Aridity-driven decoupling of delta C-13 between pedogenic carbonate and soil organic matter Academic Article uri icon


  • Abstract Pedogenic carbonate is an invaluable archive for reconstructing continental paleoclimate and paleoecology. The 13C of pedogenic carbonate (13Cc) has been widely used to document the rise and expansion of C4 plants over the Cenozoic. This application requires a fundamental presumption that in soil pores, soil-respired CO2 dominates over atmospheric CO2 during the formation of pedogenic carbonates. However, the decoupling between 13Cc and 13C of soil organic matter (13CSOM) have been observed, particularly in arid regions, suggesting that this presumption is not always valid. To evaluate the influence of atmospheric CO2 on soil 13Cc, here we performed systematic 13C analyses of paleosols across the Chinese Loess Plateau, with the sample ages spanning three intervals: the Holocene, the Late Pleistocene, and the mid-Pliocene warm period. Our paired 13Cc and 13CSOM data reveal broadly divergent trending patterns. Using a two-component CO2-mixing model, we show substantial incorporations of atmospheric CO2 (up to 60%) into soil pore space during carbonate precipitation. This result readily explains the enrichment of 13Cc and its divergence from 13CSOM. As a consequence, 13C of pedogenic carbonates formed under semiarid and/or arid conditions are largely driven by regional aridity through its control on soil CO2 composition, and thus cannot be used to evaluate the relative abundance of C3 versus C4 plants. Nonetheless, these carbonates can be applied for atmospheric CO2 reconstructions, even for periods with low CO2 levels.

published proceedings


altmetric score

  • 4.55

author list (cited authors)

  • Da, J., Zhang, Y. G., Li, G., & Ji, J.

citation count

  • 9

complete list of authors

  • Da, Jiawei||Zhang, Yi Ge||Li, Gen||Ji, Junfeng

publication date

  • October 2020