Abstract:
Pinus patula is the most intensively planted
conifer in the tropics and subtropics. The increased proportion
of corewood that results when rotation ages of pine
plantations are shortened has become a wood quality factor
of growing concern worldwide. The purpose of this study
was to develop empirically based models for predicting the
flexural properties of the wood produced from relatively
young P. patula trees. Models were based on the properties
of standing trees, and their effectiveness was evaluated at
board, tree, and compartment levels. Sample material was
obtained from 170 P. patula trees, 16–20 years old,
established in 17 compartments on the Mpumalanga
escarpment of South Africa. Multiple regression models
were developed, which managed to explain 68, 60, and
95 % of the variation in the dynamic modulus of elasticity
(MOE) on individual boards, trees, and compartments
levels, respectively. At compartment level, 80 % of the
variation in the 5th percentile MOR value could be
explained by the model. Sensitivity analyses showed that
site index at base age of 10 years, acoustic time of flight,
wood density, and ring width were influential variables in
the MOE models. The models indicated that tree
slenderness during early growth seems to play a major role
in determining the dynamic MOE and MOR of lumber.
This is in agreement with Euler’s buckling theory and the
bending stress theory. The results from this study indicated
that the MOEdyn and MOR of lumber can be accurately
predicted on especially a compartment level. The predictive
models developed can be used as management tools to
improve operational decisions around tree breeding, silvicultural
practices, and rotation ages.
