Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Biogeosciences, 14, 2429-2440, 2017
https://doi.org/10.5194/bg-14-2429-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
12 May 2017
Modelling the genesis of equatorial podzols: age and implications for carbon fluxes
Cédric Doupoux1, Patricia Merdy1, Célia Régina Montes2, Naoise Nunan3, Adolpho José Melfi4, Osvaldo José Ribeiro Pereira2, and Yves Lucas1 1Université de Toulon, PROTEE Laboratory, EA 3819, CS 60584, 83041 Toulon Cedex 9, France
2University of São Paulo, NUPEGEL, CENA, Av. Centenário, 303, CEP 13416-903 Piracicaba, SP, Brazil
3CNRS, iEES Paris, 78850 Thiverval-Grignon, France
4University of São Paulo, IEE, ESALQ, São Paulo, SP, Brazil
Abstract. Amazonian podzols store huge amounts of carbon and play a key role in transferring organic matter to the Amazon River. In order to better understand their C dynamics, we modelled the formation of representative Amazonian podzol profiles by constraining both total carbon and radiocarbon. We determined the relationships between total carbon and radiocarbon in organic C pools numerically by setting constant C and 14C inputs over time. The model was an effective tool for determining the order of magnitude of the carbon fluxes and the time of genesis of the main carbon-containing horizons, i.e. the topsoil and deep Bh. We performed retrocalculations to take into account the bomb carbon in the young topsoil horizons (calculated apparent 14C age from 62 to 109 years). We modelled four profiles representative of Amazonian podzols, two profiles with an old Bh (calculated apparent 14C age 6.8  ×  103 and 8.4  ×  103 years) and two profiles with a very old Bh (calculated apparent 14C age 23.2  ×  103 and 25.1  ×  103 years). The calculated fluxes from the topsoil to the perched water table indicate that the most waterlogged zones of the podzolized areas are the main source of dissolved organic matter found in the river network. It was necessary to consider two Bh carbon pools to accurately represent the carbon fluxes leaving the Bh as observed in previous studies. We found that the genesis time of the studied soils was necessarily longer than 15  ×  103 and 130  ×  103 years for the two younger and two older Bhs, respectively, and that the genesis time calculated considering the more likely settings runs to around 15  ×  103–25  ×  103 and 150  ×  103–250  ×  103 years, respectively.

Citation: Doupoux, C., Merdy, P., Montes, C. R., Nunan, N., Melfi, A. J., Pereira, O. J. R., and Lucas, Y.: Modelling the genesis of equatorial podzols: age and implications for carbon fluxes, Biogeosciences, 14, 2429-2440, https://doi.org/10.5194/bg-14-2429-2017, 2017.
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Short summary
Amazonian podzol soils store huge amounts of carbon and play a key role in transferring organic matter to the Amazon River. We modelled their formation by constraining both total carbon and radiocarbon. We found that the most waterlogged zones of the podzolized areas are the main source of dissolved organic matter found in the river network. The genesis time calculated considering the more likely settings runs to around 15–25 and 150–250 kyr for young and old podzols, respectively.
Amazonian podzol soils store huge amounts of carbon and play a key role in transferring organic...
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