| dc.description.abstract | Plus-tree selection of black spruce [Picea mariana (Mill.) B.S.P.)
based on increment of wood volume per unit of crown (growing space efficiency) has the potential to improve yield per hectare and avoid biased
selection of trees that have a competitive advantage in natural stands.
In 1981, and again in 1983, 200 and 400 trees from two 60 year-old upland
black spruce stands located in Northwestern Ontario were scored for
various growth parameters, crown dimensions and competition indices.
Regression analysis showed that the competition indices were poorer indicators of basal area increment (b.a.i.) than the crown parameters.
The crown parameter that best predicted b.a.i. was crown area (c.a.);
r[superscript] 2 values of 0.45 and 0.57 respectively were calculated for the two black spruce stands although the slopes differed significantly. To
test the effectiveness of baseline selection of black spruce based on
the regression of b.a.i. vs. c.a., the top 10 trees were selected from
the second stand by this method and compared to each of the top 10 trees
chosen by a height vs, age baseline method and a purely random method.
Only one tree was selected in common by each of the baseline methods.
Trees selected by b.a.i. vs. c.a. baseline were far more variable in
their size than those selected by height vs. age. Scale drawings and
statistical analysis of the selected trees did not reveal any easily identified
crop ideotype of black spruce plus-trees expressing growing
space efficiency. Wind-pollinated seed of the 29 selected trees was
collected and used to establish a short-term and a long-term progeny
test to investigate heritability of growing space efficiency. The
short-term test was conducted in a greenhouse over one growing season
and included light intensity as a treatment, while the long-term progeny
test was planted in 1984 and included spacing as a treatment.
Discriminant analysis of Marks Lake progeny helped to identify a weak
trend where the tallest progeny came from short-crowned parents. Results
of the short-term progeny test demonstrated strong family differences,
strong family x light interaction, but no selection method
differences. Some of the family differences in the progeny could be
accounted for by the maternal effect of seed weight, although after
removal of this effect by analysis of covariance, still no differences
could be detected between selection methods. Parent and progeny correlations for height and crown features were weak and often negative,
which suggests heritability estimates for characters related to growing
space efficiency are likely to be as low as estimates for growth
in general. The premature results of this study imply that if trees
selected for superior growing space efficiency have inherent advantages
in lower light intensities within mature stands, their juvenile
progeny do not express these qualities. Characters responsible for
growing space efficiency are not heritable or have not yet expressed
themselves. | |
