A importância da arquitetura hidráulica para a compreensão do padrão de distribuição de árvores em uma floresta de terra firme na Amazônia Central

Abstract

Environmental filters act directly on the distribution and composition of species. However, it is not known how soil and belowground hydric conditions are related to hydraulic characteristics of the xylem, branches and of the whole plant on a local scale. We examined wood density and anatomy, height, leaf area, specific leaf area, and the leaf area:sapwood area ratio at the branch level in valleys and plateaus of the terra-firme forest in Central Amazonia. These environments present contrasting table water depths and soil textures. We measure 20 traits related to branches, stem, and whole plant in 28 congeneric species pairs from 12 genera, each containing one valley and one plateau species. Species associated with the plateaus or valleys showed trait differences that indicate distinct investments in prevention against hydraulic failure and driving efficiency, respectively. On plateaus, species had higher wood density, lower averages of vessel size and hydraulic diameter of the vessel, smaller stem sapwood area and smaller specific leaf area. Some correlations between traits change according to the contrasting environmental conditions, demonstrating that species have different investments in traits according to the water conditions in the soil. The maximum adult stature in contrast environments was associated with different investing in conductivity efficiency through the xylem anatomy.We conclude that even in a fine scale, with few meters separating contrasting soil texture and water table depth conditions, environmental filters may impose ecological restrictions on trees that could explain species complementary distribution in Central Amazonia. These filter may be stronger in phylogenetically closely related species, which show more similarities and compete for the same resources. Thus, contrasting soil texture and water table depth conditions may be important determinants of species composition and diversity . Thus, we suggest that hydraulic attributes and their relationships with the environment must be better understood, especially on a local level.