Recovery of biogeochemical processes in restored tropical dry forest on a coal mine spoil in La Guajira, Colombia

Open-cast coal mining eliminates vegetation, alters physical and chemical characteristics of soils, and therefore limits the establishment of native vegetation by lack of sufficient moisture, increase bulk density, and low organic matter content. Restoration of extremely degraded areas through plantation of fast growing species is expected to accelerate the recovers of soil organic matter and nutrient cycles. The purposes of this study were to compare intrasystem cycling of C, N, P, and base cations in native and restored forests at an open-cast coal mine in a dry region of Colombia. Leaf-fall, standing leaf litter, and their N, P, Ca, Mg, and K contents were measured for 1 year in native forests and restored forests of various ages (7, 10, and 21 years). The exploitation of coal in La Guajira degraded soil fertility, and although tree planting was sufficient to achieve the partial recovery of soil chemistry and N cycling relative to reference conditions (i.e., native forest), a P deficiency in forest function remained unresolved even 21 years after restoration. The restoration of biogeochemical processes, particularly of critical processes of the P cycle, requires additional human interventions (such as the application of nutrient-rich litterfall from native forests of the region) that favor nutrient dynamics and lead to the recovery of a self-sustaining ecosystem. Thus, multiple efforts are needed for the restoration of these dryland forests to recover ecosystem services (such as soil fertility) that improve C sequestration and help mitigate climate change.