HR: 1340h
AN: PP43A-0589    [Abstracts]
TI: Calibration of transfer functions between phytolith, vegetation and climate for integration of grassland dynamics in vegetation models. Application to a 50,000 yr crater lake core in Tanzania.
AU: * Bremond, L
EM: bremond@cerege.fr
AF: CEREGE, Europole Mediterraneen de l'Arbois, Aix-en-Provence, 13545 France
AU: Alexandre, A
EM: alexandre@cerege.fr
AF: CEREGE, Europole Mediterraneen de l'Arbois, Aix-en-Provence, 13545 France
AU: Hely, C
EM: hely@cerege.fr
AF: CEREGE, Europole Mediterraneen de l'Arbois, Aix-en-Provence, 13545 France
AU: Vincens, A
EM: vincens@cerege.fr
AF: CEREGE, Europole Mediterraneen de l'Arbois, Aix-en-Provence, 13545 France
AU: Williamson, D
EM: williamson@cerege.fr
AF: CEREGE, Europole Mediterraneen de l'Arbois, Aix-en-Provence, 13545 France
AU: Guiot, J
EM: guiot@cerege.fr
AF: CEREGE, Europole Mediterraneen de l'Arbois, Aix-en-Provence, 13545 France
AB: Global vegetation models provide a way to translate the outputs from climate models into maps of potential vegetation distribution for present, past and future. Validation of these models goes through the comparison between model outputs and vegetation proxies for well constrained past climatic periods. Grass-dominated biomes are widespread and numerous. This diversity is hardly mirrored by common proxies such as pollen, charcoal or carbon isotopes. Phytoliths are amorphous silica that precipitate in and/or between living plant cells. They are commonly used to trace grasslands dynamics. However, calibration between phytolith assemblages, vegetation, and climate parameters are scarce. This work introduces transfer functions between phytolith indices, inter-tropical grassland physiognomy, and bio-climatic data that will be available for model/data comparisons. The Iph phytolith index discriminates tall from short grass savannas in West Africa. A transfer function allows to estimate evapo-transpiration AET/PET. The Ic phytolith index accurately estimates the proportion of Pooideae and Panicoideae grass sub-families, and potentially the C4/C3 grass dominance on East African mountains. The D/P index appears as a good proxy of Leaf Area Index (LAI) in tropical areas. These environmental parameters are commonly used as vegetation model outputs, but have been, up to now, hardly estimated by vegetation proxies. These transfer functions are applied to a 50,000 yr phytolith sequence from a crater lake (9øS; 33øE Tanzania). The record is compared to the pollen vegetation reconstruction and confronted to simulations of the LPJ-GUESS vegetation model (Stitch et. al, 2003).
DE: 3344 Paleoclimatology
DE: 1620 Climate dynamics (3309)
DE: 1640 Remote sensing
DE: 0400 Biogeosciences
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting