PLANT ESTABLISHMENT ON FLOODED AND UNFLOODED PATCHES OF A FRESH-WATERSWAMP FOREST IN SOUTHEASTERN BRAZIL

Plant establishment was studied in a swamp forest in the lowland Atlan tic rainforest in southeastern Brazil. A topographic gradient allowed a clear distinction between a periodically flooded and a permanently f looded site in the study area. Both sites were mosaics of patches: the former showed soil patches of varying sizes subject to distinct flood ing durations (from 0 to 300 d per year) and in the latter, the tank b romeliads which densely occupied the understorey, trap litter and prov ided 'suspended soil' patches. In the periodically flooded site, the o ccurrence of regenerants (< 1.0 m tall) of the actively regenerating t ree populations of Calophyllum brasiliense, Symphonia globulifera and Tovomitopsis paniculata (all Clusiaceae), originating from seed or veg etative organs, was recorded for 1 m(2) quadrats placed in flooded (n = 82) and unflooded (n = 103) patches. In the permanently flooded site , dominated by Tabebuia cassinoides (Bignoniaceae), the presence of ge rminated seedlings was counted for 400 rosettes of the terrestrial tan k bromeliad Nidularium procerum. The results showed that unflooded pat ches, including tank bromeliads, favoured seedling establishment. Howe ver, T. paniculata and T. cassinoides colonize patches where flooding lasts longer or is permanent mostly by reproducing vegetatively, while the seeds of C. brasiliense, which showed no form of vegetative repro duction, and S. globulifera are successful in colonizing flooded parch es. Germination tests and field observations indicated that, for C. br asiliense, pre- and post-dispersal seed dormancy, a two-phase seed dis persal (water and bats) and seedling tolerance to flooding accounted f or this pattern.