Tree growth and soil recovery in Amazonian lands degraded by coca cultivation and grazing

Abstract

Soil degradation resulting from illicit coca cultivation and unsustainable grazing practices poses a major challenge to ecosystem restoration in the Peruvian Amazon. This study evaluates the potential of fast-growing tree species to rehabilitate degraded soils while producing economically valuable timber. Monoculture plantations of Corymbia torelliana (eucalyptus), Calycophyllum spruceanum (capirona), Colubrina glandulosa (shaina), and Cedrelinga cateniformis (tornillo) were established on former coca and pasture lands in the Alto Huallaga Valley. We assessed tree growth and key soil physicochemical properties – including soil organic matter (SOM), bulk density (BD), pH, extractable phosphorus (P), and cation exchange capacity (CEC) – in topsoil (0–10 cm) and subsoil (10–40 cm) layers. Eucalyptus and tornillo showed the highest diameter growth, while tornillo plots had significantly higher SOM levels. Soil pH was strongly acidic across all plots, and subsoil P was lowest under tornillo. CEC was highest in eucalyptus and capirona plots. Our findings suggest that tree plantations, particularly with eucalyptus, capirona, and tornillo, represent a viable strategy for the sustainable use and rehabilitation of soils formerly used for coca cultivation and grazing.