4 BULLETIN 1059', U. S. DEPARTMENT OF AGRICULTURE. 



understood that it is the purpose of this bulletin to build a founda- 

 tion for the future on the experience of the past, and to suggest the 

 form of the superstructure rather than its architectural design. In 

 this way it is hoped to save the actual designers much needless and 

 fruitless effort. 



SCOPE. 



In surveying the present field of forest investigations and analyz- 

 ing the factors which enter into the problems and the methods 

 available for their solution, it appears that, although the number 

 of problems is great and they may vary in character from region to 

 region and from period to period, theoretically the} 7 may be conceived 

 as falling into two essential groups. These two groups are (1) 

 ecological and (2) statistical. In solving the ecological problems 

 the aim is to express relations; in solving statistical problems the 

 aim is to express the bare facts of forest growth. 



This bulletin will be concerned wholly with ecological forest 

 studies. 1 To some it may seem strange that the word " ecological " 

 should be used rather than the more inclusive " biological." The 

 choice is a question of aims and objectives. " Ecological " better ex- 

 presses the objects of the knowledge foresters seek to gain. The prac- 

 tice of forestry is in a very large degree the application of ecology. 

 As an example, a forester may be only slightly interested in the ab- 

 stract physiological fact that trees require sunlight for their develop- 

 ment. This fact is taken as a matter of course and allowed for. 

 When, however, he finds that one of two species with which he is 

 dealing requires much more sunlight than the other, or. in other 

 words, does not react so readily to the stimulus of sunlight, the for- 

 ester then finds a keen interest, because it is a practical interest, in 

 this ecological factor and its relations. 



Or, again, the matter may be expressed in this way : The forester, 

 in dealing with a given species, feels that he is dealing with a bio- 

 logical entity whose characters he may know minutely or generally 

 but which he can not change, except possibly through long-term 



1 The statistical group of problems, in distinction from the ecological, includes chiefly 

 those which deal with the determination of the amount of standing timber, its incre- 

 ment, and other quantitative changes in the stand, with only general reference to the 

 conditions governing, such as might be met in the use of arbitrary site quality classes. 

 As a matter of fact, there can be no sharp line between ecological and statistical forest 

 studies, and as forestry advances there will he a tendency to consider all growth in its 

 ecological relations. It is, however, at the outset necessary to recognize certain standard 

 methods for the measurement of growth, whatever their purpose or use. These methods 

 are distinct from the processes which are ordinarily considered as essential to progress in 

 ecology, and it is for this reason that " measurements," or statistical studies, are not 

 included in the present discussion. The method of determining the growth, volume, 

 and yield of forest stands is largely mechanical, though for sound progress it should, of 

 course, involve knowledge of biology as well as mathematics. The caliper, hypsometer, 

 scaling stick, log scale, increment borer, and tape are practically all the instruments that 

 are required. 



