CNRS European Center for Research and Education in Environmental Geosciences

Marseille, France

CNRS European Center for Research and Education in Environmental Geosciences

Marseille, France
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Ayadi K.,University of Science and Technology Houari Boumediene | Boutiba M.,University of Science and Technology Houari Boumediene | Sabatier F.,CNRS European Center for Research and Education in Environmental Geosciences | Sabatier F.,Aix - Marseille University | Guettouche M.S.,University of Science and Technology Houari Boumediene
Arabian Journal of Geosciences | Year: 2016

The Bejaia coastline is one of the most beautiful and attractive coastlines in Algeria; this is due to its landscape and ecological diversity running along it. The eastern coast of Bejaia is formed by a wide stretch of sand, occupying the bottom of the bay. Its beaches are fed by sediments carried by two main wadis that debouch into the bay: Soummam in the west and Agrioun in the east. The undertaken work in this article focuses on the study of coastal erosion, which has a significant damage on the natural patrimony. This erosion risk in perpetual evolution, by location, is dramatically affecting the beautiful sandy beaches and various infrastructures over all the coast length of the Bejaia bay. In order to map and evaluate this risk, a methodological approach has been followed. This approach is mainly based on a diachronic variation analysis in the position of the shoreline over a period of 60 years; based on a series of ortho-rectified aerial photos, satellite images, as well as DGPS topographic surveys on the ground. The results revealed significant variations in the position of the shoreline during the last 60 years, especially on both sides of Soummam and Agrioun wadis. The most observed retreat of the shoreline is in the western part of the coast, where the rate of evolution reached −7.89 m/year (beach of Sidi Ali Lebhar), whereas the shoreline retreat reached −1.75 m/year in the center of the bay and −2 m/year toward the east. © 2015, Saudi Society for Geosciences.


Gaucherel C.,French National Institute for Agricultural Research | Moron V.,CNRS European Center for Research and Education in Environmental Geosciences
International Journal of Climatology | Year: 2016

'Tipping points' (TPs) are thresholds of potentially disproportionate changes in the Earth's climate system associated with future global warming and are considered today as a 'hot' topic in environmental sciences. In this study, TP interactions are analysed from an integrated and conceptual point of view using two qualitative Boolean models built on graph grammars. They allow an accurate study of the node TP interactions previously identified by expert elicitation and take into account a range of various large-scale climate processes potentially able to trigger, alone or jointly, instability in the global climate. Our findings show that, contrary to commonly held beliefs, far from causing runaway changes in the Earth's climate, such as self-acceleration due to additive positive feedbacks, successive perturbations might actually lead to its stabilization. A more comprehensive model defined TPs as interactions between nine (non-exhaustive) large-scale subsystems of the Earth's climate, highlighting the enhanced sensitivity to the triggering of the disintegration of the west Antarctic ice sheet. We are claiming that today, it is extremely difficult to guess the fate of the global climate system as TP sensitivity depends strongly on the definition of the model. Finally, we demonstrate the stronger effect of decreasing rules (i.e. mitigating connected TPs) over other rule types, thus suggesting the critical role of possible 'stabilizing points' that are yet to be identified and studied. © 2016 Royal Meteorological Society.


Ibanez T.,CNRS European Center for Research and Education in Environmental Geosciences | Ibanez T.,Laboratoire Of Botanique Et Decologie Vegetale Appliquees | Curt T.,IRSTEA | Hely C.,CNRS European Center for Research and Education in Environmental Geosciences
Journal of Vegetation Science | Year: 2013

Questions: How do early secondary successional forest species that grow in savannas differ in their tolerance to surface fires? What are the consequences of these fire tolerances for savanna-forest dynamics and landscape management? Location: Anthropogenic savannas in the New Caledonian biodiversity hotspot (SW Pacific). Methods: We estimated the range of fire intensity in New Caledonian savannas using field survey of fuels and the BehavePlus fire behaviour model. Within the predicted range of fire line intensity, we assessed theoretical fire injury to the cambium and crown for 11 species: the dominant tree of New Caledonian savannas (Melaleuca quinquenervia) and early secondary successional forest species. Using empirical models, for each species we estimated cambium damage from depth of necrosis (as a function of fire line intensity and fire residence time) and bark thickness, and crown damage from scorch height (as a function of fire line intensity) and tree height. We compared bark thickness and tree height increment patterns among species as well as species potential fire tolerance. Results: The 11 species had very contrasting capacity to avoid fire injury to the bole cambium due to differences in bark investment patterns, but were all very exposed to scorching and crown injury. Overall, most of sampled individuals are likely top-killed by low intensity fires (<1000 kW·m-1), which are frequent according to our simulations. Conclusions: The early secondary successional forest species growing in New Caledonian savannas are poorly adapted to fire, in comparison with literature on worldwide trees in savannas. As a result, their juveniles are unlikely to reach adult size in fire-prone areas. Restoration using the most fire-tolerant species and fire prevention may be complementary strategies to manage such tropical landscapes in order to conserve biodiversity and ecosystem services. We used a combination of allometric relationships and models of fire behaviour with fire injuries to assess how savanna and early secondary successional forest species differ in their tolerance to fires. We showed that the tolerance of these species to fire is highly variable and that the investment in bark thickness seems to be the prevailing trait that differentiates them. © 2012 International Association for Vegetation Science.


Ibanez T.,CNRS European Center for Research and Education in Environmental Geosciences | Hely C.,CNRS European Center for Research and Education in Environmental Geosciences | Gaucherel C.,French Institute of Pondicherry
Austral Ecology | Year: 2013

Fires are one of the main causes of forest loss in the tropics. Understanding the dynamic edge effects is critical for managing fires and protecting forests. We measured and analysed trends in microclimatic conditions (air temperature, relative humidity and vapour pressure deficit) over 7 months along three transects extending from core savanna areas to core forest areas. We tested two hypotheses: (i) that the forest edge is subject to microclimatic edge effects, and (ii) that the depth of these edge effects increases during dry periods. Sharp changes in each microclimatic variable were consistently observed between savanna and forest throughout the study period. Microclimatic transitions took place within 5m outside the forest boundary. Drought levels increased homogenously throughout the forest and were not disproportionately severe in the vicinity of the forest edge. We suggest that these results were related to the fact that the studied period was abnormally humid due to a La Niña episode, and that under such conditions the vulnerability of the forest edge to savanna fires is relatively low. Relatively wet conditions in the savanna close to the forest edge may promote forest expansion by limiting fire spread. Prescribed fires during humid years could reduce fuel loads in savanna without affecting the forest edge, which would prevent fires during the dry years associated with El Niño episodes from having severe impacts. © 2012 Ecological Society of Australia.


Jacquet E.,French Natural History Museum | Barrat J.-A.,CNRS Oceanic Domains Laboratory | Beck P.,French National Center for Scientific Research | Caste F.,CNRS Institute of Mineralogy, Materials Physics and Cosmochemistry | And 3 more authors.
Meteoritics and Planetary Science | Year: 2016

Northwest Africa (NWA) 5958 is a carbonaceous chondrite found in Morocco in 2009. Preliminary chemical and isotopic data leading to its initial classification as C3.0 ungrouped have prompted us to conduct a multitechnique study of this meteorite and present a general description here. The petrography and chemistry of NWA 5958 is most similar to a CM chondrite, with a low degree of aqueous alteration, apparently under oxidizing conditions, and evidence of a second, limited alteration episode manifested by alteration fronts. The oxygen isotopic composition, with (increment)'17O = -4.3‰, is more 16O-rich than all CM chondrites, indicating, along with other compositional arguments, a separate parent body of origin. We suggest that NWA 5958 be reclassified as an ungrouped carbonaceous chondrite related to the CM group. © 2016 The Meteoritical Society.


Janin M.,CNRS European Center for Research and Education in Environmental Geosciences | Medini S.,CNRS European Center for Research and Education in Environmental Geosciences | Techer I.,CNRS European Center for Research and Education in Environmental Geosciences
European Food Research and Technology | Year: 2014

Olive oil represents an important ingredient in the Mediterranean diet and is appreciated both for nutritional and sensory properties, often related to geographical origin and cultivar of olive fruits employed. Fraudsters trying to seek financial gain can adulterate the product causing economic repercussions and, sometimes sanitary risks. The “protected designation of origin” (PDO) label insures a relative protection of both consumers and honest producers, since it prescribes production techniques and specific geographical origin, but one of the main problems is to set down objective tools to control these specifications. We reviewed numerous studies using various analytical tools to discriminate PDO olive oils’ geographical origin depending on (1) volatiles compounds, (2) fatty acid and triacylglycerol composition, (3) trace elements, and/or (4) stable isotope ratios, but we highlighted that, despite their efficiency, none of them could provide an irrefutable identification. However, 87Sr/86Sr signature revealed to be an optimal geographical fingerprint in the same purpose for other food products like cereals, orange juice, coffee or alcoholic beverages. Such 87Sr/86Sr studies do not exist on olive oils, probably because of analytical issues, but we propose that developing complementary 87Sr/86Sr studies could be a promising tool to re-enforce the characterization of PDO olive oils. © 2014, Springer-Verlag Berlin Heidelberg.


Moron V.,Aix - Marseille University | Moron V.,Columbia University | Barbero R.,Aix - Marseille University | Mangeas M.,Espace Inc. | And 3 more authors.
Journal of Applied Meteorology and Climatology | Year: 2013

An empirical statistical scheme for predicting September-December fires in New Caledonia in the southwestern Pacific Ocean region using a cross-validated generalized linear model has been developed for the 2000-10 period. The predictor employs July sea surface temperatures (SST) recorded over the Niño-4 box (58S-58N, 1608-2108E), which are closely related to austral spring (September-November) rainfall anomalies across New Caledonia. The correlation between the logarithm of observed and simulated total burned areas across New Caledonia is 0.87. A decrease in the local-scale skill (median correlation between the log of observed and simulated total burned areas in a 20-km radius around a rain gauge 5 0.46) around the main town (Nouméa) and its suburbs in the southwest of Grande Terre, and also in northern New Caledonia, could be associated either with a weaker climatic forcing from the Niño-4 SST index or a small-scale climatic forcing not linearly related to the El Niño-Southern Oscillation (ENSO) phenomenon. It is more likely that the decrease is tied to the influence of human-driven factors that blur the regional-scale climatic signal mostly associated with central Pacific ENSO events. © 2013 American Meteorological Society.


Medini S.,CNRS European Center for Research and Education in Environmental Geosciences | Janin M.,CNRS European Center for Research and Education in Environmental Geosciences | Verdoux P.,CNRS European Center for Research and Education in Environmental Geosciences | Techer I.,CNRS European Center for Research and Education in Environmental Geosciences
Food Chemistry | Year: 2014

The lack of a geographical identification protocol for olive oils can lead to fraud and health risks. As some works call for Sr isotopes for the geographical identification of agri-food products, this study focus on the feasibility of extracting Sr from olive oils for isotopic measurements by TIMS. In fact, existing protocols for purification of Sr are unsuitable for lipid matrix. The defined protocol is applied to samples of PDO Nîmes olive oil. The accuracy of the extraction procedure is tested against isotopic standards. The values obtained are in conformity with NIST certified values. This consistency demonstrates that no modification of 87Sr/86Sr ratio is brought about by this protocol. Consequently, the method is preliminary used on PDO Nîmes and Moroccan oils to evaluate the feasibility of a discriminant Sr signature on the two geographical products. This study provides promising results for the geographical discrimination and identification of PDO olive oils. © 2014 Published by Elsevier Ltd.


Goncalves J.,Aix - Marseille University | Vallet-Coulomb C.,Aix - Marseille University | Petersen J.,Aix - Marseille University | Hamelin B.,Aix - Marseille University | Deschamps P.,CNRS European Center for Research and Education in Environmental Geosciences
Journal of Hydrology | Year: 2015

The stable isotopes of water were used to improve the determination of the groundwater budget of the deep Saharan "Continental Intercalaire" (CI), a deep confined aquifer. Mixing processes between the CI and shallower aquifers have been described in several regional studies over the last few decades, based on observed isotopic differences between local water masses. Here, we improve the quantitative determination of the discharge flux of this aquifer in one of its main outlet regions, the Djeffara plain in Tunisia, based on geostatistics and a simple mass balance mixing model, applied before and after the beginning of extensive pumping in the 1970s. First, the average values of δ18O and δ2H were precisely documented in the mixing zone between CI water and the local recharge, based on conditional simulations using spatially distributed isotopic data. Together with the available estimate of local recharge and conservative hypotheses on the isotopic end-members, we estimate the discharge flux of the CI in the Djeffara plain at 1.78±1.03m3s-1 in 1970, probably near natural steady-state, reduced to 1.02±0.58m3s-1 in 2004 under strong anthropogenic pressure, related to the drastic increase in pumping rates in the deep CI aquifer during this period. Considering the general groundwater budget over the entire CI aquifer, we estimate a recharge value of 5.13m3s-1, or 6.5mmyr-1 over the 25,000km2 of recharge area in the Saharan Atlas. This value is in line with the evaluation of 2.1mmyr-1 obtained recently from the GRACE satellite gravity data for the overall outcrops considering that recharge occurs mostly in the Atlas region. © 2015 Elsevier B.V.


PubMed | CNRS European Center for Research and Education in Environmental Geosciences
Type: | Journal: Food chemistry | Year: 2014

The lack of a geographical identification protocol for olive oils can lead to fraud and health risks. As some works call for Sr isotopes for the geographical identification of agri-food products, this study focus on the feasibility of extracting Sr from olive oils for isotopic measurements by TIMS. In fact, existing protocols for purification of Sr are unsuitable for lipid matrix. The defined protocol is applied to samples of PDO Nmes olive oil. The accuracy of the extraction procedure is tested against isotopic standards. The values obtained are in conformity with NIST certified values. This consistency demonstrates that no modification of (87)Sr/(86)Sr ratio is brought about by this protocol. Consequently, the method is preliminary used on PDO Nmes and Moroccan oils to evaluate the feasibility of a discriminant Sr signature on the two geographical products. This study provides promising results for the geographical discrimination and identification of PDO olive oils.

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