IIKITISII FOREST TK1.1.S 



i 



is merely the result of the trees having reached the most 

 vigorous period of their growth, the stage of pole-forest. In 

 the case of most of the light-loving species of trees it 

 begins early, often reaches its maximum within the 20 3oth 

 year, maintains itself often without much diminution till 

 about the 50 6oth year, after which it diminishes. The 

 period of most active increase in girth begins later in the 

 case of oaks and in shade-bearing species, but often con- 

 tinues till the 70 Qoth year, and then begins gradually to 

 decline. 



The mean diameters at breast-height reckoned from the 

 sources already named have been calculated to be as follows 

 (in inches) : 



From this it will be seen that the Scots pine increases 

 rapidly in girth in comparison with these other trees, but 

 that with advancing age it is almost equalled by the silver 

 fir. But, as we shall presently see, on soils of the best quality 

 there are on the average about 175 stems of silver fir per acre 

 at 120 years, whilst there are only 141 of Scots pine, which 

 makes a great difference to the proprietor as regards material 

 and financial outturn, 



