oak timbers

[WDH]

Seems like the Juvinile wood is the outside new growth just under the cambiam layer rather then the "Core" of the tree, and the core is the mature wood ???

Backwoods,

Juvenile wood is produced at the apical meristem at the growing tip of the tree, and then the next 5 to 10 years growth as the young stem gets larger.  It is wood that was first produced while the tree was a young shoot or sapling, or close to the top of the tree where the stem is youngest and smallest.  Looking at a cut disk, the very center rings were produced when the stem/shoot/sapling was young.  As you move from the center of the disk, the stem is getting larger at that point, and the characteristics of the wood cells that are produced begin to change. 

As a tree ages and grows in height, it still produces juvenile wood at the youngest portion of the stem (the growing tip/top of the stem).  Think of a single point on the stem when the growing tip was at exactly that height.  As the stem continues to grow upward, wood that is produced by the annual growth ring at that single point on the stem is juvenile wood for a few growing seasons as the stem enlarges.  This young wood has thinner cell walls, and the angle of the cellulose chains that make up the cell wall are different than the wood that is laid down at that point on the stem a few years later.  This later wood has thicker cell walls and the structure of the cellulose chains changes.  This wood is called "mature" wood. 

[backwoods sawyer]

Seems like the Juvinile wood is the outside new growth just under the cambiam layer rather then the "Core" of the tree, and the core is the mature wood

Might seem that way, but not by convention or by definition. Juvenile wood is mostly used in conjunction with southern yellow pine. It is a form of reaction wood somewhat particular to those species in behavior.

Pulled out my old OSU Forestry books and I had it wrong :(


Juvenile wood is commonly defined as the zone of wood
extending outward from the pith where wood characteristics
undergo rapid and progressive changes in successively older
growth rings. Older wood beyond the juvenile core has been
referred to as mature wood, adult wood, and outer wood.
Juvenile wood differs from mature wood in that it has a
lower percentage of summerwood, lower specific gravity,
shorter tracheids with larger fibril angles, and occasionally
disproportionate amounts of compression wood, distorted
grain patterns, and pitch deposits.

The term juvenile wood is an unfortunate misnomer. True
juvenile wood is produced during the first 1 to 3 years of
growth. Thereafter, similar but not identical wood is produced
in the central core of wood at all height levels in the
stem. This wood has been referred to more appropriately as
core wood.

It has also been referred to as crown-formed
wood because it is produced either within the living crown
or in proximity to physiological processes emanating from
the living crown.