Gap-phase regeneration in a semideciduous mesophytic forest, south-eastern Brazil

The study was carried out in ten natural canopy gaps in the Santa Genebra County Reserve (22degrees49'45"S, 47degrees06'33"W) in the county of Campinas, Sao Paulo State, Brazil. The size and canopy openness of the gaps were studied using hemispherical photographs. The vegetation survey included all shrubs and trees with height greater than or equal to 0.50 m in the gaps interiors and all the individuals with PBH (perimeter at breast height) greater than or equal to 15 cm in a 3 m surrounding border of the gaps. The similarity among the gaps and among their surrounding areas was assessed by the Jaccard similarity index and by cluster analyzes. The gap size varied from 20.09 to 468 m(2), with a predominance of small gaps. The families with the greatest species richness in the gaps were Rutaceae, Rubiaceae and Euphorbiaceae. The species with the greatest number of individuals in the gaps were Coffea arabica L., Hybanthus atropurpureus (St. Hil.) Taub. and Actinostemon klotschii (Muell. Arg.) Pax, all widely distributed in the understorey. Shade-tolerant species (late secondary species) predominated in function of the predominance of small gaps. The high number of species found in the gaps reflects the importance of these disturbances in the maintenance of species diversity in the studied forest.