1,721,264 research outputs found
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
Long-term analysis and evaluation of complex agroforestry systems : application to cocoa agroforests in central Cameroon
No full textLa cacaoculture est aujourd'hui considérée comme un des principaux facteurs de déforestation en milieu tropical. Dans de nombreux pays, elle repose en effet sur un modèle technique peu durable de monoculture intensive impliquant le déplacement des zones de production. Souvent délaissés par la recherche en raison de leurs faibles rendements en cacao marchand, les systèmes agroforestiers à base de cacaoyer apparaissent aujourd'hui comme une alternative crédible pour faire face aux nouveaux enjeux de la cacaoculture mondiale. Au Centre-Sud du Cameroun, la cacaoculture repose en grande partie sur des cacaoyères agroforestières anciennes, ce qui pose l'hypothèse qu'un modèle de cacaoculture durable basé sur des systèmes de culture agroforestiers est possible. Notre objectif est de mieux comprendre le fonctionnement de ces systèmes agroforestiers à base de cacaoyer, à travers leurs caractéristiques, leurs évolutions et leurs déterminants, ainsi que les conditions de leur production en cacao marchand sur le long terme. Notre démarche articule à la fois une évaluation des systèmes agroforestiers complexes à l'échelle de la parcelle et une analyse compréhensive des pratiques techniques sur le temps long. La thèse repose sur un dispositif de recherche mis en place dans la région du Centre, dans trois zones de culture différenciables par leurs conditions pédo-climatiques (Bokito, Zima et Ngomedzap). Une enquête d'agriculteurs a été réalisée à grande échelle (1 171 exploitations regroupant 1 638 cacaoyères), complétée par des observations spécifiques réalisées dans un réseau de 61 cacaoyères exploitées par 40 agriculteurs. Résultats. (1) Nos résultats d'enquête, complétés par des observations spécifiques, ont confirmé la durabilité des systèmes agroforestiers à base de cacaoyer aux plans agro-écologique et socio-économique. (2) Dans la zone de transition forêt-savane, considérée comme sub-optimale pour la cacaoculture, nous avons montré que le modèle technique adopté par les agriculteurs leur permet d'installer sur savane des cacaoyères viables sur le long terme. (3) Une méthode participative de quantification de la valeur d'usage des espèces par les agriculteurs, appliquée sur le réseau d'observation, a confirmé la multifonctionnalité des systèmes agroforestiers et mesuré la place qu'y occupe la composante cacaoyère. (4) L'évaluation des peuplements cacaoyers, réalisée en adaptant la méthode de diagnostic agronomique régional aux systèmes complexes, a permis d'identifier les facteurs limitant le rendement en cacao marchand. Celui-ci s'avère étroitement lié à la structure des peuplements cacaoyers et à celle des peuplements associés. (5) Enfin, l'analyse compréhensive des pratiques des agriculteurs sur le long terme, en lien avec l'évolution technique des peuplements cacaoyers a confirmé la flexibilité des systèmes agroforestiers à base de cacaoyer. Cette flexibilité peut être traduite par des trajectoires d'évolution des pratiques et des trajectoires de structures spécifiques. Ce travail fournit une nouvelle base méthodologique pour l'analyse et l'évaluation des systèmes agroforestiers complexes. L'ensemble des résultats et des connaissances produites dans ce travail permet de formuler des propositions pour la mise au point d'un nouveau modèle technique en cacaoculture.Cocoa cultivation is generally considered as one of the main deforestation factors in the Tropics. Indeed, in many countries it is based on a low-sustainability technical model of intensive monocrops with shifting production zones. Cocoa agroforests, which are often neglected by research due to their low fermented dried cocoa yields, now appear to be a credible alternative for taking up the new challenges facing world cocoa production. In Centre-South Cameroon, cocoa cultivation is largely based on old cocoa agroforests, which suggests that a sustainable cocoa growing model based on agroforestry systems is possible. Our aim was to more effectively understand how these cocoa agroforests function, through their characteristics, their evolution and their determinants, along with the conditions for their long-term fermented dried cocoa production. Our approach consisted of an evaluation of cocoa agroforests on a plot scale and a comprehensive analysis of technical practices over the long term. The thesis is based on an experimental design set up in the Centre region, in three growing zones that could be differentiated through their pedo climatic conditions (Bokito, Zima and Ngomedzap). A large-scale survey was undertaken (1,171 farms grouping 1,638 cocoa plantations) completed by specific observations collected in a network of 61 cocoa agroforests managed by 40 farmers. Results. (1) Our survey results, completed by specific observations, confirmed the sustainability of the cocoa agroforestry systems from an agro ecological and socio-economic viewpoint. (2) In the forest-savannah transition zone, which is considered sub-optimum for cocoa cultivation, we confirmed that the technical model adopted by the farmers enabled them to set up cocoa agroforests on savannah that were viable over the long term. (3) In the network, a participatory method applied to quantify the use value given to the species by the farmers confirmed the multi-functionality of cocoa agroforests and measured the place occupied in it by cocoa. (4) The evaluation of the cocoa tree stands, achieved by adapting the regional agronomic diagnosis method to complex systems, revealed the factors limiting cocoa yield. It was proved that cocoa yield is closely linked to the structure of the cocoa tree stand and that of the intercropped stands. (5) Lastly, a comprehensive analysis of farmer practices over the long term, in association with the evolution of the technical management of the cocoa tree stands, confirmed the flexibility of cocoa agroforestry systems. This flexibility was reflected in the evolution pathways for specific practices and structures. This work provides a new methodological basis to assess the performance of complex agroforestry systems. All the results and knowledge produced by this work make it possible to draw up proposals for developing a new technical model for cocoa growing
Trade-offs between productivity and biodiversity on a management intensity gradient of cocoa-based agroforestry systems in Talamanca, Costa Rica
No full textLe cacaoyer (Theobroma cacao, L.) est cultivé dans les tropiques humides d'Amérique latine, d'Afrique et d'Asie. Principale source de revenus d'une agriculture essentiellement familiale, les systèmes agroforestiers à base de cacaoyers fournissent de nombreux services écologiques et contribuent à la conservation de la biodiversité. Ces systèmes associent plantes ligneuses et cultures de manière simultanée, dans une gamme importante et peu décrite de richesses et de structures botaniques. Les connaissances actuelles sur leur productivité se limitent à des essais en milieu contrôlé associant un petit nombre d'espèces. Nos travaux testent l'hypothèse d'une relation de compromis entre le niveau de productivité des cacaoyers et le niveau de biodiversité hébergée par les agroforêts à base de cacaoyers. Nous caractérisons ces compromis sur un gradient de situations de production paysannes, reposant sur la structure verticale, l'intensité de gestion de la composante végétale et le contexte bio-physique des agro-systèmes étudiés. Sur un dispositif de 36 cacaoyères paysannes situées dans la région de Talamanca, Costa Rica, nous montrons que des variations significatives de la structure végétale reflètent les modes de gestion de la parcelle et affectent le rendement par cacaoyer (295 à 667g/arbre/an) mais pas le rendement en cacao (136 kg/ha/an), ni le volume végétal global (400 m3/ha). Ces variations de la structure végétale affectent peu la diversité α des peuplements de plantes associées, d'épiphytes, d'amphibiens, de reptiles, de mamifères, d'invertébrés du sol et de la litière, mais leur diversité β répond de manière contrastée à ces variations d'habitat. Les relations de compromis que nous mettons finalement en évidence entre la productivité en cacao marchand à l'hectare ou à l'arbre et les niveaux de biodiversité atteints sont de nature (linéaire, cubique, quadratique) et de tendances (négative, postive) contrastées selon le taxon considéré et remettent en cause les résultats de certains travaux récents. Nos travaux dévoilent également des situations de compromis optimales, offrant des perspectives positives pour l'intensification écologique des systèmes agroforestiers tropicaux.Cacao (Theobroma cacao, L.) is cultivated in the humid tropics of Latin America, Africa and Asia. Cocoa-based agroforestry systems are the main source of income for smallholders' families and provide numerous ecological services and contribute to biodiversity conservation. These systems associate trees with crops simultaneously, in a wide and poorly described range of botanical and structural plant diversity. The current knowledge about their productivity is restricted to controlled trials with a low numer of associated plant species. Our work tests the hypothesis of a trade-off relationship between the level of cocoa productivity and the level of biodiversity hosted in cocoa-based agroforests. We characterize these trade-offs on a gradient of production situations, based on the vertical structure, the management intensity of the vegetal component and the bio-physical context of cocoa-based agroforests. On the base of a 36 on farm cocoa plots network located in Talamanca, Costa Rica, we show that significant variations in the vegetation vertical structure reflect farmer's management strategies and affect the cocoa yield per tree (295 to 667g/tree/year) but neither the cocoa yield per plot (136 kg/ha/year), nor the global plant volume (400 m3/ha). The variations in vegetation structure poorly affected the α-diversity of 7 plant and animal taxa, but their β-diversity gave contrasted and significant responses to habitat variations. Finally, the trade-offs relationships we display between dry cocoa productivity per hectare or per tree and the observed biodiversity levels showed contrasted forms (cubic, quadratic, linear) and tendances (positive, negative) according to the taxa considered and question results from recent publications. Our work also revealed optimal trade-off situations which offer positive prospects for the ecological intensification of tropical agroforestry systems
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
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Spatial estimation of a perennial crop yield in West Africa˸ mango case study in Senegal
No full textL’Afrique de l’Ouest fait face à des changements démographiques et climatiques qui mettent sous tension l’agriculture et la sécurité alimentaire. Les cultures fruitières, malgré les nombreux services écosystémiques qu’elles apportent (alimentation, biodiversité, etc.), pâtissent de faibles rendements, du fait de la faible quantité d’informations disponibles sur les systèmes (rendement, pratiques, diversité cultivée, etc.). Les objectifs de cette thèse sont de proposer des outils pour estimer le rendement du manguier (Mangifera indica L.) à différentes échelles et d’identifier les principaux facteurs de sa variabilité en Afrique de l’Ouest. Les outils ont été déployés dans la région des Niayes (Sénégal) pour analyser les rendements d’un réseau de 30 vergers de trois types de systèmes de culture (extensif, diversifié et intensif). À l’échelle de l’arbre, un outil, basé sur l’analyse d’image (par réseau de neurones) et la modélisation, a permis d’estimer la production de 300 manguiers. Le concept de ‘yield gap’ a été adapté pour calculer les ‘production gap’, c’est-à-dire l’écart entre la production atteignable de l’arbre (i.e., définie par sa structure et sa variété) et la production réelle. Cette méthode statistique a mis en évidence les effets de la variété et du système de culture sur les écarts de production. À l’échelle du verger, l’imagerie drone a été utilisée pour construire une carte d’occupation des sols et déterminer la structure des arbres du verger. Ces information ont permis et de modéliser et spatialiser la production de chaque manguier. L’estimation du rendement des vergers a permis l’étude des variabilités intra et inter-verger. Les distributions spatiales de la production et des caractéristiques des arbres apparaissent plus hétérogènes dans les vergers extensifs et diversifiés. L’utilisation du diagnostic agronomique régional a permis de déterminer les principaux facteurs d’élaboration du rendement de mangue dans la zone d’étude. Si la densité de manguier semble le principal moteur du rendement dans les vergers intensifs, les vergers diversifiés intensifie plutôt la production à l’échelle de l’arbre. Le climat, les pratiques culturales et la diversité cultivée sont également des facteurs mis en cause dans les variabilités de production. Ces travaux ouvrent de nouvelles voies méthodologiques pour pallier aux manques d’informations pour l’analyse de la production des arbres fruitiers tropicaux en Afrique de l’Ouest. Enfin, ces travaux identifient plusieurs facteurs (climat, pratique et diversité) impactant l’élaboration du rendement du manguier. L’étude de ces effets doit permettre d’améliorer durablement les pratiques et la production en Afrique de l’Ouest.West Africa faced many challenges including demographic growth and climate change that put agriculture and food security under pressure. In this context fruit trees, despite the numerous ecosystem services (food, biodiversity, soil fertility, microclimate, etc.) they provide, suffer low yields because of the low quantity of information available regarding the cropping systems (yields, practices, species diversity, planting density, etc.). The objectives of this thesis are to develop tools for mango (Mangifera indica L.) yield estimation at different scales and to identify drivers of yield variabilities in West Africa. Tools have been deployed, in 2017 and 2018, to analyse yields of 30 orchards depicting three cropping systems (extensive, diversified, and intensive) in the Niayes region (Senegal). At the tree scale, an image analysis tool (using deep learning algorithm), combined with models, allowed to accurately estimate the production of 300 mango trees. The ‘yield gap’ concept was adapted to compute the tree ‘production gap’ as the difference between attainable production (i.e., determined by the cultivar and the structure) and the actual production. The method, evidenced that the mango production was influenced by the cultivar and the cropping system. At the orchard scale, drone imagery was used to build land cover map and estimate the structure parameters of all trees in the orchard. These data allowed to model and spatialize the individual production of each mango tree. Orchard yield estimation allowed the study of the variability of within and between orchard yields. Tree production appear more spread out in the extensive and diversified orchards. Then, using regional agronomic diagnosis, we identify important drivers impacting orchard mango yield in the study area. While mango planting density is a key driver in intensive orchards, the yield of diversified orchards rely more on the tree production. The climate, the management practices, and the species diversity also induce yield variabilities. These studies, open new methodological paths to compensate the lack of data for fruit crop yields analysis in West Africa. Finally, this work identify several important drivers (climate, practices, and species diversity) impacting mango yields at different levels. More research should be done to explore the effects of these drivers to sustainably improve practices and production
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