Poster Session 1
L1.3 Latin America
159
76.
Does carbon storage of pastures contribute to a climate smart cattle farming
after Amazonian deforestation?
Blanfort Vincent1, Stahl Clément1,2, Fontaine Sébastien3, Picon-Cochard Catherine3, Freycon Vincent4, Blanc Lilian4, Bonal Damien5, Soussana Jean-François3, Lecomte Philippe1, Klumpp Katja3
1CIRAD, UMR 112 Tropical and Mediterranean Animal Production Systems, Campus international de Baillarguet, 34398
Montpellier, France
2INRA, UMR 0745 Ecofog, Campus agronomique, 97379 Kourou, France
3INRA, UR 874, Grassland Ecosystem Research Team, 63100 Clermont-Ferrand, France
4CIRAD, UR 105 “Biens et services des écosystèmes forestiers tropicaux”, 34398 Montpellier, France 5INRA, UMR 1137 EEF, 54280 Champenoux, France
More than 15% of Amazon forest has been converted to pastures these last decades. Some authors argued the world’s permanent pastures (30 % of total land) could potentially offset up to 4% of the global GHG emissions, having a carbon (C) storage potential equal to 0.5 Mg C.ha-1.yr-1(Schulze et al 2009). Accordingly, pastures are good candidates to increase soil uptake C in soil while ensuring a basic food production. Here we would like to assess the effects of tropical forest conversion to cattle pasture in the French Amazonia (French Guiana), by following the long-term dynamics of soil C stocks of permanent tropical pastures (Brachiaria humidicola) after deforestation from 1970. A soil inventory campaign was performed to analyse soil C and N stocks (to 1 m depth) along a pasture chronosequence of 6 months to 36 years old pastures and 4 native forest sites (total 24 sites). The annual C sequestration potential demonstrated by the chronosequence, was compared with eddy covariance flux measurements on 2 pastures and one native forest. Our study shows that old (≥ 24 years) tropical pastures resettle the recurrent C storage observed in native forest. These pastures stored between 1.8 ± 0.5 and 5.3 ± 2.1 tC ha-1 yr-1 compared with 2.6 ± 0.5 tC ha-1 yr-1 for the nearby native forest. Our finding show that old tropical pastures accumulate carbon in soil organic matter, particularly in the deep soil layers (0.2-1 m) and without loss of soil fertility. It suggests that such pastures can be exploited by farmers in the long term with appropriate practices (no fire and no overgrazing, but a mixture of grasses and legumes and a grazing rotation plan). Clearly, efforts to curb deforestation are a priority in order to preserve forest biodiversity and C stocks. But it seems now that, in a climate-smart agriculture way, the current challenge is to manage these deforested areas to maintain the productivity of agricultural ecosystems and in the same time their capacity to mitigate GES.
Acknowledgements: This study was co- funded by CIRAD, INRA, CNES, European regional development found (ERDF 2007-013) and AnimalChange project (FP7 KKBE 2010-4).
