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Continuous soil carbon storage of old permanent pastures in Amazonia
Author(s) -
Stahl Clément,
Fontaine Sébastien,
Klumpp Katja,
PiconCochard Catherine,
Grise Marcia Mascarenhas,
Dezécache Camille,
Ponchant Lise,
Freycon Vincent,
Blanc Lilian,
Bonal Damien,
Burban Benoit,
Soussana JeanFrançois,
Blanfort Vincent
Publication year - 2017
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/gcb.13573
Subject(s) - environmental science , amazon rainforest , agroforestry , soil carbon , carbon sink , ecosystem , deforestation (computer science) , biomass (ecology) , humus , plant litter , agronomy , chronosequence , litter , forestry , ecology , geography , soil water , biology , soil science , computer science , programming language
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.