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PHOTO INTERPRETATION IN FOREST INVENTORIES 
  
Fic. 1. Differences in tone on modified infrared photographs indicate different forest types. 
(1) Mixed hardwood swamp, (2) aspen birch upland, and (3) cutover conifer swamp. Original 
photo 1: 15,840, Chippewa National Forest. 
Forest types.—Foresters skilled in classifying forest types by means of 
key species on ground inventories naturally tried first to recognize these 
same species on aerial photos. They tried to rely on the tone of the photo 
and were somewhat baffled when differences clearly visible on the ground, 
such as between dark conifer and much lighter hardwood foliage, were not 
always distinguishable on aerial photos. They soon found that uniform 
stands of timber register many different tones and that the direction of light, 
the size and density of the foliage, and the resulting shadows had far more 
effect than mere differences in color so apparent on the ground. 
  
found on standard panchromatic photographs taken in spring or 
lantation with two species of conifer, (2) natural hard- 
Original photo 1:20,000, U. S. Department 
Fic. 2. Differences in tone 
fall also indicate different forest types. (1) P 
wood stand with at least two species of mature trees. 
of Agriculture, Forest Survey, Ohio,