Deeply rooted perennial plants may help build soil carbon (C) stocks, but most research has focused on shallow soils, resulting in gaps in our understanding of how the balance between decomposition and C inputs shifts and drives soil C accumulation with depth. To address this challenge, researchers at the Center for Advanced Bioenergy and Bioproducts Innovation (CABBI) assessed the distribution and assimilation of 13C-labeled simple carbon in meter-deep (3.3-foot-deep) pits under mature perennial miscanthus stands.