36 YELLOW POPLAR IN TENNESSEE. 



MATURITY OF TIMBER. 



Single trees in mixed stands. Single trees of yellow poplar can be con- 

 sidered mature financially when their annual rate of increase in value 

 becomes equal to the current rate of interest on money. If timber is held 

 after the rate of increase in value falls below the interest rate, there is a 

 loss, since if the timber had been sold, the proceeds could have been in- 

 vested as loans at the current interest rate on money. Table 13 shows the 

 rate of increase in value by growth of trees of yellow poplar under differ- 

 ent costs of logging while increasing one inch in diameter. This does not 

 include the increase in price, and the current increase in price should al- 

 ways be considered in connection with this table. While price increase 

 of large poplar has been very high in the past, the rate will probably de- 

 cline in the future. 



The rate of increase in the price of second growth for the past decade 

 has been only about 5 per cent. Although yielding well above the cur- 

 rent rate of interest, if the present rate of increase in price is also consid- 

 ered, 16 inches might be considered a diameter for cutting when the cost of 

 operating is low ; 18 inches when the cost is about $13 per 1,000 board feet ; 

 and 20 inches when the cost of operating is more than $15 per 1,000 board 

 feet. The rate of growth of the timber also affects its increase in value. 

 On the best sites, such as very fertile coves where poplar will produce 

 four and five logs 16 feet long, including the cull top log, these diameters 

 might be two inches larger respectively. On very poor sites where only 

 two and three logs can be cut from the trees, and those are sappy, knotty, 

 or otherwise low grade, the diameter for cutting can be 15 inches breast- 

 high, under a low cost of operation, 17 inches under an average cost, and 

 19 inches under a high cost of operation. 



