title: 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-1yr-1while the nearby native forest stored -3.31 ± 0.44 tC ha-1yr-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.
authors.affiliation: CIRAD, UMR Selmet, Campus International de Baillarguet, 34398, Montpellier, France.|Department of Biology, University of Antwerp, Wilrijk, 2610, Belgium.|INRA, UMR 0745 Ecofog, Campus Agronomique, 97379, Kourou, France.
authors.forename: Clément
authors.initials: C
authors.lastname: Stahl
authors.affiliation: INRA, UR 874, Grassland Ecosystem Research Team, 63100, Clermont-Ferrand, France.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Fontaine
authors.affiliation: INRA, UR 874, Grassland Ecosystem Research Team, 63100, Clermont-Ferrand, France.
authors.forename: Katja
authors.initials: K
authors.lastname: Klumpp
authors.affiliation: INRA, UR 874, Grassland Ecosystem Research Team, 63100, Clermont-Ferrand, France.
authors.forename: Catherine
authors.initials: C
authors.lastname: Picon-Cochard
authors.affiliation: Embrapa Amazônia Oriental, Empresa Brasileira de Pesquisa Agropecuária, EMBRAPA, Tv. Enéas Pinheiro s/n, Belém Pará, Brazil.
authors.forename: Marcia Mascarenhas
authors.initials: MM
authors.lastname: Grise
authors.affiliation: CIRAD, UMR Selmet, Campus International de Baillarguet, 34398, Montpellier, France.
authors.forename: Camille
authors.initials: C
authors.lastname: Dezécache
authors.affiliation: CIRAD, UMR Selmet, Campus International de Baillarguet, 34398, Montpellier, France.
authors.forename: Lise
authors.initials: L
authors.lastname: Ponchant
authors.affiliation: CIRAD, UR 105 'Forêts et sociétés', 34398, Montpellier, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Freycon
authors.affiliation: Embrapa Amazônia Oriental, Empresa Brasileira de Pesquisa Agropecuária, EMBRAPA, Tv. Enéas Pinheiro s/n, Belém Pará, Brazil.|CIRAD, UR 105 'Forêts et sociétés', 34398, Montpellier, France.
authors.forename: Lilian
authors.initials: L
authors.lastname: Blanc
authors.affiliation: INRA, UMR 1137 EEF, 54280, Champenoux, France.
authors.forename: Damien
authors.initials: D
authors.lastname: Bonal
authors.affiliation: INRA, UMR 0745 Ecofog, Campus Agronomique, 97379, Kourou, France.
authors.forename: Benoit
authors.initials: B
authors.lastname: Burban
authors.affiliation: INRA, UR 874, Grassland Ecosystem Research Team, 63100, Clermont-Ferrand, France.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Soussana
authors.affiliation: CIRAD, UMR Selmet, Campus International de Baillarguet, 34398, Montpellier, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Blanfort
mesh_terms: D018533:Biomass; D001938:Brazil; D002244:Carbon; D057965:Carbon Sequestration; D065928:Forests; D012987:Soil / Q000737:chemistry*; D014197:Trees
chemical_list: D012987:Soil; D002244:Carbon
keywords: CN coupling; carbon storage; deep soil; mixed-grass pasture; native forest