Comparison of 137Cs inventories in soils under forest stands and the deposition site indicated that the study afforestation systems have experienced appreciable net erosion over the period since the commencement of 137Cs fallout in the mid-1950s. Soil losses were the highest in Masson pine stand and the lowest in Michelia stand.
Although erosion occurred under planted forest systems, the SOC and TSN stocks in the 0–10 cm soil layer were higher at soil erosion areas than at soil deposition areas. Nevertheless, in soil layers below the 10 cm depth, the SOC stocks were the highest at the deposition site. Different forest species presented varied carbon sequestration capacities in the upper 0–10 cm soil layer with a descending order of Crape-Myrtle > Elaeocarpus > Michelia > Camphor Tree > Masson pine > Deposition site. The topsoil layers experienced the highest soil and carbon losses at Masson pine
stands, and thus the plantation of Masson pine in a subtropical erosion region is not an optimal choice to mitigate soil loss or increase carbon sequestration. Fluxes and concentrations of SOC and TSN appeared to have a similar response to afforestation under erosion. Afforestation systems may be an important component of carbon budget for the study catchment. In order to reduce the incidence and intensity of water erosion and maintain carbon in the study area, it is recommended to implement terracing and straw mulching in forest plantations and increase forest cover.