262 Forestry Quarterly. 



a rather higher number of stems than is warranted, for the 

 eventual thinning in the dominant. Besides giving greater scope 

 for future stem selection, they promote bole cleaning and protect 

 the soil. 



We are still unaware of the optimum stem number or basal 

 area per acre, and even if we know it as Schwappach determ- 

 ined for beech that the basal area after the 60 year should remain 

 between 20 and 25 square meters per hectar, practical experience 

 and observation will guide the manager more often than such 

 standards, which are expensive to use. But for doubtful cases 

 such standards are indispensable and excellent guides. 



Light management in its pure form is justified only for such 

 persistent species as oak, with which Wimmenauer reports from 

 the Hessian experimental areas "light management" produced in 

 150-160 year rotation diameters of 18 to 24 inch, i- e., stem wood 

 of first and second classes with a 2.5 per cent, interest rate on 

 production capital. Evil effects of too severe thinning are shown 

 by Endres, who points out the danger of lowering returns by 

 leaving too few trees; and Borgmann found that for spruce a 

 very moderate opening gave the maximum soil rent. But proper 

 thinning or free spacing, while it lessens wood capital, does not 

 necessarily or at least seriously lessen wood increment. There- 

 fore, the volume increment per cent, persists proportionately 

 longer at a satisfactory rate. Current increments and soil rent 

 culminate later than under the usual care, and do not sink sud- 

 denly but very slowly so that if desirable the rotation may be 

 extended one or two decades beyond culmination of the soil rent 

 without loss. Just as the poor results of our old close stands are 

 not the fault of the trees but of the method of treatment, so also 

 are the low rotations of the soil rent management not a charac- 

 teristic of the system of management, but granted that a low rate 

 of interest is allowable, they are the result of unsuitable treat- 

 ment of the stand. 



A more intense utilization of light influences time in two di- 

 rections. The quicker attainment of favored stems to the de- 

 sired diameter shortens the rotation. The higher and more per- 

 sistent growth production delays culmination and gives more 

 freedom in determining the rotation. 



Besides in thinnings, light influence is taken advantage of in 

 "overbold management" and in cutting for natural regeneration. 



