FORESTRY AND CONSERVATION 381 



Their Protective Value. To be of commercial value a species 

 must possess adaptability, usefulness, and rapidity of growth. These 

 should have foremost consideration even when planting is done 

 mainly for protection, as in the region embraced by this report. Here 

 protective planting is so absolutely essential that groves of deciduous 

 species of little commercial value, which afford shelter only during 

 summer, have been valued at $1,000 an acre. Surely, then, conifers, 

 which are more valuable commercially, and which afford protection 

 during winter when there is most need for it, should be worth a 

 slightly higher price and the extra care necessary in securing a 

 satisfactory stand. 



Conifers are sometimes objected to on account of a possible yel- 

 lowing of the leaves. This is reported as occurring during hard, 

 open winters, with occasional warm, sunny days. On the warm days 

 the leaves become active and transpire water at a time when the frost- 

 bound soil can not supply the loss, hence the drying or "yellowing." 

 This trouble is experienced mostly with trees that have no protection 

 whatever against the sudden changes of heat and cold. Deep-rooted 

 trees like Scotch and western yellow pine, etc., should be planted in 

 preference to shallow-rooted kinds. They should be planted in dense 

 stands, so that they can prevent deep freezing of the soil and protect 

 each other from midwinter stimulation. 



So far the main objection to the general planting of conifers 

 has been the excessive cost of the planting material. Experience, 

 however, has proved that coniferous stock can be grown in cjuantity 

 at a cost which does not make its use prohibitive. (F. S. Cir. 145.) 



Trees and Methods Recommended. Forest trees for windbreaks 

 should be planted in belts varying from 2 to 8 rods in width, except 

 along fence lines, where they are in single rows. The best results, 

 purely from the standpoint of forestry, will be obtained in the widest 

 belts, since trees are social in their habits. Still better tree growth 

 would be secured by planting in compact blocks. But as agriculture 

 is the fundamental industry in the region to which this plan applies, 

 the tree planting is designed only to supplement the production of 

 field crops. Eleven or 12 per cent of each quarter section is to be 

 devoted to forest. This is exclusive of the space occupied by the 

 single lines of trees in the fence rows. 



The species that may be recommended for this purpose vary for 

 each particular locality with conditions of climate, rainfall, and soil. 

 Considering the Middle Western States together, however, the fol- 

 lowing trees, when placed on hospitable soil fulfilling the require- 

 ments of each individual species, may, in the northern half of the 

 region, be successfully grown as windbreaks : Arborvita?, green ash, 

 boxelder, cottonwood, cork elm, white elm, European larch, Russian 

 wild olive, western yellow pine, Black Hills spruce, laurel-leafed wil- 

 low, Russian golden willow, and white willow. 



In the southern half of the Middle West, also the green ash, cot- 

 tonwood, white elm, Russian wild olive, and western yellow pine 

 may be successfully grown, and in addition the following species: 

 Chinese arborvitae, wild China, black locust, honey locust, mesquite, 



