12 CIRCULAR 3 3 3, U.S. DEPARTMENT OF AGRICULTURE 



The investigator should -make certain that the area on which it is 

 proposed to work is the best available for the purpose of his experi- 

 ment. To do this he must judge the area on the basis of a thorough 

 knowledge of the region and may need also to make a careful recon- 

 naissance, taking into account not only the stands' condition, stock- 

 ing, history, and adequacy for the study proposed but also climatic, 

 physiographic, and geologic features. 7 



" Readily accessible ", as used here, implies reasonable nearness 

 to good transportation facilities and to suitable headquarters. It is 

 highly important to remember that stands easily accessible today 

 may become relatively inaccessible tomorrow through abandonment 

 of logging railroads, trails, or roads, or through changes in high- 

 way location. Conversely, on national forests and other areas where 

 road, trail, stock-driveway, or railroad location plans are available, 

 these should be consulted in order not to place plots in the way of 

 new construction. 



Accessibility saves time on each visit to the plots, eliminates a 

 temptation to slight them, and enhances any demonstrational value 

 they may have. 



Not only must the stand selected be extensive enough to accommo- 

 date satisfactorily all the plots proposed, including the required con- 

 trol or check plots and the isolation strips, but preferably it should 

 be extensive enough to make possible future expansion of the 

 experiment. 



Selection of the stand may be affected by requirements as to labor, 

 supplies, water, markets, and exclusion of grazing animals, or by 

 other conditions either existing or foreseen. 



For sample plots on which long-time studies are to be undertaken, 

 permanent tenure and continuous protection must be assured. Per- 

 manent plots that cannot be safeguarded for at least 10 years are 

 of questionable value, and most permanent plots should be available 

 for at least 20 years' use. The expected period of use is governed 

 largely by such considerations as the age of the stand and its rate 

 of growth. Naturally it is shorter for rapid-growing stands than 

 for others. While some plots yield valuable results within a few 

 years, usually the value of the results increases with mounting 

 rapidity as the years pass. Undoubtedly, many plots originally 

 established for short periods will be maintained for longer periods 

 because of their increased value. 



So far as possible, plots should be established on forest areas set 

 aside for experimental purposes. 8 Experimental forests offer the 

 greatest security for investigative work because they are removed 

 from the control of any agency not immediately interested in the 

 results, because the policy governing them is definitely fixed, and 

 because they can be developed in accordance with research needs. 

 Such areas also permit concentration of experimental work, with 

 consequent reduction in travel time and increase^ in effectiveness. 

 Again, they permit the collection of certain pertinent basic data, 

 such as meteorological and phenological records, that could not be 

 collected on scattered plots. 



" Toumey, J. W. foundations op silviculture, v. 3. Ann Arbor, Mich. 1926. 

 [Mimeographed.] 



8 For Forest Service policy regarding establishment of experimental forests, see 

 appendix, p. 86. 



