THE FOREST AS A SOIL-IMPROVER 53 
wind, and fails, therefore, to form a mulch over the 
surface of the soil. 
In addition to serving as a protective blanket, this 
humus, in disintegrating, constantly furnishes min- 
eral food materials for the roots. A large part of 
this material has fallen upon the surface of the forest- 
floor in the form of leaves. Thus ingredients which 
wash into the deeper layers of the soil are brought 
again to the surface through the action of the forest. 
The best way to revive worn-out land is through the 
agency of forest-growth. The peasants of the Old 
World know well the manurial value of forest litter. 
Although the foresters protest against its removal, 
these peasants cling tenaciously to their old-time 
rights in this respect. Even in tropical countries 
where the land is very fertile, plantations are often 
abandoned, and fresh land cleared. Rob a soil of 
the humus it contains, and you rob it of its life and 
vigor. 
In the primeval woods trees mature and, after 
standing many years, fall to the ground and rot. Such 
woods are, in consequence, very irregular in nature, 
with gaps here and there, and with semi-decayed logs 
piled in every fashion, just as they happened to fall. 
In a well-eared-for forest, the trees are cut at maturity 
and removed, and thinnings and cleanings are con- 
ducted so that the conditions of the forest-floor and 
