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Continuous soil carbon storage of old permanent pastures in Amazonia

Abstract : Amazonian forests continuously accumulate carbon (C) in biomass and in soil, representing a carbon sink of 0.42-0.65 GtC yr-1 . In recent decades, more than 15% of Amazonian forests have been converted into pastures, resulting in net C emissions (~200 tC ha-1 ) due to biomass burning and litter mineralization in the first years after deforestation. However, little is known about the capacity of tropical pastures to restore a C sink. Our study shows in French Amazonia that the C storage observed in native forest can be partly restored in old (≥24 year) tropical pastures managed with a low stocking rate (±1 LSU ha-1 ) and without the use of fire since their establishment. A unique combination of a large chronosequence study and eddy covariance measurements showed that pastures stored between -1.27 ± 0.37 and -5.31 ± 2.08 tC ha-1 yr-1 while the nearby native forest stored -3.31 ± 0.44 tC ha-1 yr-1 . This carbon is mainly sequestered in the humus of deep soil layers (20-100 cm), whereas no C storage was observed in the 0- to 20-cm layer. C storage in C4 tropical pasture is associated with the installation and development of C3 species, which increase either the input of N to the ecosystem or the C:N ratio of soil organic matter. Efforts to curb deforestation remain an obvious priority to preserve forest C stocks and biodiversity. However, our results show that if sustainable management is applied in tropical pastures coming from deforestation (avoiding fires and overgrazing, using a grazing rotation plan and a mixture of C3 and C4 species), they can ensure a continuous C storage, thereby adding to the current C sink of Amazonian forests.
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Déposant : Migration Prodinra <>
Soumis le : mercredi 27 mai 2020 - 02:22:41
Dernière modification le : jeudi 4 mars 2021 - 09:18:03

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Clement Stahl, Sébastien Fontaine, Katja Klumpp, Catherine Picon-Cochard, Marcia Mascarenha Grise, et al.. Continuous soil carbon storage of old permanent pastures in Amazonia. Global Change Biology, Wiley, 2017, 23 (8), pp.3382-3392. ⟨10.1111/gcb.13573⟩. ⟨hal-02629172⟩



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