19 
The whole secret of forest management then consists in so balancing 
light conditions in the forestthat the largest amount of wood possible 
is formed in the trunk without much branching; that is to say, to secure 
the greatest amount of foliage on the largest number of individuals 
that may develop on the areas to best proportions. 
UNDERGROWTH. 
From the soil trees derive mainly that most needful element of growth, 
water. Itis, therefore, very necessary not only to preserve sufficiency of 
moisture in the soil, but also to keep the soil in such condition that the 
rainsandsnows can penetrate it. This is done by keeping the soil shaded 
and covered with the natural litter and undergrowth, which checks 
undue evaporation and preserves the granular structure of the soil so 
favorable to percolation. | 
Undergrowth, therefore—not, however, the grass and weeds which 
transpire more water than their shade prevents from evaporating— 
should be fostered, and the protection of the soil, especially of poor 
soil, against sun and wind must also be kept in view in the amount of 
thinning to be done. 
MIXED GROWTH—LIGHT INFLUENCES. 
To understand technical forest management, especially the practice 
of thinning, it is necessary to realize that in the vegetable world, as in 
the animal world, there is a constant struggle for supremacy going on 
between the different species as wellas among tlie individuals of thesame 
species. The methods used in this warfare are various, and both offen- 
sive and defensive. One species seeks to gain a foothold by prolific 
production of seed, and perhaps of light-winged seeds which the winds 
will carry everywhere, like those of the ubiquitous aspen. Another 
species ‘shades out” its rivals by dense foliage. Firs and spruces are 
examples of this class. Others again develop a superiority of the root 
system, enabling them to endure shade and other privations until the 
overtopping rivals succumb to the influence of time. The oak is an 
example of this kind. In this way the alternation of forest growth, so 
often remarked upon, finds a natural and rational explanation. 
Now, the task of the forest manager is to interfere in this warfare in 
favor of the species which he desires to propagate and have specially 
develop for his own objects by reducing the chances of reproduction 
and supremacy of the undesirable species. 
Mixed forest growth is the rule in the world; in the natural forest, 
with few excepted localities, there are usually several species occupy- 
ing the ground together. The forester knows that there are various 
advantages resulting from this arrangement, and he fosters the mixed 
growth, although the management of a mixed forest presents more 
difficulties and requires more knowledge and judgment than the forest 
