Modelling the genesis of equatorial podzols: age and implications for carbon fluxes

Author(s)

Doupoux, Cedric ; Merdy, Patricia ; Montes, Celia Regina ; Nunan, Naoise ; Melfi, Adolpho Jose ; Ribeiro Pereira, Osvaldo Jose ; Lucas, Yves

• Document type: Journal article
• Source: BIOGEOSCIENCES; v. 14, n. 9, p. 2429-2440, MAY 12 2017.
• Web of Science Citations: 3

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 C-14 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 C-14 age from 62 to 109 years). We modelled four profiles representative of Amazonian podzols, two profiles with an old Bh (calculated apparent C-14 age 6.8 x 10(3) and 8.4 x 10(3) years) and two profiles with a very old Bh (calculated apparent C-14 age 23.2 x 10(3) and 25.1 x 10(3) 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 x 10(3) and 130 x 10(3) 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 x 10(3)-25 x 10(3) and 150 x 10(3)-250 x 10(3) years, respectively. (AU)

• FAPESP's process: 11/03250-2 - Quantification and dynamics of carbon associated with deep spodic horizons of Amazon Forest soils, towards possible climatic changed
• Grantee: Célia Regina Montes
• Support Opportunities: Regular Research Grants
• FAPESP's process: 12/51469-6 - Modelling the dynamics of equatorial forest soil deep carbon in changing environments - C-PROFOR
• Grantee: Adolpho José Melfi
• Support Opportunities: Research Projects - Thematic Grants