4 BULLETIN 105!>, U. S. DEPARTMENT OF AGRICULTURE. 



SCOPE. 



In surveying the present field of forest investigations and analyzing 

 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 they 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 

 expresses the objects of the knowledge foresters seek to gain. The 

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

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

 abstract physiological fact that trees require sunlight for their 

 development. 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 

 forester 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 

 breeding. On the other hand, the environment of this entity can 

 to a considerable degree be controlled, and its reactions to changes 

 in environment can be observed. His concern is therefore not with 

 the physiological functioning in relation to a given environment. 



Control of environment is the cornerstone of the practice of for- 

 estry. The art of the forester is primarily the art of utilizing to best 



1 The statistical group of problems, in distinctions from the ecological, includes chiefly those which deal 

 with the determination of the amount standing timber, its increment, and other quantitative changes in 

 the stand, with only general reference to the conditions governing, such as might be met in the use of arbi- 

 trary site quality classes. As a matter of fact, there can be no sharp line between ecological and statistical 

 foiest studies, and as forestry advances there will be a tendency to consider all growth in its ecological rela- 

 tion 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 ordi - 

 narily considered as essential to progress in ecology, and it is for this reason that ' 'measurements,' ' or statis- 

 tical 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 knowl- 

 edge 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. 



