Fitossociologia e estrutura do componente arbóreo de um remanescente de floresta urbana no maciço da Pedra Branca, Rio de Janeiro - RJ

Abstract

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.