Soil radiocarbon abundance in global forest ecosystems controlled by climate and soil properties

Background Soil is the largest carbon pool on land. A small proportional change of soil carbon may lead to strong feedback to the climate system. However, how climate and soil properties affect soil carbon storage at regional or global scales remain inconclusive.Methods The spatial distribution of radiocarbon abundance (Delta C-14) in forest ecosystems and its driver factors were analyzed using a global database, International Soil Radiocarbon Database (ISRaD). Delta C-14 and its relationships with climate and soil properties were studied using data from 320 sampling sites containing 641 soil profiles in global forest ecosystems. Linear mixed-effects model analyses were performed to determine the relationships.Results Based on the Delta C-14 measurements available in the global database, we found that soil organic matter (SOM) stability was higher in boreal forests than in tropical and temperate forests. However, the SOM stability of temperate forests was lower than that of tropical forests. Soil Delta C-14 decreased with depth in the three forest ecosystems. Delta C-14 decreased faster in boreal and tropical forest than that in the temperate forest, especially across the first meter. We also revealed that the surface SOM stability was affected by temperature and precipitation and their interaction. At last, we revealed that iron-aluminum oxides and soil pH in mineral soils was more important for preserving SOM in deeper soil.Conclusion Our results illustrate the different effects of climate and soil properties on SOM persistence in various soil layers and vegetation types, providing new ways to better understand and predict soil carbon dynamics.

Automated summary

Based on data from the International Soil Radiocarbon Database (ISRaD), this study analyzed the spatial distribution of radiocarbon abundance in forest ecosystems and identified the factors influencing soil carbon storage. The findings highlight the importance of climate and soil properties in determining soil organic matter stability and provide insights into soil carbon dynamics.