a laboratory germination of more than 85%, were tested by four laboratories using the electrical conductivity test, as described in the ISTA Rules (ISTA 2015). All laboratories consistently identified the same significant differences in the seed lot conductivity and the results were repeatable within laboratories and reproducible between laboratories. This provides evidence in support of the addition of Cicer arietinum (Desi type), to the ISTA Rules as a species for which the conductivity test can be applied.EEA OliverosFil: Khajeh-Hosseini, Mohammad. University of Mashhad. Faculty of Agriculture. Department of Crop Science,Ferdowsi; IránFil: Gallo, Carina Del Valle. Instituto Nacional de TecnologĂa Agropecuaria (INTA). EstaciĂłn Experimental Agropecuaria Oliveros; ArgentinaFil: Wagner, Marie-Helene. Station Nationale d’Essais de Semences; FranciaFil: Ilbi, Hulya. Ege University. Faculty of Agriculture. Department of Horticulture; TurquĂ
Growth dynamics after historic disturbance in a montane forest and its implications for an endangered epiphytic lichen
Bolli J.C., Wagner H.H., Kalwij J.M., Werth S., Cherubini P., Scheidegger C. and Rigling A. 2008. Growth dynamics after historic disturbance in a montane forest and its implications for an endangered epiphytic lichen. Bot. Helv. 118: 111 - 127. Endangered forest species are often negatively affected by disturbances, which may have long-lasting effects on the distribution, abundance and genetic diversity of such species. To understand the effects of historic disturbances, detailed knowledge of the conditions for survival and recolonisation is needed, and this requires precise information on the perimeter and severity of historic disturbance events. We reconstructed a major historic disturbance (intensive logging followed by windthrow and fire in 1871) in the Swiss Jura mountains to analyse its effect on the disturbance-sensitive epiphytic lichen Lobaria pulmonaria. Tree-ring analysis of old and young Norway spruce trees (Picea abies L.), sampled systematically on a 100 m grid, revealed that (1) the disturbance was of intermediate severity, (2) a large, well-defined area of disturbance was created, and (3) an undisturbed zone remained in the centre of the disturbed area. Acomparison with lichen genetic data from a previous survey revealed that genetic diversity was particularly high in the remnant zone. These results suggest that the lichen survived there, and that it re-colonised the disturbed area both from the edge and from the remnant undisturbed zone. This illustrates that a detailed reconstruction of historic disturbances, as achieved with dendroecology, is very important for understanding the recolonisation process and thus, the conditions for the long-term persistence of disturbance-sensitive species in a dynamic landscap
Spatial and Seasonal Patterns of Cattle Habitat use in a Mountain Wooded Pasture
Management-oriented models of cattle habitat use often treat grazing pressure as a single variable summarizing all cattle activities. This paper addresses the following questions: How does the spatial pattern of cattle effects vary between cattle activities in a highly heterogeneous landscape? Do these patterns change over the grazing season as forage availability decreases? What are the respective roles of natural and management-introduced structures? We estimated the intensity of herbage removal, dung deposition and trampling after each of three grazing periods on a grid of 25mĂ—25m cells covering an entire paddock in the Swiss Jura Mountains. We found no significant positive correlations between cattle effects. Spatial patterns weakened through the season for grazing and trampling, whereas dunging patterns changed little between grazing periods. Redundancy analysis showed that different cattle effects were correlated with different environmental variables and that the importance of management-introduced variables was highest for herbage removal. Autocorrelograms and partial redundancy analyses using principal coordinates of neighbour matrices suggested that dunging patterns were more coarse-grained than the others. Systematic differences in the spatial and seasonal patterns of cattle effects may result in complex interactions with vegetation involving feedback effects through nutrient shift, with strong implications for ecosystem management. In heterogeneous environments, such as pasture-woodland landscapes, spatially explicit models of vegetation dynamics need to model cattle effects separatel
Spatial and Seasonal Patterns of Cattle Habitat use in a Mountain Wooded Pasture
Management-oriented models of cattle habitat use often treat grazing pressure as a single variable summarizing all cattle activities. This paper addresses the following questions: How does the spatial pattern of cattle effects vary between cattle activities in a highly heterogeneous landscape? Do these patterns change over the grazing season as forage availability decreases? What are the respective roles of natural and management-introduced structures? We estimated the intensity of herbage removal, dung deposition and trampling after each of three grazing periods on a grid of 25 m Ă— 25 m cells covering an entire paddock in the Swiss Jura Mountains. We found no significant positive correlations between cattle effects. Spatial patterns weakened through the season for grazing and trampling, whereas dunging patterns changed little between grazing periods. Redundancy analysis showed that different cattle effects were correlated with different environmental variables and that the importance of management-introduced variables was highest for herbage removal. Autocorrelograms and partial redundancy analyses using principal coordinates of neighbour matrices suggested that dunging patterns were more coarse-grained than the others. Systematic differences in the spatial and seasonal patterns of cattle effects may result in complex interactions with vegetation involving feedback effects through nutrient shift, with strong implications for ecosystem management. In heterogeneous environments, such as pasture-woodland landscapes, spatially explicit models of vegetation dynamics need to model cattle effects separately
Exploration of the Windward Passage and Jamaica Channel: Tectonic Gateways to the Caribbean Sea
The Ocean Exploration Trust (OET) Workshop on Telepresence-Enabled Exploration of the Caribbean Region was convened in November 2012 to plan for the 2013 field season with the idea that Exploration Vessel (E/V) Nautilus and its Corps of Exploration would spend only one year working in the Gulf of Mexico and the Caribbean Sea. However, the strong showing of interest in the area from the international group of marine scientists who submitted white papers to and participated in that workshop was so impressive the Trust and its Nautilus Advisory Board decided to schedule a second year in this area of the world before moving on to the Pacific Ocean, as originally planned.
This fifth Oceanography supplement chronicles the 2014 field season: four months of exploration in the Gulf of Mexico and the Caribbean Sea, as well as rapid growth in our science, technology, engineering, and mathematics (STEM) education and outreach programs and continued research on best practices of telepresence and archaeological oceanography
QUANTIFYING DISPERSAL AND ESTABLISHMENT LIMITATION IN A POPULATION OF AN EPIPHYTIC LICHEN
Dispersal is a process critical for the dynamics and persistence of metapopulations, but it is difficult to quantify. It has been suggested that the old-forest lichen Lobaria pulmonaria is limited by insufficient dispersal ability. We analyzed 240 DNA extracts derived from snow samples by a L. pulmonaria-specific real-time PCR (polymerase chain reaction) assay of the ITS (internal transcribed spacer) region allowing for the discrimination among propagules originating from a single, isolated source tree or propagules originating from other locations. Samples that were detected as positives by real-time PCR were additionally genotyped for five L. pulmonaria microsatellite loci. Both molecular approaches demonstrated substantial dispersal from other than local sources. In a landscape approach, we additionally analyzed 240 snow samples with real-time PCR of ITS and detected propagules not only in forests where L. pulmonaria was present, but also in large unforested pasture areas and in forest patches where L. pulmonaria was not found. Monitoring of soredia of L. pulmonaria transplanted to maple bark after two vegetation periods showed high variance in growth among forest stands, but no significant differences among different transplantation treatments. Hence, it is probably not dispersal limitation that hinders colonization in the old-forest lichen L. pulmonaria, but ecological constraints at the stand level that can result in establishment limitation. Our study exemplifies that care has to be taken to adequately separate the effects of dispersal limitation from a limitation of establishment
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