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See detailDynamique de la haute atmosphère de Vénus
Stiepen, Arnaud ULg

Book published by Editions Universitaires Européennes (2014)

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See detailDynamique de la végétation d'altitude en Afrique centrale atlantique depuis 17 000 ans BP. Analyses préliminaires de la carotte de Bambili (Nord-Ouest du Cameroun).
Assi Kaudjhis, Chimène Cloche M ULg; LEZINE, ANNE - MARIE; Roche, Emile ULg

in Geo-Eco-Trop : Revue Internationale de Géologie, de Géographie et d'Ecologie Tropicales (2008), 32

This article presents the preliminary results of pollen analyses carried out on a 13.5m long core taken from the shore of the crater lake of Bambili, Cameroon (05°56'11.9N; 10°14' 31.6E; 2273m alt.). This ... [more ▼]

This article presents the preliminary results of pollen analyses carried out on a 13.5m long core taken from the shore of the crater lake of Bambili, Cameroon (05°56'11.9N; 10°14' 31.6E; 2273m alt.). This allows us to reconstruct the history of montane forest ecosystems from Atlantic Central Africa since 17 000 years BP. Well diversified microflora, show several changes. At the base of the pollen sequence, the vegetation is dominated by herbaceous plant populations such as Poaceae, associated with “dry” plant types from Amaranthaceae/ Chenopodiaceae families and tree and shrub plant types from savannas and open forest formations types such as Gnidia, Lannea, Combretaceae, Cussonia… The montane forest expansion started from 14 080cal BP with the appearance of the pioneer taxon Myrica. This taxon is followed by Schefflera, Podocarpus, Olea, Syzygium… which widely expanded in the immediate surroundings of the lake from 12 310 to 4 590 cal BP. After this date, the montane forest was strongly reduced. However a short phase of forest regrowth is recorded around 2000 BP during which Schefflera dominated the forest assemblage. [less ▲]

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See detailDynamique de modification de l'habitat physique de reproduction des pondeurs lithophiles sous gravier. Cas de deux frayères à ombre dans l'Aisne
Parkinson, Denis; Petit, François ULg; Houbrechts, Geoffrey ULg et al

in Bulletin de la Société Géographique de Liège (2001), 40

D’octobre 1998 à mars 1999, nous avons étudié dans l’Aisne, petit affluent ardennais de l’Ourthe, la dynamique de modification de deux bancs de gravier utilisés comme frayère par l’ombre commun en mars ... [more ▼]

D’octobre 1998 à mars 1999, nous avons étudié dans l’Aisne, petit affluent ardennais de l’Ourthe, la dynamique de modification de deux bancs de gravier utilisés comme frayère par l’ombre commun en mars-avril 1998. L’étude a été réalisée dans deux stations du cours inférieur de l’Aisne où se sont succédé quatre crues morphogènes. Dans chaque station, nous avons déterminé à intervalle d’environ 1 mois, la profondeur d’érosion et la hauteur de dépôt des sédiments (méthode de la barre d’érosion à chaînes), la granulométrie des matériaux des couches de surface et de subsurface, le dépôt des sédiments fins (placement de pièges à sédiments) et la perméabilité du substrat (méthode du standpipe). En complément, nous avons entrepris dans une station de l’Aisne moyenne, une caractérisation de divers éléments de la dynamique fluviale : identification des débits mobilisateurs (par marquage colorimétrique des sédiments en place), estimation de la vitesse de déplacement de la charge de fond (par étude de la dispersion longitudinale de scories, résidu d’anciennes industries métallurgiques) et estimation des quantités de sédiments charriés par la rivière (à partir des données de dragage). [less ▲]

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See detailDynamique de population de la Pie-grièche écorcheur (Lanius collurio) dans le sud-est de la Belgique : modélisation de l’influence du climat.
Metzmacher, Maxime ULg; van Nieuwenhuyse, Dries

in Revue d'Ecologie (La Terre et la Vie) (2012), 67(4), 353-374

In some areas of Western Europe, red-backed shrike populations, following a strong decline in the third quarter of the 20th century, were re-established in recent decades. Variations in climate seem to ... [more ▼]

In some areas of Western Europe, red-backed shrike populations, following a strong decline in the third quarter of the 20th century, were re-established in recent decades. Variations in climate seem to have played a crucial part in this striking evolution by modulating the species breeding success. In order to test this hypothesis, the annual fluctuations of several of these populations in south-eastern Belgium were compared with the variations in a series of climatic factors. This study derives from a number of censuses, completed during the breeding period between 1979 and 2008, and the data from the weather stations closest to the populations studied. The modelling of climate influence on annual population fluctuations is based on a Partial Least Squares regression (PLS), following the classification of variables using a latent variable approach. From 1980 to 2008, for the April-August period, the mean minimum temperature tended to rise. During these five months, rainfall intensity reached a minimum in the 1990’s and increased significantly thereafter. During the three last decades, rainfall intensity for June tended to decrease whereas that for August increased. The annual variations of these monthly averages were very high. As for breeding population fluctuations, our results highlighted the significant role of various parameters related to minimum temperature and pluviometry during the breeding period. Spring and cold wet summer periods seem to have a significant negative impact on the rate of breeder recruitment. These results suggest that the breeding success of red-backed shrike can benefit from global climate change due to the higher success rate of broods. This however applies provided that its habitat is preserved – in terms of quality and surface area – and that this warming does not generate overly high rainfall during a critical period of its breeding cycle. The importance of climatic factors in population fluctuations for this shrike provides opportunities for further investigation, particularly in studying the mechanisms that underlie these variations. [less ▲]

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See detailDynamique des constructions maritimes et offshores
Marchal, Jean ULg

Learning material (1979)

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See detailDynamique des forêts irrégulières et mélangées: de la modélisation aux recommandations sylvicoles
Ligot, Gauthier ULg

Conference (2014, April 29)

Close-to-nature management of forests has been increasingly advocated and practiced. However forest managers often face difficulties in maintaining the mixture of species with different shade tolerance ... [more ▼]

Close-to-nature management of forests has been increasingly advocated and practiced. However forest managers often face difficulties in maintaining the mixture of species with different shade tolerance. We studied this issue in uneven-aged acidophile medio-European beech forests. In these forests, while forest management has achieved regular timber production, it has rarely succeeded in promoting a diversified natural regeneration. In view of this, our objective is to refine our knowledge about the dynamic of uneven-aged mixed forests using a modelling approach. A set of consistent models were carried out to describe stand dynamic with, in particular, models of regeneration growth and light interception. The models were then implemented in a simulator in order to perform prospective analysis. In contrast to expectations, we found that saplings of beech, the shade-tolerant species, had the highest height growth rate at all light levels. Beech saplings reached an optimum growth at transmittance of 10%, whereas oak saplings needed more than 20%. These results indicate that oak saplings are systematically outcompeted by beech saplings across the light gradient. Thus, the control of canopy opening is not sufficient to promote the natural regeneration of oak beneath a stand also containing beech. Taking into account these latter results, we compared cutting strategies varying in type and intensity. Creating gaps of about 500 m² provided adequate light for small regeneration clumps. Cutting from below, species-specific cutting and uniform cutting were also appropriate but uniform cutting required higher harvest intensity. Cutting from above weakly increased understory light and promoted rather shade tolerant species. Finally we provided indications on different strategies that promote the regeneration of less-shade tolerant species, depending on the spatial aggregation of saplings, and the desired post-harvest stand structure and composition. [less ▲]

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See detailDynamique des groupes, dispositif de formation et apprentissage
Faulx, Daniel ULg

in Cahiers Internationaux de Psychologie Sociale (2010), 86(2), 345-349

Etude d'une expérience structurée questionnant les liens entre la dynamique d'un groupe et l'apprentissage qui peut être développé par les apprenants. Au centre du propos, le lien entre la dynamique de ... [more ▼]

Etude d'une expérience structurée questionnant les liens entre la dynamique d'un groupe et l'apprentissage qui peut être développé par les apprenants. Au centre du propos, le lien entre la dynamique de groupe, en partie stimulée par le dispositif, et les effets d'une action de formation. [less ▲]

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See detailDynamique des inégalités et fragilités sociales à la lumière du rapport entre emploi, famille et sécurité d'existence
Gavray, Claire ULg; Born, Michel ULg

Book published by Service Fédéraux des Affaires Scientifiques, Techniques et Culturelles (1995)

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See detailDynamique des nouveaux Systèmes Locaux de Santé (SYLOS) en 2013
Belche, Jean-Luc ULg

Scientific conference (2013, November 26)

Présentation de la dynamique Sylos dans 3 contextes locaux en région liégeoise en 2013 (Wallonie-belgique).

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See detailDynamique des paysages forestiers et savanicoles du Sud et du Nord-Est du Burundi
Havyarimana, F; Bigendako, M J; Bogaert, Jan ULg et al

Poster (2012)

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See detailDynamique des populations de trois adventices des céréales en vue de la mise au point de méthodes intégrées de leur contrôle
Vandersteen, Joëlle ULg; Bodson, Bernard ULg

in Bodson, Bernard; de proft, Michel (Eds.) Livre Blanc 2011 (2011, February 23)

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See detailDynamique des structures tourbillonnaires participant à la production du bruit de fente
Glesser, Martin; Billon, Alexis ULg; Valeau, Vincent et al

Conference (2006, April)

Des sons auto-entretenus (sifflements de forte intensité) peuvent être produits par les bouches de soufflage des systèmes de ventilation. L'impact du jet produit par la bouche sur une grille de protection ... [more ▼]

Des sons auto-entretenus (sifflements de forte intensité) peuvent être produits par les bouches de soufflage des systèmes de ventilation. L'impact du jet produit par la bouche sur une grille de protection située en aval induit une perturbation pouvant remonter l'écoulement et venir exciter le jet à sa naissance, établissant ainsi une boucle d'auto-entretien. Pour certains nombres de Reynolds et distances "sortie du jet / obstacle", un couplage entre les sons auto-entretenus et le conduit de soufflage est observé. La résonance du conduit contrôle alors la fréquence et amplifie le niveau sonore. Cette étude s'intéresse à la production sonore résultant de ce couplage. Les structures tourbillonnaires crées dans les couches de cisaillement du jet jouent un rôle prépondérant : la synchronisation entre leur création ou leur impact sur l'obstacle et le champ acoustique rayonné par le conduit résonnant influe fortement sur la production sonore. Or les résultats disponibles dans la littérature pour des configurations géométriques ressemblantes ne permettent pas de clarifier cette synchronisation. Un dispositif expérimental où un jet plan rectangulaire heurte une plaque fendue (configuration géométrique appelée bruit de fente) est donc étudié à l'aide de mesures vélocimétriques. La comparaison de la fluctuation du signal de vitesse dans le cône potentiel du jet (directement lié à la vitesse acoustique) et du signal de vitesse dans la couche de cisaillement (contenant des informations sur le passage des structures tourbillonnaires) permet de clarifier la dynamique de ces structures. L'information obtenue permet alors d'évaluer la synchronisation entre le champ acoustique et le champ tourbillonnaire. Cette étude contribuera à terme a l'implémentation d'un modµele du bruit de fente basé sur la théorie aéroacoustique de Howe. [less ▲]

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See detailDynamique des transactions foncières et vulnérabilité rurale au Niger : cas des communes rurales de Tchadoua et Yaouri
Lawali Mani, Sitou ULg

Doctoral thesis (2011)

Summary In Niger, agriculture is the principal activity of the rural populations. Unfortunately the access to the land becomes very difficult to the farmers in the center-south of the country. This area ... [more ▼]

Summary In Niger, agriculture is the principal activity of the rural populations. Unfortunately the access to the land becomes very difficult to the farmers in the center-south of the country. This area is confronted to the space saturation and the emergence of the land transactions whose causes, process and impacts on the agricultural households are little known. The study undertaken in the rural municipality of Tchadoua and Yaouri aimed at analyzing the dynamics of the land transactions in bond with the rural vulnerability in terms of the stakes of access and management of the grounds, but also their securisation. The problems were studied with a multidisciplinary approach. The analyses (quantitative and qualitative) were carried out on the basis of the data collected in the village areas of Maijanguero and Gomba through cards of investigations and semi-structured interviews with a sample of 30% of the households. We also used participatory observations of agricultural practices and consultation of different sources of documentation. Administration and others authorities have been also interviewed aswel as members of the land commissions and the intermediaries of the transactions. The results obtained show that the problem of access and management of the land in these agricultural areas is an important concern for rural producers. The land blocking due to the strong demographic pressure and the increase of economic stakes (crop rent) influence the excessive parceling out of the grounds and the individualization of the farms. This individualization supports consequently, the emergence of the commercial land speculations for the profit of the economic operators installed from now in logic of monopolization of grounds. The purchase, the pledge and the lease constitute the principal access modes to the ground instead of old forms of solidarity (gift, loan). Also, the new agrarian initiatives of assistance appear and take part in the improvement of the socio-economic conditions of the rural households. The results also made it possible to highlight a diversity of trajectories of the exploitations. The land ‘’monetarisation’’ influenced strongly the land management and reinforced the exclusion of the vulnerable groups. The strong changes of technical transformation and farming system are observed. It as revealed as the land accumulation or ‘’décapitalisation’’ depends of the type of farm, its strategy and its revenue. Indeed, three tendencies become apparent from the trajectories: great manufacturing units with dominant commercial accumulate land, use the hired labor work and araw cash crop (souchet); a strong land ‘’decapitalisation’’ at the extremely vulnerable and without viable strategy of adaptation in the long term. Lastly, the small farm witch made a diversification and a strong intensification, and there resist to the multiple attempts of land spoliation. These last constitute a model of stable and durable farm whose strategy is based primarily on the agricultural intensification through effective and less expensive agroforestry practices to increase their production and their land capital. The informel and discrete character of land transactions and the networks of intermediation by which are negotiated the land sales accentuate the land insecurity and contribute to increase the land prices. The analysis of the securisation practices of the land rights proves that legal formalization though timid, reduced considerably the frequency of the rural conflicts and offers agricultural opportunities of investments. However, the land commissions encounter difficulties which, slow down the generalization of the legal formalization of transactions. All things considered, the land problem remains a central stake of development thus, the securisation of the land rights of the rural poor must be a priority of the priorities to reach a durable food safety. It is thus urgent to make the land commissions more operational in their giving the means of operation in order to ensure a broad diffusion of the procedures of formalization for more impact and also encouraging the producers through small subsidies to practice the carrying agri-environmental measurements. [less ▲]

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See detailDynamique du carbone inorganique dans l'estuaire de l'Escaut. Premiers résultats
Frankignoulle, Michel; Bourge, Isabelle; Canon, Christine et al

in Bulletin de la Société Royale des Sciences de Liège (1992), 61

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