Mixed-species afforestation promotes soil organic carbon by shaping fine root vertical distribution and morphology

A field experiment was conducted in three even-aged and similarly managed plantations (<i>Castanopsis hystrix</i> monoculture, <i>Pinus massoniana</i> monoculture, and <i>C. hystrix-P. massoniana</i> mixed plantation) in subtropical China. We measured species-specific fine root biomass, root morphological traits, particulate organic C (POC), and mineral-associated organic C (MOC) across different soil depths to assess how fine root vertical distributions and changes influence SOC in different plantations.