Despite the considerable number of studies published about tree gaps in tropical regions, none of them addresses the regeneration of plant species in natural gaps in the Amazonian seasonally flooded forests. These forests undergo a large fluctuation of the water level which may vary up to 15 meters between the high and low water seasons, flooding extensive areas along rivers and streams. The objective of this study was to determine whether differences in the duration of annual flooding could affect the parameters of size, species diversity, and composition in natural gaps. This study sampled 10 natural gaps in black water floodplain forests of different areas and flood levels along the Tarumã-Mirim River, a tributary of the Rio Negro, in the State of Amazonas, Brazil. There was a significant increase in gap size, varying from 101 to 1.001 m2, in relation to the level of flooding. There was also a significant increase in species diversity, varying from 14 to 51 species, depending upon the increase in the level of flooding. The species composition in the gaps was closely related to the level of flooding, resulting in gaps located in areas subjected to a long flooding period being colonized mainly by species with a high flooding tolerance, whereas gaps located in regions of short periods of inundation were mainly colonized by species with a low flooding tolerance. In conclusion, the gap size, diversity, and floristic composition within the gaps of the black water flooded forests sampled in this study were related to the level of flooding, demonstrating that that annual flooding duration influenced these parameters.
Amazon; gaps; igapó forests; plant regeneration
