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Seed rain in a monodominant Brosimum rubescens Taub. forest and an adjacent mixed forest in the Araguaia River Valley, Mato Grosso State, Brazil

Patches of monodominant Brosimum rubescens forest occur at the transition zones between the Cerrado and the Amazonian Biomes. Seed rain was studied at two sites at the monodominant forest and another site at a nearby mixed forest in Nova Xavantina, MT (14º50'47''S e 52º08'37''W). The hypothesis was that the pattern of seed rain differs at the monodominant forest from the mixed forest due to the massive fruiting of Brosimum rubescens. Eleven seed-traps (0,5×0,5 m) were set up at three portions of the forests, totalling 33 traps. Two portions (22 traps) were at the monodominant forest and one (11 traps) at a mixed forest. They were monitored from August 2003 to July 2004. The seed were classified as wind dispersed or dispersed by other mechanisms but not wind and the forests were compared regarding number and biomass of seeds and species richness. Number of seeds and biomass were compared at the three forest portions through the seasons. Wind dispersed, small seeded species were more evenly dispersed over the year that those big seed ones. Seed rain was affected by forest type and seasonality. At the monodominant forest the dispersion peak of non-wind dispersed seeds occurred at the dry season with most of the seed biomass belonging to B. rubescens. Abundant seed production, dispersion at the dry season and the development of a seedling bank, seems to be an advantage to the monodominant species. At the dry season the competition for dispersers is low, and the germination at the beginning of the rains allow the seedlings a full growth season.

monodominant forest; seed rain; Brosimum rubescens; Amazônia; Cerrado


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