40 YELLOW POPLAR IN TENNESSEE. 



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

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

 poplar. 



Approximate 

 Diameter classes Number of trees per cent of 



per acre on av- each diameter 



breast-high erage quality class which should 



sites exist in a normal 



Inches stand 



2- 4 280 . 54.00 



5- 8 151 30.00 



9-12 57 11.00 



13-1G 19 4.00 



17-20 5 1.00 



above 20 1 .30 



Total per acre 513 



Since this table is based on fully stocked pure stands, it is necessary in 

 the consideration of a mixed stand to ascertain the average number of 

 trees of the different diameter classes per acre. The relation of this num- 

 ber in each diameter class to the corresponding table number gives the 

 proportional annual yield which is to be expected from this diameter class 

 when mature, that is, when larger than 20 inches in diameter. 



If in place of 19 trees to the acre, in the 13 to 16 inch diameter class 

 there were 6 trees, the proportion of stocking would be 6-19, so far as this 

 diameter class were concerned. The annual yield per acre from a fully 

 stocked stand is 430 board feet, consequently the annual yield with the 

 proportion of stocking given would be 6-19X430=135 board feet. If 

 the average diameter of the 6 trees per acre in this diameter class were 

 15 inches, it would be (see table 13) 22 years before they were 20 inches 

 and ready to cut. If the interval between cuttings was 10 years the yield 

 would be 10X135=1,350 board feet per acre at that time. This is based 

 on the assumption that poplar trees growing in groups in mixed stands 

 have approximately the rate of growth that they have in pure stands. In 

 strict selection or natural irregular stands in which single trees of yellow 

 poplar compete with slower growing species, the young poplars are more 

 persistent than when they occur in pure groups, and a smaller proportion 

 of them die during the life of the stand. 



If such mixed selection stands where the yellow poplar trees occur as 

 single trees, the crown spread of the dominant trees is the most reliable 

 basis to use in determining the proportion which yellow poplar contributes 

 to the stocking of the stand. There is given below the average diameter 

 of the crown spread in feet of dominant and intermediate trees of yellow 

 poplar from 7 to 22 inches in diameter breast-high. Dominant trees, 



