Resumen
- A study was carried out to evaluate the use of Acacia mangium plantations in reactivating biogeochemical cycles of soil nutrients in a soil degraded by alluvial goldmining. Fine litterfall production was 10.4 Mg ha-1 yr-1 and it was dominated by the leaf fraction 5.7 Mg ha-1 (55%). The highest nutrient return found corresponded to nitrogen (N) (69 kg ha-1) and the lowest to phosphorus (P) (0.5 kg ha-1). The results of a litter-bag study indicated that the annual decomposition constant (k) ranged from 1.25 to 1.80. Chemical composition of the leaf litter (e.g., N and P concentrations, C/N and N/P ratios, and phenols content) and rainfall play an important role in the decay process, which was characterized by a slow release of N, Ca, and Mg from the leaf litter, while P was immobilized. The C return to soil from the decomposition of the leaf litterfall oscillated between 2.0 and 2.4 Mg ha-1, which was lower than expected, likely because the mesh size of the litter bags restricted our observation only for the leaf fraction. The A. mangium plantations showed a great potential in the reclamation of these degraded soils due to the high values of fine litter production and nutrient return, which contributed to the reactivation of biogeochemical cycles. Therefore, the soil under this plantation showed significant increases in chemical and physical properties respect to unplanted soil: nitrogen content (0.24 vs. 0.5%), available P (2.48 vs. 6.53 mg kg-1), cation exchange capacity (6.12 vs. 11.19 cmolc kg-1), organic matter content (6.14 vs. 18.66%, and aggregate stability (73.0 vs. 85.35%). A. mangium plantations have a high potential to remediate soils degraded by alluvial gold-mining.