Florística e estrutura do componente epifítico vascular na mata da reserva da Cidade Universitária

Ricardo Dislich

This work assesses floristics and structure of epiphytes, here defined as vascular plants usually found living on others, without parasitizing them, during at least a part of their life cycles. The study site, the reserve of the Cidade Universitária "Armando de Salles Oliveira" (nearly 46o43W, 23o33S), in São Paulo-SP (Brazil), is a secondary forested area isolated in urban environment and represents one of the few forested areas in this city. The climate type is Köppens Cwa, the mean annual temperature is 19,2 oC and the mean annual precipitation is 1207 mm. Polypodiaceae (9 species), Bromeliaceae (8), Orchidaceae (6), Moraceae (5), Araceae (4), Cactaceae (3), Piperaceae (1), Blechnaceae(1) and Araliaceae (1) are the families of epiphytes found at the study site, making up 38 species, 3 of them being exotic. Epiphytes are 12% of the vascular plant species cited for the reserve. This species richness is larger than expected in face of the little mean annual precipitation. All main epiphytic life forms are represented. The structure of the epiphyte community upon all the trees with girth of trunk at the height of 1,30 m (GBH) with more than 40 cm was studied in a 2000 m2 plot inside the reserve. The trees location inside the plot was mapped and species, height, GBH and presence/absence of lianas were recorded for each of them. From 86 trees, 29 were of Alchornea sidifolia, 10 of Croton floribundus and 8 of Piptadenia gonoacantha, the most abundant species. Pterocarpus rohrii, Rollinia sylvatica and Myrcia tenuivenosa are cited for the first time for the reserve. Two different subareas could be distinguished inside the plot as to the successional stage of the trees, an evidence for the mosaic character of the vegetation. DBH frequency distributions predict the decline of the most abundant species populations and consequent deep changes in the structure of the forest. A total census of the epiphytic stands more than 15 cm long was made upon all sampled trees. A stand was defined as a compact group of plants well separated from conspecifics. 380 stands were found, on 58 trees(67% of total). For each stand, height of attachment, branch or trunk diameter, inclination, height zone (trunk, lower, middle or upper crown), type of substrate (hole, fork or bark) and epiphyte species were recorded. The five more abundant species were analysed as to the distribution along the variables. They were: Microgramma squamulosa (75 stands), Rhipsalis baccifera (67), Pleopeltis astrolepis (57), Aechmea bromeliifolia (52) and Polypodium hirsutissimum (45). Tree height and DBH were positively correlated with number of stands and number of epiphyte species. There is great variability between tree species in these aspects. P. rohrii and Casearia sylvestris are the species with highest numbers of stands per tree. Tree characteristics such as species, DBH, successional stage, successional vegetation stage and presence/absence of lianas dont seem to have influence on epiphyte composition on them. Epiphytes show broad vertical and diameter distributions. Species vertical and diameter distributions overlap largely and, as a consequence, there is no distinct stratification. A. bromeliifolia showed preference for establishment in holes. Lower crown and trunk were the zones with the largest number of stands. Epiphytes as a whole show preference for middle heights in the forest (ca. 8 m), large diameters (10-30 cm), horizontal to middle and positive inclinations. R. baccifera showed preference for P. rohrii as support tree; P. hirsutissimum and P. astrolepis showed preference for A. sidifolia. M. squamulosa is the most ubiquituous epiphytic analyzed species.

AUTOR(ES)

DATA DE PUBLICAÇÃO

RESUMO

ASSUNTO(S)

ACESSO AO ARTIGO

Documentos Relacionados