Influence of Biological Factors on Connectivity Patterns for Concholepas concholepas (loco) in Chile

In marine benthic ecosystems, larval connectivity is a major process influencing the maintenance and distribution of invertebrate populations. Larval connectivity is a complex process to study as it is determined by several interacting factors. Here we use an individual-based, biophysical model, to disentangle the effects of such factors, namely larval vertical migration, larval growth, larval mortality, adults fecundity, and habitat availability, for the marine gastropod Concholepas concholepas (loco) in Chile. Lower transport success and higher dispersal distances are observed including larval vertical migration in the model. We find an overall decrease in larval transport success to settlement areas from northern to southern Chile. This spatial gradient results from the combination of current direction and intensity, seawater temperature, and available habitat. From our simulated connectivity patterns we then identify subpopulations of loco along the Chilean coast, which could serve as a basis for spatial management of this resource in the future

Shifts in structural diversity of Amazonian forest edges detected using terrestrial laser scanning

Forest edges are an increasingly common feature of Amazonian landscapes due to human-induced forest frag-mentation. Substantial evidence shows that edge effects cause profound changes in forest biodiversity and productivity. However, the broader impacts of edge effects on ecosystem functioning remain unclear. Assessing the three-dimensional arrangement of forest elements has the potential to unveil structural traits that are scalable and closely linked to important functional characteristics of the forest. Using over 600 high-resolution terrestrial laser scanning measurements, we present a detailed assessment of forest structural metrics linked to ecosystem processes such as energy harvesting and light use efficiency. Our results show a persistent change in forest structural characteristics along the edges of forest fragments, which resulted in a significantly lower structural diversity, in comparison with the interior of the forest fragments. These structural changes could be observed up to 35 m from the forest edges and are likely to reflect even deeper impacts on other ecosystem variables such as microclimate and biodiversity. Traits related to vertical plant material allocation were more affected than traits related to canopy height. We demonstrate a divergent response from the forest understory (higher vegetation density close to the edge) and the upper canopy (lower vegetation density close to the edge), indicating that assessing forest disturbances using vertically integrated metrics, such as total plant area index, can lead to an erroneous interpretation of no change. Our results demonstrate the strong potential of terrestrial laser scanning for benchmarking broader-scale (e.g. airborne and space-borne) remote sensing assessments of forest distur-bances, as well as to provide a more robust interpretation of biophysical changes detected at coarser resolutions.Peer reviewe

Shifts in structural diversity of Amazonian forest edges detected using terrestrial laser scanning

Forest edges are an increasingly common feature of Amazonian landscapes due to human-induced forest fragmentation. Substantial evidence shows that edge effects cause profound changes in forest biodiversity and productivity. However, the broader impacts of edge effects on ecosystem functioning remain unclear. Assessing the three-dimensional arrangement of forest elements has the potential to unveil structural traits that are scalable and closely linked to important functional characteristics of the forest. Using over 600 high-resolution terrestrial laser scanning measurements, we present a detailed assessment of forest structural metrics linked to ecosystem processes such as energy harvesting and light use efficiency. Our results show a persistent change in forest structural characteristics along the edges of forest fragments, which resulted in a significantly lower structural diversity, in comparison with the interior of the forest fragments. These structural changes could be observed up to 35 m from the forest edges and are likely to reflect even deeper impacts on other ecosystem variables such as microclimate and biodiversity. Traits related to vertical plant material allocation were more affected than traits related to canopy height. We demonstrate a divergent response from the forest understory (higher vegetation density close to the edge) and the upper canopy (lower vegetation density close to the edge), indicating that assessing forest disturbances using vertically integrated metrics, such as total plant area index, can lead to an erroneous interpretation of no change. Our results demonstrate the strong potential of terrestrial laser scanning for benchmarking broader-scale (e.g. airborne and space-borne) remote sensing assessments of forest disturbances, as well as to provide a more robust interpretation of biophysical changes detected at coarser resolutions

Shifts in structural diversity of Amazonian forest edges detected using terrestrial laser scanning

Forest edges are an increasingly common feature of Amazonian landscapes due to human-induced forest frag-mentation. Substantial evidence shows that edge effects cause profound changes in forest biodiversity and productivity. However, the broader impacts of edge effects on ecosystem functioning remain unclear. Assessing the three-dimensional arrangement of forest elements has the potential to unveil structural traits that are scalable and closely linked to important functional characteristics of the forest. Using over 600 high-resolution terrestrial laser scanning measurements, we present a detailed assessment of forest structural metrics linked to ecosystem processes such as energy harvesting and light use efficiency. Our results show a persistent change in forest structural characteristics along the edges of forest fragments, which resulted in a significantly lower structural diversity, in comparison with the interior of the forest fragments. These structural changes could be observed up to 35 m from the forest edges and are likely to reflect even deeper impacts on other ecosystem variables such as microclimate and biodiversity. Traits related to vertical plant material allocation were more affected than traits related to canopy height. We demonstrate a divergent response from the forest understory (higher vegetation density close to the edge) and the upper canopy (lower vegetation density close to the edge), indicating that assessing forest disturbances using vertically integrated metrics, such as total plant area index, can lead to an erroneous interpretation of no change. Our results demonstrate the strong potential of terrestrial laser scanning for benchmarking broader-scale (e.g. airborne and space-borne) remote sensing assessments of forest distur-bances, as well as to provide a more robust interpretation of biophysical changes detected at coarser resolutions

Global ensemble projections reveal trophic amplification of ocean biomass declines with climate change

While the physical dimensions of climate change are now routinely assessed through multimodel intercomparisons, projected impacts on the global ocean ecosystem generally rely on individual models with a specific set of assumptions. To address these single-model limitations, we present standardized ensemble projections from six global marine ecosystem models forced with two Earth system models and four emission scenarios with and without fishing. We derive average biomass trends and associated uncertainties across the marine food web. Without fishing, mean global animal biomass decreased by 5% (±4% SD) under low emissions and 17% (±11% SD) under high emissions by 2100, with an average 5% decline for every 1 °C of warming. Projected biomass declines were primarily driven by increasing temperature and decreasing primary production, and were more pronounced at higher trophic levels, a process known as trophic amplification. Fishing did not substantially alter the effects of climate change. Considerable regional variation featured strong biomass increases at high latitudes and decreases at middle to low latitudes, with good model agreement on the direction of change but variable magnitude. Uncertainties due to variations in marine ecosystem and Earth system models were similar. Ensemble projections performed well compared with empirical data, emphasizing the benefits of multimodel inference to project future outcomes. Our results indicate that global ocean animal biomass consistently declines with climate change, and that these impacts are amplified at higher trophic levels. Next steps for model development include dynamic scenarios of fishing, cumulative human impacts, and the effects of management measures on future ocean biomass trends

Les frontières et l'économie.

Minard Philippe, Verley P. Les frontières et l'économie.. In: Revue du Nord, tome 76, n°307, Octobre-décembre 1994. pp. 897-899

Evaluation du couple "champ lointain" d'un rotor d'hélicoptère en vol stationnaire (analyse de résultats issus de simulations numériques de mécanique des fluides)

Dans cette thèse, une formulation pour l extraction du couple champ lointain d un rotor d hélicoptère en vol stationnaire est présentée. Cette formulation est dérivée de la méthode d extraction de la traînée champ lointain d un avion, basée sur les travaux de van der Vooren et Destarac [?, ?, ?]. Un outil développé à l Onera à partir de cette théorie permet de donner une analyse complète de la traînée aérodynamique d un avion. Il est basé sur l analyse physique et locale de l écoulement calculé autour de l aéronef, et décompose la traînée totale, aussi appelée traînée mécanique, en composantes physiques. Ces composantes physiques peuvent être définies comme suit : 1) la traînée d onde, 2) la traînée visqueuse, 3) la traînée induite. L adaptation de la méthode d extraction de la traînée d un avion à un rotor en vol stationnaire nécessite l utilisation du couple rotor à la place de la traînée de l avion, ce qui donne la décomposition suivante : 1) le couple d onde, 2) le couple visqueux, 3) le couple induit. Les simulations de rotor diffèrent de celles de l avion dans la mesure où les équations d Euler (ou RANS) ne sont pas écrites dans le même repère de référence : les simulations d avion utilisent généralement une formulation en vitesse relative tandis que les simulations d un rotor d hélicoptère utilisent la vitesse absolue projetée dans le repère relatif. Cette différence conduit à deux formulations différentes des équations de l écoulement, et nécessairement deux formulations différentes de l extraction de la traînée ou du couple. Ce changement de repère implique aussi des changements dans les quantités thermodynamiques utilisées, en particulier l utilisation de la rothalpie à la place de l enthalpie d arrêt pour déterminer le couple dû aux phénomènes irréversibles. Une application de cette méthode est présentée sur un rotor quadripale créé pour cette étude et montre comment cette nouvelle approche peut améliorer la précision de l extraction des performances d un rotor à partir de résultat issu de la simulation numérique.In this thesis, a formulation for far-field torque extraction in the case of a hovering rotor is presented. This formulation is derived from an aircraft far-field drag extraction method, based on van der Vooren and Destarac s works [?, ?, ?]. A tool was previously developed at Onera to give an aerodynamic comprehensive analysis of aircraft drag, based on physical and local analysis of the computed flow field surrounding the aircraft. It decomposes the total drag, also called mechanical drag, into its physical components. These physical components can be defined as : 1) wave drag, 2) viscous drag, 3) induced drag. The adaptation of the method to a rotor in hover leads to consider rotor torque instead of aircraft drag, which gives the following decomposition : 1) wave torque, 2) viscous torque, 3) induced torque. Rotor simulations differ from aircraft ones inasmuch as the Euler (or RANS) equations are not written in the same reference frame : aircraft simulations use the relative velocity formulation while rotor simulations use the absolute velocity projected in the relative frame. This difference leads to two different formulations of the flow equations, and necessarily two different formulations of the drag or torque extraction. This change of reference frame also implies some changes in the thermodynamical quantities used, in particular the use of the rothalpy instead of the stagnation enthalpy to determine the torque due to irreversible phenomena. An application of this method is described on a four-bladed rotor created for this study and shows how this method can improve rotor performance extraction from numerical simulations.ORLEANS-SCD-Bib. electronique (452349901) / SudocSudocFranceF

Globalisation, régulation et transformations des entreprises

Débat à paraître dans Entreprises et Histoire, 2019/1, n°94 Numéro spécial sur « Globalisation et transformation des entreprises » Patrick Verley, auteur de L'échelle du monde. Essai sur l'industrialisation de l'Occident, 2 e éd., Paris, Gallimard, 2013 et Jean-Philippe Robé, auteur de Le temps du monde de l'entreprise. Globalisation et mutation du système juridique, Paris, Dalloz, 2015 répondent à nos questions sur la généalogie de la globalisation, l'évolution des entreprises en son sein et sur les risques actuels d'une bataille généralisée sans règles.International audiencePatrick Verley, auteur de L’échelle du monde. Essai sur l’industrialisation de l’Occident, 2e éd., Paris, Gallimard, 2013 et Jean-Philippe Robé, auteur de Le temps du monde de l’entreprise. Globalisation et mutation du système juridique, Paris, Dalloz, 2015 répondent à nos questions sur la généalogie de la globalisation, l’évolution des entreprises en son sein et sur les risques actuels d’une bataille généralisée sans règles.Les termes de mondialisation et de globalisation sont souvent utilisés comme des mots-valises. Quelles représentations ou définitions de la mondialisation et de la globalisation ont votre préférence ?Jean-Philippe Robé : Je ne trouve pas cette question de vocabulaire très enrichissante. C’est un des seuls points de désaccord que j’ai avec Alain Supiot, qui insiste sur la différence à faire entre les deux termes. Pourquoi pas. Mais comment pourrions-nous avoir un tel débat en anglais ? Il n’y a qu’un seul terme en anglais, globalization, et nous allons avoir du mal à en restreindre l’usage du fait d’un supplément de richesse de la langue française. Maintenant, sur le fond, je crois qu’il faut bien distinguer deux phénomènes – la géographie des échanges et les structures de pouvoirs – pour ensuite examiner leurs relations. La géographie des échanges s’appuie sur des pouvoirs qui permettent aux échanges d’exister ; et les pouvoirs qui aident aux échanges influent sur leur géographie. Les premiers échanges au long cours ont été des échanges au sein d’empires qui précèdent les États comme structures de pouvoir englobantes

Implementation of an end-to-end model of the Gulf of Lions ecosystem (NW Mediterranean Sea). II. Investigating the effects of high trophic levels on nutrients and plankton dynamics and associated feedbacks

The end-to-end OSMOSE-GoL model parameterized, calibrated and evaluated for the Gulf of Lions ecosystem (Northwestern Mediterranean Sea) has been used to investigate the effects of introducing two-ways coupling between the dynamics of Low and High Trophic Level groups. The use of a fully dynamic two-ways coupling between the models of Low and High Trophic Levels organisms provided some insights in the functioning of the food web in the Gulf of Lions. On the whole microphytoplankton and mesozooplankton were found to be preyed upon by High Trophic Levels planktivorous groups at rates lower than 20% and 30% of their respective natural mortality rates, but these relatively low rates involved some important alterations in the infra-seasonal and annual cycles of both High and Low Trophic Levels groups. They induced significant changes in biomass, fisheries landings and food web interactions by cascading effects. Spatial differential impacts of High Trophic Levels predation on plankton are less clear except in areas in which primary productivity is high. Higher predation rates on plankton groups were encountered within the area of the Rhone river's influence and in areas associated to the presence of mesoscale eddies in the Northwestern part of the Gulf of Lions, especially. Generally, the pressure of the High Trophic Levels predation was the highest in areas of highest biomass whatever the plankton group considered. The two-ways coupling between Low and High Trophic Levels models revealed both bottom-up and top-down controls in the ecosystem with effects on planktivorous species similar to those observed in the field. The use of the end-to-end model enabled to propose a set of potential mechanisms that may explain the observed decrease in small pelagic catches by the French Mediterranean artisanal fisheries over the last decade