Vegetated subsoil exposed during geotechnical operations has massive carbon storage potential: a study of 13C partitioning into soil respiration and different soil fractions

Rossi Lorenzo, Stokes Alexia, Cardinael Rémi, Merino-Martin Luis, Derrien Delphine, Milcu Alex, Roy Jacques, Devidal Sébastien, Piel Clément, Plain Caroline, Russo Giacomo, Mao Zhun. 2019. Vegetated subsoil exposed during geotechnical operations has massive carbon storage potential: a study of 13C partitioning into soil respiration and different soil fractions. In : Soil organic matter in a stressed world. Symposium oral abstracts. Adelaideaa : s.n., Résumé, p. 89. International Symposium on Soil Organic Matter (SOM 2019). 7, Adelaide, Australie, 6 Octobre 2019/11 Octobre 2019.

Résumé : Geotechnical operations such as embankment construction influence soil carbon (C) storage since massive amounts of C-poor subsoil are brought to the surface. We hypothesize that subsoil can sequester relatively more C than C-rich topsoil due to its lower C-saturation. We excavated topsoil (0.0 to 0.3 m) and subsoil (1.1 to 1.4 m) from the same profile. We sieved soil and sowed Medicago sativa and Lolium perenne (n=6 pots of each species x soil). Controls were soil with no vegetation (n=6 x soil). To trace the fate of C, pots were incubated for 6 months under a continuously 13C-enriched-CO2 (2%) in three growth chambers with controlled conditions. Soil respiration (CO2 and 13C) was quantified every 2 weeks and was higher in the topsoil, due to greater root and microbiological activity. The 13C enrichment of the respired C was significantly higher in M. sativa regardless of soil type. After 6 months, soils were divided into four different fractions: particulate organic matter (POM), fine POM, silt, silt+clay, and total C and 13C enrichment were analyzed. Results show that the total C (g new C/cm3 soil) stored depended on root biomass. Topsoil had significantly more biomass, and stored more labeled plant derived-C, especially under M. sativa. However, when results were weighted as new C stored in cm3 of soil per g of root biomass, subsoil stored relatively more C, especially in POM and silt+clay fractions (increase in new C stored in subsoil compared to topsoil for POM: M. sativa +135%, L. perenne +33% and for silt+clay: M. sativa +56%, L. perenne +16%). The higher relative increase of organo-mineral protected C in subsoil corroborates the hypothesis that C saturation influences C storage and protection. Vegetating subsoil with appropriate species could act as a major C sink, valorizing geotechnical infrastructures as resources for carbon storage.

Auteurs et affiliations

• Rossi Lorenzo, University of Cassino (ITA)
• Stokes Alexia, INRA (FRA)
• Cardinael Rémi, CIRAD-PERSYST-UPR AIDA (ZWE) ORCID: 0000-0002-9924-3269
• Merino-Martin Luis, INRA (FRA)
• Derrien Delphine, INRA (FRA)
• Milcu Alex, CNRS (FRA)
• Roy Jacques, CNRS (FRA)
• Devidal Sébastien, CNRS (FRA)
• Piel Clément, CNRS (FRA)
• Plain Caroline, Université de Lorraine (FRA)
• Russo Giacomo, University of Cassino (ITA)
• Mao Zhun, INRA (FRA)

Source : Cirad-Agritrop (https://agritrop.cirad.fr/593978/)

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