Holocene history of fire, vegetation and land use from the central Pyrenees (France)

International audienceLocated on a mountain pass in the west-central Pyrenees, the Col d'Ech peat bog provides a Holocene fire and vegetation record based upon nine 14C (AMS) dates. We aim to compare climate-driven versus human-driven fire regimes in terms of frequency, fire episodes distribution, and impact on vegetation. Our results show the mid-Holocene (8500-5500 cal yr BP) to be characterized by high fire frequency linked with drier and warmer conditions.However, fire occurrences appear to have been rather stochastic as underlined by a scattered chronological distribution. Wetter and colder conditions at the mid-to-late Holocene transition (4000-3000 cal yr BP) led to a decrease in fire frequency, probably driven by both climate and a subsequent reduction in human land use. On the contrary, from 3000 cal yr BP, fire frequency seems to be driven by agro-pastoral activities with a very regular distribution of events. During this period fire was used as a prominent agent of landscape managemen

Fire frequency and landscape management in the northwestern Pyrenean piedmont, France, since the early Neolithic (8000 cal. BP)

International audienceBoth quantitative reconstruction of fire frequency from charcoal counts and pollen analysis were undertaken on a 312 cm sediment core from Gabarn peat bog. An 8000 yr cal. BP palaeofire record and vegetation history were established on the basis of nine 14C (AMS) dates. As anthropogenic Inferred Fire Frequency (IFF) has seldom been studied, we test and discuss two different methods of frequency calculation. Our results shows a clear Holocene bipartition at c. 3500–4000 cal. BP characterized by a three times decrease in Mean Fire Interval (MFI): from 7000 to 4000 cal. BP, MFI = 530 yr; from 4000 to 400 cal. BP, MFI = 160 yr. In an Atlantic vegetation context, we hypothesize this fire regime with such episode frequency to be mainly controlled by human activities. This hypothesis is supported by comparisons with other European quantified palaeofireregimes (Swiss Alps, northern Italy) whether they are controlled by climate, man or both. Taking into account the pollen record, we interpret the Gabarn palaeofire record links with human pressure and land use. Our results suggest that the relationship between fire frequency and human pressure is not always linear. Fire frequency could also reflect land-use shifts and changing use of fire within agro-pastoral activitie

A history of long-term human-environment interactions in the French Pyrenees inferred from the pollen data

International audienceOver the last decade, several research programs have been involved in studying the socioecological history of the Pyrenean Mountains using sedimentary records preserved in lakes and bogs. Their main focus was on understanding human exploitation of natural resources and its environmental consequences. Recovering these “memories” buried for thousands of years in sediments requires interdisciplinary efforts dealing with the analysis of a large number of bio-indicators. The study of those bio-indicators has become a multi-proxy process which combines the classicalstudy of fossil pollen and spores with macro-charcoal (size >150 m m) and nonpollen palynomorphs (algae, fungal spores, etc.) data

A possible dividing line between massive planets and brown-dwarf companions

Brown dwarfs are intermediate objects between planets and stars. The lower end of the brown-dwarf mass range overlaps with the one of massive planets and therefore the distinction between planets and brown-dwarf companions may require to trace the individual formation process. We present results on new potential brown-dwarf companions of Sun-like stars, which were discovered using CORALIE radial-velocity measurements. By combining the spectroscopic orbits and Hipparcos astrometric measurements, we have determined the orbit inclinations and therefore the companion masses for many of these systems. This has revealed a mass range between 25 and 45 Jupiter masses almost void of objects, suggesting a possible dividing line between massive planets and sub-stellar companion

Solid state synthesis and X-ray diffraction characterization of Pu 3+(1-2x)Pu4+xCa2+xPO4

In the framework of the 1991 French law concerning nuclear waste management, several studies have been carried out in order to elaborate crystalline matrices for specific immobilization of the radionuclides. In the case of high level and long-lived minor actinides (Np, Am and Cm), which are high level and long-lived radioactive elements, monazite, a light rare earth (Re) orthophosphate with general formula Re3+PO4 (with Re = La to Gd), has been proposed as a host matrix, thanks to its high resistance to self irradiation and its low solubility. Monazite crystallizes in the monoclinic space group P21/n. In this structure, trivalent cations (Re3+) could be substituted by an equivalent amount of bivalent (A2+) and tetravalent (B4+) cations, allowing the simultaneous incorporation of Am3+, Cm3+ and Np4+. According to Podor's work1, the limit of a tetravalent element incorporation in monazite is related to its size in the ninefold coordination (RIX)

A possible dividing line between massive planets and brown-dwarf companions

Brown dwarfs are intermediate objects between planets and stars. The lower end of the brown-dwarf mass range overlaps with the one of massive planets and therefore the distinction between planets and brown-dwarf companions may require to trace the individual formation process. We present results on new potential brown-dwarf companions of Sun-like stars, which were discovered using CORALIE radial-velocity measurements. By combining the spectroscopic orbits and Hipparcos astrometric measurements, we have determined the orbit inclinations and therefore the companion masses for many of these systems. This has revealed a mass range between 25 and 45 Jupiter masses almost void of objects, suggesting a possible dividing line between massive planets and sub-stellar companions.Comment: 4 pages, 3 figures, submitted to IAUS 276 conference proceeding

Grazing activities and biodiversity history in the Pyrénées - new insights on high altitude ecosystems in the framework of a Human-Environment Observatory

International audienceReconstruction of the relationship between pastoral activities and vegetation history in the central Pyrenees demonstrates the importance of grazing pressure in the maintenance of floristic diversity in highland regions that have been abandone

Les émotions à l’épreuve du genre

Les émotions sont souvent considérées comme un puissant marqueur de genre, jouant un rôle central dans les délimitations culturelles et sociales du masculin et du féminin. Depuis la théorie antique des tempéraments, en effet, le masculin est du côté des émotions chaudes et sèches (colère, fureur, hardiesse, haine), le féminin, du côté des émotions froides et humides (modestie, douceur, crainte, pudeur, compassion, langueur). Dans le monde occidental, on considère aussi que les émotions sont d..