Tropical Forest Restoration - Seedball Potential on Costa Rican Farmland

Regeneration and restoration methodologies of tropical ecosystems on Costa Rican pastureland and farms are limited to primarily natural regeneration, direct seeding, tree planting, and stake planting. Seedballing is a common practice in Japan used to reduce predation and labor costs and increase the germination rate of broadcasted seeds. I studied germination and survival of ten small seeded plant species comparing seedballing, direct seeding and control treatments (Helianthus annuus, Fagopyrum esculentum, Oryza sativa, Amaranthus cruentus, Senna reticulata, Carica papaya, Erythrina costaricensis, Solanum torvum, Flemingia macrophylla, and Triumfetta bogotensis) and two large seeded tree species using only direct seeding (Tabebuia rosea and Syzygium aqueum) because it was not logical to make seedballs with these larger varieties. These seeds were planted among 15 terraces in the Coto Brus region of Costa Rica at 1200 meters in elevation. Results showed that seedballing does not have a significant advantage over direct seeding. Overall, only Erythrina, Fagopyrum, and Syzygium had germination rates above 5% and all species had similar germination rates when direct seeded or seedballed. Germination was always best on the terraces near the forest edge, especially in the lowest elevation terraces, although seedling survival had the opposite effect. By the end of the experiment, germination of all seeds had virtually ceased, whereas the death rate was increasing rapidly. These results suggest that seedballing mix prescribed in Japan is not compatible or necessary for direct seeding of wet tropical species and may be best suited to drier climates where seedballing has been practiced more extensively.

KEYWORDS: Costa Rica, tropical forest restoration, secondary forest, seedball, seed germination, seedling survival, terrace, orientation, deforestation, pasture, abandoned farmland