on ground vs. photosampling. This estimate applies to the 1961 
mortality area andincludes samples in lightly killed stands as well 
as in stands where complete mortality occurred. Since the error 
term was computed for one standard deviation, it is expected that 
this interval will include the true mean two times out of three. 
Applying the above volume loss per acre over the 544,000 acres 
of host type within the 1961 mortality boundary gives a total volume 
estimate of 120,224,000 £ 29,920,000 cubic feet, or approximately 
1.5 million cords of dead balsam fir and white spruce. This es- 
timate of the volume loss for the spruce-fir type is within a 25 
percent error, which is considered acceptable for this type of 
survey. However, studies will be continued in 1964 in an effort to 
improve upon sampling designs and to strengthen mortality esti- 
mates. 
The estimated losses to date represent a 30 percent reduction 
in spruce-fir volume since the inception of the outbreak, and tree 
mortality will continue for some time after the epidemic subsides. 
The dead timber still standing will be afire hazard for many years. 
The sample photography technique for arriving at volume es- 
timates of mortality resulting from insect damage is timesaving 
and much less expensive than present ground methods. Quite 
probably, the same technique could be employed to estimate the 
volume of dead trees in other problem areas. 
