1,721,145 research outputs found
Monitoring mangrove change using very high spatial resolution satellite images for coastal zone management
No full textLa situation des mangroves dans le monde reste préoccupante malgré la prise de conscience de leur rôle dans le maintien de la biodiversité côtière. Les pratiques non durables de l’aquaculture extensive sont toujours majoritairement mises en cause. Le besoin d’une meilleure gestion côtière se fait sentir depuis une vingtaine d’années. Il faut reconnaitre que les avancées restent insuffisantes, particulièrement en Indonésie. Ce travail de thèse a été réalisé dans le cadre du projet INDESO. Ses objectifs étaient de décrire les changements dans les mangroves en termes de superficie, de structuration ou de composition spécifique afin d’étudier, à fine échelle spatiale, la diversité des peuplements de palétuviers, leur capacité de régénération et les tendances d’évolution de l’écosystème. Pour cela, j’ai utilisé 28 images satellitaires de télédétection optique à très haute résolution spatiale (THRS) acquises dans la période de 2001 à 2015 sur deux sites d’étude, Bali, Indonésie. J’ai participé aux inventaires forestiers et à l’identification des espèces de palétuviers du stade plantule au stade adulte. J’ai procédé par analyse visuelle des images pour différencier les plantations de palétuviers des forêts naturelles. J’ai examiné les différences entre les signatures spectrales des différentes formations de palétuviers en fonction des configurations angulaires. J’ai réalisé sur chaque image une classification supervisée qui m’a permis de comptabiliser avec une précision de quelques mètres carrés la superficie occupée par les mangroves et d’évaluer la robustesse d’une cartographie à fine échelle de zonations de mangroves.Les résultats obtenus sur l’estuaire du Perancak dégradé par l’aquaculture montrent que la surface de mangrove augmente après 2001 mais que les pratiques de plantations dans cette région n’ont rien à voir avec la réhabilitation de mangroves. Des différences majeures entre plantations et forêts naturelles existent. Ces plantations sont des cultures à très forte densité de Rhizophora, alors que les faciès naturels sont dominés par Avicennia et Sonneratia. Nos résultats montrent que la capacité de régénération dans ces plantations reste très inférieure à celle observée dans les forêts naturelles et que, si régénération il y a, c’est avec des plantules des espèces natives. A partir de l’analyse des imges, nous avons identifié les 136 bassins qui ont fait l’objet de plantations et donné l’année du semis. Le suivi de l’évolution du nombre de pixels classés ‘mangrove’ à l’intérieur de chaque bassin planté montre une grande variabilité des taux d’expansion sur 14 ans, ceci suggérant des conditions environnementales spécifiques à chaque bassin et donc l’inconséquence des pratiques généralisées de plantations à Rhizophora. Enfin, les capacités de colonisation des espèces natives y compris à l’intérieur de certains bassins semblent avérées dans cet estuaire pourtant très fragmenté. Les résultats obtenus sur les mangroves protégées de la région de Nusa Lembongan montrent le potentiel des images multi-spectrales satellitaires THRS pour cartographier différentes zonations de mangroves. Ce potentiel de discrimination est observé assez stable au cours du temps entre 4 espèces. Toutefois, des configurations angulaires avec un soleil de face ou un angle de visée proche de la verticale pourraient générer de la confusion notamment sur les peuplements à canopée ouverte. Nous avons obtenu probablement les premières cartes de mangrove de Nusa Lembongan qui montrent la complexité des zonations forestières et soutiennent l’enjeu de leur protection.L’ensemble de mon travail plaide pour une meilleure interprétation physique de la variabilité des signatures spectrales et texturales de mangrove. Il fournit des recommandations comme la nécessité d’un moratoire sur les monocultures à Rhizophora et des méthodes simples, embryons de futurs observatoires locaux pour l’évaluation et le suivi des plans de gestion côtière mis en place.The situation of world’s mangroves remains a matter of concern, despite the public awareness about their role in the sustainability of coastal biodiversity. Extensive and intensive aquaculture practies are mainly called into question. The need for a better integrated coastal zone management arises since a couple of decades. It must be recognized that progress is insufficient especially in Indonesia.The present PhD work has been carried out in the frame of the INDESO project. The objective was to describe mangrove changes in terms of area expansion, forest structure and species composition before studying, at fine scales, the diversity of mangrove stands, their regeneration capacity and the evolution trends of the whole ecosystem in a given region.In order to achieve this aim, i used 28 very high spatial resolution (VHSR) optical satellite images aquired between 2001 and 2015. I also participated in forest inventories and species identification from the seedling to the adult stages. I visually analysed the set of images for allowing the discrimination of planted mangroves from natural ones. I examined the influence of acquisition geometry parameters on the variability of mangrove spectral signatures. Thanks to supervised maximum likelihood classifications, I succeeded in evaluating the expansion area of mangrove with an accurracy of few square meters and I proceeded in assessing the robustness of fine scale mapping of mangrove zonations.Results obtained in the analysis of the Perancak estuary highlighted that mangrove area is expanding since 2001. The plantation practices were however presented as disrespectful of any sustainable management plan. Indeed, our simple field data indicated strong differences between mangrove plantations and natural forests. Plantations were shown to be cultures of only Rhizophora species with high planting density whereas natural forest stands are composed of Sonneratia and Avicennia mangrove trees. In addition, we highlighted that the regeneration capacity in planted areas remains very lower than the ones clearly observed in natural areas. Moreover, the only regenetive process in plantations seems to be with native species and not with the planted ones. From the analysis of the VHSR images, we identified aquaculture ponds that were planted and their planting year. Consequently, we suceeded in monitoring the mangrove expansion inside every planted pond. Important variability of expansion rate was pointed out, this suggesting contrasting environments in each pond and the inadequacy of cultures of Rhizophora everywhere. The observation of natural colonization in many areas of the estuary, pond floors included, was an interesting point to mention.Besides, results obtained in the study of the protected mangrove region of Nusa Lembongan assessed the potential of multispectral VHSR satellite images for mapping mangrove zonations. Four mangrove zonations mainly dominated by different species exhibit signatures that can be differentiated over years. Different image acquisition parameters may, however, generate confusion in classification. This is particularyly true when forest stands with open canopies are observed with sun frontward or with a near vertical viewing angle because of sun light interaction with the clear waters. We probably obtained the first detailed maps of mangrove zonations in the region. They showed a complex spatial organization of mangrove zonations.The whole of my work advocated for further remote sensing works aiming at the physical interpretation of spectral and textural signatures of mangroves. It provided recommendations such as a moratorium onf Rhizophora plantation and simple methods that will be, we hope, starting points for closing the knowledge gap that hampers monitoring of future coastal zone management plans
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Towards better biomass predictions using 3D radiative transfer modeling at very fine scale
No full textInternational audienc
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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