DETAILS OF THE METHOD 95 



not cut many of the smaller trees may be used in the logging 

 operations, for skids, corduroying roads, etc., or simply de- 

 stroyed in felling and getting out the timber. A certain 

 amount of destruction is a necessary accompaniment to log- 

 ging, but such wasteful use and destruction may be so extreme 

 as to threaten the continued existence of the selection forest. 

 In order to provide for enough old trees per acre it is necessary 

 that numerous seedlings start every few years. These seed- 

 lings undergo a rapid decrease in numbers due to competition 

 and other natural causes as they grow in size and advance 

 toward maturity. Definite information as to the number of 

 trees per acre of different sizes needed to secure steady pro- 

 duction under the selection method is not available for most 

 of our species. As an illustration the following data for yel- 

 low poplar have been taken from "Yellow Poplar in Tennes- 

 see," by W. W. Ashe.^ See also pp. 317-318 in the Selection 

 System in Indian Forests . . . , by Caccia.^ 



Number of trees per acre in different diameter classes, required to obtain a 

 continuous yield from a fully stocked group selection stand of pure yellow- 

 poplar. The cutting limit is approximately 20 inches. 



Diameter, Number of trees 



Breast High, per acre on average 



Inches quahty sites 



2-4 280 



5- 8 151 



9-12 57 



13-16 19 



17-20 5 



Above 20 I 



Total '.'.[^'.'.'.'.\'.'.'.'.'. JTs 



If to these natural causes are added destruction by the 

 lumberman, there may be no representatives left of certain 

 ages to come to maturity. It is essential for successful appli- 

 cation of the selection method that waste of small trees be 

 kept at the minimum. 



