SILVICULTCRAL MANAGEMENT OF BLACK SPRUCE IN MINNESOTA 51 



species will not dominate the future stand unless released by the cut- 

 ting out of competing trees. 



The responses of the residual stands, both after partial cutting and 

 after clear cutting in alternate strips, were unsatisfactory. The par- 

 tially cut plot sustained a net loss of 4.4 cords per acre in the first 

 7 years, or 19 percent of the volume left after cutting. During the 

 following 4 years losses continued at about the same rate. Thirty- 

 seven percent of the mortality during the first 7 years was caused by 

 uprooting and breaking. The remainder of the loss was in trees that 

 died standing. Most of this latter type of mortality seemed to be 

 associated with the severe droughts of 1934 and 193fi. although the 

 uncut check plot lost comparatively few trees and made a net gain in 

 volume of 2.2 cords per acre during the same 7-year period. 



Table 11. — Reproduction per acre by speck* in an upland black- spruce 

 stand 7 years after treatment 



Overstory and soil 

 treatment 



Seedlings per acre Basis 



! mil- 



Black 

 spruce 



Jack \^ph Pa P er 

 pine ; AS P en ; birch 



1 i 



Oth- 

 ers l 



! acre 

 Total *£*■ 



Num- 



Clear-cut area: her 



Duff undisturbed 2 2.500 



Duff removed 425 



Clear-cut strips: 



Duff undisturbed 1. 570 



Duff torn up 1.282 



Duff removed 3,190 



Partiallv cut area: 



Duff undisturbed ! 300 



Duff torn up 1.353 



Duff removed 750 



Uncut strips: Duff tin dis- 

 turbed 2,180 



Check plot: Duff undis- 

 turbed 770 



Xum- Xum- Xum- 

 her her her 



200 2, 200 150 

 2. 656 2. 356 27 



247 1. 591 591 

 294 1. 553 659 

 600 1, 390 1, 420 





 517 418 

 950 400 



130 470 450 



10 



Num- Xum- Num- 

 ber her her 

 100 5. 150 20 

 68 5, 532 73 



97 4. 096' 93 

 47 3. 835 85 

 10 6. 610 100 



300 20 



217 2. 505 60 



2. 100 20 



40 3. 270 100 



150 930 100 



1 White pine, red pine, and a very few balsam fir. 



2 Low poorly drained spot — not a good sample of upland conditions. 



The uncut strips in the strip cutting suffered a net loss of 8.2 cords 

 per acre or 24 percent in 7 years. In the following 4 years over 8 cords 

 per acre more were lost. Uprooting and breakage were the chief kinds 

 of injury. In upland black spruce these causes of loss are greater 

 than in swamps. 



The conclusion from these studies is that upland black spruce should 

 be clear cut around 70 to 90 years old. whenever the stands show signs 

 of opening up and becoming subject to breakage and uprooting. It 

 is probable that in the future light thinnings could be made at an age 

 of 35 to 50 years, by taking out merchantable jack pine, aspen, and 

 balsam fir. This would help materially to increase the yield of spruce 

 and encourage the establishment of advance reproduction of black 

 spruce. 



