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www.clim-past-discuss.net/5/1187/2009/
doi:10.5194/cpd-5-1187-2009
© Author(s) 2009. This work is distributed
under the Creative Commons Attribution 3.0 License.
Climate and CO2 modulate the C3-C4 balance and δ13C signal in simulated vegetation
1CEFE, UMR 5175 CNRS, 1919, route de Mende, 34293, Montpellier cedex 5, France
2ISEM, UMR 5554 CNRS/Univ. Montpellier II, Case 61, 34095 Montpellier cedex 5, France
Abstract. Fossil pollen data and δ13C measurements from cores collected in peatbogs or lakes have shown major changes in the terrestrial vegetation during Late Quaternary. Although the effect of climate on the C3-C4 balance has been discussed for 50 years, the impact of a low atmospheric CO2 during the Last Glacial Maximum (LGM) was emphasized recently and conflicting evidence exists. In this paper, we use a physiologically-based biome model (BIOME4) in an iterative mode to simulate vegetation response to changing mean climate conditions and atmospheric CO2 partial pressure (pCO2). In particular, we investigate the transition from LGM to present conditions in two sites which changed from either a C4- or a C3-dominated vegetation to the opposite pole, respectively at Kuruyange (Burundi) and Lingtaï (Central Loess Plateau, China). The response of the C3-C4 balance and δ13C signal in the simulated vegetation are investigated. The results show that the vegetation is primarily sensitive to temperature and pCO2. Rainfall impacted the simulated variables below a threshold which decreased with higher pCO2. Climate and pCO2 interacted differently between the two sites showing indirect effects on the δ13C signal. Moreover, the plant functional types (PFTs) differed in their composition and in their response between the two sites, emphasizing that the competition between C3 and C4 plants cannot be hardly considered as a simple binary scheme. Our results confirm the advantages of using process-based models to understand past vegetation changes and the need to take account of multiple drivers when the C3-C4 balance is reconstructed from a palaeo-δ13C signal.
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Notice on Discussion StatusCitation: Flores, O., Gritti, E. S., and Jolly, D.: Climate and CO2 modulate the C3-C4 balance and δ13C signal in simulated vegetation, Clim. Past Discuss., 5, 1187-1213, doi:10.5194/cpd-5-1187-2009, 2009. Bibtex EndNote Reference Manager XML
