36 REPORT OF COMMISSION VII 
cially if mapping is done concurrently with field work. Stereoscopic study of 
contact prints, however, is recommended to assure greater accuracy and more 
efficiency. Some cultural features required to complete an inventory for manage- 
: ment use can be located by photo-interpretation. Fence lines, for example, 
| appear as fine dark lines crossing a grassland area, or perhaps are represented 
| by visible cleared strips where they go through brushy or wooded types. Water- 
| ing holes and troughs, and salt licks, if too small to be visible on the photos, may 
| be located by the convergence of stock trails and a light-toned zone of trampled 
| 
  
bare soil. Springs or seeps which might be developed for stock water can be 
recognized in open types by the dark staining of moist ground, or by an isolated 
clump of willows or other hydrophyllic vegetation occurring in an otherwise 
dry type. Windmills, corrals, and similar structures are recognizable by shape, 
| shadow, and other characteristics. 
| Past experience has shown that the use of aerial photos in range inventories 
will result in more accurate type maps and more reliable density estimates 
than can be obtained by ground methods alone, and at a lower cost (Reid, 1944). 
4. SOILS AND MINERALS INVENTORIES 
Agriculture and forestry are intimately associated with the study of soils. 
Inventories of both vegetation and soils are prerequisites to determination of 
  
  
FrG. 2. An example of the use of aerial photos in wild land soils inventory. Kind of parent 
material is indicated by degree to which topography is dissected by drainage. Series of soil is indi- 
cated by vegetation cover, e.g. cypress and digger pine trees occupy the serpentine while ponderosa 
pine and Douglas fir trees are found elsewhere. (U. S. Navy Photo.) 
land use and land management objectives. Under natural conditions, we find 
vegetation and soil harmoniously balanced, and the nature of the ground 
cover often has a very definite correlation with the soil on which it grows. When 
the natural cover is removed or disturbed, as by clearing and cultivation, or 
logging, or burning, such correlations are upset. Nondetailed soil surveys in 
undisturbed wild land areas can be conducted with a minimum of field work, 
aided by correlations with vegetation as interpreted on the photos. The more 
man has disturbed an area, the more ground work is required to locate soil 
| boundaries and to determine the nature of the soil. 
| | Most soil inventory work done to date with the aid of photos is closely re- 
lated to geologic interpretation. Drainage patterns and land forms can be 
plainly seen with the aid of a stereoscope, and these provide valuable clues to 
the nature of thesoils (U. S. Navy 1945; Jenkins et aJ., 1946) (Figure 2). Examples 
of some recognizable features are alluvial valleys, terraces, volcanic flows, 
igneous intrusives, serpentine, etc. Such classifications are very broad, but have 
value in reconnaissance inventories. 
More detail mapping of soils by series or by series groups requires more or