THE IMPORTANCE OF DENSITY IN SYLVICULTURE. 5 
shading the ground. It must be mentioned, however, that there 
is a limit to the degree of density, and if this is exceeded, the 
development of even the most vigorous trees will be prejudicially 
interfered with. 
It is only of importance to encourage growth in height and 
cleanness of stem during the time when the trees are making 
most of their height-growth, and the duration of this period will 
depend upon the species and the character of the situation. In 
this connection, also, the forester will have to determine what 
proportion of the stem he desires to see clear of branches. 
Nothing would be gained, for instance, by attempting to grow 
beeches with clear boles as long as those of the spruce or 
Scots fir. 
After this stage has been reached, the forester should direct 
operations in such a way that the trees shall attain an average 
diameter which will satisfy the demands of the timber market. 
From this period onwards the encouragement of growth in thick- 
ness harmonises more and more with the production of the 
maximum mass of timber. To attain this object, it becomes 
necessary to see that the larger class of trees are accorded an 
increased amount of growing space. The most important question 
now comes to be: To what extent shall the wood be artificially 
interfered with, or, in other words, what amount of thinning is 
most advantageous ! 
In their struggle for existence a large number of trees perish, 
and these are utilised by the proprietor of the wood as soon as 
they can be turned into money. Besides trees which are totally 
dead, one finds others which, though still alive, are hardly making 
any growth, and beyond these there are others in all the various 
degrees of development up to the largest stems. According as 
the operation of thinning is confined to (a) the dead and dying, 
(65) those that are completely over-grown by their neighbours, or 
(c) those whose crowns are considerably curtailed, one has to 
distinguish three degrees of intensity in thinning, which may be 
defined as weak, moderate, and strong. If one goes further with 
the removal of trees, and fells those with fully developed crowns 
—as is sometimes done—the operation is called ‘ lightening,” 
‘light thinning,” or ‘‘ felling for light.” 
A weak thinning exerts no effects, beneficial or otherwise, upon 
the trees that remain. Such an operation is confined to the 
removal from the wood of material that is without influence on 
