e conditions exist, the woodland requires
immediate attention. Otherwise, as time goes on, it deteriorates
more and more, the struggle for space among the crowded and
suppressed trees becomes more keen, the insects in the dying trees
multiply and disease spreads from tree to tree. Under such
conditions, the soil deteriorates and the older trees begin to
suffer.

[Illustration: FIG. 141.--Second Stage of Deterioration. The Surface
Soil of the Wooded Area Has Washed Away and the Trees Have Died.]

The attention required for the proper care of woodland may be summed
up under the four general heads of _soil preservation_, _planting_,
_cutting_, and _protection_.

Improvement by soil preservation: The soil in a wooded area can best be
preserved and kept rich by doing two things; by retaining the
fallen leaves on the ground and by keeping the ground well covered
with a heavy growth of trees, shrubs and herbaceous plants. The
fallen leaves decompose, mix with the soil and form a dark-colored
material known as _humus_. The humus supplies the tree with a
considerable portion of its food and helps to absorb and retain the
moisture in the soil upon which the tree is greatly dependent. A
heavy growth of trees and shrubs has a similar effect by serving to
retain the moisture in the soil.

Improvement by planting: The planting of new trees is a necessity on
almost any wooded area. For even where the existing trees are in
good condition, they cannot last forever, and provision must be made
for others to take their place after they are gone. The majority of
the wooded areas in our parks and on private estates are not
provided with a sufficient undergrowth of desirable trees to take
the place of the older ones. Thus, also, the open gaps must be
planted to prevent the soil from deteriorating.

Waste lands on farms which are unsuited for farm crops often offer
areas on which trees may profitably be planted. These lands are
sufficiently good in most cases to grow trees, thus affording a
means of turning into value ground which would otherwise be
worthless. It has been demonstrated that the returns from such
plantations at the end of fifty years will yield a six per cent
investment and an extra profit of $151.97 per acre, the expense
totaling at the end of fifty years, $307.03. The value of the land
i