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Mot(s)-clé(s) : réserve de biosphère
 

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A review of prokaryotic populations and processes in sub-seafloor sediments, including biosphere:geosphere interactions - new window
  • description : 
    A general review of the sub-seafloor biosphere is presented. This includes an update and assessment of prokaryotic cell distributions within marine sediments, current deepest 1922 m, and the impact of this on global sub-seafloor biomass estimates. ... déplier
    A general review of the sub-seafloor biosphere is presented. This includes an update and assessment of prokaryotic cell distributions within marine sediments, current deepest 1922 m, and the impact of this on global sub-seafloor biomass estimates. These global estimates appear relatively robust to different calculation approaches and our updated estimate is 5.39 x 1029 cells, taking into consideration new data from very low organic matter South Pacific Gyre sediments. This is higher than other recent estimates, which is justified as several sediments, such as gas hydrate deposits and oil reservoirs, can have elevated cell concentrations. The proposed relationship between elevated cell concentrations and Milankovitch Cycles in sequential diatom rich layers at some sites, demonstrates not only a dynamic deep biosphere, but that the deep biosphere is an integral part of Earth System Processes over geological time scales. Cell depth distributions vary in different oceanographic provinces and this is also reflected in contrasting biodiversity. Despite this there are some clear common, sub-seafloor prokaryotes, for Bacteria these are the phyla Chloroflexi, Gammaproteobacteria, Planctomycetes and the candidate phylum JS1, and for Archaea uncultivated lineages within the phylum Crenarchaeota (Miscellaneous Crenarchaeotal Group and Marine Benthic Group B), Euryarchaeota (SAGMEG, Marine Benthic Group-D/Thermoplasmatales associated groups) and Thaumarchaeota (Marine Group I). In addition, spores, viruses and fungi have been detected, but their importance is not yet clear. Consistent with the direct demonstration of active prokaryotic cells, prokaryotes have been enriched and isolated from deep sediments and these reflect a subset of the total diversity, including spore formers that are rarely detected in DNA analyses. Activities are generally low in deep marine sediments (~ 10,000 times lower than in near-surface sediments), however, depth integrated activity calculations demonstrate that sub-surface sediments can be responsible for the majority of sediment activity (up to 90%), and hence, are biogeochemically important. Unlike near-surface sediments, competitive metabolisms can occur together and metabolism per cell can be 1,000 times lower than in culture, and below the lowest known maintenance energies. Consistent with this, cell turnover times approach geological time-scales (100 - 1,000's of years). Prokaryotic necromass may be an important energy and carbon source, but this is largely produced in near-surface sediments as cell numbers rapidly decrease. However, this and deposited organic matter may be activated at depth as temperatures increase. At thermogenic temperatures methane and other hydrocarbons, plus H2, acetate and CO2 may be produced and diffuse upwards to feed the base of the biosphere (e.g. Nankai Trough and Newfoundland Margin). Temperature activation of minerals may also result in oxidation of sulphides and the formation of electron acceptors, plus H2 from low temperature (~ 55 °C) serpentenisation and water radiolysis. New mineral surface formation from fracturing, weathering and subduction etc. can also mechanochemically split water producing both substrates (H2) and oxidants (O2, H2O2) for prokaryotes. These and other biosphere:geosphere interactions may be important for sustaining a globally significant sub-seafloor biosphere.Replier
  • Date de publication :  01/06/2014
  • Producteur :  Institut français de recherche pour l'exploitation de la mer (Ifremer)
 
Echanges biosphère-atmosphère : flux de matière et transport turbulent. - new window
  • Date de publication :  01/01/2000
  • Producteur :  Institut national de la recherche agronomique (Inra)
 
Impacts from ice-nucleating bacteria on deep convection : implications for the biosphere-atmosphere interaction in climate change. - new window
  • description : 
    A cloud modeling framework is described to simulate ice nucleation by biogenic aerosol particles, as represented by airborne ice-nucleation active (INA) bacteria. It includes the empirical parameterization of heterogeneous ice nucleation. The ... déplier
    A cloud modeling framework is described to simulate ice nucleation by biogenic aerosol particles, as represented by airborne ice-nucleation active (INA) bacteria. It includes the empirical parameterization of heterogeneous ice nucleation. The formation of cloud liquid by soluble material coated on such insoluble aerosols is represented and determines their partial removal from deep convective clouds by accretion onto precipitation. Preliminary simulations are performed for a case of deep convection over Oklahoma. If present at high enough concentrations, as might occur in proximity to land sources, INA bacteria are found to influence significantly: - (1) the average numbers and sizes of crystals in the clouds; (2) the horizontal cloud coverage in the free troposphere; and (3) precipitation and incident solar insolation at the surface, which influence rates of bacterial growth. At lower concentrations, the corresponding responses of cloud fields appear much lower or are ambiguous. In nature, the growth rates of INA bacteria on leaves prior to emission into the atmosphere are known to be highly dependent on temperature, precipitation and plant species. Consequently, the open question emerges of whether emissions of such ice nucleating biogenic particles can then be modified by their own effects on clouds and atmospheric conditions, forming a weak feedback in climate or microclimate systemsReplier
  • Date de publication :  01/01/2000
  • Producteur :  Institut national de la recherche agronomique (Inra)
 
Les engagements internationaux - new window
  • description : 
    La convention de Ramsar du 2 février 1971 relative aux zones humides d'importance internationale a été ratifiée par la France le 1er octobre 1986. Chaque partie contractante désigne les zones de son territoire à inscrire et s'engage à favoriser leur ... déplier
    La convention de Ramsar du 2 février 1971 relative aux zones humides d'importance internationale a été ratifiée par la France le 1er octobre 1986. Chaque partie contractante désigne les zones de son territoire à inscrire et s'engage à favoriser leur conservation.Au cours de l'année 2011, six nouveaux sites Ramsar ont été désignés en France, dont trois en métropole (deux en Aquitaine et un en Corse) et trois en Outre-mer (Saint-Martin, Mayotte et l'île Europa). Ainsi, au 1er janvier 2012, on dénombre 32 sites en France métropolitaine couvrant 7 701 km2 dont plus de 670 km2 en mer et 13 km2 sur le lac Léman. Outremer, trois sites ont été désignés en Guyane (2 461 km2 dont 623 km2 en mer), un en Guadeloupe (291 km2 dont 228 km2 en mer), un en Martinique (202 ha), un à Mayotte (126 ha), un à Saint-Martin (30 km2), ainsi que le lagon de Moorea en Polynésie (environ 5 000 ha), l'île Europa (2 058 km2) et la réserve naturelle nationale des Terres australes françaises (23 704 km2 dont 16 140 km2 en mer).Les réserves de biosphère s'inscrivent dans le cadre du Programme Man and Biosphere (MAB) de l'Unesco, né en 1971, sous la forme d'un programme de coopération scientifique international, portant sur les interactions entre l'homme et son environnement. En 2012, on dénombre 610 réserves de biosphère dans 117 pays.Il en existe huit en France métropolitaine ainsi qu'une en Guadeloupe et une en Polynésie. On distingue trois zones pour chaque réserve de biosphère : la zone centrale, la zone tampon et enfin, l'enveloppe la plus extérieure, l'aire de coopération. Ces trois zones couvrent respectivement 947, 4 085 et 6 200 km2 en métropole et 221, 304 et 1 946 km2 en Guadeloupe. Les zones centrales, qui peuvent être disjointes, s'appuient le plus souvent sur des espaces protégés existants. En métropole, 1,8 % de la superficie de ces zones centrales est en mer, 15% en Guadeloupe. Quant aux zones tampon, 7,8 % de leur superficie est en mer en métropole et 3,8 % en Guadeloupe.La réserve de biosphère des Vosges du Nord est couplée depuis 1998 avec la réserve de biosphère de Pfälzerwald en Allemagne, constituant ainsi une réserve de biosphère transfrontalière. Télécharger la carte La France est également signataire d'autres conventions internationales, qui ne se traduisent pas par la mise en place d'outils propres de protection des espaces naturels, ces conventions s'appuyant en partie sur les outils existants. C'est le cas notamment des conventions alpine et de Barcelone, qui reconnaissent respectivement les Alpes et la Méditerranée comme des espaces unitaires à préserver dans une démarche de développement durable. Voir aussi... www.ramsar.org/indexfr.htm (Convention de Ramsar)Site de la convention de Ramsar.www.mab-france.org (Réseau français des réserves de biosphère)Présentation du programme MAB et des réserves MAB françaises.www.unesco.org/mab (Programme MAB de l'UNESCO)Accès à la liste des réserves de biosphère du monde avec leur description.Replier
  • Date de publication :  01/01/2000
  • Producteur :  Ministère chargé de l'environnement - Service de la donnée et des études statistiques (SDES)
 
Biopollatm : Biosphère et pollution atmosphérique en zone rurale et périurbaine. Rapport de fin de contrat. - new window
  • description : 
    Le projet BIOPOLLATM vise à mieux comprendre les interactions biosphère-atmosphère dans le domaine de la pollution atmosphérique. On cherche (1) à comprendre les modalités d'impacts de plusieurs polluants sur le fonctionnement des plantes et (2) le ... déplier
    Le projet BIOPOLLATM vise à mieux comprendre les interactions biosphère-atmosphère dans le domaine de la pollution atmosphérique. On cherche (1) à comprendre les modalités d'impacts de plusieurs polluants sur le fonctionnement des plantes et (2) le rôle de la biosphère comme source et puits dans la pollution atmosphérique locale et régionale. Des caractéristiques fortes de BIOPOLLATM sont (1) une intégration entre des approches biologiques et physiques, à l'interface des sciences de la vie, de la terre et de l'atmosphère, (2) l'objet d'étude privilégié qui sont les écosystèmes cultivés en zones périurbaines et (3) l'intégration d'échelle, allant de la plante à la région selon les thématiques scientifiques et appliquées concernées. Ce rapport fait un point sur l'avancement du projet après 2 ans de travail (le projet se poursuit dans le cadre de PRIMEQUAL notamment, avec un financement du MEDD/DPPR). Il se compose de trois parties : - un rappel sur les objectifs et l'organisation du projet - un rapport plus détaillé sur les travaux conduits, organisé en trois grands domaines : o impact de l'ozone sur le fonctionnement des couverts végétaux à différentes échelles et selon différentes approches, allant de la modification des enzymes impliquées dans la photosynthèse jusqu'à la modélisation de l'impact sur le rendement des cultures ; o échanges de polluants entre un couvert végétal et l'atmosphère, organisé autour du développement et la validation d'un modèle à résistance à deux couches, destiné d'une part à être utilisé par les écophysiologistes/agronomes pour estimer les quantités de polluant absorbées par la végétation et, d'autre part, à être utilisé comme interface surface-atmosphère dans des modèles de chimie atmosphérique ; o une présentation des bases de données créées et des dispositifs expérimentaux créés dans le cadre de ce projet pour l'étude des échanges de polluants entre les surfaces naturelles et l'atmosphère. Ces acquis perdureront au delà du projet et pourront être utilisés par nos équipes et d'autres pour la poursuite de ce type de travaux. - Une synthèse des résultats acquis et une présentation des perspectives de ce travail à échéance de deux ans.Replier
  • Date de publication :  01/01/2004
  • Producteur :  Institut national de la recherche agronomique (Inra)
 
Dynamics of ammonia exchange with cut grassland: strategy and implementation of the GRAMINAE Integrated Experiment. - new window
  • description : 
    A major international experiment on ammonia (NH3) biosphere-atmosphere exchange was conducted over intensively managed grassland at Braunschweig, Germany. The experimental strategy was developed to allow an integrated analysis of different features ... déplier
    A major international experiment on ammonia (NH3) biosphere-atmosphere exchange was conducted over intensively managed grassland at Braunschweig, Germany. The experimental strategy was developed to allow an integrated analysis of different features of NH3 exchange including: a) quantification of nearby emissions and advection effects, b) estimation of net NH3 fluxes with the canopy by a range of micrometeorological measurements, c) analysis of the sources and sinks of NH3 within the plant canopy, including soils and bioassay measurements, d) comparison of the effects of grassland management options on NH3 fluxes and e) assessment of the interactions of NH3 fluxes with aerosol exchange processes. Additional technical objectives included the inter-comparison of different estimates of sensible and latent heat fluxes, as well as continuous-gradient and Relaxed Eddy Accumulation (REA) systems for NH3 fluxes. The prior analysis established the spatial and temporal design of the experiment, allowing significant synergy between these objectives. The measurements were made at 7 measurement locations, thereby quantifying horizontal and vertical profiles, and covered three phases: a) tall grass canopy prior to cutting (7 days), b) short grass after cutting (7 days) and c) re-growing sward following fertilization with ammonium nitrate (10 days). The sequential management treatments allowed comparison of sources-sinks, advection and aerosol interactions under a wide range of NH3 fluxes. This paper describes the experimental strategy and reports the grassland management history, soils, environmental conditions and air chemistry during the experiment, finally summarizing how the results are coordinated in the accompanying series of papers.Replier
  • Date de publication :  01/01/2004
  • Producteur :  Institut national de la recherche agronomique (Inra)
 
Analysis and modelling of the evaporation-transpiration partition under controlled conditions (RUBIC), using stable isotopes of water - new window
  • description : 
    Rainfall recycling by evapotranspiration from continental surfaces is certainly the most unknown component of the global water cycle. This is due to the large variability of rainfall as well as the heterogeneity of these continental surfaces, both ... déplier
    Rainfall recycling by evapotranspiration from continental surfaces is certainly the most unknown component of the global water cycle. This is due to the large variability of rainfall as well as the heterogeneity of these continental surfaces, both in time and space. Traditional measuring methods including the Bowen ratio, the eddy correlation and the water balance estimation (micro lysimeter, sap flow) have been used since the 70s for a monitoring of real evapotranspiration fluxes over crops and others plant covers. A complementary method consists in using isotopic biogeochemistry. When making specific hypothesis, it is possible to identify and quantify the different sources of the atmospheric water vapour (vegetation and soil at different scales). Analysis of the heavy stable isotopic ratios of water in both liquid and vapour phases: 18O and 2H can allow determining the " history " of the water in the soil since the last rainfall event (infiltration, re-evaporation) or the root extraction depths. Field campaigns measurements (plants and soils), interpreted using the Keeling Plot method (Keeling, 1958) allowed some progress in the partition between evaporation and transpiration understanding (e.g. Yepez et al., 2003; Williams et al., 2004). But the experimental design is not sufficient to mechanistically describe the water processes involved. The study of all the interactions is not possible due to the large number of controlling variables describing climate, vegetation and soil characteristics. The BIIBA research team (Isotopic Biogeochemistry for the study of Biosphere-Atmosphere Interactions) from the Research Institute BioEMCo (Biogeochemistry and Ecology of Continental Environments) studies the vapour and liquid water fluxes within the soil and vegetation (at the plant and small cover scale). Experiments are conducted in the field and in controlled conditions inside biogeochemical reactors called RUBIC (Reactor Used for Continental Isotopic Biogeochemistry). Controlled conditions allow a monitoring and regulation of climatic parameters (net radiation, air temperature, vapour pressure deficit, CO2 partial pressure, and wind speed). It is also easier to fix soil (structure, texture, and water content) and vegetation (specie and seeding density) parameters. A monolith experiment (including soil and growing plant) was carried out in one of our reactors. The collected data allow us to improve our understanding of the partition of evapotranspiration into soil evaporation and plant transpiration and to assess the hypothesis often made in isotopic biochemistry of a stationary state reached in the two reservoirs (soil and plant). These data also allow the evaluation of the hypothesis included in a transfer module of heavy stable isotopes of water within the bare soil and the plant (Braud et al., 2005). The latter is coupled to a SVAT model (Soil-Plant-Atmosphere Transfer) called SiSPAT (Simple Soil Plant Atmosphere Transfer model. Braud et al., 1995; Braud 2000; 2002) and was extended to take into account isotopes transfer within the vegetation (root extraction and transpiration). The poster will present the experimental device RUBIC. Then, we will emphasize the functioning mechanisms identified from data analysis and derived from the intrinsic properties of stable isotopes as natural tracers of water movement and history. We will also present our first modelling results of the partition between evaporation and transpiration simulated using SiSPAT_Isotope.Replier
  • Date de publication :  01/01/2004
  • Producteur :  Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (Irstea)
 
Understanding protected area resilience: a multi-scale socioal-ecological approach. - new window
  • description : 
    Protected areas (PAs) remain central to the conservation of biodiversity. Classical PAs were conceived as areas that would be set aside to maintain a natural state with minimal human influence. However, global environmental change and growing ... déplier
    Protected areas (PAs) remain central to the conservation of biodiversity. Classical PAs were conceived as areas that would be set aside to maintain a natural state with minimal human influence. However, global environmental change and growing cross-scale anthropogenic influences mean that PAs can no longer be thought of as ecological islands that function independently of the broader social-ecological system in which they are located. For PAs to be resilient (and to contribute to broader social-ecological resilience), they must be able to adapt to changing social and ecological conditions over time in a way that supports the long-term persistence of populations, communities, and ecosystems of conservation concern. We extend Ostrom's social-ecological systems framework to consider the long-term persistence of PAs, as a form of land use embedded in social-ecological systems, with important cross-scale feedbacks. Most notably, we highlight the cross-scale influences and feedbacks on PAs that exist from the local to the global scale, contextualizing PAs within multi-scale social-ecological functional landscapes. Such functional landscapes are integral to understand and manage individual PAs for long-term sustainability. We illustrate our conceptual contribution with three case studies that highlight cross-scale feedbacks and social-ecological interactions in the functioning of PAs and in relation to regional resilience. Our analysis suggests that while ecological, economic, and social processes are often directly relevant to PAs at finer scales, at broader scales, the dominant processes that shape and alter PA resilience are primarily social and economicReplier
  • Date de publication :  01/01/2015
  • Producteur :  Institut national de la recherche agronomique (Inra)
 
Investigating the stomatal, cuticular and soil ammonia fluxes over a growing tritical crop under high acidic loads. - new window
  • description : 
    Ammonia concentration and fluxes were measured above a growing triticale field for two months during May and June 2010 at the NitroEurope crop site in Grignon (Fr-Gri) near Paris, France. The measurement campaign started 15 days following a 40 kg N ... déplier
    Ammonia concentration and fluxes were measured above a growing triticale field for two months during May and June 2010 at the NitroEurope crop site in Grignon (Fr-Gri) near Paris, France. The measurement campaign started 15 days following a 40 kg N ha−1 application of an ammonium nitrate solution. A new mini-wedd (Wet Effluent Denuder) flow injection analyser with three channels (ROSAA, RObust and Sensitive Ammonia Analyser) was used to measure NH3 fluxes using the aerodynamic gradient method. The measured ammonia concentrations varied from 0.01 to 39 μg NH3 m−3 and were largely influenced by advection from the nearby farm. The ammonia fluxes ranged from -560 to 220 ng NH3 m−2 s−1 and averaged -29 ng NH3 m−2 s−1. During some periods the large deposition fluxes could only be explained by a very small surface resistance, which may be partly due to the high concentrations of certain acid gases (HNO3 and SO2) observed in this suburban area. Ammonia emissions were also observed. The canopy compensation point Cc was around 1.5 μg NH3 m−3 on average. The canopy emission potential Γc (Cc normalised for the temperature response of the Henry equilibrium) decreased over the course of the measurement campaign from Γc = 2200 to Γc = 450, the latter value being close to the median stomatal emission potential (Γs) and lower than the median ground emission potential (Γg) for managed ecosystems reported in the literature. The temporal dynamics of the measured NH3 flux compared well with the Surfatm-NH3 model using fitted parameters. The subjectivity of the model fitting is discussed based on a sensitivity analysis.Replier
  • Date de publication :  01/01/2015
  • Producteur :  Institut national de la recherche agronomique (Inra)