Recovery in soil carbon stock but reduction in carbon stabilization after 56-year forest restoration in degraded tropical lands

Background/Question/Methods

• Carbon (C) sequestration in forest soils play a pivotal role in global C balance by offsetting sources of carbon sources of carbon dioxide to the atmosphere. However its function has been vastly limited by deforestation and may be improved through afforestation eventually. Here we conducted a field study in degraded tropical forests of south China. The aim was to evaluate the recovery of soil C stock following afforestation by comparing different C fractions in soils (0-10 cm and 10-20 cm) in two reforested forests [a restored secondary forest (RSF) and a managed Eucalyptus plantation (MEP)] to those in a bare land (BL) and a nearby undisturbed forest (UF).

Results/Conclusions

• Results showed that after 56-year afforestation at the bare lands, C stocks in both soil layers were significantly increased with the increase greater at the RSF than MEP, while C recalcitrant indexes (RI) were reduced. Soil C stock at the RSF site recovered to a similar level as the UF, but soil RI at the RSF site was still lower than UF particularly in the 10-20 cm layer. The soil C sequestration capacity (SCS_capacity), considered as the product of soil C stock and its RI, followed the order: UF>RSF>MEP>BL. Our results demonstrate that afforestation on degraded tropical lands could recover soil C stock within a few decades, but C stabilization was decreased.