Active Restoration Initiates High Quality Forest Succession In A Deforested Landscape In Amazonia

Abstract Background: Amazonia is well known for its high natural regeneration capacity; for this reason, passive restoration is normally recommended for the recovery of its degraded forests. However, highly deforested landscapes in southern Amazonia require active restoration. Since restoration methods can shape the quality and speed of early forest recovery, this study aimed to verify how active restoration pushes non-resilient sites towards forest recovery. Methods: We evaluated early forest succession at active restoration sites, i.e. soil plowing, direct seeding of pioneer species and seedling stock planting at low density. We analyzed forest structure, diversity and species composition in two age classes, 0.5 – 3.5 and 4.5 – 7.5 years old. As reference, we evaluated natural regeneration as performed on more resilient sites in the same region. We sampled 36 active restoration and 31 natural regeneration sites along the Madeira river, southern Amazonia. Results: Active restoration triggered succession to similar or higher levels of forest structure than sites where natural regeneration was taking place. The most dominant species did not overlap between active restoration and natural regeneration sites. The overall composition of species was different between the two restoration methods. Dominant species and size class distribution indicate that active restoration is performing successfully. Conclusions: Soil preparation combined with a high availability of seeds of pioneer trees resulted in a high stem density and basal area of facilitative pioneer trees. Planted seedlings added species diversity and increased density of large trees. Interventions to increase the odds of natural regeneration can be effective for non-resilient sites located in resilient landscapes.