Finally, the aerial photographs are to be used to compile the past history of 
the tract insofar as possible. We have already seen that old fires can frequently 
be traced on the photographs. The same is true for early logging operations, wind- 
storms, sleet storm, and severe insect and disease epedimics. The magnifying pocket 
stereoscope is usually used by foresters in the careful stereoscopic study necessary 
for detailed photointerpretation. 
For the Itasca management survey, the total cost of the ground survey is 
estimated to be 10 cents per acre of $ 64 per square mile (2.06 cents per hectare). 
Allotting 100 man-days for the volume strips, and 50 man-days for the growth 
plots, that should permit the running of 2500 chains of */,-chain strip (31'/, miles 
or 50,000 metrs) and the establishment of 100 growth plots. These amounts should 
provide an adequate sample of all the important timber stands in the management 
area of 32,000 acres (50 square miles, 13,000 hectares). 
THE MANAGEMENT PLAN 
Obtaining the field data is only the first step in the preparation of the mana- 
gement plan. The area of each stand must be determined. The growth and volume 
values must be compiled and applied to the entire tract. Once the data are assem- 
bled, the plans for the mangement of the tract must be evolved. These include 
several items: 
First, the amount of timber that can be cut from the tract during each period 
of years must be determined. This computation follows standard methods and is 
based upon (1) the volume of the tract with relation to the volume that should be 
there to obtain the greatest production of values. (2) the area of each age class 
within each type and site class, and (3) the silvicultural condition of the various 
timber stands. Since each of these factors are assessed by the photo-interpretation 
and ground survey procedures outlined above, aerial photographs play an impor- 
tant part in the regulation of cut. 
Second, a specific cutting plan must be evolved. Taking into consideration 
local logging practices and local markets, logging areas (or chances) must be located 
and outlined. To serve these areas, truck roads and skid roads must be efficiently 
placed. Finally, the actual pattern of the logging must be fixed on maps and on the 
ground. Whether the cutting is to take the form of strips, spots, or clearcut areas, 
the location and amount of the cutting must definitely be controlled. All of these 
items can best be located by the forester on stereoscopic pairs of aerial photo- 
graphs. Considerable ground checking will be required, but much of the planning 
can be carried out by photo-interpretation. The savings in time and costs here 
probably outweigh the better-known savings resulting from the use of aerial 
photographs in forest inventory. 
Third, the management plan must consider the silvicultural improvement of 
timber stands not scheduled to be harvested in the near future. Weed species must 
be cleaned out of valuable young stands. Middle-aged stands must be partially cut 
to release the better stems for added growth. Trees that would normally die before 
final harvest must be salvaged. Unstocked and poorly stocked areas must be plant- 
ed to return them to productive use. Again, in all these items, aerial photographs 
play an important part. The approximate amount and vigor of weed species can 
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