RESEARCH METHODS IN STUDY OF FOREST ENVIRONMENT. 147 



Bates (145) in discussing the actual measure of heat available for 

 use in the plant. The first of these influences may be practically 

 ignored, as was the case with humidity, if there is available a record 

 which has integrated all the factors in evaporation. It is believed, 

 however, that most ecological studies will be found deficient if the 

 record of wind movement is not obtained. 



To obtain a record of wind movement in the forest which may cause 

 mechanical injury, the anemometer should undoubtedly be placed 

 almost at the tops of the tree crowns, where the most severe winds 

 will be encountered. A strong support is needed to prevent loss of 

 record at the most critical times. 



In the study of reproduction and of other shall plants, it may even 

 be necessary to dig a pit for the stem of the anemometer in order that 

 the cups may be close to the ground surface. 



The standard Robinson anemometer is the most practical instru- 

 ment for all outside work. Because of a friction factor, it underrates 

 wind of low velocity such as is often characteristic of the forest floor, 

 and slightly overrates the high velocities. The amount of wind move- 

 ment may be read on the dial of the instrument to tenths of miles, 

 and the anemometer may also be electrically comiected to a register 

 so as to give a record of each mile of wind movement. Because it 

 records no less than a mile of wind movement, the Robinson ane- 

 mometer is not wholly satisfactory from the standpoint of mechani- 

 cal injury to trees. It is possibly more true in mountainous regions 

 than elsewhere that the winds of greatest velocity are gusty, and it 

 seems likely that the gusts of only a few seconds' duration may have 

 at least twice the mean velocity recorded for whole miles. While 

 daily or more frequent readings of the anemometer dial may be 

 sufficient where a definite use of the wind record can not be foreseen, 

 in many cases the occurrence of maximum and minimum velocities, 

 the movement by day and by night, etc., as obtainable from the elec- 

 trically operated register, will be desired. Since the current required 

 for operation is only for 2 or 3 volts, connection with the anemometer 

 in the field may be made with the crudest sort of conductors, using 

 wire fences, or insulated wire laid on the ground. In this way the 

 register may be in a protected place and receive due attention. 



Apparently the only apparatus capable of recording momentary 

 high velocities is the Dines pressure-tube anemometer, the use of 

 which in the forest is hardly feasible. 



Wind vanes with connections and registering device are obtain- 

 able, and may possibly be desired at one station in a locality. There 

 is, however, no ecological significance in wind direction; and if there 

 were, it is probable that a single observation on prevailing direction 

 each day and night would be amply sufficient. 



