total volume will be products of area and mean-volume -per -acre by classes. 

 A sample of the photo volume plots will be field examined to provide a check on 

 photo volume measurements. 



Growth, species, diameter distribution and mortality data will be obtained from 

 examination of field plots located at random within the various sampling strata 

 of cominercial forest land. These locations will be one-half-acre rectangular 

 plots selected from the volume sample plots. Present plans call for measuring 

 about 100 field plots. 



Contracts to photograph the forest area of the Interior using infrared film were 

 negotiated and most of the flying completed in 1959. Figure 2 shows the survey 

 units of the Interior, areas for which aerial photographs are on hand, and the 

 approximate direction of flight lines. 



Interpretation of photo plots was begun in the fall of 1959. By January 1, I960 

 about 50 percent of the photo interpreting job for unit seven was completed. 



The three stereograms in figure 3 show the quality of the photographs being 

 used and indicate some of the detail that can be seen on photos of this scale. In 

 stereogram A, note the caribou herd grazing in the dark colored, tundra area. 

 The lighter toned area is better drained and covered with grass and low brush. 

 Stereogram B shows commercial forest area with some cottonwood and aspen 

 along the stream and a mixture of aspen and spruce adjoining. The dominant 

 trees are 80 to 90 feet tall. An old burned area, now restocking to aspen shows 

 up sharply in stereogram C. Many stems from the previous stand are visible 

 on the ground. In the center area is a spruce-aspen stand and a dense stand of 

 aspen saplings and poles. In the upper right-hand corner is a stand of spruce. 



^ Indicators of Forest Land Classes in Interior Alaska- -Topographic situa- 

 tions and forest vegetation conditions were studied over a wide range of land 

 and vegetation classes. The objectives of the study were to (1) develop a basis 

 for recognizing land capable of producing industrial wood and land not capable 

 of such production; (2) determine guides or criteria, applicable to air photos, 

 for separating burned areas into broad forest land classes. Details of the study 

 are described in Station Paper No. 10 "Indicators of forest land classes in air- 

 photo interpretation of the Alaska Interior". Examples of the criteria are: 



White spruce--a fairly good indicator of commercial forest land; 

 usually absent from muskeg forests, intolerant of poorly 

 drained, cold, wet soils; permafrost absent or at depths 

 of 24-36 inches. 



Black spruce--a characteristic muskeg tree in Alaska, usually 



on cold, wet, poorly drained sites; permafrost 12-20 inches 

 below moss and lichen layer; this type on north-facing slopes 

 and slopes of less than 10 percent indicates noncommercial 

 sites. 



