WHITE PINE UNDER FOREST MANAGEMENT. 13 
In dense young stands most of the lower branches die from shade, 
growth is largely concentrated in the tops, and height growth is there- 
fore rapid. Since the amount of food manufactured by the tree is 
proportionate to the amount of f oliage, which in dense stands is small, 
wood is produced ver}^ slowly, and diameter growth is correspond- 
ingly slow. Thus while trees in the open are relatively short, with 
thick trunks and large, brandling crowns, forest-grown trees are tall, 
with long, slender trunks (comparatively free from large branches if 
in mixture with hardwoods), and relatively short and narrow crowns. 
An open-grown tree actually contains more wood than a forest-grown 
tree of the same age, but its value, volume for volume, is much less. 
The difference lies not only in the better form of the forest-grown tree, 
but also in the actual structure of its wood, which contains more 
thick- walled mechanical tissue and less thin- walled water-conducting 
cells than that of open-grown trees. 
In fully stocked sapling and pole stands, the stems are straight, 
slender, tapering, and smooth barked, with numerous whorls of small 
branches. At the end of this period the live crown is usually con- 
fined to the upper two-thirds of the stem. As the tree matures the 
bole becomes more cylindrical, and the crown loses its regularity 
and compactness. A characteristic defect of white pine, from a com- 
mercial standpoint, is its retention of dead branches, which causes the 
lumber to be knotty. In dense stands the branches, and consequently 
the knots they leave, are smaller than in the case of open-grown trees. 
Moreover, when in mixture with hardwoods, the slender dead branches 
are readily broken off by the swaying limbs of the broadleaf trees. 
The exceptionally clear boles of the virgin white pine which grew in 
dense hardwood forests were undoubtedly the result both of the 
shading and death of the branches while still small, and of the 
mechanical breakage of the small branches by the impact of spreading 
limbs of near-by trees. (See PL I.) 
When white pine grows on the thin soils of ridges at high altitudes 
it produces a short and rapidly tapering trunk, while the crown, if 
exposed to severe winds, is likely to be distorted. One of the first 
considerations in planting white pine should be the quality of the site, 
since upon this depends the rate of growth and also, to some extent, 
the form which the trees will have. 
The classification of trees according to the number of logs they 
will yield, practiced by timber estimators, illustrates the practical 
importance of form in determining the value of trees. Foresters have 
carried this still further, and on the basis of thousands of measure- 
ments of felled white pines have determined the average contents in 
board feet and cubic feet of trees of all the forms and sizes ordinarily 
found. Such figures are given in the volume tables (pp. 64-68). 
