Tamanho, forma, alometria e crescimento em algumas especies de cecropia (Cecropiaceae) do Brasil

AUTOR(ES)
DATA DE PUBLICAÇÃO

1999

RESUMO

Size, form, allometry and growth were studied in some Cecropia species, from Amazonian and Southeastern BraziI. Architectural patterns and scaling of stem and crown was studied in five Amazonian species: Cecropia concolor, C. palmata, C. purpurascens, C. ulei and C. sciadophylla, in Manaus (AM); and in three Southeastern species Cecropia glaziovii, C. hololeuca and C. pachystachya, in Linhares (ES). The species are myrmecophytes except C. hololeuca and C. sciadophylla. Height, diameter, height of first branching, number of branches, number of leaves, total leaf area, internode length and bifurcation ratio were measured for undamaged trees. In both areas, size and architectural characters are displayed as a gradient from open habitats to forest. Forest-inhabiting C. hololeuca and C. sciadophylla had similar architectures, with low bifurcation ratios, and big leaves. Cecropia concolor and C. pachystachya measure up to 13 m in height with smaller leaves and occur typically in open habitats. The remaining species occupy forest margins and are intermediate between these two extremes. The scaling relationships were studied with log-transformed variables and regressed on height. Three models of optimal mechanical designs of trees - elastic, constant stress and geometric similarity were tested for Cecropia. None of the models can totally describe Cecropia, but geometric similarity was a close approximation. Species differ significantly in diameter-height relationships. Most of species did not vary in diameter-height relationships between unbranched and branched individuaIs. The crown-height relationships of species studied were similar. Numbers of branches and leaves showed some variation among species and are related to height of first branching. Total leaf area had a constant allometric relationship for species, although regression intercepts differed according to species leaf areas. The growth and leaf longevity of saplings of the three southeastern species was studied during one year, in Nova Lima, MG. Cecropia glaziovii and C. pachystachya produced more internodes.yr-1 than C. hololeuca. Maximum values of height and diameter increments were higher for the two myrmecophytes than the non-myrmecophyte C. hololeuca, but medians did not differed significantly. Internodes.yr-1 and height increment was positively correlated with monthly rainfall for the three species. Leaf emergence was higher in myrmecophytic species. Leaf mortality was higher for C. glaziovii leaves than for the other species. Leaf longevity of C. hololeuca and C. pachystachya was higher (±7 months) than that of C. glaziovii (±4 months). Architectural and allometric analysis of the eight Cecropia species, showed that, although they are considered typical pioneer trees, morphological variation founded could be related to light gradient occupation of species. Differences found in growth and leaf longevity of the three species could influence ant occupation of species

ASSUNTO(S)

mutualismo arvores - crescimento

ACESSO AO ARTIGO

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