52 CIRCULAR 791, U. S. DEPARTMENT OF AGRICULTURE 



SWAMP BORDER TYPE 



Black spruce frequently grows in swamp borders but does not occupy 

 extensive areas. In northeastern Minnesota are a good many low-lying 

 poorly drained areas underlain with boulders in which the humus layer 

 and mosses are so shallow that they should be classified as swamp 

 border rather than as true swamp. The trees in such stands are very 

 susceptible to uprooting because of the wet condition of the soil. 

 There is no alternative to clear cutting when the timber commences to 

 uproot and break or adjoining forest types are cut heavily. 



The success of spruce reproduction in swamp borders seems to 

 depend chiefly upon the negative factor of what competing tree species 

 are present. For example, aspen, when present, suckers very vigor- 

 ously after clear cutting in swamp borders and paper birch and balsam 

 fir seed-in aggressively. The young aspen and birch quickly overtop 

 spruce seedlings. Care in logging prevents damage to advance repro- 

 duction of spruce and will help in maintaining a representation of 

 this species. 



MIXED TYPES 



In stands where black spruce is outnumbered by other species, the 

 management requirements of the major species will be the ruling con- 

 siderations in deciding how to handle the spruce. Efforts thus far 

 made to favor black spruce over jack pine have failed because the 

 spruce, especially on uplands, lacks windfirmness (fig. 27) (11). The 

 logging of jack pine is, of course, an entirely different process from the 

 gradual natural breaking up of an overmature stand. The reactions 

 that occur are considerably different from the successional changes in 

 stands left in a natural condition. Hence, black spruce must be cut 

 when jack pine is mature. There is reason to believe that the same 

 thing is true for black spruce associated with paper birch or quaking 

 aspen. Of course, the spruce could well be favored by releasing it 

 from overtopping trees during improvement or intermediate cuttings 

 while the stands still were young. Release cuttings have been advo- 

 cated in Michigan (32), and in the northeast the release of young 

 spruce has proven highly successful (31). 



SUMMARY 



Black spruce, a tree having exceptionally good qualities for pulp- 

 wood, forms the principal cover on V/ 2 million acres of productive 

 swamplands in northern Minnesota. It is also the principal species 

 adapted to a large area of deforested swamps. Spruce pulpwood is 

 in much demand, and timber stands are being depleted rapidly. Con- 

 siderable numbers of black spruce Christmas trees can be obtained 

 from swamps where growth is too poor for the production of pulp- 

 wood. Black spruce grows well on upland soils but usually occurs 

 there only in mixture with other species of trees. 



In swamps, black spruce has few competitors and forms stable types 

 that regenerate naturally from seedlings, and to some extent by lay- 

 ering. Many swamp stands are even-aged because of regeneration 

 after forest fires. On uplands black spruce reseeds most successfully 

 following forest fires. In the absence of periodic burns it tends to be 

 replaced by balsam fir, white spruce, and paper birch. 



