Density Distribution and Characteristics
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Distinct Ring Softwoods
Shown here is a wood density profile for a typical distinct ring softwood. Note the low density or specific gravity at the center, the rapidly increasing density through the juvenile period, and the slow, steady increase thereafter until the tree reaches an advanced age. Remember that juvenile wood forms for the first 5-20 years of the life of a woody stem, with the highest proportion of juvenile wood cells being formed during the earliest years. Remember also that juvenile wood is actively produced even by very old trees as long as growth in height is occuring; juvenile wood in these trees continues to form at the tip of the main stem and in branches. |
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There is a widespread belief that rapid growth
of distinct ring softwoods leads to low wood density. However, there is
only a weak relationship between growth rate and wood density in these
species.
In general, it has been noted that low density is due to an age effect rather than to a fast growth rate. In two trees of the same species and same diameter, one grown rapidly and the other more slowly, the wood of the more rapidly grown tree will tend to have a lower average density. This has led some researchers to erroneously conclude that low density wood results from rapid growth. In this case, the lower average density in the more rapidly grown tree results from the fact that it is younger and composed of a larger proportion of low density juvenile wood, which occupies the center or core of the stem. |
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| When two trees of the same age are compared, wood density tends to be quite similar, indicating that the growth rate of distinct ring softwoods has little impact on wood density. |
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