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Calibration des fonctions de transfert entre assemblages phytolithiques, structure des végétations et variables bioclimatiques actuelles, pour l'intégration de la dynamique des biomes herbacés dans les modèles de végétation

Abstract : Grassland biomes are currently dominating the inter-tropical zone, but main proxies used do not reflect properly their range. Therefore, modeling activities and paleo-reconstructions in these zones are not convincing. Phytoliths are amorphous silica that precipitate in and/or between living plant cells. They are commonly used to trace grass dynamics. However, calibration between phytolith assemblages, vegetation, and climate parameters are scarce. This thesis introduces transfer functions between phytolith indices, modern inter-tropical grassland physiognomies, and bio-climatic constraining variables. In a near future, we would like to (1) integrate phytolith data in the biomization method that allows reconstructing vegetation biomes, (2) improve and validate some vegetation models. In West Africa, the Iph phytolith index allows discriminating tall from short grass savannas. A transfer function is proposed to estimate the evapotranspiration (AET/PET). Results are good, similar and complementary to the pollen biomization estimates. The Ic index, studied on an altitudinal gradient in East Africa, permits to accurately estimate the proportion of Pooideae and Panicoideae grass sub-families, and so potentially the C4/C3 grass dominance. For the first time, a vegetation marker, the D/P index, has been quantitatively calibrated as proxy of Leaf Area Index, along a forest-savanna transition. Finally, a discriminant analysis using all the modern assemblages presents six phytolith biomes. These biomes, when integrated into the pollen biomization method, will improve the definition of vegetation transition such as desert/savanna/forest.
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https://tel.archives-ouvertes.fr/tel-00008000
Contributor : Laurent Bremond <>
Submitted on : Tuesday, January 11, 2005 - 2:53:07 PM
Last modification on : Wednesday, October 14, 2020 - 3:49:30 AM
Long-term archiving on: : Friday, April 2, 2010 - 9:06:02 PM

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  • HAL Id : tel-00008000, version 1

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Laurent Bremond. Calibration des fonctions de transfert entre assemblages phytolithiques, structure des végétations et variables bioclimatiques actuelles, pour l'intégration de la dynamique des biomes herbacés dans les modèles de végétation. Géologie appliquée. Université de droit, d'économie et des sciences - Aix-Marseille III, 2003. Français. ⟨tel-00008000⟩

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