1,721,030 research outputs found
Effect of tillage and static abiotic soil properties on microbial diversity
No full textISI Document Delivery No.: GW9QSTimes Cited: 0Cited Reference Count: 75Legrand, Fabienne Picot, Adeline Cobo-Diaz, Jose Francisco Carof, Matthieu Chen, Wen Le Floch, GaetanBrittany Region [13008022]; French Association for Research and Technology ANRT [2014/108]; Agriculture & Agri-Food Canada [97, 1134, 1136]; Government of Canada's Genomics Research and Development Initiative (GRDI) Shared Priority Project - Metagenomics Based Ecosystem Biomonitoring (Ecobiomics) [J-001263]This work was supported by the Brittany Region [Grant #13008022 Rhisotox] and the French Association for Research and Technology ANRT [Grant #2014/108]. It was certified by the Foodstuff Cluster of the Future (Valorial). The computational infrastructure was partially supported by Agriculture & Agri-Food Canada-funded projects (proposal ID #97, #1134 & #1136) and the Government of Canada's Genomics Research and Development Initiative (GRDI) Shared Priority Project - Metagenomics Based Ecosystem Biomonitoring (Ecobiomics) (J-001263).02Elsevier science bvAmsterdam1873-0272Agricultural soil microbial communities are largely impacted by agronomic practices, soil physicochemical properties and climatic conditions. To understand how these factors induce changes in fungal and bacterial communities in soil, we used a metabarcoding approach to profile the microbial communities of 31 agricultural wheat fields with maize as previous crop, representative of usual crop rotation in Brittany, France. Our results clearly highlighted the importance of tillage for both bacteria and fungi, with species richness and evenness significantly higher in fields under minimum tillage practices than in fields under conventional tillage, despite that the core microbiota was similar between fields under these two practices. The functional diversity of the bacterial communities, predicted using FAPROTAX, was also significantly higher in fields under minimum tillage notably that involved in nitrogen cycling (denitrification, respiration). We also observed that animal manure increased bacterial richness and evenness compared to chemical fertilization only. Interestingly, fungal diversity was less sensitive to disturbance than bacterial communities. We also identified taxa groups as potential bioindicators of a specific agronomic practice, such as the strong association between animal manure application and Hydrogenophaga, Mycoplana and Sphingopyxis, as well as the enrichment of oligotrophic Acidobacteria under conventional tillage
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
Contribution à la conception et l'évaluation de systèmes agricoles diversifiés, durables et résilients
No full textFonctionnement de peuplements en semis direct associant du blé tendre d'hiver (Triticum aestivum L.) à différentes plantes de couverture en climat tempéré
No full textInnovative crop management systems have to be proposed to achieve objectives of modern agriculture such as productivity, respect of the environment, and profitability. No-till crop management systems with a living cover crop are of primary interest since they can reach these objectives. If these crop management systems really present some advantages in tropical climate, they are almost unexplored in temperate climate. This work proposes to increase scientific knowledge about these particular crop management systems in order to facilitate their conception and evaluation in temperate climate.The study was based on field experiments carried out during three cash crop growing seasons in Grignon (Yvelines, France) since 2002. Treatments involved a winter wheat (Triticum aestivum L.) crop grown (i) on its own on a conventional-till soil, (ii) on its own on a no-till soil, and (iii) on a no-till soil with six different living cover crops. By associating an analytic approach to a systemic one, global aim of this work was to comprehend, according to the cover crop species, (i) the effects of the different no-till/living cover crop management systems on cash crop yield while underlying sensitivity periods to stresses for this crop, (ii) competition or facilitation for light and nitrogen between intercropped species, and (iii) short-term changes in soil structure as well as hydraulic properties.This study showed that living cover crops may reduce, sometimes importantly, wheat grain yield, depending mainly on the cover crop species, their management practices, and the climatic conditions; wheat sensitivity periods to stresses depended also on these three factors. Furthermore, the study highlighted that competition for light between intercropped species was the most detrimental process to wheat grain yield. On a short-term basis, soil structure little changed from a no-till soil without a living cover crop to a no-till soil with a living cover crop. Nevertheless, the study showed that hydraulic properties may change according to the absence or the presence of a living cover crop on a no-till soil without revealing important variations of these soil hydraulic properties from one living cover crop species to another.The work increased scientific and technical knowledge on the functioning of no-till/living cover crop management systems in temperate climate. It showed feasibility as well as risks of these crop management systems; it allowed us to identify new research axis to increase knowledge and to provide some references in order to reduce these risks.Des systèmes de culture innovants doivent être proposés pour répondre aux nouveaux objectifs de l'agriculture qui devront allier productivité, respect de l'environnement et rentabilité économique. Les systèmes de culture en semis direct sous couvert végétal (SCV) avec cultures associées permettraient d'atteindre ces objectifs. Si ces systèmes ont en effet montré des intérêts en climat tropical, ils sont presque inexistants en climat tempéré.Cette thèse se propose d'accroître les connaissances scientifiques sur ces systèmes particuliers pour faciliter leur conception et leur évaluation en climat tempéré. Le travail repose sur un dispositif expérimental mis en place à Grignon (Yvelines, France) en 2002 pour trois campagnes culturales. Du blé tendre d'hiver (Triticum aestivum L.) est semé (i) dans un sol labouré, (ii) directement dans les résidus de la culture précédente et, (iii) directement dans six plantes de couverture différentes. En combinant sur ce dispositif une double approche, systémique et analytique, les objectifs de la thèse sont de comprendre, selon l'espèce de couverture, (i) l'impact des différents SCV avec cultures associées sur le rendement de la culture de vente en mettant en évidence les phases de sensibilité aux stress de cette culture, (ii) les relations de compétition et/ou de facilitation pour l'azote et la lumière entre les espèces associées et, (iii) l'évolution, à court terme, de la structure du sol et de ses propriétés hydriques.Ce travail montre que la présence d'une plante de couverture peut réduire, parfois fortement, le rendement de la culture de vente, différemment selon l'espèce de couverture, sa conduite technique et les conditions climatiques ; les phases d'élaboration du rendement qui sont perturbées dans ces situations culturales dépendent aussi de ces trois facteurs. De plus, l'étude met en évidence que la compétition pour le rayonnement lumineux entre les espèces associées est le processus le plus défavorable au rendement du blé.A court terme, il n'apparaît pas de différences marquées entre la structure d'un sol non travaillé sans plante de couverture et celle d'un sol non travaillé avec une plante de couverture. Toutefois, l'étude révèle que les propriétés hydriques peuvent être modifiées selon l'absence ou la présence d'une plante de couverture sur un sol non travaillé sans démontrer de variations importantes de ces propriétés selon l'espèce de couverture.La thèse fournit des informations scientifiques et techniques sur le fonctionnement, en climat tempéré, de peuplements associant sur un sol non travaillé, une culture de vente à différentes plantes de couverture. Elle montre la faisabilité mais aussi les risques des SCV avec cultures associées ; elle permet d'identifier des axes de recherche pour compléter les connaissances et fournir des références pour réduire ces risques
Fonctionnement de peuplements en semis direct associant du blé tendre d'hiver (Triticum aestivum L.) à différentes plantes de couverture en climat tempéré
No full textInnovative crop management systems have to be proposed to achieve objectives of modern agriculture such as productivity, respect of the environment, and profitability. No-till crop management systems with a living cover crop are of primary interest since they can reach these objectives. If these crop management systems really present some advantages in tropical climate, they are almost unexplored in temperate climate. This work proposes to increase scientific knowledge about these particular crop management systems in order to facilitate their conception and evaluation in temperate climate.The study was based on field experiments carried out during three cash crop growing seasons in Grignon (Yvelines, France) since 2002. Treatments involved a winter wheat (Triticum aestivum L.) crop grown (i) on its own on a conventional-till soil, (ii) on its own on a no-till soil, and (iii) on a no-till soil with six different living cover crops. By associating an analytic approach to a systemic one, global aim of this work was to comprehend, according to the cover crop species, (i) the effects of the different no-till/living cover crop management systems on cash crop yield while underlying sensitivity periods to stresses for this crop, (ii) competition or facilitation for light and nitrogen between intercropped species, and (iii) short-term changes in soil structure as well as hydraulic properties.This study showed that living cover crops may reduce, sometimes importantly, wheat grain yield, depending mainly on the cover crop species, their management practices, and the climatic conditions; wheat sensitivity periods to stresses depended also on these three factors. Furthermore, the study highlighted that competition for light between intercropped species was the most detrimental process to wheat grain yield. On a short-term basis, soil structure little changed from a no-till soil without a living cover crop to a no-till soil with a living cover crop. Nevertheless, the study showed that hydraulic properties may change according to the absence or the presence of a living cover crop on a no-till soil without revealing important variations of these soil hydraulic properties from one living cover crop species to another.The work increased scientific and technical knowledge on the functioning of no-till/living cover crop management systems in temperate climate. It showed feasibility as well as risks of these crop management systems; it allowed us to identify new research axis to increase knowledge and to provide some references in order to reduce these risks.Des systèmes de culture innovants doivent être proposés pour répondre aux nouveaux objectifs de l'agriculture qui devront allier productivité, respect de l'environnement et rentabilité économique. Les systèmes de culture en semis direct sous couvert végétal (SCV) avec cultures associées permettraient d'atteindre ces objectifs. Si ces systèmes ont en effet montré des intérêts en climat tropical, ils sont presque inexistants en climat tempéré.Cette thèse se propose d'accroître les connaissances scientifiques sur ces systèmes particuliers pour faciliter leur conception et leur évaluation en climat tempéré. Le travail repose sur un dispositif expérimental mis en place à Grignon (Yvelines, France) en 2002 pour trois campagnes culturales. Du blé tendre d'hiver (Triticum aestivum L.) est semé (i) dans un sol labouré, (ii) directement dans les résidus de la culture précédente et, (iii) directement dans six plantes de couverture différentes. En combinant sur ce dispositif une double approche, systémique et analytique, les objectifs de la thèse sont de comprendre, selon l'espèce de couverture, (i) l'impact des différents SCV avec cultures associées sur le rendement de la culture de vente en mettant en évidence les phases de sensibilité aux stress de cette culture, (ii) les relations de compétition et/ou de facilitation pour l'azote et la lumière entre les espèces associées et, (iii) l'évolution, à court terme, de la structure du sol et de ses propriétés hydriques.Ce travail montre que la présence d'une plante de couverture peut réduire, parfois fortement, le rendement de la culture de vente, différemment selon l'espèce de couverture, sa conduite technique et les conditions climatiques ; les phases d'élaboration du rendement qui sont perturbées dans ces situations culturales dépendent aussi de ces trois facteurs. De plus, l'étude met en évidence que la compétition pour le rayonnement lumineux entre les espèces associées est le processus le plus défavorable au rendement du blé.A court terme, il n'apparaît pas de différences marquées entre la structure d'un sol non travaillé sans plante de couverture et celle d'un sol non travaillé avec une plante de couverture. Toutefois, l'étude révèle que les propriétés hydriques peuvent être modifiées selon l'absence ou la présence d'une plante de couverture sur un sol non travaillé sans démontrer de variations importantes de ces propriétés selon l'espèce de couverture.La thèse fournit des informations scientifiques et techniques sur le fonctionnement, en climat tempéré, de peuplements associant sur un sol non travaillé, une culture de vente à différentes plantes de couverture. Elle montre la faisabilité mais aussi les risques des SCV avec cultures associées ; elle permet d'identifier des axes de recherche pour compléter les connaissances et fournir des références pour réduire ces risques
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
Economic and environmental benefits from crop-livestock complementarities through local legume production : a modelling approach for western France
No full textCette thèse de doctorat porte sur les complémentarités culture-élevage permises par les légumineuses, dans la région de l'Ouest de la France. Une évaluation économique et environnementale de ces complémentarités est réalisée depuis l’échelle de l’exploitation agricole jusqu’à celle de la région.Le principal apport de cette thèse est l’élaboration d’un modèle bioéconomique SYNERGY qui modélise les échanges locaux de cultures (dont les légumineuses) et d’effluents entre des exploitations de grandes cultures et des exploitations d'élevage. Ce modèle prend en compte l’effet précédent des légumineuses et comprend des rations alternatives avec ces cultures riches en protéines. Les principaux résultats de simulation montrent que les aides couplées aux légumineuses accroissent leurproduction mais n’engendrent pas une meilleure valorisation des complémentarités techniques. Un moyen d’accroître l'utilisation de légumineuses en alimentation animale est de labelliser les produits animaux sans OGM. Cependant, les échanges locaux simulés restant faibles, les légumineuses sont en grande partie importées de l’extérieur de la région. Ainsi, les résultats économiques et environnementaux ne sont pas améliorés à l’échelle régionale et l'autonomie en protéines diminue. Enfin, à l’échelle des filières, nous montrons que les échanges de légumineuses engendrent des coûts de transaction élevés, peu réduits par les contrats existants. Le développement de marchés valorisant les ressources locales pourrait encourager la culture de légumineuses.This Ph.D. thesis studies crop-livestock complementarities enabled by legumes in the region of western France. Economic and environmental assessment of these complementarities is performed from the farm scale to the regional scale. The main contribution of this research is the development of the bio-economic model SYNERGY, which represents local exchanges of crops (including legumes) and manure between crop-oriented farms and livestock-oriented farms. This model represents the pre-crop effect of legumes and includes alternative rations with these high-protein crops. The main simulation results show that coupled subsidies to legumesincrease their production but do not lead to better valuation of technical complementarities. One way to increase the use of legumes in animal feed is to label GMO-free animal products. However, since the simulated local exchanges of legumes remain low, these crops are largely imported from outside the region. Thus, the economic and environmental results do not improve at the regional scale, and protein self-sufficiency decreases.Finally, at the scale of the agro-food chain, exchanges of legumes lead to high transaction costs, which current contracts reduce only slightly. Developing markets that value local resources could foster legume production.increase their production but do not lead to better valuation of technical complementarities. One way to increase the use of legumes in animal feed is to label GMO-free animal products. However, since the simulated local exchanges of legumes remain low, these crops are largely imported fro
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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