This study aimed to evaluate the structure and floristics of shrubs and trees in areas of
northern and southern slopes in the southern portion of the Maciço da Pedra Branca, Rio de
Janeiro, RJ. We tested the hypothesis that different component orientations may influence the
structure and floristic changes. In a sample area of 9.700 m2, divided into ten areas, were
surveyed 1508 individuals, distributed in 324 species, 154 genera and 52 families. The
families richest in species were: Myrtaceae, Lauraceae, Fabaceae, Rubiaceae and
Euphorbiaceae. The Diversity Index Shannon-Wiener (H ') was 5.093 nats / indiv., And the
evenness (J) was 0.881. Horizontal structure in the species Joannesia princeps, Piptadenia
gonoacantha e Pseudopiptadenia contorta, Meternichia princeps, Apuleia leiocarpa,
Astrocaryum aculeatissimum, Chrysophyllum flexuosum reached the highest value of
phytosociological importance. A phytosociological analysis of each individual area indicated
significant floristic and structural variations, with a trend toward greater diversity is found in
areas of higher altitude and farther from the urban perimeter. Of the 324 species found in the
study, 124 were found exclusively on the north side, 100 on the southern slope and 100
occurred in both strands. The exclusive species and more frequent on the north side were
Brosimum guianense e Annona cacans, Zollernia ilicifolia, Couratari pyramidata, Lecythis
pisonis e Gallesia integrifolia. On the southern slope, the exclusive species that stood out
were Cariniana estrellensis, Cabralea canjerana, Eugenia microcarpa. Cluster analysis
among the ten areas indicated, in general, greater similarity due to the proximity between
areas than for the orientation of the slope, however comparing the north and south closer
together, it is observed that the highest diversity indices, most proportion of rare species and
unique and the most advanced stages of succession were found on the southern slope. The
cases where this did not happen were observed in areas closer to the urban boundaries that
regardless of the slope were less floristic diversity. The diameter distribution model presented
inverted J, with a diameter range quite variable between areas. No pattern was found between
the diameter distribution and orientation of the slope. Comparing the flora of Pedra Branca
with other forest areas in Rio de Janeiro, there was generally a low floristic similarity. The
major floristic identity occurred with the work in-house Pedra Branca, Serra da Tiririca, and
Tijuca Forest. Works out of the city showed floristic similarity below 25%. The high diversity
of the studied area is a reflection of its high environmental heterogeneity, related to
differences in altitude, slope orientation, successional stage and history of use, which puts the
Pedra Branca as a strategic area for species conservation in Rio de Janeiro.
