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Increase in soil stable carbon isotope ratio relates to loss of organic carbon: results from five long-term bare fallow experiments

Authors
  • Menichetti, Lorenzo1
  • Houot, Sabine2
  • van Oort, Folkert3
  • Kätterer, Thomas4
  • Christensen, Bent T.5
  • Chenu, Claire6
  • Barré, Pierre7
  • Vasilyeva, Nadezda A.6, 8
  • Ekblad, Alf9
  • 1 Swedish University of Agricultural Sciences, Department of Soil and Environment, Uppsala, 75007, Sweden , Uppsala (Sweden)
  • 2 INRA, UMR Environnement et Grandes Cultures, Thiverval-Grignon, 78850, France , Thiverval-Grignon (France)
  • 3 INRA, Unité Pessac, Versailles, 78026, France , Versailles (France)
  • 4 Swedish University of Agricultural Sciences, Department of Ecology, Uppsala, 75007, Sweden , Uppsala (Sweden)
  • 5 Aarhus University, AU-Foulum, Department of Agroecology, Tjele, 8830, Denmark , Tjele (Denmark)
  • 6 AgroParisTech, UMR 7618 BIOEMCO, Bâtiment EGER, Thiverval-Grignon, 78850, France , Thiverval-Grignon (France)
  • 7 Laboratoire de Geologie, UMR8538, Ecole Normale Supérieure, Paris, 75005, France , Paris (France)
  • 8 North-Eastern Federal University, Yakutsk, Russia , Yakutsk (Russia)
  • 9 Örebro University, School of Science and Technology, Örebro, 70182, Sweden , Örebro (Sweden)
Type
Published Article
Journal
Oecologia
Publisher
Springer-Verlag
Publication Date
Oct 25, 2014
Volume
177
Issue
3
Pages
811–821
Identifiers
DOI: 10.1007/s00442-014-3114-4
Source
Springer Nature
Keywords
License
Yellow

Abstract

Changes in the 12C/13C ratio (expressed as δ13C) of soil organic C (SOC) has been observed over long time scales and with depth in soil profiles. The changes are ascribed to the different reaction kinetics of 12C and 13C isotopes and the different isotopic composition of various SOC pool components. However, experimental verification of the subtle isotopic shifts associated with SOC turnover under field conditions is scarce. We determined δ13C and SOC in soil sampled during 1929–2009 in the Ap-horizon of five European long-term bare fallow experiments kept without C inputs for 27–80 years and covering a latitudinal range of 11°. The bare fallow soils lost 33–65 % of their initial SOC content and showed a mean annual δ13C increase of 0.008–0.024 ‰. The 13C enrichment could be related empirically to SOC losses by a Rayleigh distillation equation. A more complex mechanistic relationship was also examined. The overall estimate of the fractionation coefficient (ε) was −1.2 ± 0.3 ‰. This coefficient represents an important input to studies of long-term SOC dynamics in agricultural soils that are based on variations in 13C natural abundance. The variance of ε may be ascribed to site characteristics not disclosed in our study, but the very similar kinetics measured across our five experimental sites suggest that overall site-specific factors (including climate) had a marginal influence and that it may be possible to isolate a general mechanism causing the enrichment, although pre-fallow land use may have some impact on isotope abundance and fractionation.

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