Search

Your search keyword '"Dubiez A"' showing total 656 results
Start Over Author "Dubiez A"
656 results on '"Dubiez A"'

2. 40 years of forest dynamics and tree demography in an intact tropical forest at M’Baïki in central Africa

Author

Fabrice Bénédet, Sylvie Gourlet-Fleury, Félix Allah-Barem, Fidèle Baya, Denis Beina, Guillaume Cornu, Luc Dimanche, Émilien Dubiez, Éric Forni, Vincent Freycon, Frédéric Mortier, Dakis-Yaoba Ouédraogo, Nicolas Picard, Vivien Rossi, Olivia Semboli, Yves Yalibanda, Olga Yongo-Bombo, and Adeline Fayolle

Subjects
Science
Abstract

Abstract A vast silvicultural experiment was set up in 1982 nearby the town of M’Baïki in the Central African Republic to monitor the recovery of tropical forests after disturbance. The M’Baïki experiment consists of ten 4-ha Permanent Sample Plots (PSPs) that were assigned to three silvicultural treatments in 1986 according to a random block design. In each plot, all trees with a girth at breast height greater than 30 cm were spatially located, numbered, measured, and determined botanically. Girth, mortality and newly recruited trees, were monitored almost annually over the 1982–2022 period with inventory campaigns for 35 years. The data were earlier used to fit growth and population models, to study the species composition dynamics, and the effect of silvicultural treatments on tree diversity and aboveground biomass. Here, we present new information on the forest stand structure dynamics and tree demography. The data released from this paper cover the three control plots and constitute a major contribution for further studies about the biodiversity of intact tropical forests.

Published
2024
Full Text
View/download PDF

5. Structural basis for competitive binding of productive and degradative co-transcriptional effectors to the nuclear cap-binding complex

Author

Etienne Dubiez, Erika Pellegrini, Maja Finderup Brask, William Garland, Anne-Emmanuelle Foucher, Karine Huard, Torben Heick Jensen, Stephen Cusack, and Jan Kadlec

Subjects
CP: Molecular biology, Biology (General), QH301-705.5
Abstract

Summary: The nuclear cap-binding complex (CBC) coordinates co-transcriptional maturation, transport, or degradation of nascent RNA polymerase II (Pol II) transcripts. CBC with its partner ARS2 forms mutually exclusive complexes with diverse “effectors” that promote either productive or destructive outcomes. Combining AlphaFold predictions with structural and biochemical validation, we show how effectors NCBP3, NELF-E, ARS2, PHAX, and ZC3H18 form competing binary complexes with CBC and how PHAX, NCBP3, ZC3H18, and other effectors compete for binding to ARS2. In ternary CBC-ARS2 complexes with PHAX, NCBP3, or ZC3H18, ARS2 is responsible for the initial effector recruitment but inhibits their direct binding to the CBC. We show that in vivo ZC3H18 binding to both CBC and ARS2 is required for nuclear RNA degradation. We propose that recruitment of PHAX to CBC-ARS2 can lead, with appropriate cues, to competitive displacement of ARS2 and ZC3H18 from the CBC, thus promoting a productive rather than a degradative RNA fate.

Published
2024
Full Text
View/download PDF

7. Effect of helium as process gas on laser powder bed fusion of Ti-6Al-4V studied with operando diffraction and radiography

Author

Camille Pauzon, Steven Van Petegem, Eduard Hryha, Cynthia Sin Ting Chang, Samy Hocine, Helena Van Swygenhoven, Charlotte de Formanoir, and Sophie Dubiez-Le Goff

Subjects
helium, laser powder bed fusion, operando radiography, operando x-ray diffraction, process gas, spatters, Materials of engineering and construction. Mechanics of materials, TA401-492
Abstract

The utilisation of helium as process gas in laser powder bed fusion limits the generation of Ti-6Al-4V hot and incandescent spatters and enhances their cooling rate. In the present study, operando X-ray diffraction using synchrotron X-rays permits to verify that the cooling rates experienced by the deposited material are not significantly affected by the process gas unlike spatters. Topography measurements of the top printed surface reveal lower roughness of He-produced samples, attributed to the previously observed reduction of spatters with He and thus a reduction of redepositions on the powder bed and printed surfaces. Operando radiography provides with insights on the spatter formation mechanisms namely particle entrainment, agglomeration, melting and spheroidization.Highlights The top surface average roughness of samples produced with He is lower than that of Ar equivalent Deposited Ti-6Al-4V cooling rates during LPBF are not significantly affected by the use of He Grain size and orientation of Ti-6Al-4V is similar when processing under Ar, He, and a mixture of both Operando radiography permits to identify the mechanisms of Ti-6Al-4V spatter formation

Published
2022
Full Text
View/download PDF

13. Enjeux de l'implication des populations locales dans les initiatives de restauration forestière en Afrique centrale

Author

Peroches, Adrien, Mallet, Bernard, Chesnes, Marion, Dubiez, Emilien, Guizol, Philippe, Lescuyer, Guillaume, Peltier, Régis, Peroches, Adrien, Mallet, Bernard, Chesnes, Marion, Dubiez, Emilien, Guizol, Philippe, Lescuyer, Guillaume, and Peltier, Régis

Abstract

En Afrique centrale, la dégradation forestière et la déforestation ont principalement lieu dans le complexe rural, constitué d'une mosaïque agricole et arborée. La restauration et la pérennisation de ces espaces passe par des actions avec et pour les populations locales. Les expériences passées montrent : (i) un besoin d'intégrer la diversité des acteurs afin de proposer des solutions adaptées aux bénéficiaires ciblés, (ii) l'importance des bénéfices économiques à court et moyen terme pour que les populations locales s'impliquent vraiment dans les initiatives de restauration forestières et (iii) la nécessité de penser au-delà des logiques actuelles de projets. La présente note recommande ainsi que les futures initiatives de restauration forestière intègrent les populations locales d'Afrique centrale dans leur multiplicité et soient en mesure de proposer des appuis techniques diversifiés, adaptés aux conditions locales et offrant des opportunités économiques aux bénéficiaires. Il est aussi recommandé de travailler sur le temps long à l'émergence de conditions économiques et de modèles de gouvernance à même de pérenniser les interventions. Enfin, il est également recommandé de développer la capitalisation à partir des initiatives passées et en cours.

Published
2024

16. First evaluation of the use of assisted natural regeneration by central african farmers to restore their landscapes

Author

Arnot Kpolita, Emilien Dubiez, Olga Yongo, and Régis Peltier

Subjects
Assisted natural regeneration, Slash-and-burn, Central african republic, Agroforestry, Improved fallow, Forest Landscape Restauration, Forestry, SD1-669.5, Plant ecology, QK900-989
Abstract

On the outskirts of the city of Bangui, the capital of the Central African Republic, fuelwood production, slash-and-burn agriculture and artisanal timber exploitation are causing deforestation and forest ecosystem degradation.Within the framework of the REDD+ Component of the South-West Regional Development Project, the implementation of Assisted Natural Regeneration during weeding (ANRw) in the slash-and-burn system was proposed and set up by 23 volunteer farmers on 24 fields with an average area of 0.22 ha in two villages (Boteke and Salanga).The objective of the study was to characterise the floristic structure of the juvenile woody vegetation resulting from ANRw in these two villages. More specifically, it aimed to: 1) describe the methods used to inform and raise awareness amongst farmers who volunteer to practise ANRw; 2) identify the main species conserved by the farmers; 3) identify the reasons or factors that motivated farmers to choose these species; 4) identify the biological and ecological characteristics of these species; and 5) evaluate the height growth of young trees preserved by ANRw over a 14-month period.The third inventory of the 24 plots (volunteers' fields) gave 1,668 woody plants preserved by ANR on 5.35 ha (312 trees ha−1), divided into 42 genera, 47 species and 23 families.These results show that ANRw is a simple technique to implement and can help maintain trees in fields in areas where pressure on the forest is high. In the supported villages, communities have shown an interest in applying this technique to reintroduce trees in the fields. This technique should be popularised in other places to improve the sustainable management of anthropized forest landscapes. In addition, volunteers who have tested ANRw say they are willing to continue practicing it. However, despite this genuine initial enthusiasm, this restoration drive will need to be monitored and supported due to the current context of extreme poverty and economic, social and political instability.

Published
2022
Full Text
View/download PDF

19. Fertigungsverfahren PBF-LB/M

Author

Deckers, Tobias, primary, Ammann, Thomas, additional, Forêt, Pierre, additional, Dubiez-Le-Goff, Sophie, additional, and Witt, Gerd, additional

Published
2023
Full Text
View/download PDF

21. Effect of the Process Atmosphere Composition on Alloy 718 Produced by Laser Powder Bed Fusion

Author

Camille Pauzon, Andreas Markström, Sophie Dubiez-Le Goff, and Eduard Hryha

Subjects
additive manufacturing, laser powder bed fusion, process gas, nitrogen, argon, oxygen content, Mining engineering. Metallurgy, TN1-997
Abstract

The detrimental effect of nitrogen and oxygen when it comes to the precipitation of the strengthening γ’’ and γ’ phases in Alloy 718 is well-known from traditional manufacturing. Hence, the influence of the two processing atmospheres, namely argon and nitrogen, during the laser powder bed fusion (L-PBF) of Alloy 718 parts was studied. Regardless of the gas type, considerable losses of both oxygen of about 150 ppm O2 (≈30%) and nitrogen on the level of around 400 ppm N2 (≈25%) were measured in comparison to the feedstock powder. The utilization of nitrogen as processing atmosphere led to a slightly higher nitrogen content in the as-built material—about 50 ppm—compared to the argon atmosphere. The presence of the stable nitrides and Al-rich oxides observed in the as-built material was related to the transfer of these inclusions from the nitrogen atomized powder feedstock to the components. This was confirmed by dedicated analysis of the powder feedstock and supported by thermodynamic and kinetic calculations. Rapid cooling rates were held responsible for the limited nitrogen pick-up. Oxide dissociation during laser–powder interaction, metal vaporization followed by oxidation and spatter generation, and their removal by processing atmosphere are the factors describing an important oxygen loss during L-PBF. In addition, the reduction of the oxygen level in the process atmosphere from 500 to 50 ppm resulted in the reduction in the oxygen level in as-built component by about 5%.

Published
2021
Full Text
View/download PDF

22. Effect of layer thickness on spatter properties during laser powder bed fusion of Ti-6Al-4V

Author

Pauzon, Camille, Raza, Ahmad, Hanif, Imran, Dubiez-Le Goff, Sophie, Moverare, Johan, Hryha, Eduard, Pauzon, Camille, Raza, Ahmad, Hanif, Imran, Dubiez-Le Goff, Sophie, Moverare, Johan, and Hryha, Eduard

Abstract

High layer thicknesses for laser powder bed fusion are promising for productivity increase. However, these are associated with increased process instability, spatter generation and powder degradation, crucial for alloys sensitive to oxygen. The effect of increasing layer thickness from 30 to 60 mu m is studied focusing on Ti-6Al-4V spatter formation during LPBF and its characterisation, with scanning and transmission electron microscopy, combustion analysis and X-ray photoelectron spectroscopy. Results indicate that spatters are covered with a uniform Ti-Al-based oxide layer and Al-rich oxide particulates, the thickness of which is about twice that present on virgin powder. The oxygen content was about 60% higher in spatters compared to the virgin powder. The study highlights that increasing the layer thickness to 60 mu m permits to reduce the total generation of spatters by similar to 40%, while maintaining similar spatter characteristics and static tensile properties. Hence, this allows to increase build rate without compromising process robustness.

Published
2023
Full Text
View/download PDF

23. A practicable and reliable test for metal powder spreadability : development of test and analysis technique

Author

Hulme-Smith, Christopher, Mellin, P., Marchetti, Lorenzo, Hari, Vignesh, Uhlirsch, M., Strandh, E., Saeidi, K., Dubiez-Le Goff, S., Saleem, S., Pettersson, V., Memarpour, A., Jakobsson, K., Meurling, F., Hulme-Smith, Christopher, Mellin, P., Marchetti, Lorenzo, Hari, Vignesh, Uhlirsch, M., Strandh, E., Saeidi, K., Dubiez-Le Goff, S., Saleem, S., Pettersson, V., Memarpour, A., Jakobsson, K., and Meurling, F.

Abstract

A crucial step in the powder bed metal additive manufacturing process is the formation of a thin layer of powder on top of the existing material. The propensity of the powder to form thin layers under the conditions used in additive manufacturing is critically important, but no test method has yet been established to measure this characteristic, which is sometimes referred to as spreadability. The current work spreads a single layer of powder using commercial equipment from the paint and food industries and derives the density of a layer of powder, which is of a similar thickness to that in additive manufacturing. Twenty-four powders from eight suppliers have been tested and the density of the layers has been measured as a function of various parameters. Twenty-two of the powders successfully form thin layers, with a density of at least 40% of each powder’s apparent density. Hall flow time did not correlate with the spread layer density, although the two powders that did not spread did not pass through the Hall funnel. The roughness of the plate onto which the powder was spread, the recoater speed, the layer thickness, particle size and aspect ratio all affect the measured layer density. Results of the new test are repeatable and reproducible. These findings can be used to develop a test for spreadability for metal powders that can be used for additive manufacturing, which will help to improve the quality of printed components., QC 20230524

Published
2023
Full Text
View/download PDF

24. Guide pratique de restauration forestière en Afrique Centrale

Author

Dubiez, Emilien, Guizol, Philippe, Bisimwa, Benjamin, Fotso, Christian, Peroches, Adrien, Peltier, Régis, Lescuyer, Guillaume, Dubiez, Emilien, Guizol, Philippe, Bisimwa, Benjamin, Fotso, Christian, Peroches, Adrien, Peltier, Régis, and Lescuyer, Guillaume

Abstract

Ce guide pratique a été produit dans le cadre de la composante 2 " Elaboration de mesures locales de régénération et de reboisement des espèces ligneuses et d'agroforesterie " du projet, mise en oeuvre par le Centre de coopération Internationale en Recherche Agronomique pour le Développement (CIRAD).

Published
2023

25. Guide pratique de production en pépinière des plants forestiers et fruitiers en Afrique Centrale

Author

Dubiez, Emilien, Guizol, Philippe, Bisimwa, Benjamin, Fotso, Christian, Peroches, Adrien, Peltier, Régis, Lescuyer, Guillaume, Dubiez, Emilien, Guizol, Philippe, Bisimwa, Benjamin, Fotso, Christian, Peroches, Adrien, Peltier, Régis, and Lescuyer, Guillaume

Abstract

Ce guide pratique a été produit dans le cadre de la composante 2 " Elaboration de mesures locales de régénération et de reboisement des espèces ligneuses et d'agroforesterie " du projet, mise en oeuvre par le Centre de coopération Internationale en Recherche Agronomique pour le Développement (CIRAD).

Published
2023

29. Reduction of incandescent spatter with helium addition to the process gas during laser powder bed fusion of Ti-6Al-4V

Author

S. Dubiez-Le Goff, Eduard Hryha, B. Hoppe, Camille Nicole Géraldine Pauzon, Pierre Forêt, T. Pichler, T. Nguyen, and Publica

Subjects
laser powder bed fusion, Fusion, Incandescent light bulb, spatter, Materials science, Argon, Laser scanning, Scattering, Analytical chemistry, chemistry.chemical_element, Shadowgraphy, Laser, Helium, Industrial and Manufacturing Engineering, process gas, law.invention, chemistry, law, Physics::Atomic and Molecular Clusters, Titanium Ti-6Al-4V, Physics::Atomic Physics
Abstract

The effect of the process gas during laser powder bed fusion (L-PBF) was investigated using high-speed shadowgraphy while melting Ti-6Al-4V powder under high purity argon, helium, and a mixture of both, on a laboratory-scale machine. These recordings reveal that the generation of incandescent spatters can be reduced by at least 60% using pure helium and by ∼30% using addition of helium to argon in comparison to the use of traditional argon. The quantity of colder spatters appeared unaffected by the change of process gas. Different configurations of gas flow versus laser scanning direction were investigated and revealed that fumes and spatters are less accumulated at the laser spot with helium addition. Furthermore, the use of the argon–helium mixture proved to be as efficient as pure argon in the dragging and extraction of the fumes. Shadowgraphs revealed the more rapid expansion of fumes in helium-rich atmospheres, limiting the accumulation of scattering objects close to the laser spot and thus melt pool instability. These results were correlated to process snapshots on an industrial-scale system, confirming the reduction of hot spatter generation. Finally, the findings put in evidence the more rapid cooling of spatters with helium addition to the process gas – a promising aspect to limit powder bed degradation during L-PBF. In addition, the use of mixtures of helium and argon would be economically interesting compared to pure helium, typically more expensive than the traditionally used argon.

Published
2021
Full Text
View/download PDF

33. List of contributors

Author

Aitkaliyeva, A., primary, Allen, T., additional, Asayama, T., additional, Bai, X.M., additional, Balbaud, F., additional, Blat-Yrieix, M., additional, Buckthorpe, D., additional, Cabet, C., additional, Dalle, F., additional, David, P., additional, de Carlan, Y., additional, Dubiez-Le Goff, S., additional, Dubuisson, Ph., additional, Fazio, C., additional, Gosset, D., additional, Guzonas, D., additional, Hall, G.N., additional, He, L., additional, Henry, J., additional, Ignatiev, V., additional, Jones, A.N., additional, Kaito, T., additional, Le Flem, M., additional, Malaplate, J., additional, Maloy, S.A., additional, Marsden, B.J., additional, Miller, B., additional, Mummery, P.M., additional, Muroga, T., additional, Novotny, R., additional, Ohtsuka, S., additional, Park, J.Y., additional, Penttilä, S., additional, Ribis, J., additional, Rouillard, F., additional, Sauzay, M., additional, Séran, J.-L., additional, Surenkov, A., additional, Treifi, M., additional, Ukai, S., additional, Wen, H., additional, and Zinkle, S.J., additional

Published
2017
Full Text
View/download PDF

38. First evaluation of the use of Assisted Natural Regeneration by Central African farmers to restore their landscapes

Author

Kpolita, Arnot, Dubiez, Emilien, Yongo, Olga Diane, Peltier, Régis, Kpolita, Arnot, Dubiez, Emilien, Yongo, Olga Diane, and Peltier, Régis

Abstract

On the outskirts of the city of Bangui, the capital of the Central African Republic, fuelwood production, slash-and-burn agriculture and artisanal timber exploitation are causing deforestation and forest ecosystem degradation. Within the framework of the REDD+ Component of the South-West Regional Development Project, the implementation of Assisted Natural Regeneration during weeding (ANRw) in the slash-and-burn system was proposed and set up by 23 volunteer farmers on 24 fields with an average area of 0.22 ha in two villages (Boteke and Salanga). The objective of the study was to characterise the floristic structure of the juvenile woody vegetation resulting from ANRw in these two villages. More specifically, it aimed to: 1) describe the methods used to inform and raise awareness amongst farmers who volunteer to practise ANRw; 2) identify the main species conserved by the farmers; 3) identify the reasons or factors that motivated farmers to choose these species; 4) identify the biological and ecological characteristics of these species; and 5) evaluate the height growth of young trees preserved by ANRw over a 14-month period. The third inventory of the 24 plots (volunteers' fields) gave 1,668 woody plants preserved by ANR on 5.35 ha (312 trees ha−1), divided into 42 genera, 47 species and 23 families. These results show that ANRw is a simple technique to implement and can help maintain trees in fields in areas where pressure on the forest is high. In the supported villages, communities have shown an interest in applying this technique to reintroduce trees in the fields. This technique should be popularised in other places to improve the sustainable management of anthropized forest landscapes. In addition, volunteers who have tested ANRw say they are willing to continue practicing it. However, despite this genuine initial enthusiasm, this restoration drive will need to be monitored and supported due to the current context of extreme poverty and economic, social and p

Published
2022

39. Les plantations forestières en Afrique centrale

Author

Bertaux, Paul, Baltzer, Carla, Angulo, Jessenia, Bosworth, Charlie, Clinquart, Pierre, Diangana, Daniel, Dubiez, Emilien, Fleming, Timothy, Freycon, Vincent, Goma, Maurice, Harmand, Jean-Michel, Henson, Michael, Howard, Mike, Matkovich, Shauna D., Moukini, Régis, Mushiete, Olivier, Ndikumagenge, Cléto, Ndabirorere, Salvatore, Pahkasalo, Tapani, Peltier, Régis, Van Den Plas, Robert, Smith, Andries, Silva, Luis N., Tieguhong, Julius C., Eba'a Atyi, Richard, Bertaux, Paul, Baltzer, Carla, Angulo, Jessenia, Bosworth, Charlie, Clinquart, Pierre, Diangana, Daniel, Dubiez, Emilien, Fleming, Timothy, Freycon, Vincent, Goma, Maurice, Harmand, Jean-Michel, Henson, Michael, Howard, Mike, Matkovich, Shauna D., Moukini, Régis, Mushiete, Olivier, Ndikumagenge, Cléto, Ndabirorere, Salvatore, Pahkasalo, Tapani, Peltier, Régis, Van Den Plas, Robert, Smith, Andries, Silva, Luis N., Tieguhong, Julius C., and Eba'a Atyi, Richard

Abstract

La demande de bois augmente partout dans le monde et cette tendance va inévitablement s'accélérer durant le XXIe siècle pour les débouchés traditionnels, mais aussi les secteurs de la construction (36 % des émissions de gaz à effet de serre), de la bioénergie, de la chimie verte et de toutes les industries qui chercheront progressivement à se biosourcer et à se décarboner dans le cadre de l'avènement d'une économie verte durable et relocalisée près de ses ressources et des marchés locaux.

Published
2022

41. The Central African farmers protect their fallow trees to prevent the savannisation of their landscape

Author

Kpolita, Arnot, Dubiez, Emilien, Yongo, Olga Diane, Peltier, Régis, Kpolita, Arnot, Dubiez, Emilien, Yongo, Olga Diane, and Peltier, Régis

Abstract

Background: In the traditional slash-and-burn system, widely used in southern CAR, the forest is felled and then burnt, and maize, followed by cassava and banana crops, are planted in the ashes. Three or four years later, the plot is abandoned and left fallow without any management until its next clearing. A study of the evolution of the landscape south of Bangui, the country's capital, shows that this practice leads to the retreat of the forest, replaced initially by a patchwork of degraded forest and Chromolaena odorata scrub, then by Imperata cylindrica savannahs where agriculture becomes almost impossible. To avoid this degradation of ecosystems, leading to soil impoverishment, biodiversity loss, carbon emissions and the flight of populations, the PDRSO project introduced farmers in several villages to an Assisted Natural Regeneration (ANR) technique that protects young trees during the cropping cycle so that a stand of trees, and not invasive bushes and grasses, later occupies the land during the fallow cycle. Method: A negotiation phase between the farmers and the researchers made it possible to choose the species of interest and the technique to conserve them. Monitoring of 24 plots with ANR and 20 control plots without ANR, made it possible to assess the growth of woody plants. Surveys of farmers who had participated in the operation and those who had not, allowed us to assess their perception of the method and their willingness to continue it over time. Results: Two years after being selected, the young trees already are larger than the main invasive species and are impeding their establishment In addition, the farmers see the importance of preventing their village territory from being transformed into barren savannah. Difficulties reported include insecurity of land tenure, lack of support from the administration, the brevity of projects, and the difficulty of fighting fires due to lack of collective organization, all in an environment of civil war. Discus

Published
2022

44. Latitudinal shift in the timing of flowering of tree species across tropical Africa: insights from field observations and herbarium collections

Author

Fidèle Baya, Sylvie Gourlet-Fleury, Steven Janssens, Kasso Daïnou, Dakis-Yaoba Ouédraogo, Hans Beeckman, Jan J. Wieringa, Emilien Dubiez, Jean-Louis Doucet, Bhely Angoboy Ilondea, Adeline Fayolle, Piet Stoffelen, and Olivier J. Hardy

Subjects
0106 biological sciences, herbarium specimen, rainfall, Species distribution, F62 - Physiologie végétale - Croissance et développement, Conditions météorologiques, Biology, 010603 evolutionary biology, 01 natural sciences, Latitude, Lophira alata, 03 medical and health sciences, dry season, Floraison, Dry season, medicine, reproductive phenology, Ecology, Evolution, Behavior and Systematics, 030304 developmental biology, flowering, 0303 health sciences, Précipitation, Comportement reproductif, Phenology, Ecology, Facteur du milieu, Seasonality, Climatic hinge, medicine.disease, Herbarium, Spatial variability, timber species, Arbre pour bois de construction, Longitude, Biologie
Abstract

Temporal and spatial patterns in flowering phenology were assessed for eight tropical African tree species. Specifically, the frequency and seasonality of flowering at seven sites in central Africa were determined using field data, graphical analysis and circular statistics. Additionally, spatial variation in the timing of flowering across species range was investigated using herbarium data, analysing the relative influence of latitude, longitude and timing of the dry season with a Bayesian circular generalized linear model. Annual flowering was found for 20 out of the 25 populations studied. For 21 populations located at the north of the climatic hinge flowering was occurring during the dry season. The analysis of herbarium collections revealed a significant shift in the timing of flowering with latitude for E. suaveolens, and with the timing of the dry season for M. excelsa (and to a lesser extent L. alata), with the coexistence of two flowering peaks near the equator where the distribution of monthly rainfall is bimodal. For the other species, none of latitude, longitude or timing of the dry season had an effect on the timing of flowering. Our study highlights the need to identify the drivers of the flowering phenology of economically important African tree species., SCOPUS: ar.j, info:eu-repo/semantics/published

Published
2020
Full Text
View/download PDF

47. Rapport d'étude sur le bilan offre/demande de la ressource bois-énergie dans le bassin d'approvisionnement de Bangui en République Centrafricaine

Author

Dubiez, Emilien, Akodewou, Amah, and Bénédet, Fabrice

Abstract

La superficie du bassin d'approvisionnement en bois-énergie du complexe urbain Bangui/Bimbo a été estimée à de 440 000 ha par la présente étude. L'occupation des sols de ce bassin d'approvisionnement est dominée par les forêts (33%), le complexe culturale (31 %) et les savanes (28%). Les forêts sont dominantes dans la partie sud du bassin d'approvisionnement et les savanes sont dominantes dans sa partie nord. Les flux d'approvisionnement de charbon de bois et de bois de feu ont été localisés et quantifiés à l'échelle des communes (Gazull et al. 2018) pour localiser la demande urbaine en bois-énergie. La demande rurale a également été calculée puis prise en compte dans le bilan global de la demande à l'échelle du bassin d'approvisionnement en bois-énergie du complexe urbain de Bangui/Bimbo. L'offre, à l'échelle des communes, a été calculée en déterminant les superficies des différents types d'occupation du sol par commune et en calculant les possibilités annuelles de production (t/ha/an) en fonction des données de productivité des différentes formations végétales (FAO, 2009). La possibilité de production annuelle sur l'ensemble du bassin serait légèrement supérieure à 1 millions de tonnes de bois. Le bilan offre/demande est donc encore excédentaire à l'échelle du bassin d'approvisionnement ou la demande du complexe urbain de Bangui/Bimbo a été estimée à 534 600 tonnes eq. bois/an et la demande des ménages ruraux situés dans le bassin d'approvisionnement à 16 700 tonnes soit une demande globale de 551 300 tonnes eq. bois par an. Au total ce sont 52 % de l'offre potentielle de production annuelle qui répond actuellement à la demande urbaine du complexe urbain Bangui/Bimbo en bois-énergie. Au sein des différentes communes, il existe une disparité de pression. La commune la plus sollicitée pour l'exploitation de la ressource en bois est la commune de Damara ou 81 % de l'offre potentielle de production est actuellement exploitée pour répondre à la demande urbaine en bois-énergie, suivi de la commune de Bimbo avec 61 % et la commune de Mongoumba avec 46 %. Le déséquilibre entre l'offre et la demande en bois-énergie est plus marqué dans le Nord et dans la périphérie proche de Bangui que dans le Sud, conduisant à une surexploitation des savanes dans la partie nord du bassin d'approvisionnement en bois-énergie du complexe urbain Bangui/Bimbo.

Published
2022

48. Einfluss heliumhaltiger Prozessgase auf den Laser-Strahlschmelzprozess

Author

Tobias Deckers, Thomas Ammann, Pierre Forêt, Sophie Dubiez-Le-Goff, Kai Zissel, and Gerd Witt

Subjects
Maschinenbau, Strategy and Management, General Engineering, Management Science and Operations Research
Abstract

Kann das Prozessgas bei der Optimierung des PBF-LB/M-Prozesses (z. B. Schichtstärke, Belichtungsgeschwindigkeit oder Prozessierbarkeit neuer Materialen) eine Schlüsselrolle einnehmen? Dieser Beitrag liefert einen Einblick über den aktuellen Forschungsstand der Linde GmbH in Bezug auf heliumhaltige Prozessgase und Vorstellung des neuartigen Prozessgases ADDvance® Laser230. Aufgrund seiner Zusammensetzung ermöglicht das Gasgemisch, die Prozessproduktivität und -stabiliät entscheidend zu verbessern.

Published
2022

49. Rapport comparatif des pratiques de production de bois-énergie dans le Nord et le Sud du bassin d'approvisionnement en bois-énergie de la ville de Bangui en République Centrafricaine

Author

Dubiez, Emilien

Abstract

Deux études ont été conduites auprès des producteurs de charbon de bois et de bois de feu dans le bassin d'approvisionnement en bois-énergie de la ville de Bangui. La première étude a été conduite dans le cadre du Projet de Développement de la Région du Sud-Ouest de la RCA (PDRSO) en 2018 et la seconde a été conduite en décembre 2021 dans le cadre du présent programme. Ces deux enquêtes conduites par le CIRAD ont permis de caractériser l'organisation des filières bois-énergie et les pratiques des producteurs de charbon de bois et de bois de feu à la fois sur la partie Sud de Bangui (2017), domaine Congo-Guinéen caractérisé par la forêt, et la partie Nord de Bangui (2021), domaine Soudano-Guinéen caractérisé par une végétation de savane. Au total, 114 enquêtes ont été conduites auprès des producteurs de charbon de bois dont 53 dans la zone Sud et 61 dans la zone Nord. Pour le bois de feu, ce sont 71 enquêtes qui ont été conduites au total dont 40 dans la zone Sud et 31 dans la zone Nord. Ces enquêtes ont été conduites dans quatre sous-préfectures limitrophes de Bangui et contribuant à l'approvisionnement en bois-énergie, à savoir Bimbo, Boali, Damara et M'Baïki. Concernant la filière charbon de bois, l'expérience des producteurs de charbon de bois est plus importante dans la zone Nord (25 ans) que dans la zone Sud (14 ans). En effet, la filière charbon de bois dans la zone sud est plus récente que celle de la zone Nord. Parmi les producteurs enquêtés dans la zone Nord, onze pourcents sont des femmes (7 enquêtes sur 61) et aucune femme n'a été enquêtée dans la zone Sud. La majorité des producteurs enquêtés pratique une ou plusieurs autres activités (87 % dans la zone nord et 98 % dans la zone sud) dont 92 % pratiquent l'agriculture. Parmi les producteurs enquêtés, 36 % des producteurs achètent le bois pour produire le charbon de bois et 35 % sont des ayants droits accédant gratuitement à la ressource. Il existe des différences entre la zone Sud et la zone Nord. 67 % des producteurs de charbon de bois de la zone Sud achètent le bois alors qu'ils sont seulement 10 % dans la zone Nord. Dans la zone Nord, la majorité des producteurs sont des ayants droits (54 %) alors qu'ils sont seulement 10 % dans la zone Sud. Les producteurs prélèvent les arbres majoritairement dans les jachères forestières (46 %) lors de leur ouverture pour l'installation des champs. Le second milieu ou les arbres sont prélevés est la savane avec 26 %. Enfin, 18 % des producteurs prélèvent le bois dans les forêts galeries mais ce type de végétation se retrouve seulement dans la partie nord et est le lieu le plus exploité (33 %) par les producteurs. Pour les producteurs de la zone sud, ce sont les jachères qui sont le plus exploitées pour la production de charbon de bois (70 %). Indistinctement, un producteur de charbon de bois produit annuelle en moyenne 11 tonnes de charbon de bois. Dans la partie Nord du bassin d'approvisionnement, les producteurs produisent plus de deux fois plus de charbon de bois (15 tonnes) que les producteurs de la zone Sud (7 tonnes). Concernant la filière bois de feu, l'expérience des producteurs de bois de feu est plus importante dans la zone nord (13 ans) que dans la zone Sud (7 ans) comme pour les producteurs de charbon de bois. Vingt-trois pourcents des producteurs sont des femmes (7 enquêtés) dans le nord du bassin alors qu'un seul enquêté est une femme dans la partie sud du bassin (2,5 %). La majorité des producteurs pratique une ou plusieurs autres activités (77 % dans la zone nord et 95 % dans la zone sud) en plus de la production de bois de feu dont 75 % pratiquent l'agriculture. Parmi les producteurs enquêtés, 24 % des producteurs achètent la ressource pour produire le bois de feu en achetant les arbres. La part d'achat des arbres est légèrement supérieur dans la zone sud (27 %) que dans la zone nord (19 %). Globalement, les producteurs prélèvent les arbres majoritairement dans les jachères forestières (39 %) lors de leur ouverture pour l'installation des champs et en savane (31 %). Dans la zone Nord, les producteurs prélèvent majoritaire le bois en savane (63 %) alors que dans la zone Sud, les producteurs prélèvent majoritairement le bois lors de l'ouverture des jachères forestières (63 %). La distance moyenne d'accès à la ressource pour les producteurs de la zone Nord est de 4,5 km et ceux de la zone Sud est de 3 km. Dans la partie Nord du bassin d'approvisionnement, les producteurs produisent 37 tonnes en moyenne de bois de feu par an et ceux de la zone Sud produisent 35 tonnes de bois de feu par an.

Published
2022

50. Enjeux fonciers, exploitation des ressources naturelles et Forêts des Communautés Locales en périphérie de Kinshasa, RDC

Author

Vermeulen, C., Dubiez, E., Proces, P., Mukumary, SD., Yamba, TY., Mutambwe, S., Peltier, R., Marien, JN., and Doucet, JL.

Subjects
Land management, suburban areas, fuelwood, wood energy, forest resources, population pressure, regulations, participatory rural appraisal, Democratic Republic of the Congo, Biotechnology, TP248.13-248.65, Environmental sciences, GE1-350
Abstract

Land issues, exploitation of natural resources, and Forests of Rural Communities in the periphery of Kinshasa, DRC. Peri-urban forests are under strong anthropic pressure. Any activity needs a previous identification of stakeholders, landscape perception, socio-economic trends in local communities and their relationships with land and natural resources. Kinshasa (capital of Democratic Republic of Congo, DRC) is a 10 millions inhabitants city with rapid growth and increasing impacts on surrounding villages linked with forest natural resources. This paper describes the relationship amongst local communities stakeholders and their relations with land areas and wood resources. Two areas surrounding Kinshasa (Bas-Congo and Bateke Plateaux) are considered as major fuel-wood and charcoal supply zones for the city. Those two areas are different in terms of land pressure (very high in Bas-Congo and focused on riparian forests on Bateke Plateaux), but show the same pattern of overuse of the forest and woody natural resources. In both areas, local management of forest resources by the traditional authorities (heads of village or lineage) has failed. Local population willingness for reforestation and forest restoration activities is much more important in Bas-Congo than on Bateke Plateaux. In both areas, shifting cultivation due to slash and burn practices for agricultural and charcoal practices are more and more quick. This has strong negative impact on the potential of regeneration process with local forest species. Sustainability of forest natural resources management by communities is discussed in regard to the on going negotiations on community based forest management regulations.

Published
2011

Catalog

Books, media, physical & digital resources
See catalog results