2008, une année d'animations au service des sciences de la Terre en Bretagne.

Bilan régional de l'Année Internationale de la Planète TerreVous trouverez dans ce rapport un bilan du "programme CAREN" pour l'Année de la Terre, ou plus exactement de l'Année Internationale de la Planète Terre 2008. Il s'agit d'une année patronnée par l'UNESCO et l'Union Internationale des Sciences Géologiques (IUGS) avec un programme scientifique et des animations de sensibilisation du "grand public" partout dans le monde, avec une idée forte : "Les Géosciences au service de l'humanité" L'effort du programme scientifique a porté sur 10 grands thèmes multidisciplinaires, concernant la société : - la Terre et la santé - construire un environnement sain - le climat - climats anciens, climats futurs - les eaux souterraines - pour un usage durable - l'océan - la Planète Bleue - les sols - l'épiderme de la Terre - la Terre profonde - de la croûte au noyau - les mégapoles - aller plus loin, construire autrement - les risques naturels - minimiser les risques, maximiser la prévention - les ressources - vers un usage durable - la Terre et la vie - origine de la biodiversité (thème co-dirigé par l'Allemagne et la France) La Fédération Française de Géologie (dont Cécile Robin - MC à l'université de Rennes 1 / Géosciences Rennes - est la correspondante en Bretagne) et le CAREN (Centre armoricain de recherches en environnement, et plus particulièrement le laboratoire de Géosciences Rennes), ainsi que le BRGM Bretagne, se sont engagés dans cette manifestation internationale et ont proposé un ensemble d'animations de culture scientifique sur le thème "Représenter et comprendre la Terre" (sous la forme d'expositions, festivals, conférences, excursions, interventions dans les écoles, etc. etc.), qui ont touché au final près de 8000 personnes.Vous trouverez donc dans ce rapport un bilan complet de ce programme d'animations en Bretagne

La Méditerranée au pied des Andes : l’invention des paysages viticoles dans le Cône Sud ?

Au sein de la nouvelle planète vitivinicole, l’Argentine et le Chili s’affichent comme leaders du sous-continent latino-américain en termes de superficie viticole (8e et 10e rangs mondiaux), de volume de vins produits (5e et 8e rangs mondiaux) et de volumes exportés (9e et 5e rangs mondiaux) (OIV, 2012). Si la culture de la vigne date dans les deux pays de la colonisation et est donc ancienne, elle a subi depuis une vingtaine d’années une transformation profonde des modes de culture et des pr..

Les liens invisibles entre agriculture de proximité et commerce alimentaire dit "ethnique"

International audienceLa littérature scientifique concernant les agricultures de proximité, i.e. celles qui se pratiquent à proximité des marchés qu’elles desservent, s’est beaucoup renouvelée ces dernières années sous l’effet d’un intérêt réaffirmé pour l’agriculture urbaine et périurbaine . Si ces études ont surtout été attentives aux logiques de reterritorialisation que traduisent ces agricultures, certains auteurs soulignent la nécessité, d’une part, de mieux appréhender la diversité de ces agricultures de proximité, de leurs protagonistes, de leurs facteurs d’évolution et, d’autre part, de reconsidérer leurs transformations du point de vue agricole (géographie et sociologie agricoles, agronomie) . Elles appellent de surcroît une mise en tension avec les situations d’injustice socio-spatiale qui naissent tant de l’évolution des relations villes / campagnes que de la dynamique des systèmes agro-alimentaires . De nouvelles formes de vulnérabilité se repèrent en effet : difficultés d’accès à une alimentation de qualité pour les consommateurs ; mise à l’écart d’une partie des consommateurs et des producteurs des nouveaux réseaux malgré la proximité géographique ; précarisation des conditions de travail de certains agriculteurs .La recherche exploratoire dont nous proposons de présenter les résultats dans cette communication se penche sur des pratiques agricoles qui se déploient en marge des agricultures de proximité classiquement étudiées et des représentations positives associées actuellement aux agricultures urbaines et périurbaines du point de vue des « populations aisées et éduquées » des centres-villes. Elle vient souligner la diversité de cette nouvelle catégorie tant en termes d’acteurs que de modes d’exploitation (statut foncier, main d’œuvre, assolements, commercialisation….)Un premier travail sur deux paysages d’« agriculture de filières longues » (la Plaine de France dans le Val-d’Oise et le Comtat Venaissin dans les Bouches-du-Rhône) a ainsi permis de mettre à jour l’existence de certaines formes d’exploitations agricoles directement liées à des marchés urbains de niche du commerce dit « ethnique » (alimentation méditerranéenne ou asiatique). Le caractère « invisible » ou caché de ces formes d’agricultures de proximité (lieux d’installation, parcellaire singulier, statut précaire, informalité…) a impliqué de mobiliser plusieurs méthodes d’investigation : exploration empirique, observation participante sur l’exploitation, entretiens semi-directifs et photo-interprétation, enquêtes sur les marchés de revente. Les premiers résultats obtenus permettent de montrer l’existence de liens originaux entre le commerce dit « ethnique » implanté dans les centres urbains et la réorganisation spatiale des espaces agricoles de proximité. Ils apportent aussi des éléments sur les différentes trajectoires des travailleurs agricoles au sein de ces réseaux d’agriculture de proximité

Sunflower Associated With Legumes-Based Cover Crop : A Way To Increase Nitrogen Availability For The Following Winter Wheat?

Sunflower is one of the most important crop of organic crops systems in the South of France. In this region, sunflower is mostly cultivated before soft winter wheat, which is very often deficient in nitrogen because of a lack of nitrogen in the soil when the wheat needs it. To increase the soil nitrogen availability, one way is to introduce a legumes-based cover crop before wheat, which is sown just after the previous crop harvest. Thus, the time between sunflower harvest and wheat sowing is often too short to produce enough biomass. An alternative is to sow the cover crop during the sunflower cultivation, so to be intercropped into it. In a trial repeated over 3 years (from 2015 to 2017) in the southwest of France, Terres Inovia tested this practice, by intercropping 3 kinds of legumes-based cover crops into sunflower: alfalfa, purple vetch and legumes mixture. Over the 3 years, the growth of the cover crops was satisfying, and the average amount of nitrogen returned to soil after cover crops destruction was of 40 kg N/ha for purple vetch, 18 kg N/ha for alfalfa and 19.5 kg N/ha for legumes mixture. Nevertheless, cover crops impact severely sunflower performance because of competition for water and poor weed control due to no hoeing. Sunflower yield was reduced on average by 45% over the 3 years. This economic loss was partially compensated by a benefit on wheat yield, which was observed in 2016 and 2018, but only for wheat following sunflower intercropped with alfalfa

Random walks and polymers in the presence of quenched disorder

After a general introduction to the field, we describe some recent results concerning disorder effects on both `random walk models', where the random walk is a dynamical process generated by local transition rules, and on `polymer models', where each random walk trajectory representing the configuration of a polymer chain is associated to a global Boltzmann weight. For random walk models, we explain, on the specific examples of the Sinai model and of the trap model, how disorder induces anomalous diffusion, aging behaviours and Golosov localization, and how these properties can be understood via a strong disorder renormalization approach. For polymer models, we discuss the critical properties of various delocalization transitions involving random polymers. We first summarize some recent progresses in the general theory of random critical points : thermodynamic observables are not self-averaging at criticality whenever disorder is relevant, and this lack of self-averaging is directly related to the probability distribution of pseudo-critical temperatures $T_c(i,L)$ over the ensemble of samples $(i)$ of size $L$. We describe the results of this analysis for the bidimensional wetting and for the Poland-Scheraga model of DNA denaturation.Comment: 17 pages, Conference Proceedings "Mathematics and Physics", I.H.E.S., France, November 200

A global perspective on marine photosynthetic picoeukaryote community structure

A central goal in ecology is to understand the factors affecting the temporal dynamics and spatial distribution of microorganisms and the underlying processes causing differences in community structure and composition. However, little is known in this respect for photosynthetic picoeukaryotes (PPEs), algae that are now recognised as major players in marine CO2 fixation. Here, we analysed dot blot hybridisation and cloning–sequencing data, using the plastid-encoded 16S rRNA gene, from seven research cruises that encompassed all four ocean biomes. We provide insights into global abundance, α- and β-diversity distribution and the environmental factors shaping PPE community structure and composition. At the class level, the most commonly encountered PPEs were Prymnesiophyceae and Chrysophyceae. These taxa displayed complementary distribution patterns, with peak abundances of Prymnesiophyceae and Chrysophyceae in waters of high (25:1) or low (12:1) nitrogen:phosphorus (N:P) ratio, respectively. Significant differences in phylogenetic composition of PPEs were demonstrated for higher taxonomic levels between ocean basins, using Unifrac analyses of clone library sequence data. Differences in composition were generally greater between basins (interbasins) than within a basin (intrabasin). These differences were primarily linked to taxonomic variation in the composition of Prymnesiophyceae and Prasinophyceae whereas Chrysophyceae were phylogenetically similar in all libraries. These data provide better knowledge of PPE community structure across the world ocean and are crucial in assessing their evolution and contribution to CO2 fixation, especially in the context of global climate change

1H-NMR-Based Metabolic Profiling of Maternal and Umbilical Cord Blood Indicates Altered Materno-Foetal Nutrient Exchange in Preterm Infants

Background: Adequate foetal growth is primarily determined by nutrient availability, which is dependent on placental nutrient transport and foetal metabolism. We have used 1H nuclear magnetic resonance (NMR) spectroscopy to probe the metabolic adaptations associated with premature birth. Methodology: The metabolic profile in 1H NMR spectra of plasma taken immediately after birth from umbilical vein, umbilical artery and maternal blood were recorded for mothers delivering very-low-birth-weight (VLBW) or normo-ponderal full-term (FT) neonates. Principal Findings: Clear distinctions between maternal and cord plasma of all samples were observed by principal component analysis (PCA). Levels of amino acids, glucose, and albumin-lysyl in cord plasma exceeded those in maternal plasma, whereas lipoproteins (notably low-density lipoprotein (LDL) and very low-density lipoprotein (VLDL) and lipid levels were lower in cord plasma from both VLBW and FT neonates. The metabolic signature of mothers delivering VLBW infants included decreased levels of acetate and increased levels of lipids, pyruvate, glutamine, valine and threonine. Decreased levels of lipoproteins glucose, pyruvate and albumin-lysyl and increased levels of glutamine were characteristic of cord blood (both arterial and venous) from VLBW infants, along with a decrease in levels of several amino acids in arterial cord blood. Conclusion: These results show that, because of its characteristics and simple non-invasive mode of collection, cord plasma is particularly suited for metabolomic analysis even in VLBW infants and provides new insights into the materno-foetal nutrient exchange in preterm infants

Oilseed and protein crops grown in French organic farms: an overview of cultivation practices for sunflower and soybean

The development of organic agriculture in France was steady since 2010 but became stronger since 2014. Like other crops, the cultivated areas of organic soybean and sunflower doubled from 2014 to 2018. With a view to better characterize cultural practices in organic production, Terres Inovia and ITAB (in collaboration with Agence Bio) conducted in 2016 and 2017 a national farmers’ survey. These surveys reveal that sunflower was mainly cultivated over the same types of soil than in conventional production but were integrated in more diversified rotations. The main differences between organic and conventional systems concern sowing date and weed control. Organic sunflower was sown very lately compared to conventional one, which impacted the yield severely. Weed were controlled through ploughing, mechanical weeding and crop rotation and weed control was judged as satisfying by a major part of producers. Concerning soybean, a great difference is the use of irrigation which is almost systematic in conventional but concerned only 50% of cultivated area in organic production. Contrary to sunflower, soybean is integrated in short crop rotation, particularly when it was irrigated. This demonstrated the high profitability of soybean in organic systems. Like for sunflower, weed control done through ploughing, mechanical weeding, and crop rotation and weed control was also judged satisfying; nevertheless, criteria on harvest impurities are more severe and to respect them, organic farmers also use hand weeding in complement. These surveys will be reconducted over the years to be able to follow the changes of cultural practices over the years