Regeneration Ecology of Eperua grandiflora (Caesalpiniaceae), a Large-Seeded Tree in French Guiana

Abstract

Long-term studies were conducted in French Guiana on the recruitment pattern of a large-seeded (47.6 g fresh weight) tree species: Eperua grandiflora (Caesalpiniaceae). Fruiting, seed dispersal by gravity, seed predation and seedling damages, and early seedling survival were analyzed from 1987 through 1988 (20-month period) at one tree standing on a slope. Most seeds land within 10-20 m of the parent, and a small fraction (5%) appeared to be secondarily dispersed by scatterhoarding rodents. As predicted by the Janzen-Connell model, clumped seeds and seedlings below the parent suffered post-dispersal predation and damages, respectively, by several families of insects, ants, and mammals. But because of large seed reserves, young seedlings were able to renew leaves or terminal meristems after defoliation or stem damage. Whether early seedling survival (7 months) was distance-dependent, mortality was nowhere near complete, and seedling survival during the next 12-month period (19-months post-germination) was independent of distance. Thus, juveniles persisted in a dumped population under parent tree. Dynamics of juveniles were studied from 1984 through 1989 and two 2500 m2 plots; an understory-environment (mature parent) and a gap-environment (dead parent). The proportion of juveniles greater than 100 cm tall was higher in the gap plot than in the understory plot. Although juveniles were very tolerant of understory conditions, they grew more rapidly in the gap. Occurence of young trees in the closed vicinity of parent trees is likely to result from poor dispersal of seeds, high survival beneath parents and high understory-tolerance of juveniles.