Amélioration du module d'élasticité du bois de Mélèze hybride (Larix ...

JACQUES Dominique. (2003). Improvement of modulus of elasticity of
Hybrid Larch (Larix x eurolepis Henry) wood through clonal selection
(doctoral degree). B-5030 Gembloux, Faculté universitaire des Sciences
agronomiques de Gembloux, 292 pages, 115 tables, 26 figures.
Summary
The main objective of this study is to evaluate the interest and possibility
of integrating variation in the mechanical properties of hybrid larch into
clonal selection.
The approach is focused on the assessment of modulus of elasticity, which
is considered to be the basic trait of wood for structural purposes.
The experimental material comprises 4 forest stage clonal tests of hybrid
larch, aged 13-17 years and 2 nursery stage tests of 3-4 year old plants. The
clonal tests are composed of 96 clones selected amongst families collected
from a hybrid seed orchard itself composed of 42 genetically diverse “plustrees”
of European and Japanese larches.
From this study it appears that modulus of elasticity is a highly heritable
trait of great variability which facilitates efficient clonal selection. Clonal
selection applied to this characteristic simultaneously improves both modulus
of rupture in static bending as well as compression stress parallel to grain,
contributing to good mechanical properties of the timber.
Indirect estimation of modulus of elasticity via basic density or using the
Pilodyn or Sylvatest reduces the time and cost required for assessment of
mechanical properties and shortens the selection cycle through the use of
younger plants, at the expense of only a slight loss in genetic gain.
These genetic and technical results provide the opportunity to improve
significantly variety selection in Hybrid Larch, to make recommendations for
forest practice, and to open new avenues of research.