Effect of restoration methods on natural regeneration in the Brazilian Atlantic Forest

Climate change and ecosystem degradation have achieved unprecedented levels nowadays. In this context, assessing restoration projects to recover native vegetation and ecosystem services is fundamental to understanding the success of these initiatives. This study evaluated the effects of different restoration techniques on the basal area, diversity, and composition of regenerating and planted species in a restoration area in the Atlantic Forest, Southeast Brazil. The experiment consisted of three treatments: row planting (ROW, 2 × 2 m spacing); nucleation (NUC, 13 individuals/nucleus, 5 × 5 m spacing); and control with passive restoration (PAS). The active restoration techniques had different planting densities at project implementation (NUC: 5.200 seedlings ha-1; ROW: 2.177 seedlings ha-1). A floristic survey was carried out within 8 sampling units (15 × 15 m) per treatment 10 years after implementation of the project, including all planted and regenerating individuals with a diameter at ground level > 2.5 cm. The abundance, basal area, and species richness of the planted and regenerated communities were estimated. The active restoration techniques (ROW and NUC) resulted in higher values of basal area, abundance and species richness compared to passive restoration (PAS). A higher abundance of natural regeneration was observed in ROW than in NUC. Additionally, the rarefaction curves suggested a trend toward higher diversity indices in ROW. Regarding the successional trajectory, greater variation in species composition was observed in ROW after 10 years of planting. The species composition was similar in ROW and NUC and differed from the composition in PAS. The species identified as indicator species in each treatment were Annona glabra L. in ROW, Trema micranthum (L.) Blume in NUC, and Vernonanthura polyanthes (Sprengel) Vega & Dematteis in PAS. Our study revealed that active restoration techniques, such as seedling planting in rows and nuclei, were more effective in restoring ecological indicators than passive restoration. These results emphasize the importance of restoration techniques in enhancing plant community diversity and structure in the Brazilian Atlantic Forest.