Simultaneous effects of reintroduction strategy and seed size on the initial development of two tropical tree species in an abandoned eucalyptus plantation

Abstract

Seedling planting is the most common strategy used to reintroduce tropical native tree species; however, direct sowing has simplicity and operational ease advantages. Functional traits such as seed size and growth rates have been shown to be relevant for better plant performance. We evaluated the effects of intraspecific variation in seed size and the reintroduction strategy simultaneously on the development of Hymenaea courbaril (L.) and Enterolobium timbouva (Mart.) introduced in an abandoned eucalyptus plantation over 462 days. Plants from small, medium and large seeds were reintroduced by planting seedlings and direct seeding. Both species achieved high rates of emergence and survival was high in the two reintroduction strategies. Seed size was not related to emergence and mean time to emergence for either species. The survival of both species was higher than 74% in the field, and seed size had little effect on survival rates. In general, H. courbaril plants introduced by direct sowing had higher growth, and seed size correlated positively with stem size. In contrast, the growth of E. timbouva plants introduced by seedling planting was higher than in plants introduced by direct sowing regardless of seed size. The light requirements of this species seem higher than for H. courbaril. Our results suggest the feasibility of reintroducing species by direct sowing in eucalyptus understory, but since plant growth varies between species, there may be a balance between the advantage of the initial plant size provided by planting seedlings and the advantage of a better root development provided by direct sowing.