Fine root and soil carbon stocks are positively related in grasslands but not in forests

However, FRC inputs can also enhance SOC loss through priming. Here, we tested the broad-scale relationships between SOC and FRC at 43 sites across the US National Ecological Observatory Network.

We found that SOC and FRC stocks were positively related with an across-ecosystem slope of 7 ± 3 kg SOC m −2 per kg FRC m −2 , but this relationship was driven by grasslands. Grasslands had double the across-ecosystem slope while forest FRC and SOC were unrelated. Furthermore, deep grassland soils primarily showed net SOC accrual relative to FRC input.