Evaluating carbon dynamics in soil aggregates using δ13C following long-term vegetation restoration near a surface mine in a semi-arid region.

[Display omitted] • The proportion and OC content of large aggregates were affected by vegetation types. • The direction of carbon flows was from small aggregates to silt + clay size classes. • Tree plantation slowed carbon flows of aggregates. • Roots are more likely to be the starting point of carbon flow at 15–30cm depth. The vegetation restoration of land post‑mining can promote soil structure development and increase organic carbon storage. The response of soil carbon sequestration pathways to different recovery modes is poorly understood, especially in soils of reclaimed surface-mine areas. Here, long-term carbon dynamics were characterized by examining aggregate-associated carbon contents and carbon flow pathways following vegetation restoration of reclaimed land near a surface mine. Six long-term restoration areas were represented by Populus alba trees, Amorpha fruticosa shrubs, and grassland. During the long-term restoration process the contribution of aggregates to SOC (12.5 to 46.1%), δ13C values (-25.91 to –23.65‰) and percentages of particulate organic carbon in large soil aggregates of tree plantations showed the maximum increase and shrubland showed the minimum. The direction of carbon flows was from small aggregates to silt + clay size classes, and tree plantations slowed the carbon flows of aggregates. With increasing soil depth, roots were more likely to be the starting point of carbon flow in aggregates. This analysis of the natural δ13C signature reveals the mechanism of organic carbon stabilization under long-term vegetation restoration near a surface mine in a semi-arid region. [ABSTRACT FROM AUTHOR]