16 PRINCIPLES OF AMERICAN" FORESTRY. 



ble indexes to the value of the soil for agricultural purposes. 

 For instance, land on which Black Walnut, Hard Maple, 

 Hackberry, or Hickory grow to large size is of good quality, 

 for grasses, grains, and other agricultural crops, while Black 

 Oak is generally abundant on dry, gravelly ridges and 

 sandy soil. Where White Pine in Minnesota and Wisconsin 

 is the prevailing tree, the land is generally of good quality. 

 Norway Pine will endure more drought than the White Pine, 

 outgrows it, and becomes the prevailing tree on drier land 

 there, while the Jack Pine is the most abundant on the very 

 dry sandy lands. In the more humid climate of the Eastern 

 States, the White Pine grows on very sandy soils. 



Mechanical Condition of Land in Forests. The agri- 

 culturist aims to keep the soil porous, yet moderately com- 

 pact, that the roots may penetrate it easily and the subsoil 

 waters may be readily transmitted upwards to the roots of 

 plants. He aims to prevent the soil from becoming too 

 compact and the loss of water from evaporation by cul- 

 tivating the surface soil, and to keep out standing water 

 by drainage. The forest-grower cannot rely upon such 

 methods, because they are too expensive or entirely imprac- 

 ticable. He may indeed plough for his first planting and 

 cultivate the young trees, but after a few years cultivation 

 will become impossible and the effects of the first prepara- 

 tion will be lost. He must therefore attain his object in 

 another way, that is, by mulching the soil. The shading 

 is done at first by planting very closely, so that the ground 

 may be protected as soon as possible from sun and wind. 

 The shade should be maintained well throughout the life of 

 the tree, even if more planting is necesesary to accomplish 

 it, and if in later life the trees get thin in the tops or die 

 out, it may become necessary to plant underbrush to pro- 

 tect the land. 



Undergrowth in Forests may be rather injurious in pre- 

 venting the proper development of young trees, but it is 



