Littérature scientifique sur le sujet « Arbres de Greg »

Size variability within a cohort can have profound effects on community ecology and evolution. Although competition for resources generally increases size variability, the effect of (non-consumptive) predation on this demographic trait remains relatively poorly understood. Existing models suggest a positive correlation between growth rate (mediated by resource level) and expression of size variability (as measured by the coefficient of variation) in prey cohorts. We tested this prediction by exposing the tadpoles of the Japanese Forest Green Treefrog (Rhacophorus arboreus (Okada and Kawano, 1924) = Zhangixalus arboreus (Okada and Kawano, 1924)) to the non-lethal presence of gape-limited Japanese Fire-bellied Newts (Cynops pyrrhogaster (Boie, 1826)) at low and high predator densities in an outdoor mesocosm experiment. Tadpole growth rates and periphyton biomass increased with newt density. But in contrast to prediction, elevated growth rates did not increase but, reversely, decreased cohort size variability in the tadpoles. We discuss two potential mechanisms behind this outcome. First, increased resource availability mediated by predator feeding may have reduced the strength of competition, ultimately leading to more evenly distributed resource gains among individuals; second, if smaller individuals grew relatively faster than larger individuals, as to quicken entry to a size refuge against the gape-limited predator, then inter-individual size differences could diminish over time.

The development of connections between thalamic afferents and their cortical target cells occurs in a highly precise manner. Thalamic axons enter the cortex through deep cortical layers, then stop their growth in layer 4 and elaborate terminal arbors specifically within this layer. The mechanisms that underlie target layer recognition for thalamocortical projections are not known. We compared the growth pattern of thalamic explants cultured on membrane substrates purified from cortical layer 4, the main recipient layer for thalamic axons, and cortical layer 5, a non-target layer. Thalamic axons exhibited a reduced growth rate and an increased branching density on their appropriate target membranes compared with non-target substrate. When confronted with alternating stripes of both membrane substrates, thalamic axons grew preferentially on their target membrane stripes. Enzymatic treatment of cortical membranes revealed that growth, branching and guidance of thalamic axons are independently regulated by attractive and repulsive cues differentially expressed in distinct cortical layers. These results indicate that multiple membrane-associated molecules collectively contribute to the laminar targeting of thalamic afferents. Furthermore, we found that interfering with the function of Eph tyrosine kinase receptors and their ligands, ephrins, abolished the preferential branching of thalamic axons on their target membranes, and that recombinant ephrin-A5 ligand elicited a branch-promoting activity on thalamic axons. We conclude that interactions between Eph receptors and ephrins mediate branch formation of thalamic axons and thereby may play a role in the establishment of layer-specific thalamocortical connections.

Pests and diseases have been reported by Myanmar foresters and plantation owners as significant challenges to the quality and quantity of wood supply from natural and planted forests. As part of a FAO project on strengthening local capacity in forest health, questionnaire surveys on pests and diseases and a needs assessment were conducted among companies/organizations involved in growing forests. Thirteen and 12 participants responded to the two surveys, respectively. Respondents grew 10 different tree species, namely Tectona grandis, Acacia mangium, Acacia hybrid, Eucalyptus spp., Gmelina arborea, Swietenia macrophylla, Paulownia kawakamii, Xylia xylocarpa, Bruguiera sexangula and Rhizophora apiculata. Growers recognized pests of teak but were less familiar with pests of the other tree species. Diseases were only reported from teak and A. mangium. Weeds were reported only from mature plantations. Workers were mostly educated only up to primary school level. None were trained in pest and disease management and most did not know about invasive alien species (IAS) and integrated pest and disease management (IPM). Based on the needs identified from the surveys, three workshops were conducted for over 100 local participants.

SummaryFrom mid-September 1993 to February 1994 avian species were inventoried at eight sites selected to sample the major biogeographic areas and threatened habitats of Masoala Peninsula of north-eastern Madagascar. The sites ranged from 10 to 1100 m elevation. Three forest types were inventoried: six sites included primary lowland rainforest (0–700 m), one site was characterized as moist montane forest (above 700 m), and one site was classified as littoral forest. Bird species and distribution were sampled using point counts and line transects, tree observations and opportunistic sightings; 85 avian species were detected. Line transects were the most productive technique for number of species detected. Twenty-four detected species were shared by all inventory sites. Six threatened and six near-threatened species were observed with notes on their ecology and behaviour. One endangered species, the Madagascar Serpent-eagle Eutriorchis astur, was first observed along a forest edge and then sighted several times at forest interior sites, suggesting that this secretive endangered raptor is not as rare as previously thought. Another species of indeterminate status, the Madagascar Red Owl Tyto soumagnei, was discovered by two villagers near one inventory site in modified habitat. Several rare and near-threatened species were found to be common throughout Masoala Peninsula: Scaly Ground-roller Brachypteracias squamiger, Short-legged Ground-roller B. leptosomus, Red-breasted Coua Cona serriana, Brown Mesite Mesitornis unicolor, Helmet Vanga Euryceros prcvostii, Bernier's Vanga Oriolia bernieri and Rand's Warbler Randia pseudozosterops; the last was only found along pristine riverine habitat. Three species were detected only at the high elevation montane forest: Grey-crowned Greenbul Phyllastrephus cinereiceps, Forest Rock-thrush Pseudocossyphus sharpei and Madagascar Brush-warbler Nesillas typica. Forest degradation from subsistence agriculture, shifting cultivation and fuelwood collecting threatens natural resources and biodiversity but conservation and development efforts can provide alternatives to meet the needs of the local people.Depuis la moitié du mois de septembre 1993 jusqu'au février 1994, nous avons inventorié la communauté avienne dans huit sites représentant la grande partie des habitats naturels de la Presqu'île de Masoala, Nord-Est de Madagascar. Ces sites ont des altitudes comprises entre 10 et 1100 m. Trois types de forêt ont été inventoriés: six sites de forêt primaire de basse altitude (0–700 m), un site considéré comme forêt humide de montagne (plus de 700 m), et le dernier classé comme for^t littorale. L'échantillonage était fait par point d'écoute et ligne de transect. Certains grands arbres ont été utilisés comme poste d'observation. Quatre-vingts cinq espèces d'oiseaux étaient détectées. Vingt quatre espèces sont communes aux sites inventoriés. Six espèces classées comme menacé et six autres en train de l'être sont observées avec des notes sur leur écologie et comportement. Une espèce en danger, l'Aigle serpentaire Eutriorchis astur, était observée pour la première fois le long d'une bordure forestière et puis vue plusieurs fois en pleine forèt. Ce qui suggère que cette espèce en danger et trèsdiscrète n'est pas très rare comme on a toujours pensé. Une autre espèce de statut indéterminé, l'Effraie de Soumagne Tyto soumagnei était découverte par deux villageois près d'un site d'inventaire dans un habitat dégradé. Quelques espèces rares et en train d'être menacées semblaient communes dans toute la Presqu'île de Masoala: Rollier terrestre écailleux Brachyptcracias squamiger, Rollier terrestre leptosome B. leptosomus, Coua de Serre Couci scrriana, Mésite unicolore Mesitornis unicolor, Eurycère de Prévost Euryceros prevostii, Oriolie de Bernier Oriolia bernieri et la Fauvette de Rand Randia pseudozosterops. Cette dernière se trouve seulement dans les habitats longeant les cours d'eau. Trois espèces sont seulement observées dans une forêt de haute altitude de montagne: Bulbul a tête grise Phyllastrepluis cinereiceps, Merle de roche de forêt Pseudocossyphus sharpei et la Fauvette de Madagascar Nesillas typica. La dégradation forestière causée par le besoin de surface cultivable, la culture itinérante et la collecte de bois de chauffe, menacent les ressources naturelles et la biodiversité du milieu. Seulement, la conservation en parallèle avec des efforts de développement peut fournir une alternative aux besoins de la population locale. Ceci est parmi les objectifs du Projet Masoala; cherchant des alternatives pour la population locale en même temps que la création d'un Pare National qui pourrait protéger une grande partie de bloc forestier de basse altitude de Madagascar, plus de 210.000 hectares.

HETTE S., HENDOUX F., HALLÉ F., 2017.LES ARBRES AMOUREUX. FRANCE, LASALAMANDRE, 144 P.WEISHAAR S. E., KREISER L., MILNE J. E.,ASHIABOR H., MEHLING M. (EDS), 2017. THEGREEN MARKET TRANSITION: CARBON TAXES,ENERGY SUBSIDIES AND SMART INSTRUMENTMIXES. UNITED KINGDOM, EDWARD ELGARPUBLISHING, XVI-287 P.COUZENS E., PATERSON A., RILEY S.,FRISTIKAWATI Y. (EDS), 2017. PROTECTINGFOREST AND MARINE BIODIVERSITY: THEROLE OF LAW. UNITED KINGDOM, EDWARDELGAR PUBLISHING, XI-336 P.VOGEL A., FÉTIVEAU J., GROEBER S.,DESBUREAUX S., 2017. GOUVERNANCEPARTAGÉE DES AIRES PROTÉGÉES ÀMADAGASCAR. QUEL CONTENU DONNER À LACOGESTION ? RETOURS D’EXPÉRIENCES DUPROJET HAFAFI D’APPUI À LA CRÉATION DESAIRES MARINES ET CÔTIÈRES PROTÉGÉESD’ANKIVONJY ET D’ANKAREA. FRANCE, GRET,136 P.PEYA M. I., 2018. THE BLUE FUND:MECHANISM OF FINANCING ANDMANAGEMENT OF THE CONGO BASIN FOR THEPROTECTION OF THE GLOBAL ENVIRONMENT.FRANCE, L’HARMATTAN, 236 P.FLEURY C., PRÉVOT A.-C., 2017. LE SOUCIDE LA NATURE : APPRENDRE, INVENTER,GOUVERNER. FRANCE, CNRS, 378 P.ASHTON M. S., KELTY M. J., 2018. THE PRACTICE OFSILVICULTURE: APPLIED FOREST ECOLOGY. UNITEDKINGDOM, WILEY, XVII-758 P.DE REFFYE P. (COORD.), JAEGER M. (COORD.),BARTHÉLÉMY D. (COORD.), HOULLIER F. (COORD.),2018. ARCHITECTURE DES PLANTES ETPRODUCTION VÉGÉTALE : LES APPORTS DE LAMODÉLISATION MATHÉMATIQUE. FRANCE, QUÆ,357 P.JAGDISH CHANDER DAGAR, VINDHYA PRASAD TEWARI(EDS), 2017. AGROFORESTRY: ANECDOTAL TOMODERN SCIENCE. GERMANY, SPRINGER, XIII-879 P.GÉRARD J. (COORD.), GUIBAL D., CERRE J.-C., PARADIS S., 2016. ATLAS DES BOIS TROPICAUXCARACTÉRISTIQUESTECHNOLOGIQUESET UTILISATIONS. QUÆ, 1 000 P.

La thèse de doctorat est l'étude des arbres et des rochers dans la peinture sur vases attique. La notion anachronique de paysage dans l'image y est abandonnée au profit d'une conception de spatialité qui ne dissocie plus l'espace de l'image et celui de son support matériel, le vase. Les rochers et les arbres dans les images n'y servent donc pas à représenter un espace propre à l'image qui constituerait le lieu des figures, mais participent directement à la représentation et la caractérisation des figures, qui elles sont à comprendre comme se trouvant sur le vase et non pas dans un espace pictural autonome. L'introduction présente une courte histoire des recherches sur la nature et le paysage dans l'art grec. Une première partie donne un aperçu chronologique des emplois iconographiques d'arbres et de rochers. Une deuxième partie tente de définir le concept de spatialité qui régit l'emploi des éléments de paysage. Une troisième partie étudie des aspects sémantiques
The doctorate studies the ways in which trees and rocks are depicted in Attic vase-painting. The anachronistic notion of landscape is replaced by a concept of spatiality that does no longer differentiate between the pictorial space and the space of the vase and his viewer: The trees and rocks do not depict a space within the picture, that is, they do not represent the scene of the figures, but rather take part in the depiction and characterisation of the figures themselves. These figures should be understood both concretely and metaphorically as standing on the ground line as a part of the vase. The introduction gives a short review of the past research on nature and landscape in Greek art. The first part presents the different iconographies of trees and rocks in chronological order. The second part defines the general concept of spatiality that rules the iconographic use of trees and rocks in vase painting. The third part studies semantic aspects of trees and rocks