Radial variation of wood functional traits reflect size-related adaptations of tree mechanics and hydraulics

1) Wood serves for mechanical support, water transport and storage. These functions are provided for by different cells with a large variation in wood anatomy among species but also within individual trees. The latter often reflects ontogenetic adjustments, related to tree size or age, which can be studied by looking at patterns of radial variation in wood. 2) We quantified radial variation in wood density (WD) and wood anatomy and ask how ontogenetic changes of wood functions are controlled in five canopy tree species in western Thailand. We ask if there are trade-offs between these main functions of wood, how ontogenetic trends are linked to differences in growth trajectories and shade tolerance among tree species and if wood properties are mainly controlled by tree age or by size. 3) In all species studied, vessel fraction, vessel size, theoretical hydraulic conductivity (Kh) and fibre wall thickness significantly increased with tree diameter. While the ray fraction also increased in...