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Forskningsartikel2015Vetenskapligt granskad

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

Menichetti, Lorenzo; Houot, Sabine; van Oort, Folkert; Kätterer, Thomas; Christensen, Bent T.; Chenu, Claire; Barré, Pierre; Vasilyeva, Nadezda A.; Ekblad, Alf


Changes in the C-12/C-13 ratio (expressed as delta C-13) 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 C-12 and C-13 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 delta C-13 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 11A degrees. The bare fallow soils lost 33-65 % of their initial SOC content and showed a mean annual delta C-13 increase of 0.008-0.024 aEuro degrees. The C-13 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 (epsilon) was -1.2 +/- A 0.3 aEuro degrees. This coefficient represents an important input to studies of long-term SOC dynamics in agricultural soils that are based on variations in C-13 natural abundance. The variance of epsilon 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.


Stable carbon isotope ratio; Isotope fractionation; Rayleigh distillation; Natural abundance; Soil organic carbon

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2015, Volym: 177, nummer: 3, sidor: 811-821
Utgivare: SPRINGER