RESEARCH METHODS IN" STUDY OF FOREST ENVIRONMENT. 5 



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 of the plant as such, but with its 

 physiological functioning in relation to a given environment. 



Control of environment is the cornerstone of the practice of 

 forestry. The art of the forester is primarily the art of utilizing 

 to best advantage the biological forces active in forest growth, 

 through his ability to modify the environment. Any considerable 

 use of forests means interference with the natural conditions and 

 modification of some of the environmental factors, the sum total 

 of which determined the character of the present forest. Forestry 

 adapts this interference to produce the best results, from the stand- 

 point of human needs. Therefore it has been thought best in this 

 bulletin to take up each of the environmental factors separately, 

 and to introduce only such a discussion of physiological facts as 

 seems necessary to a proper conception of the methods of study of 

 the environment. 



Ecological forest studies deal with all problems which involve the 

 determination of the effect of environmental conditions on repro- 

 duction, initiation, growth, and physiological functions. To this 

 group belong such studies as the seed production of different species 

 in different seasons and conditions; the characteristics of seeds as 

 related to their origin; the correlation between the composition, suc- 

 cession, and growth of forest vegetation on the one hand, and the 

 conditions of the evironment on the other; the vast field of prob- 

 lems in natural reproduction and methods of cutting for definite 

 silvicultural purposes; the various phases of forestation, including 

 the germination of seed, requirements for shade and water of the 

 different species, the planting of forest trees, and their competition 

 for moisture and light with herbaceous and shrubby vegetation; and 

 many similar problems. The methods and instruments available for 

 the study of the ecological forest problems are essentially the same 

 as those which are used in the study of the physiology and ecology 

 of plants in general. They involve the measurements of such aerial 

 conditions as precipitation, air temperature, the evaporating power 

 of the air. wind velocity and wind direction, and sunshine intensity; 

 and 3uch subterranean conditions as temperature and moisture of 

 the soil, its depth, structure, and chemical composition. The func- 

 tioning of the tree in response to these conditions must also be meas- 

 ured by the means recognized and used by plant physiologists. The, 

 methods and instruments used in physiology, meteorology, and soil 

 physics, therefore, are applicable in ;i large measure (<> the study of 

 ecological fores! problems, though often with modifications necessi- 

 tated by the character of the, plant and of its environment. 



