Phytosociology and floristic composition of the arboreal component of the transition Lowland - Lower Montane Ombrophilous Dense Forest at Núcleo Picinguaba/Serra do Mar State Park, Ubatuba, southeastern Brazil

Abstract

In a 1-ha plot divided into 100 subplots of 10 × 10 m, all trees with at least 15 cm of perimeter at breast height (DBH = 4.8 cm) were marked and had their heights estimated and perimeter taken. The rock cover (rocks over 50 cm diameter) was estimated in five classes of frequency, and records were made for individuals growing directly on rocks. We found 1,274 trees matching the sampling criteria, which belong to 41 botanical families (highlighting Myrtaceae, Rubiaceae and Fabaceae) and 142 species or morphotypes. The most important (Importance Value Index) species are: Euterpe edulis, Mollinedia schottiana, Bathysa mendoncaei, Coussarea accedens, Rustia formosa and Guapira opposita. Shannon's diversity index was 4.05 nats/ind and Pielou's equability was 0.82. The average tree height is of 9 m and the canopy is at around 18 m. The trees' average diameter is 13.9 cm, and 29 individuals surpass 50 cm DBH. The basal area for the 1-ha plot (live trees only) is 30.27 m². A direct relation was found between rock cover and lesser species richness and number of individuals per subplot. No relationship was found between rock cover and the mean height or mean diameter of stems in the subplots. 34 tree species in this area are able to grow on rocks; 11 of which do not grow roots to the soil, particularly Euterpe edulis and Guapira opposita. The height and diameter of the individuals that grow on rocks is not statistically different from the remaining in the plot.