RESEARCH METHODS IN STUDY OF FOREST ENVIRONMENT. 13 

 SPECIAL OBSERVATIONS ON CLIMATE AND SOIL OF LOCALITY. 



To obtain concrete information on restricted localities and specific 

 forest types it will be necessary in most instances for forest investi- 

 gators to establish apparatus and make observations independently. 

 In the more important respects the accepted procedure of meteor- 

 ologists and the standard instruments may be used by the foresl 

 investigator, but the latter will also require many data not obtained 

 in routine meteorological work, and, especially in the location of 

 instruments, will be compelled to vary procedure according to local 

 needs. 



LOCATION OF INSTRUMENTS FOR THE STUDY OF THE GROWTH OF FOREST STANDS. 



Atmospheric conditions affecting the growth of forest stands a- 

 a whole should naturally be measured at a distance from the ground 

 which will represent the mean height of the sensitive portion of tl it- 

 tree; that is, the mean elevation of the crown. Thus, if a stand 

 were generally devoid of green limbs for the first 10 feet of the stem- 

 and had an average total height of 70 feet, the observations should 



be at 10 4 ^— > or 40 feet from the ground. Measurements of the 



li^ht received by the stand should obviously be made at an elevation 

 where none of the light is intercepted. The same result may some- 

 times be obtained by measurements near the ground in a large open- 

 ing on the same site. Soil conditions should be measured at all 

 depths which the roots of the trees may be reasonably expected to 

 reach. The depth will be less in heavy than in lighl <oils. In gen- 

 eral, however, it is believed that an extreme depth of 4 feet is suffi- 

 cient, though any evidence to the contrary should change the pro- 

 cedure. The rule of measuring soil temperatures at the surface and 

 1 and 4 feet may be followed. If it should appear necessary in using 

 the data, the temperatures at other depths may be obtained by plot- 

 ting the known values and by interpolating on the curve which may 

 be drawn for any given period, assuming the temperature at 20 or 30 

 feet to be always equal to the local mean annual temperature. Sim- 

 ilarly, soil moisture may be determined at the surface and at 1. 2, :>, 

 and possibly 4 feet, and, by projecting the curve formed by plotting 

 the moisture of these points the moisture at greater or intermediate 

 depths may be approximated. 



LOCATION OF INSTRUMENTS FOR THE STUDY OF CONDITIONS AFFECTING 



REPRODUCTION. 



It is only logical to assume that, before a definite plant formation 

 or forest type can be developed, there must exist conditions favorable 

 to ' germination and development of the small and very sensitive 



