84 FORESTRY IN NEW ENGLAND 



and hence volume growth of the trees rises, but there always is a 

 point beyond which heavier thinnings, while possibly still in- 

 creasing the rate of growth on the individual trees, lower the 

 growth of the stand as a whole. This is because the gaps be- 

 tween trees become so large that the total growth per acre from 

 the few fast-growing trees is less than would be secured from 

 those left after a lighter thinning. 



Accretion cuttings are too heavy to secure the highest growth 

 per acre, although phenomenal growth on individual trees may 

 result. 



Thinnings of Grades A and B interfere so Httle with the 

 natural competition that their effect in increasing the rate of 

 growth of a stand is negligible. A Grade C thinning is needed 

 to appreciably increase the growth rate, and at the same time 

 this grade does not so open the stand as to prevent the pro- 

 duction of clear timber. For most owners in New England, 

 Grade C or occasionally Grade D thinnings will be the most 

 valuable. 



In making thinnings of whatever grade it should always be 

 remembered that the trees to be cut are chosen on the basis of 

 their crown development. Too often a beginner examines the 

 spacing of the trees on the ground and endeavors to cut wherever 

 the number of trees is great, with the object of securing a uni- 

 form spacing of the trunks. This is altogether wrong and can 

 be easily avoided if the crowns of the trees are used as the guide 

 in selection. 



Another method of thinning, somewhat different from the 

 one already described, is known as the French method because 

 of its origin and use in France. By this method certain trees 

 are selected, when the stand is about thirty years of age, which 

 will be favored and are to form the final crop at the end of the 

 rotation. The number of trees per acre to be selected varies 

 with the species, the product to be produced, and various other 

 factors, but for the purpose of this discussion may be said to 

 range from one to two hundred. 



When these trees have been picked out a thinning is made 



