Functional trait radial patterns in tropical trees of the Brazilian Amazon with contrasting wood density

Understanding the radial and longitudinal variation in wood density provides insights into the physiological properties of xylem tissue, particularly hydraulic conductivity. This study aimed to assess the functional characteristics of xylem, including anatomical, hydraulic and physicochemical properties, in both radial (heartwood and sapwood) and longitudinal positions within tropical trees. Samples were collected from a managed forest area in Amazonas, Brazil. The study hypothesised that functional traits would differ among species from distinct ecological groups (medium and high wood density). The results indicated a reduction in wood density in both radial and longitudinal directions. Aqueous extractive content ranged from 3.75% to 17.22%, with no significant differences between density groups, heartwood and sapwood, or bottom and top positions. Vessel diameter ranged from 94.45 μm to 247.71 μm. Hydraulic conductivity was highest in the medium density group (0.50–0.70 g cm−3), indicating a potential trade-off between water transport efficiency and mechanical resistance. The elucidated relationships between chemical characteristics (aqueous extractives) and anatomical traits (vessel diameter) provide insight about classifying tropical tree species according to their wood density.