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

• Published in: Plant and soil 2009-10, Vol.323 (1-2), p.309-322
• Main Authors: Epron, Daniel, Marsden, Claire, Thongo M'Bou, Armel, Saint-André, Laurent, d'Annunzio, Rémi, Nouvellon, Yann
• Format: Article
• Language: English
• Subjects: Afforestation; Agricultural soils; Agronomy. Soil science and plant productions; Animal, plant and microbial ecology; Biological and medical sciences; Biomedical and Life Sciences; C; Carbon; Carbon cycle; Carbon dioxide; Chronosequence; Chronosequences; Ecology; Eucalyptus; Forest soils; Forestry; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Life Sciences; Organic matter; Organic soils; Plant Physiology; Plant resources; Plant Sciences; Plantations; Rainforests; Regular Article; Resource allocation; Savanna soils; Savannahs; Savannas; Soil carbon; Soil composition; Soil depth; Soil dynamics; Soil organic carbon; Soil organic matter; Soil science; Soil Science & Conservation; Soil-plant relationships. Soil fertility; Soil-plant relationships. Soil fertility. Fertilization. Amendments; Tropical environments; Tropical plantation; Vegetal Biology
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1007/s11104-009-9939-7

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.