28 THE NATIONAL FOREST MANUAL. 



than three or four years. Reports on these examinations may be 

 called for as deemed advisable by the district forester. 



The district forester may, as he deems advisable, call upon for- 

 est assistants or other officers for special reports deal- 

 mSh?S soncurrent m g with current methods of marking, estimating, 

 brush disposal, seed collection, combating insect in- 

 festations, and other matters of a technical character. 



Small experiments, initiated by the supervisor or other Forest offi- 

 cers, in silvical investigations, reforestation, range im- 

 provemeiit, and the like, whose primary object is to 

 inform and interest the field force and which are 

 conducted at slight cost under the regular Forest allotments, are 

 encouraged. 



EXPERIMENT STATIONS. 



Stations for intensive investigations, including long-time experi- 

 ments and the development of methods of exact research, will be 

 established from time to time on selected Forest areas. Such stations 

 will form an integral part of the investigative work -of the district 

 and will be under the direction of the district forester. Substations, 

 conducting studies similar to those at the main station and under 

 the direction of the officer in charge of the main station, may be 

 established as far as necessary to include a range of forest condi- 

 tions typical of the entire district. 



The Forest officer in charge of the experiment station will have the 

 same relation to the district forester as a supervisor, 

 Ration to super- and will report directly to the district forester. He 

 will have no authority in the administration of the 

 National Forest, excepting areas withdrawn for experimental pur- 

 poses. The supervisor will have no jurisdiction over experimental 

 areas aside from furnishing the necessary protection. Areas to be 

 used for experimental purposes will be withdrawn only upon mutual 

 agreement between the officer in charge of the station and the super- 

 visor. In case of disagreement, the matter will be referred to the 

 district forester for settlement. 



The experiment station should cooperate fully with other bureaus 

 oration ^ ^ e G. vemmen t, and with private institutions 



and individuals, at the discretion of the district 

 forester. 



The investigative work conducted at experiment stations covers 

 sub -ects for stud three main groups of problems: Forest problems 

 proper, including individual tree studies and stand 

 studies; problems concerned with the indirect influences of the for- 

 est; and problems concerned with artificial reforestation. 



Individual tree studies will embrace chiefly investigations of the 

 Tree studies silvical characteristics of different species, such as 



habitat, light, moisture, and soil requirements, form 

 and volume, growth, reproduction, phenology, and enemies and dis- 

 eases. The requirements of trees should be studied not only by gen- 

 eral observations, but by actual measurements of the physical factors 

 affecting their growth, and the results should be expressed, as far as 

 possible, in absolute figures. 



