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Technical
Section |
(Page 1 of 2) |
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What's the
botanical
difference for
Hardwoods vs.
Softwoods? |
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The
cross section of a tree shows the following well defined
features in succession from the outside to the center: (1)
bark and cambium layer; (2)
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wood, which in most species is clearly differentiated into
sapwood and heartwood; and (3) pith, the small central core.
The pith and bark are excluded from finished lumber.
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Most branches originate at the
pith, and their bases are inter-grown with the wood of the
trunk as long as they are alive. These living branch
bases constitute ingrown or tight knots. After the
branches die, their bases continue to be surrounded by the
wood of the growing trunk and thus loose or encased knots
are formed. After the dead branches fall off, the
studs become overgrown and subsequently clear wood is
formed. |
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FAS and Selected grades of
hard-woods are cut from the outside part of the log.
Therefore, FAS and Select grades will have more sapwood than
the |
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common grades. All
growth in either diameter or length takes place in wood
already formed; new growth is purely the addition of new
cells, not the further development of existing cells. The cambium layer is the only growing part of the tree. |
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Native
species of trees and the wood produced by these trees are divided
into two botanical classes-hardwoods, which have broad leaves, and
softwood, which have needle-like or scale-like leaves. This
botanical classification is sometimes confusing, because there is
no direct correlation between it and the hardness or softness of
the wood. Generally, hardwoods are more dense than
softwoods, but some hardwoods are softer than many softwoods. |
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