Regular Article

Plant and Soil

, Volume 323, Issue 1, pp 309-322

First online:

Soil carbon dynamics following afforestation of a tropical savannah with Eucalyptus in Congo

  • Daniel EpronAffiliated withNancy Université, Université Henri Poincaré, Faculté des Sciences, UMR 1137, Ecologie et Ecophysiologie ForestièresINRA, UMR 1137, Ecologie et Ecophysiologie Forestières, Centre de NancyUMR INRA UHP ‘Ecologie et Ecophysiologie Forestières’, Université Henri Poincaré Email author 
  • , Claire MarsdenAffiliated withNancy Université, Université Henri Poincaré, Faculté des Sciences, UMR 1137, Ecologie et Ecophysiologie ForestièresUR2PI, BP 1291CIRAD, UPR-80
  • , Armel Thongo M’BouAffiliated withNancy Université, Université Henri Poincaré, Faculté des Sciences, UMR 1137, Ecologie et Ecophysiologie ForestièresUR2PI, BP 1291
  • , Laurent Saint-AndréAffiliated withCIRAD, UPR-80
  • , Rémi d’AnnunzioAffiliated withUR2PI, BP 1291CIRAD, UPR-80
  • , Yann NouvellonAffiliated withUR2PI, BP 1291CIRAD, UPR-80

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Abstract

Soil organic matter is a key factor in the global carbon cycle, but the magnitude and the direction of the change in soil carbon after afforestation with Eucalyptus in the tropics is still a matter of controversy. The objective of this work was to understand the dynamics of soil carbon in intensively managed Eucalyptus plantations after the afforestation of a native savannah. The isotopic composition (δ) of soil carbon (C) and soil CO2 efflux (F) were measured on a four-age chronosequence of Eucalyptus and on an adjacent savannah. δ F was used to partition F between a C3 component and a C4 component, the latter corresponding to the decomposition of a labile pool of savannah-derived soil carbon (C SL). The mean residence time of CSL was 4.6 years. This further allowed us to partition the savannah-derived soil carbon into a labile and a stable (C SS) carbon pool. C SL accounted for 30% of soil carbon in the top soil of the savannah (0–5 cm), and only 12% when the entire 0–45 cm soil layer was considered. The decrease in C SL with time after plantation was more than compensated by an increase in Eucalyptus-derived carbon, and half of the newly incorporated Eucalyptus-derived carbon in the top soil was associated with the clay and fine silt fractions in the 14-year-old. stand. Increment in soil carbon after afforestation of tropical savannah with Eucalyptus is therefore expected despite a rapid disappearance of the labile savannah-derived carbon because a large fraction of savannah-derived carbon is stable.

Keywords

13C Chronosequence Eucalyptus Soil carbon Savannah Tropical plantation