January 22, 1915] 



SCIENCE 



119 



the beginning to consider the forest not 

 merely as an aggregation of individual 

 trees but as communities of trees — tree 

 societies — and first from purely utilitarian 

 reasons, developed a science upon which the 

 practise of silviculture now rests. 



Forestry as a natural science, therefore, 

 deals with the forest as a community in 

 which the individual trees influence one 

 another and also influence the character 

 and life of the community itself. As a 

 community the forest has individual char- 

 acter and form. It has a definite life his- 

 tory; it grows, develops, matures and 

 propagates itself. Its form, development 

 and final total product may be modified by 

 external influences. By abuse it may be 

 greatly injured and the forest as a living 

 entity may even be destroyed. It responds 

 equally to care and may be so molded by 

 skillful treatment as to produce a high 

 quality of product, and in greater amount 

 and in a shorter time than if left to nature. 

 The life history of this forest community 

 varies according to the species composing 

 it, the density of the stand, the manner in 

 which the trees of different ages are 

 grouped, the climatic and soil factors which 

 affect the vigor and growth of the indi- 

 vidual trees. The simplest form of a forest 

 community is that composed of trees of one 

 species and all of the same age. When 

 several species and trees of different ages 

 occupy the same ground, the form is more 

 complex, the crowns overlapping and the 

 roots occupying different layers of the soil. 

 Thus, for instance, when the ground is 

 occupied with a mixed stand of Douglas fir 

 and hemlock, the former requiring more 

 light, occupies the upper story, and because 

 of its deeper root system extends to the 

 lower lying strata of the soil. The hemlock, 

 on the other hand, which is capable of grow- 

 ing under shade, occupies the understory, 

 and having shallow roots utilizes largely the 

 top soil. 



There are forest communities, such for 

 instance as those typical of northwestern 

 Idaho, where western larch, Douglas fir, 

 western white pine, white fir, western red 

 cedar and hemlock will all grow together. 

 Such a forest is evidently a very complex 

 organism, the stability of which is based on 

 a very nice adjustment between the differ- 

 ent classes and groups occupying the same 

 ground. Any change in one of these classes 

 or groups must necessarily affect the other. 

 If, for instance, in the Douglas fir-hemlock 

 forest, the Douglas fir is cut out, the re- 

 maining hemlock trees are likely to die 

 out because their shallow roots are left 

 exposed to the drying effect of the sun and 

 wind. It is only by a thorough understand- 

 ing of such mutual adjustments that the 

 forester is capable of intelligently handling 

 the forest. "With the great number of spe- 

 cies that are found in this country, with the 

 great variety in climatic and other physical 

 factors which influence the form of the 

 forest, it is self-evident that there are many 

 forest communities, each with distinctive 

 biological characteristics, which offer a wide 

 field for scientific inquiry. Amid the great 

 volume of administrative phases of the 

 work in the Forest Service this main objec- 

 tive has never been lost sight of in 

 handling the national forests. The Forest 

 Service is now spending nearly $300,000 

 annually for research work, it maintains 

 eight forest experiment stations and one 

 thoroughly equipped forest products labo- 

 ratory, and is doing this work solely to 

 study the fundamental laws governing the 

 life of the forest and their effect upon the 

 final product — wood. 



Forestry may be called tree sociology 

 and occupies among natural sciences the 

 same position as sociology among human- 

 istic sciences. Sociology may be based 

 upon the physiological functions of man 

 as a biological individual. A physician, 

 however, is not a sociologist, and social 



