78 WINDBREAKS. 



ESTIMATES AND DISCUSSION OF SPECIES. 

 COTTONWOOD. 



Cottonwood is not a long-lived tree, but grows very rapidly when 

 young, so that at the end of a few years it yields a good rental in fuel. 

 The lumber from cottonwood is relatively much more valuable, but 

 can not be harvested profitably until the tree attains a breastheight 

 diameter of at least 12 inches. The larger cottonwood trees contain 

 a very large proportion of merchantable lumber about 80 per cent 

 of the total volume. The wood is used for coarse lumber. Its tough- 

 ness fits it for bridge planking and it is also used to some extent for 

 pulp. In the prairie States, cottonwood brings about $10 per thous- 

 and board feet on the stump, an,d $2 per cord for fuel. A large part 

 of the volume of cottonwood could be utilized for posts which can be 

 made very serviceable by preservative treatment. 1 



In the following estimates logs are used for lumber down to a diame- 

 ter, outside bark, of about 8 inches, and allowance is made for very large 

 or loose knots. Fuel has been estimated with the bark on at the rate 

 of 90 cubic feet per cord, taking all limbs and unmerchantable parts 

 down to a middle diameter limit of 2 inches. 



All of the cottonwood stands for which figures are given have been 

 produced on Class A situations; in Kansas, on the sandy bottom 

 lands of the Arkansas River; in Nebraska, on the Platte and Loup 

 River bottoms, and in Minnesota, on low, continually moist, and 

 fairly rich land, The height of trees in Minnesota is strikingly 

 greater than in Kansas or Nebraska for groves of the same age. 



The acreage chargeable to cottonwood rows has been computed 

 on the basis of the damage to -corn crops. Table 3 shows that with 

 north-south rows this amounts to 132.38 per cent of the crop which 

 might be grown on a strip as wide as the height of the trees. Supply- 

 ing this factor 1.3238 for CFin equation (1), we have, for a cotton- 

 wood row 1 mile long 



1. 3238 XffXjX 5280 



43560 



where H is the height of the trees in feet. In a case like No. 3 (Table 

 17), consisting of 5 rows, 3 feet apart (total thickness 12 feet), we get, 



by equation (3) 



' _ (12+1.3238 X//X|) 5280 



43560 



No measurements of crops south of cottonwood have been made, 

 On the basis of the amount of shade on that side it may be estimated 

 that the damage to crops will not exceed 20 per cent. Adding this 

 to the measured damage on the north side, 63.9 per cent, gives for th( 

 east-west row CF= 0.839 and the equation for acreage, 



0.839 X/7x}X 5280 

 A ~ 43560 



i Forest Service Circular 117, "The Preservative Treatment of Fence Posts." 



