96 THE SELECTION METHOD 



Graves described a method of limiting the cut^ which has 

 been used to some extent in the United States Forest Service 

 reports and elsewhere. Under this method different diam- 

 eter limits of cutting are assumed, the number of trees of 

 each diameter and the present yield of timber cutting to the 

 limit calculated, and then by means of current diameter 

 growth data the dimension and volume of the trees left 

 standing below the limit are estimated at the end of a stated 

 period, such as 30 years. In speaking of the method Graves 

 says "a Hmitation of cut, based on this method of study, 

 maintains the rate of growth of the forest and guarantees 

 succeeding cuts at short intervals." Since all the calcula- 

 tions are based on current growth for a relatively short 

 period without consideration of the proper distribution of 

 the entire series of age classes, the method does not guarantee 

 cuts at short intervals except the one immediately following 

 the present cut. 



Modifications of the Selection Method. — Group Selection. — 

 In defining the selection method it was stated that the trees 

 cut at any one time might be standing singly or in small groups. 

 (See Fig. 32.) There are certain advantages in maintaining a 

 group-wise arrangement of the trees of the same age. Less 

 breakage among younger trees is caused in felling and remov- 

 ing the oldest age class. The cost of logging may be slightly 

 reduced. More light is provided for the development of seed- 

 lings and young trees. This is of especial importance in the 

 case of light demanding species. Trees intolerant of shade 

 cannot be managed under a method of single tree selection. 



By varying the size of the group great flexibility in applica- 

 tion is possible. The oldest groups may contain only two to 

 five trees and from this range up to more than a hundred 

 occupying one to four acres. Where the groups occupy more 

 than a quarter of an acre the stand tends to lose its uneven- 



