• Atlantic Rainforest;
  • density;
  • diversity;
  • functional groups;
  • growth;
  • herbivory;
  • leaf toughness;
  • pioneers;
  • plant defenses;
  • reforestation;
  • saponins;
  • seedling

In this study, seedling growth and herbivory were monitored during the first 4 years of plot development in a large-scale reforestation experiment in Brazil's Atlantic Rainforest (Mata Atlântica). Seedlings were planted in a factorial design testing two levels of density, three levels of diversity, and the presence or absence of pioneer species at the Reserva Natural Vale in the Brazilian state of Espírito Santo. In addition, we studied the effect of herbivory on seedling growth and the potential for plant defenses to limit herbivory. Seedling growth was higher in the low-density plantings, and seedlings attained the greatest height in the low-diversity plots, which had a higher density of fast-growing species. The inclusion of pioneer species resulted in a significant decrease in the growth of neighboring seedlings. Interactions between herbivory, plant defenses, and seedling growth were complex. In general, defenses such as saponins and leaf toughness reduced herbivory, but when herbivory was high, seedling growth was reduced. Across treatments, mean height without herbivore damage was 240.8 cm, and with 50% herbivory mean height was 101.5 cm. Overall, to limit insect damage and promote seedling success, plant defense characteristics and ecological interactions should be carefully considered in reforestation projects.