Losses in merchantable volume on all cuttings culminated during 

 the first 5-year period after logging, then decreased to small annual 

 amounts during the other three periods (figure l)„ On the light cutting 

 the annual loss of 300 board feet per acre during the first period sur- 

 passed by more than three times the losses suffered on the other two 

 cuttings. Insects accounted for more than 90 percent of this large 

 mortality. Apparently bark beetles multiplied rapidly in large-sized 

 cull material left on the ground in the light cutting, then attacked 

 and killed living trees. ^/ About 70 percent of the volume losses on 

 the heavy cutting and only 24 percent on the medium cutting were caused 

 by insects. On the other hand, wind accounted for 59 percent of the 

 losses on the medium cutting in the first period. During the other 

 three 5-year periods, v/ind caused about 50 percent of the losses on 

 each of the cuttings. 



Ingrowth contributed a large part of the total growth on the 

 heavy cutting but negligible amounts on the other cuttings (figure l). 

 The differences between the amounts of ingrowth are due primarily to 

 the greater number of near-merchantable trees in the residual stand 

 on the heavy cutting plus the faster growth per tree associated with 

 more growing space. 



Periodic net annual growth paralleled the growth on reserve 

 stands plus ingrowth during the last three 5-year periods after log- 

 ging (figure 1). For the first period, however, high mortality off- 

 set growth and resulted in net losses on all cuttings. 



Growth of Indi vidual Trees 



The growth of individual reserve sawtimber trees by diameter 

 class, vigor class, species, and intensity of cutting was analyzed by 

 covariance methods. Although linear regression was used in this 

 analysis, it is not presumed that such a relationship would hold if a 

 greater range of diameters were involved. Therefore, the results 

 should not be projected for trees larger than 28 inches in diameter. 



Differences in adjusted mean 20-y8ar board-foot growth by diameter 

 classes were not significant between immature and mature age groups for 

 either ponderosa pine or Douglas-fir within the respective cuttings. 

 Immature traes were generally about 120 years old, while mature trees 



5_/ Evenden, James C. An instance of insect damage resulting 

 from zero-margin selective cutting of ponderosa pine. North. Rocky 

 Mtn. Forest and Range Expt . Sta., Applied Forestry Note 84, 4 pp. 

 1938. 



