Direct seeding reduces costs, but it is not promising for restoring tropical seasonal forests

Abstract

Direct seeding is a potential technique to restore forests; however, further studies are needed before its application on a large scale. We carried out a field experiment in a deforested area in southern Brazil to test the technical and economic feasibility of a direct seeding system with high tree species diversity to restore the tropical seasonal forest. We also compared species performances and tested the effects of seed size and successional group on tree seedling emergence and development. The trial was established at two different sowing times using 31 tree species. For two years after sowing we evaluated seedling emergence, establishment, survival and early growth of tree species, weed competition and costs for plantation establishment and early maintenance. Most species had low seedling emergence and establishment, but high survival rates, implying that low seedling emergence is the main barrier to community assembly that must be overcome. The most successful species had larger seeds, belonged to non-pioneer categories and had slower growth rates. Final costs after two years were lower than has been reported in the literature for most restoration planting using seedlings both in Brazil and elsewhere; however, seedling density was low. Although direct seeding may be a feasible alternative to decrease planting costs, the poor species performances and low seedling density may reduce its applicability. Thus, we recommend direct seeding only in association with the planting of pioneer species seedlings.