SYLVICULTURE 



II. To increase the volume increment per acre. 



III. To increase the quality increment of favorably predestined 

 mess-mates. 



IV. To reduce the danger from forest fires (dead and dying 

 trees), insect pests and fungi plagues. 



V. To remove cripples and wolves. 



VI. Early financial returns. 



VII. Reduction of investment. 



\ ill. Shortening of the rotation by feeding a lesser number of 

 mess-mates on a relatively larger amount of food (viz. moisture, 

 heat, lignt, mineral matter, etc.). 



lA. Regulation of the relative proportion of species in mixed 

 pole woods. 



B. riie season for thinning depends upon local climate, season- 

 able prices of labor, advisability of peeling and intensity of thin- 

 ning. The season usually selected for thinning in Europe is the 

 late winter when the main cuttings are completed. 



C. The time for thinning. Thinnings should begin in the late 

 tliicket stage and should be repeated, to begin with, in five-year 

 intervals, say from tue year thirty to sixty. Thereafter the inter- 

 vals are increased up to the year eighty or ninety. A preparatory 

 cutting, although conducted like a thinning, is no thinning, since 

 its purpose is regeneration. Thinnings stop at the end of the pole 

 stage. Where poles are non-salable, for instance, in European moun- 

 tain districts and almost everywhere in America (excepting Biltmore 

 Estate), thinnings cannot be made. 



D. The material supplied by thinning may consist of firewood, 

 pulp wood, mine props, fence posts, telephone poles, hop poles, hoop 

 poles, tool handles, bolts for spokes, locust pins, tannin wood, etc. 



In European practice the number of cubic feet obtained by thin- 

 nings during the course of a rotation per acre equals one-quarter or 

 one-half of the number of cubic feet obtained by the final cut. 

 Heavy thinnings, as practiced in Denmark, are said to yield as many 

 cubic feet in the aggregate of a rotation as the final cut. 



The tool used for thinning is invariably the axe. 



E. Kinds of thinnings: The old doctrine was: "Thin early, fre- 

 quently, moderately!" 



This rule has been gradually abandoned during the past twenty 

 years. The method of thinning naturally differs according to the 

 purpose of it. William Schlich distinguished between quality thin- 

 nings, made to improve the timber quality of the trees left; and 

 quantity thinnings meant to result in the maximum production of 

 wood fibre per acre per annum. 



131 



