Relação da área foliar com a área do xilema ativo em árvores juvenis de seis espécies dominantes na Amazônia Central

Abstract

The leaf area to sapwood area ratio (LA:SA; pipe model) is fundamental to understand the allocation of resources and the hydraulic architecture of plants. In this study, we tested (1) how the LA:SA ratio differs between branch and whole tree, (2) how it changes with tree height, and (3) how it changes along the hydro-edaphic gradient. In a rain tropical forest in Central Amazonia we destructively sampled 121 individuals of six dominant tree species (18-23 per specie) for measurement of leaf and sapwood area both for the whole plant and for a branch of the same individual. We found that: (1) the leaf area and the sapwood area showed an isometric ratio (1:1) for both measurements made in the branch and for the whole plant; but the LA:SA ratio is higher in the branches than in the tree, (2) it decreases with increasing tree height, and (3) tends to increase with distance from water-table but is not consistent between species. We attribute these changing patterns to: (1) higher hydraulic resistance in the branches, influence of branch woody density and apical dominance index (2) less allocation in leaf area to optimize growth height and (3) as a response of plants to limited light or the ratio LA:SA is influenced by other morphological and hydraulic traits. We conclude that juvenile trees in a tropical forest have an isometric relationship between LA and SA for branches and whole tree, but there are some patterns of change in the allocation of leaf area per unit of sapwood: the measuring scale (branch or whole plant), the tree height and the distance from water table, however, there is no same trend among species. Then, generalized interpretations should be made with caution. Specifically, for a better understanding of the hydraulic function of the plants are necessary studies oriented to change and coordination of the LA:SA ratio and the structural and hydraulic characteristics within the individual, across different species, environments and seasonal.