CHOICE OF SPECIES IN ARTIFICIAL REGENERATION 45 



The initial cost of the successful artificial regeneration of oak 

 in southern New England is more than twice that of white pine. 

 The expectation value of oak under a 75-year rotation, therefore, 

 must be far above that of white pine in order to justify the arti- 

 ficial regeneration of the former on soil suitable for both species. 

 With species such as catalpa and locust, grown for posts or poles 

 under a rotation of 20 years, an increase of $6 per acre in the 

 regeneration with compound interest at 5 per cent means that the 

 crop when harvested must yield but $15.92 more per acre. 



Even where the longer rotation will give higher returns from 

 the investment, the owner may desire species that will give the 

 earliest possible returns, i.e., those that can be grown profitably 

 under a short rotation. In cases of this kind species must be 

 selected that: 



a. Make rapid early growth. 



b. Command a good market in small sizes. 



In the prairie regions of the Middle West, white willow, cot- 

 tonwood, and box elder are grown under short rotation for fuel 

 and other purposes, although the wood is soft and of inferior 

 quality. The rapidity of growth and the consequent large vol- 

 ume of wood produced in a comparatively short period often 

 justify the use of these species. Locust and catalpa not only make 

 rapid juvenile growth but also produce wood of high technical 

 quality and command a high price in small sizes. 



6. Species Selected Primarily for the Protection which 

 They Afford 



Trees that are grown primarily for the protection which they 

 afford should be effective in one or more of the following ways: 



a. In checking the velocity of the wind. 



b. In preventing land slipping on steep slopes. 



c. In preventing soil erosion by both wind and water. 



d. In regulating stream flow. 



e. In improving the soil. 



Hemlocks, pines, spruces, and most other conifers are par- 

 ticularly desirable for windbreaks because of their persistent 

 foliage. These are very effective during winter and spring, the 

 seasons of highest wind velocity. Broadleaved species with dense, 

 heavy foliage such as maple and beech are particularly effective 

 in summer. Thin-foliaged species, on the other hand, such as 



