46 YELLOW POPLAR IN TENNESSEE. 



of which, in addition to lessening overcrowding, is the elimination of 

 trees of undesirable species from the stand. The smaller trees with the 

 poorest formed stems should be removed. Thinnings in young stands 

 should be light, but should be repeated as soon as the crowns of the trees 

 have again become so close together that they interfere. The crowns will 

 seldom touch after the trees have reached small-pole size. Thinnings of 

 this character do not retard height growth or materially interfere with 

 the cleaning of the stem of branches. Thinnings in young stands should 

 never be severe enough to permit the development of large branches. 

 (Fig. 8.) 



The second period in thinning is after the stand has reached the large- 

 pole stage and the trees, according to site, are from 80 to 110 feet in 

 height. Clear length of stem has already been developed, and but slight 

 additional growth in height will take place. The best trees should be iso- 

 lated. These will soon form large crowns and rapid growth in diameter 

 will take place. Additional diameter means not only increased volume,, 

 but a higher proportion of upper grades. The diameter of the trees is 

 more important than their number. It will be far more profitable to have 

 70 trees per acre which have average diameters of 20 inches than 160 

 trees which have diameters of 15 inches. The 20-inch trees have a stump- 

 age value of $3.61 each under an operating cost of $12 per 1,000 board 

 feet, or $252.70 an acre. The 15-inch trees have a stumpage value of 

 83 cents each or only $132.80 an acre. The yield in board feet is approxi- 

 mately the same in both cases about 23,000 feet per acre. (See Fig-. 1.) 



The trees removed in thinning from stands after they have passed the 

 sapling stage, should pay for all thinnings. Even-aged second growth 

 stands have a form of forest which requires thinning in order to develop 

 their maximum yields. It is impossible for lumbermen economically to 

 apply thinnings on a large and rough tract, until a suitable form of forest 

 shall have been developed. But second growth stands, owned by farmers 

 or others who live on their land, even when they are irregular in form, 

 but which are in easy handling distance of a market, can be profitably 

 thinned at any time, although the profits are greater from stands in which 

 a definite form has been secured. 



There are many thousand acres of even-aged, second-growth stands in 

 Tennessee which could be profitably thinned, even if no returns were ob- 

 tained from the thinnings. Table 17 shows the composition and range of 

 diameters of the different species in such a stand. 



