New paper on soil carbon

In this study, we carried out a two-year incubation experiment using 21 temperate agricultural soils that differed in their initial soil organic carbon (SOC) contents. We added ¹³C-labeled plant litter to trace how new carbon is decomposed and stabilized. Throughout the experiment, we measured carbon retention in bulk soil and fine/coarse fractions, as well as carbon losses as CO₂. Selected samples were further analyzed using NanoSIMS imaging to visualize microscale carbon accumulation.

We found that soils with higher existing SOC retained a slightly larger share of newly added carbon, and that new mineral-associated carbon continued to form even in soils with high fine-fraction carbon loadings. This suggests that, within the range we studied, initial SOC levels did not strongly limit mineral-associated carbon formation, and that microbial processing and microscale organic matter patterns are important for stabilization.

https://doi.org/10.1111/gcb.70646