The C isotopic composition (δ
13C) of pedogenic carbonates reflects the photosynthetic pathway of the predominant local vegetation because pedogenic (secondary) CaCO
3 is formed in isotopic equilibrium with soil CO
2 released by root and rhizomicrobial respiration. Numerous studies show the importance of pedogenic carbonates as a tool for reconstructing paleoecological conditions in arid and semiarid regions. The methodological resolution of these studies strongly depends on the time scale of pedogenic carbonate formation, which remains unknown. The initial formation rate can be assessed by
14C labeling of plants grown on loess and subsequent incorporation of
14C from rhizosphere CO
2 into newly formed carbonate by recrystallization of loess CaCO
3. We tested the feasibility of
14C and
13C tracers for estimating CaCO
3 recrystallization rates by simultaneous
14C and
13C labeling and comparison with literature data.
14C labeling was more efficient and precise in assessing recrystallization rates than
13C labeling. This is connected with higher sensitivity of
14C liquid scintillation counting when compared with δ
13C measurement by IRMS. Further, assessment of very low amounts of incorporated tracer is more precise with low background signal (natural abundance), which is true for
14C, but is rather high for
13C. Together, we obtained better reproducibility, higher methodological precision, and better plausibility of recrystallization rates calculated based on
14C labeling. Periods for complete CaCO
3 recrystallization, extrapolated from rates based on
14C labeling, ranged from 130 (125–140) to 240 (225–255) y, while it was ≈ 600 (365–1600) y based on the
13C approach. In terms of magnitude, data from late‐Holocene soil profiles of known age provide better fit with modeled recrystallization periods based on the
14C approach.
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