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VARIABILITY OF RADIOCARBON RESERVOIR AGE EFFECTS IN LAKES AND RIVERS IN ANATOLIA AND LESSER CAUCASUS
- Michel Fontugne, Christine Hatté, Nadine Tisnérat-Laborde, Vincent Ollivier, Catherine Kuzucuoğlu
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- Radiocarbon , First View
- Published online by Cambridge University Press:
- 16 May 2024, pp. 1-11
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Multiproxy sedimentary sequence analysis constitutes the basis for reconstructions of past paleoenvironments and climate evolution. These sequences are, for the most part, obtained by coring in lakes, maars or crater lakes whose waters can record volcanic activity or karstic contributions, especially in Eastern Anatolia and the Lesser Caucasus. The reservoir age effect in these geological contexts leads to an apparent aging of the radiocarbon ages which also affects the plants and animals developing in or near these waters and consequently the population consuming them. We present here some results obtained from modern samples taken from Mediterranean, central and eastern Anatolian lakes, from the Van and Sevan lakes and along the Kura River and its tributaries from the Lesser Caucasus. The effect of volcanic CO2 outgassing in the vicinity of maar crater lakes is also discussed.
Fixed or mixed? Variation in tree functional types and vegetation structure in a forest-savanna ecotone in West Africa
- George K.D Ametsitsi, Frank Van Langevelde, Vincent Logah, Thomas Janssen, Jose A Medina-Vega, Hamza Issifu, Laurianne Ollivier, Koos den Hartogh, Thomas Adjei-Gyapong, Stephen Adu-Bredu, Jon Lloyd, Elmar M Veenendaal
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- Journal:
- Journal of Tropical Ecology / Volume 36 / Issue 4 / July 2020
- Published online by Cambridge University Press:
- 23 July 2020, pp. 133-149
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We analysed thirty-five 400-m2 plots encompassing forest, savanna and intermediate vegetation types in an ecotonal area in Ghana, West Africa. Across all plots, fire frequency was over a period of 15 years relatively uniform (once in 2–4 years). Although woodlands were dominated by species typically associated with savanna-type formations, and with forest formations dominated by species usually associated with closed canopies, these associations were non-obligatory and with a discrete non-specialized species grouping also identified. Across all plots, crown area index, stem basal area and above-ground biomass were positively associated with higher soil exchangeable potassium and silt contents: this supporting recent suggestions of interplays between potassium and soil water storage potential as a significant influence on tropical vegetation structure. We also found an average NDVI cover increase of ~0.15% year−1 (1984–2011) with plots dominated by non-specialized species increasing more than those dominated by either forest- or savanna-affiliated species. Our results challenge the traditional view of a simple forest vs. savanna dichotomy controlled by fire, and with our newly identified third non-specialized species grouping also potentially important in understanding ecotonal responses to climate change.
New pollen evidence from Nariani (Georgia) for delayed postglacial forest expansion in the South Caucasus
- Erwan Messager, Sébastien Nomade, Bruno Wilhelm, Sébastien Joannin, Vincent Scao, Ulrich Von Grafenstein, Inga Martkoplishvili, Vincent Ollivier, Ana Mgeladze, Jean-Pascal Dumoulin, Arnaud Mazuy, Soumaya Belmecheri, David Lordkipanidze
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- Journal:
- Quaternary Research / Volume 87 / Issue 1 / January 2017
- Published online by Cambridge University Press:
- 06 February 2017, pp. 121-132
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The nature and timing of environmental changes throughout the last glacial-interglacial transition in the South Caucasus, and more widely in eastern Europe, are still not fully understood. According to certain pollen records, forest expansion occurred in many areas several millennia after what is considered worldwide as the onset of the Holocene. The current problem we face is that the time lag in forest expansion varies from one sequence to another, sometimes with no delay at all. Moreover, the potential forcing/controlling factors behind this complex pattern, contrary to the almost synchronous global Holocene warming, are still a matter for debate. Accordingly, we revisit the issue of forest expansion through vegetation history obtained in the South Caucasus using a new pollen record, retrieved from the Nariani paleolake (South Georgia). These data attest to a steppic phase, initially dominated by Amaranthaceae-Chenopodiaceae (12,700–10,500 cal yr BP), then by Poaceae (10,500–9000 cal yr BP), culminating with a more forested phase (9000–5000 calyrBP). Although some palaeoclimatic regional reconstructions show a wet early Holocene, we interpret the delay in forest expansion recorded in Nariani (2500 years) as the result of reduced spring precipitation, which would have limited forest development at that time.
The science of EChO
- Giovanna Tinetti, James Y-K. Cho, Caitlin A. Griffith, Olivier Grasset, Lee Grenfell, Tristan Guillot, Tommi T. Koskinen, Julianne I. Moses, David Pinfield, Jonathan Tennyson, Marcell Tessenyi, Robin Wordsworth, Alan Aylward, Roy van Boekel, Angioletta Coradini, Therese Encrenaz, Ignas Snellen, Maria R. Zapatero-Osorio, Jeroen Bouwman, Vincent Coudé du Foresto, Mercedes Lopez-Morales, Ingo Mueller-Wodarg, Enric Pallé, Franck Selsis, Alessandro Sozzetti, Jean-Philippe Beaulieu, Thomas Henning, Michael Meyer, Giuseppina Micela, Ignasi Ribas, Daphne Stam, Mark Swain, Oliver Krause, Marc Ollivier, Emanuele Pace, Bruce Swinyard, Peter A.R. Ade, Nick Achilleos, Alberto Adriani, Craig B. Agnor, Cristina Afonso, Carlos Allende Prieto, Gaspar Bakos, Robert J. Barber, Michael Barlow, Peter Bernath, Bruno Bézard, Pascal Bordé, Linda R. Brown, Arnaud Cassan, Céline Cavarroc, Angela Ciaravella, Charles Cockell, Athéna Coustenis, Camilla Danielski, Leen Decin, Remco De Kok, Olivier Demangeon, Pieter Deroo, Peter Doel, Pierre Drossart, Leigh N. Fletcher, Matteo Focardi, Francois Forget, Steve Fossey, Pascal Fouqué, James Frith, Marina Galand, Patrick Gaulme, Jonay I. González Hernández, Davide Grassi, Matt J. Griffin, Ulrich Grözinger, Manuel Guedel, Pactrick Guio, Olivier Hainaut, Robert Hargreaves, Peter H. Hauschildt, Kevin Heng, David Heyrovsky, Ricardo Hueso, Pat Irwin, Lisa Kaltenegger, Patrick Kervella, David Kipping, Geza Kovacs, Antonino La Barbera, Helmut Lammer, Emmanuel Lellouch, Giuseppe Leto, Mercedes Lopez Morales, Miguel A. Lopez Valverde, Manuel Lopez-Puertas, Christophe Lovi, Antonio Maggio, Jean-Pierre Maillard, Jesus Maldonado Prado, Jean-Baptiste Marquette, Francisco J. Martin-Torres, Pierre Maxted, Steve Miller, Sergio Molinari, David Montes, Amaya Moro-Martin, Olivier Mousis, Napoléon Nguyen Tuong, Richard Nelson, Glenn S. Orton, Eric Pantin, Enzo Pascale, Stefano Pezzuto, Ennio Poretti, Raman Prinja, Loredana Prisinzano, Jean-Michel Réess, Ansgar Reiners, Benjamin Samuel, Jorge Sanz Forcada, Dimitar Sasselov, Giorgio Savini, Bruno Sicardy, Alan Smith, Lars Stixrude, Giovanni Strazzulla, Gautam Vasisht, Sandrine Vinatier, Serena Viti, Ingo Waldmann, Glenn J. White, Thomas Widemann, Roger Yelle, Yuk Yung, Sergey Yurchenko
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- Journal:
- Proceedings of the International Astronomical Union / Volume 6 / Issue S276 / October 2010
- Published online by Cambridge University Press:
- 10 November 2011, pp. 359-370
- Print publication:
- October 2010
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The science of extra-solar planets is one of the most rapidly changing areas of astrophysics and since 1995 the number of planets known has increased by almost two orders of magnitude. A combination of ground-based surveys and dedicated space missions has resulted in 560-plus planets being detected, and over 1200 that await confirmation. NASA's Kepler mission has opened up the possibility of discovering Earth-like planets in the habitable zone around some of the 100,000 stars it is surveying during its 3 to 4-year lifetime. The new ESA's Gaia mission is expected to discover thousands of new planets around stars within 200 parsecs of the Sun. The key challenge now is moving on from discovery, important though that remains, to characterisation: what are these planets actually like, and why are they as they are?
In the past ten years, we have learned how to obtain the first spectra of exoplanets using transit transmission and emission spectroscopy. With the high stability of Spitzer, Hubble, and large ground-based telescopes the spectra of bright close-in massive planets can be obtained and species like water vapour, methane, carbon monoxide and dioxide have been detected. With transit science came the first tangible remote sensing of these planetary bodies and so one can start to extrapolate from what has been learnt from Solar System probes to what one might plan to learn about their faraway siblings. As we learn more about the atmospheres, surfaces and near-surfaces of these remote bodies, we will begin to build up a clearer picture of their construction, history and suitability for life.
The Exoplanet Characterisation Observatory, EChO, will be the first dedicated mission to investigate the physics and chemistry of Exoplanetary Atmospheres. By characterising spectroscopically more bodies in different environments we will take detailed planetology out of the Solar System and into the Galaxy as a whole.
EChO has now been selected by the European Space Agency to be assessed as one of four M3 mission candidates.