WHAT THE EVIDENCE SAYS
Radiocarbon measurements across 42 dryland sites showed that topsoil soil-inorganic carbon consistently carried a measurable modern-carbon signature relative to radiocarbon-dead carbonate. In Chinese drylands, the modern imprint generally weakened with aridity; in a nine-site Chinese subset it declined sharply with depth. Across the full dataset, soil pH and the radiocarbon signature of organic carbon were the strongest predictors.
WHY IT MATTERS / OUR READ
If shallow inorganic carbon exchanges with contemporary carbon more than assumed, dryland carbon accounting and interpretation of carbonate signals may need a more dynamic process model rather than treating the pool as uniform geological background.
CAVEATS / UNCERTAINTY
A modern radiocarbon signature is not a measurement of net new carbonate formation or net carbon sequestration; isotopic exchange and recrystallization can produce the signal. Depth patterns were evaluated at nine Chinese sites, and aridity relationships were clearest in the Chinese drylands because Iran and Spain had fewer sites and narrower gradients.
SOURCE
Global Change Biology · Original evidence
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