30 



so far as their physical effect upon the other trees is concerned. There 

 are good reasons, however, why suppressed trees should be cut. They 

 will make little, if any, future growth, and their wood will deteriorate 

 in quality. Eventually they will die and may become a breeding 

 place for injurious fungi and insects. 



PLANTING PLAN. 



The Forest Service has made a number of plans for forest planta- 

 tions in Illinois. One which should have a permanently instructive 

 value is that which is being carried out by the Northern Illinois State 

 Normal School at De Kalb. A rectangular area, 198 feet by 281 feet, 

 was set aside for the plantation. The soil is a black prairie loam, 

 from 8 to 12 inches deep, underlaid by a gravelly subsoil which tree 

 roots can easily penetrate. There are 54 rows of trees, 198 feet long 

 and 5.2 feet apart, running east and west. Each row contains 

 approximately 33 trees, spaced 6 feet apart in the row. Beginning 

 on the north side of the plantation, the first nine rows are European 

 larch, the next 36 rows an equal mixture of black walnut, white ash, 

 and wild cherry, and the last 9 rows, on the south side, white pine. 

 This required 297 seedlings each of larch and pine, and 396 each of 

 walnut, white ash, and wild cherry, a total of 1,780 trees. On the 

 accompanying diagram (fig. 2), which shows the arrangement of the 

 plantation, larch is designated by L, white pine by P, white ash by A, 

 black cherry by C, and black walnut by W. It will be seen that the 

 first trees in alternate rows are, respectively, at the edge of the planta- 

 tion and 3 feet from the edge. 



The equilateral-triangle method of spacing was used, since it places 

 each tree equally distant from all surrounding trees. In this way the 

 ground is fully utilized and the trees will develop symmetrically. In 

 the mixed plantation of walnut, ash, and cherry each tree is com- 

 pletely surrounded by trees of the two other species, and an ideal 

 mixture is thus secured. 



SHELTER BELTS. 



Forest planting in Illinois has been mainly for shelter belts, and 

 the species used have been the rapid-growing ones. When it is con- 

 sidered, however, that the shelter belt around the farm buildings 

 should be as permanent as the buildings themselves, it might in the 

 end be better to plant slower-growing, longer-lived species, such as 

 white pine, elm, oak, sugar maple, or even ash. Since the chief 

 function of a shelter belt is protection against winter storms, white 

 pine, wherever it will thrive, will serve this purpose well, and will, 

 in addition, last for many years. 



[Cir. 81] 



