GROWTH. 



17 



. GROWTH 



The possibility of profitable management of yellow poplar largely de- 

 pends upon the rate of growth of the young trees, both as individual trees 

 in mixed stands and when in pure groups or pure stands. Table 1 gives 

 the rate of growth of young trees in mixed stands, and of the dominant 

 trees in irregularly thinned stands in height, diameter, volume in board 

 feet, circular sawed ^4-inch kerf, cubic feet of wood only without bark, 

 and cords of 160 cubic feet of peeled wood, measured after it is stacked 

 and dry. The peeled cordwood is measured as required for paper-pulp 

 stock. 



TABLE 1. Rate of growth of young trees of yellow poplar. 



Scattered trees in the mixed forest 



Dominant trees in 



The rate of growth of single young trees in the mixed hardwood forest 

 is stower than that of the larger or dominant trees in pure even-aged 

 groups which occur in cut-over land and in old fields. This is largely 

 clue to the fuller light conditions under which the pure even-aged groups 

 grow. The narrow crowned intermediate trees in the pure stands, whose 

 tops do not enjoy full sunlight, have nearly the same rate of growth as 

 the scattered trees in the mixed, many-aged forest. It is believed that by 

 systematically thinning young stands, an average diameter of 20 inches, 

 breast high, can be obtained for all trees in a stand when 60 years old. 



The figures in Table 1 are an average of the growth under many diffi- 

 cult conditions of soil and moisture. On the less favorable sites, such as 

 upper slopes and on wet bottoms, the rate of growth is slower than that 

 of the average; on the more favorable sites, such as the better coves and 

 limestone valleys, the rate of growth is more rapid. Individual trees in 

 particular will be found, which depart widely from the average espe- 



