Floristic and structural differences, between two altitudinal quotas, of the Submontane Atlantic Rainforest within the Serra do Mar State Park, municipality of Ubatuba/SP, Brazil

Abstract

This study presents a comparative analyzes of two areas of Atlantic Rain Forest, in the municipality of Ubatuba (SP), Brazil, and tests the hypothesis that floristic composition and phytosociological structure change along an altitudinal gradient. Two 1-ha plots were installed, respectively, at 190 (PLOT G) and 350 m (PLOT I) above see level, and within these plots all individuals with DBH > 4.8 cm were sampled, measured and identified. In total we found 252 species, belonging to 134 genera and 53 families, diversity H' of 4.425 nats/individual, and 103 species (41% of total) common to both plots. But, among the 10 top species in Absolute Dominance only two: Cryptocarya mandioccana and Sloanea guianensis were found in both plots. In PLOT G we found 1496 individuals distributed in 152 species, 101 genera and 41 families, with H' = 3.961 nats/individual and 48 exclusive species (32%). In PLOT I we found 1993 individuals distributed in 203 species, 111 genera, 50 families, with H' = 4.339 nats/individual and 100 exclusive species (49%). Supporting our hypothesis, the comparative analyzes showed that there are significant differences in density (p < 0.01, t = 7.10), richness (p < 0.01, t = 7.76) and volume (p = 0.02, t = 2.44), between the two sampled areas. The pattern here observed shows that the plot installed closer to the middle of the Serra do Mar slope (350 m) presented a higher number of individuals, higher richness and higher scores of volume, when compared to that closer to the base of the slope (190 m).