Abstract:
Douglas-fir trees from 39 open-pollinated families
at four test locations were assessed to estimate
heritability of modulus of elasticity (MOE) and basic
density. After trees were felled, sound velocity was
measured on 4-m logs with the Director HM200. Disks
were taken to estimate dry and green wood density;
dynamic MOE was estimated as green density × (sound
velocity)2. Heritability estimates of MOE (across-site
h2=0.55) were larger than those for total height (0.15) and
diameter at breast height (DBH; 0.29), and similar to those
for density (0.59). Negative genetic correlations were found
for MOE with height (rA=−0.30) and DBH (rA=−0.51), and
were similar to those found for density with height (rA=
−0.52) and DBH (rA=−0.57). The partial correlations of
height with MOE and density, while holding DBH constant,
were positive, implying that the observed negative correlations
between height and the wood properties were a
function of the high positive correlation between height and
DBH and the strong negative correlations between DBH
and the wood properties. Taper [DBH/(height−1.4)] was
found to be negatively associated with MOE. Selection for
MOE may produce greater gains than selection for density
because MOE had a larger coefficient of additive variation
(9.6%) than density (5.1%). Conversely, selection for
growth may have a more negative impact on MOE than
density because of the greater genetic variation associated
with MOE. Family mean correlations of the wood quality
traits with stem form and crown health were mostly
nonsignificant.
