l6o INTERMEDIATE CUTTINGS — THINNINGS 



ning may be desirable in dense stands. During this period 

 the tendency of the trees to expand laterally is not great and 

 hence the loss of growth through keeping the stand dense is 

 small. 



The third stage begins when the trees in the stand show a 

 strong tendency for lateral development. It is the longest 

 period of the three and thinnings to increase the growth of 

 the trees and the yield of the stand are demanded. In this 

 stage the trees are capable after thinnings of increasing 

 largely their rate of growth. 



It is possible for a stand in need of a thinning to remain so 

 long unthinned that it fails to respond when finally such a 

 cutting is made. In a case of this kind the competition has 

 continued so long and fiercely and the struggle between the 

 individuals has been so even that diameter and height growth 

 have suffered and the crowns, even of the dominant trees, have 

 been reduced to small tufts at the tops of weak slender stems. 

 After a thinning in such a stand the trees left are apt to suffer 

 from drought, sunscald and insect attacks, be thrown or 

 broken by wind and have apparently lost the ability to 

 respond with increased growth. Stands densely stocked, 

 growing on poor soil, are the ones most hkely to be in this 

 condition. The appearance of the crowns and boles, particu- 

 larly the length of crown in relation to the total height of the 

 tree, is the best indication of whether a stand has gone un- 

 thinned so long as to be incapable of profiting by a thinning. 



Methods of Making Thinnings. — From what has been said 

 previously, it will be evident that the relative position of the 

 crowns of the trees is of primary importance in determining 

 which trees should be removed and which left. The thinning 

 must provide opportunity for expansion of the crowns and 

 root systems of the trees left and must see that sufficient crown 

 spread remains to fully stock the area. Crown classes furnish 



