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We tested the relationship between the length of pasture use and the density, richness, and composition of naturally regenerating tropical seasonal deciduous forest in pastures. We sampled regenerating trees in 25 pastures distributed in four age classes ranging from < 6 to 40 yr of use. Density and composition of regenerating trees did not change with pasture age, but richness was lower in 25- and 40-yr-old pastures. Nonetheless, a number of species seem to be able to resprout even after 40 yr of ranching.

We studied the effect of forest gaps and cattle grazing on survival and growth of seedlings of seven native tree species, planted in dry forest fragments with different intensities of past logging in Central Brazil. Seedling survival after 12 mo ranged from 35 to 77 percent among species. Survival of most species was similar in gaps and understory in minimally disturbed forest remnants, but was lower in the gaps of more heavily logged forests. In contrast, growth was much higher in gaps than in understory in minimally disturbed forests, but for most species was similar in gaps and understory in more heavily logged forests. We did not detect an effect of cattle on seedling survival. Seedlings of the most commonly logged species show a high potential to survive and grow when planted in logged forests.

Physical damage caused by litterfall is a source of seedling mortality that can be influenced by environmental disturbances, such as the isolation of forest fragments due to habitat destruction. The impact of physical damage in seedling mortality was evaluated in forest fragments and continuous forests in central Amazonia using artificial seedlings. A total of 11 reserves distributed among three sites were studied: three 1-ha, three 10-ha, two 100-ha, and three continuous forest reserves. In each reserve, ten transects each comprised of ten artificial seedlings were monitored for one year at four-week intervals. Survival curves were compared using failure time analysis, and the effect of reserve size on artificial seedling mortality after one year was analyzed with a categorical model. In the analysis of survival curves, artificial seedling survival was significantly greater in the continuous forest than in the 10-ha reserve at one site only, a result that may have occurred by chance. After one y...

Phenology, floral biology, the reproductive system, and pollination of the macauba palm, Acrocomia aculeata were studied in Central Brazil. The species is arborescent, single-stemmed, and reaches heights of up to 16 m. Flowering occurs between August and December, peaking between October and November. Fruit fall (harvest) is between June and March, with a peak in November. Inflorescences are androgynous with marked protogyny. The basic pollination syndrome is by beetles, with wind playing a secondary role. The principal pollinators are Andranthobius sp. (Curculionidae), Mystrops cf mexicana (Nitidulidae) and Cyclocephala forsteri (Scarabaeidae). Cross-pollination between different individuals (xenogamy) accounts for most of the reproductive system. However, the species is self-compatible, with geitonogamy accounting for a significant percentage of fruit set. The combination of two pollination strategies (wind and insects) with a flexible reproductive system (crossand self-pollination) suggests that A. aculeata can be highly successful in the colonization of new areas, as is evidenced by the ample distribution of species in the Neotropics.