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be segregated in order to obtain relative values. Grassland commonly has this 
general characteristic appearance, yet it must be broken into many parts for 
purposes of valuation, and as guides for distribution of livestock. Large browse 
areas have a similar appearance, but usually may be identified by the rougher 
texture of the photograph. Some of the areas of smaller browse are very 
difficult to distinguish from grassland. Meadows are usually distinctive by their 
lighter shade and by their location. Definite rules must be followed in order to 
secure uniformity of interpretation. 
Various species of trees usually have common kind of vegetative growth 
beneath. This may be of forage value, or it may not. Thick reproduction rarely 
supports appreciable forage, while open stands of old trees usually support 
forage. The outlines of the areas covered by various kinds of trees are difficult 
to map from the ground. Because of the characteristic appearance of the various 
kinds of trees, the outlining of such areas is more readily done from photo- 
graphs. By segregating the tree species, the herbaceous cover or the waste areas 
beneath often are roughly mapped. 
Color is a valuable asset in determining the species of herbaceous vege- 
tation from pictures. Only a start has been made in the use of color photo- 
graphy for this purpose. Many grasses, forbs, browse and trees have a charac- 
teristic color or shade sometime during their season of growth. Many grasses 
change color when approaching maturity, or after maturity. Also, many decid- 
uous trees have color changes. Most browse species may readily be distinguished 
by their autumn colors. Shades of color are more distinguishable and interpre- 
table than the tones of a black and white print. Color photographs, taken at a 
time when such colors are apparent, more definitely identify differences, more 
accurately depict the areas covered by such species, and reduce the amount of 
ground work necessary. 
Research in color photography, in the use of longer focal length lenses in 
the interpretation of larger scale pictures, and in photographing at various 
seasons and times of day, are needed to make photographs easier to interpret. 
Each country and region has its own particular conditions and problems, 
crops and species as indicated in the publication of J. W. B. Sisam, “The Use 
of Aerial Survey in Forestry and Agriculture.” The interpretation of each, 
while all follow the general pattern, must be worked out locally. 
SOILS AND MINERALS INVENTORY 
Donald J. Belcher. 
Any report on the status of inventories on soils and minerals must be di- 
vided into two parts. It is necessary to separate them because the work in soils 
has broadly advanced in many different areas and it differs materially from the 
work in mineral search. The mineral field has been spearheaded along narrow 
and more specific lines because of commercial interests. The work in soils has 
been conducted chiefly by universities and public agencies for the purpose of 
mapping soils for agriculture and engineering purposes. Surveys of the field and 
the literature show that there is a rather well established and common basis for 
the identification and mapping of soils from aerial photographs. On the other 
hand, the material that is available on mineral inventories is extremely limited, 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
   
   
  
  
  
  
  
  
  
   
    
  
  
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