TENDING OF CROWDED WOODS. 



209 



open woods cannot preserve the fertility of the locality ; 

 hence they are only admissible on fertile localities, or 

 special measures must be taken to preserve the fertility 

 of the soil. 



These considerations govern the most profitable grow- 

 ing space in any particular case. It is conceivable that 

 under certain conditions the correct policy is to remove 

 all dead, suppressed, and dominated trees, and even a 

 portion of the dominant trees, while in others the 

 dominated and even suppressed trees may have to be 

 carefully husbanded, so as to realize the objects of 

 management in the highest possible degree. 



b. Age of Wood. 



As the number of trees per acre decreases gradually 

 from several thousands to a comparatively small number 

 at maturity, it follows that the growing space increases 

 with advancing age, though not evenly. Statistics 

 collected on this point in the Black Forest by Pro- 

 fessor Schuberg, gave the following results for mixed 

 forests of Spruce, Silver Fir, Scotch Pine, and Beech : 



These data show that the increased requirement of 

 space between the 20th and 40th year amounts to 



VOL. II. 



