SILVICULTURAL MANAGEMENT OF BLACK SPRUCE IX MINNESOTA 25 



Sphagnum mosses (Sphagnum spp.), of which there are several 

 distinct kinds in spruce swamps (fig. 17) , occur in places that are too 

 wet for hypnum. in openings in stands, and most abundantly in de- 

 forested or thinly stocked areas. Although seeds frequently germi- 

 nate on the moist live sphagna, the seedlings seldom survive for long 

 because they are engulfed by the faster growing mosses. There is, 

 however, one kind of sphagnum that grows much slower than the 

 others on which seedlings may become successfully established. 



After a swamp stand has been thinned, cut clear, or burned, 

 sphagnum mosses quickly invade and cover hummocks of moist peat 

 and decayed stumps. These sphagna are the smaller varieties. They 

 do not appear to offer too serious competition to the black spruce 

 seedlings that germinate on the same places. One or -2 years later 

 the taller, faster growing varieties commence to invade the wetter 

 parts of the swamp surface. These spread rapidly and soon cover 

 small plants, including many spruce seedlings, shorter varieties of 

 sphagna, and slash. Thus, the most favorable time for successful 

 establishment of seedlings is the first year after the opening of the 

 stand. 



Black spruce usually becomes successfully established somewhat 

 more readily in clearings than under tree cover (20) . In a test based 

 on 128 small artificially sown plots, ten two-year-old seedlings were 

 produced per 100 seeds in a recently cleared area in comparison to 7 

 seedlings of the same age under a moderate cover of jack pine, black 

 spruce, and aspen. In this respect, black spruce differs somewhat 

 from white spruce and balsam fir that seem to be benefitted more by 

 partial shade (table 6). Of course, during years of severe drought 

 such as 1936, small shallow-rooted black spruce seedlings in clearings 

 are largely destroyed (table 3). 



Table 6. — Establishment of black spruce, white spruce, and balsam fir 

 seedlings under partial tree cover and no tree cover 





5-year 



-old seedl 



ings l 



Tree cover 



Black 

 spruce 



White 

 spruce 



Balsam 



fir 



None 



Number 



118 



72 



Xu m ber 

 107 

 170 



X umber 

 103 



Thinned to 40 percent of original stand 2 



149 



1 Basis, 400 seeds for each table entry. Seeds dropped on freshly scarified 

 mineral soil. No artificial watering or weeding. 



2 Timber overstory predominantly jack pine with some black spruce and aspen. 



Studies of reproduction in northeastern Minnesota have revealed 

 that insects sometimes destroy the tiny new seedlings and some losses 

 are caused by frost-heaving on mineral soil and ashes, but no direct 

 injury by frost was discovered. Black spruce begins its shoot growth 

 in the spring about 7 to 10 days later than white spruce. 



Black spruce seedlings grow most rapidly when they are wholly 

 free from vegetative competition (20) . Seedlings on upland soil that 



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