COTTONWOOD IN THE MISSISSIPPI VALLEY. 29 
Tree growing on lands outside the levees is to some extent hazard- 
ous on account of the erratic movements of the river. Through the 
tremendous erosive power of the Mississippi its banks are continu- 
ally caving in and its course changing. Of the 1,500,000 acres of 
unprotected land now available for timber production there may be, 
at the end of 35 years, the period required to produce a merchantable 
stand of cottonwood, nearly a million acres unaffected by the river's 
action. Attempts at systematic management of cottonwood in this 
region should therefore be confined to areas where the river will not 
encroach upon the timber before it has matured. A fairly close 
approximation can usually be made of the distance which the river 
will cut back into the present bank within a given period of years 
by comparing the distance cut during the same number of years in 
the past. . 
PURE STANDS. 
Cottonwood will not tolerate shade. Direct overhead light is essen- 
tial at all stages of its growth. Cottonwood should therefore be 
logged clear. The common practice of cutting to a diameter limit, 
which removes only the largest trees, is entirely unsuitable. Cutting 
the largest trees enables the stumpage owner to make the first cut 
earlier, i. e., while many of the trees are still unmerchantable, and to 
_ cut the remainder within from 5 to 6 years, when they have had the 
benefit of the increased light. Sometimes an area is cut over three 
times in 10 years. After each cutting vines and low shrubs spring 
up in abundance and almost entirely preclude natural reproduction. 
These conditions justify the removal in one cut of all the cottonwood 
on the ground that can be profitably handled, regardless of its possi- 
bilities of growth if left for another 5 or 10 years. Twenty or 30 
small trees, 15 to 18 inches in diameter breasthigh, yielding perhaps 
3,500 or 4,000 board feet, might in another 10 years cut 10,000 board 
feet. These 10 years, however, represent nearly a third of the time 
required to grow a stand which will yield 29,000 feet per acre. If it 
is remembered also that by gradual cutting the initial cost necessary 
to clear away the excessive undergrowth is much increased the greater 
profitableness of the clear cutting system is evident. 
NATURAL REPRODUCTION VERSUS PLANTING. 
Under the clear cutting system the renewal of the stand may be 
obtained either by natural reproduction, secured by leaving seed 
trees on the cut-over area, or by planting. Natural and artificial 
restocking both have definite advantages. Other things being 
equal, planting is likely to be more costly, since it entails the rais- 
ing or purchase of planting stock and the labor of setting it out. 
The cost of natural reproduction is represented by the value of the 
