328 Forestry Quarterly. 



is not without influence on managerial measures for correction, pos- 

 sible in one case and not in the other. 



Still more important in the tending of the crop is the manner of 

 its original formation and the biological characteristics of the spe- 

 cies, for they influence density and character of crown. Density is 

 a function of the method of formation as well as species, site and 

 age. 



In even-aged stands, crown cover is greater in youth than later, 

 reaching its maximum when the clearing process begins for lack of 

 light. The beginning of this process is indicated by shorter shoots 

 or cessation of shoot formation on the lower branches. In natural 

 regeneration this maximum of density comes earlier, but lasts a 

 shorter time than in open plantations. The stage of greatest densi- 

 ty — in conifers indicated by a continuously green layer of litter on 

 the ground, in broad-leaf trees less certainty in the crowning is of 

 greatest import for determining the manner of tending the crop. 



That light-needing and shade-enduring species show great diff'er- 

 ences in beginning, intensity, and duration of maximum density calls 

 for diflPerence in treatment. Perfect crown cover is a difi'erent thing 

 with light-needing species and with shady ones. The better the site 

 the sooner crown cover closes up, but also the shorter is the period 

 of maximum density, due to vigorous growth. The cover formed by 

 a smaller number of trees is often more perfect than that of a larger 

 number, on account of better individual crown development. Hence 

 density of stock is an important factor in determining degrees and 

 forms of crown cover. 



Tending the crop means regulating density, for on density de- 

 pends form of bole and technical value, as well as quantity of pro- 

 duction. The judgment as to whether and when with given species 

 and given sites to make a thinning is the most important question in 

 tending the crop. 



Light. As branches die off for lack of light diameter growth is 

 retarded until by the death of individuals crown development of the 

 remaining trees is enlarged vertically and horizontally. It is not 

 demonstrated, yet not entirely to be disregarded, that this retard- 

 ation of diameter growth may be due to retention of meteoric water 

 in the crowns and resulting dryness of soil. Since, however, the 

 period of minimum rate of growth falls together with the end of 



