24 



CIRCULAR 791, U. S. DEPARTMENT OF AGRICULTURE 



Figure 16. — Vigorous 3-year-old seedlings, up to 12 inches in height, established on 

 rotten wood the summer following clear-cutting of the original stand. Sphag- 

 num moss also has invaded the area but cannot engulf such fast-growing 

 seedlings. 



The common hypnum moss (Oalliergon schreberi) which often 

 forms as almost continuous ground cover under densely stocked mer- 

 chantable black spruce stands, both on uplands and in swamps, creates 

 a dry, poorly decomposed organic layer that practically precludes 

 establishment of seedlings. However, this moss can exist only under 

 heavy overhead shade, and it quickly disappears when the timber is 

 thinned or clear-cut. 



• i 



'9 



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F-372658 



Figure IT. — Several types of sphagnum mosses collected on the Kawishiwi Ex- 

 perimental Forest. They illustrate the great variation in rates of height 

 growth among sphagna. The tallest one at the right is approximately 7 inches 

 high. 



