40 CIRCULAR 791, U. S. DEPARTMENT OF AGRICULTURE 



quently results in the removal of many vigorous trees and the leaving 

 of decadent, smaller ones. In thinly stocked spots, where the in- 

 dividual trees are large, cutting is heavy; in dense patches, cutting 

 is light. 



The length of time between partial cuts depends upon the quantity 

 of growing stock left, its rate of growth, the size of the individual 

 trees, and the volume that is needed to make a satisfactory cut per 

 acre. Obviously, frequent light cuts will result in the greatest re- 

 covery of wood since comparatively few trees will die and be wasted, 

 and the growing space will be kept more continuously occupied. 



In accessible easily logged areas where settlers or individual loggers 

 sometimes are willing to take as little as 3 or 4 cords per acre, cuts 

 can be made at intervals of perhaps 8 to 10 years on average sites. In 

 poorly accessible districts where considerable outlays for roads and 

 camps are required, few operators can be induced to log less than 60 

 percent of the volume, or about 12 to 18 cords per acre in good stands. 

 In such instances, second cuts equal in volume to the first ones prob- 

 ably cannot be made in less than 70 to 100 years without still further 

 depleting the growing stock. The presence of farmer-loggers and a 

 road system in forested areas greatly improves the opportunities 

 for full utilization and good forest management. 



No special measures are needed to obtain reproduction in swamps 

 where partial cutting is being practiced. Uncut stands generally have 

 considerable numbers of seedlings and saplings present (table 7). 

 Thinning of the overstory aids the growth of these and disturbance 

 of the soil by logging often encourages the establishment of still more. 

 An example of the stocking of reproduction 6 years after partial cut- 

 ting in a mature swamp stand is shown below : 



Black spruce re- 

 production per 

 acre {number) 

 Height class (feet) : 



1, 472 



1 1, 288 



2 320 



3 48 



4 88 



5+ 1 512 



Total 3,728 



1 Trees from 4.6 feet in height to 3.5 inches d. b. h. 



Sometimes open stands have a heavy cover of Labrador tea that 

 seriously retards both the establishment and growth of seedlings, 

 but in which careful counts will show that stocking actually is reason- 

 ably good. Since Labrador tea cannot endure heavy shade, the spruce 

 eventually will suppress most of it and reproduction conditions will 

 improve. 



The occasional swamp, where speckled alder invades the site 

 strongly, probably cannot be kept in spruce type because the heavy 

 leaf-fall from the alder smothers the tiny spruce seedlings. As 

 mentioned previously, it is believed that spruce became established on 

 such sites only by means of forest fires. No silvicultural measure that 

 appears to be economically practicable has been proposed for regener- 

 ating spruce in alder swamps. 



