Data from: 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 all species except
Neolitsea, axial parenchyma changed significantly only in Afzelia, the
species with by far the largest axial parenchyma fraction. The average WD
and Kh reflect the phenology, with deciduous and shade-intolerant Toona
and Melia having low WD and high Kh, and shade-tolerant brevi-deciduous
Chukrasia and evergreen Neolitsea having higher WD and low Kh. Deciduous
Afzelia, however, had the lowest Kh and second-highest WD. The radial
gradients in WD and Kh also reflect within-species differences in growth
rates during ontogeny. 4) The relationship between WD and its underlying
anatomical components varied substantially among species. Modulating fibre
wall thickness and vessel size enables growing trees to increase water
transport capacity and mechanical strength at the same time. Across
species, tree diameter had a stronger effect than age on all parameters
except for fibres. 5) Given the very substantial within-tree size-related
variation in wood traits, tree size is an essential parameter to include
in comparative studies on the functional ecology of wood. Analyzing
ontogenetic changes in wood can advance our understanding of the different
ecological strategies of trees.