10 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 
conservation of soil fertility, we may, from what has been said, 
deduce the following conclusions :— 
(1) That the area should be closely stocked to begin with, and 
that, up till the period when the greater part of height- 
growth has been made, a wood should be kept dense. 
(2) That from this time onwards the thinning should gradu- 
ally become stronger, such strong thinnings beginning 
earlier, and being carried further, when quantity rather 
than quality is the object in view. 
(3) That in the case of Scots fir woods, closeness should be 
maintained as far as possible right through the rotation. 
(4) That where increase in diameter is accompanied by an 
(5) If 
increased value per cubic foot, the degree of thinning 
may be pushed to its fullest extent, for in this case any 
appreciable reduction in the total yield of timber will be 
more than counterbalanced by the increased value of 
what is obtained. 
thinning has been carried so far that a close canopy 
cannot be restored by the accelerated development of 
the crowns of the remaining trees, the forester must 
secure sufficient shading of the ground, either by 
encouraging the growth of the seedlings that naturally 
spring up underneath the parent trees, or an underwood 
—a so-called soil-protection wood—must be established 
artiticially by seeding or planting. 
