The Climate Control of Soil Organic Carbon Dynamics Inferred From Speleothem Radiocarbon Ages.

The complexity of processes affecting soil organic carbon (SOC) turnover on spatio‐temporal scales often hinders the extrapolation of results from specific sites to larger scales. This study presents Holocene speleothem U‐Th ages paired with 14C ages of carbonate and dissolved organic carbon (DOC) through three caves located on a north‐south transect through China. The deviations of speleothem 14CDOC ages from the U‐Th ages show clearly spatial variability, and they are positively correlated with mean ages of modern SOC and soil turnover time, suggesting that deviations can be used to infer the SOC turnover. We further demonstrate that slow SOC turnover (large deviation) was associated with weak monsoon (low temperature/less precipitation) on temporal scales. Our findings reveal that climate dominates the speleothem 14CDOC ages and SOC turnover. As global warming likely will intensify, the accelerated turnover of SOC, particularly at higher latitude areas, may partially offset the existing soil carbon stock. Plain Language Summary: Understanding the controls of the soil organic carbon (SOC) turnover on spatio‐temporal scales is of great significance to predict the soil carbon stock. The current knowledge of SOC turnover on the longer temporal scale is scarce due to a lack of accurate chronology. Here, we present Holocene speleothem U‐Th ages paired with 14C ages of carbonate and dissolved organic carbon (DOC) through three caves located on a north‐south transect through China. We found the deviations of speleothem 14CDOC ages from the baseline U‐Th ages positively and negatively correlated with soil turnover time and climate variables (i.e., temperature and precipitation), respectively. Concretely, long turnover time as indicated by large deviations was associated with weaker monsoon (low temperature and less precipitation), and vice versa. It suggests that climate dominates SOC turnover and the speleothem 14CDOC ages. Our study not only provides a compelling approach to diagnose the past cycling of SOC under climate shifts exceeding present‐day variability and but also projects a promising perspective for studying the interactions between SOC turnover rates and climate changes on broad spatio‐temporal scales. Meanwhile, it creates an opportunity to evaluate the changes in SOC turnover rates for the future. Key Points: Using 14C ages of dissolved organic carbon in speleothem as an alternative approach to date the speleothem is questionableThe deviations of speleothem 14CDOC from the U‐Th ages can be used to infer the turnover of the soil organic carbon (SOC)Climate dominates the speleothem 14CDOC ages and SOC turnover on spatio‐temporal scales [ABSTRACT FROM AUTHOR]