14 



CIRCULAR 791. U. S. DEP.1KTMEXT OF AGRICULTURE 



In northeastern Minnesota where black spruce frequently grows in 

 mixture with even-aged stands of jack pine on loamy soils, the ma- 

 jority of the spruce trees, although smaller, are of the the same age as 

 the jack pine. Not infrequently there is a fair stocking of black 

 spruce reproduction. It is believed that in such stands, when the 

 jack pine succumbs to old age. it will be replaced by black spruce, white 

 spruce, balsam fir. and paper birch (11). 



The Effect of Forest Feres 



Swamp forests ordinarily are not subject to lire but during drought 

 periods when water levels are low they can burn very fiercely, and 

 when they do spruce timber is killed ahnostly entirely. Peat samples 

 containing charcoal, sometimes in different strata, have been found 

 at widely scattered points throughout northern Minnesota, showing 

 that fires occurred in swamps long before this region was settled by 

 white men ( % 8 . 



A rather surprising characteristic of black spruce is its ability to 

 regenerate promptly and abundantly after f urest fires ( 3. IS. 2b i . 

 This is accomplished in a manner not unlike that in which jack pine 

 reproduces itself. The serotinous and persistent cones are largely 



Figure 10. — CI se-up view of fire-blackened bur still sound a :.- - 



situated near the tips of the trees where they are least likely to be con- 

 sumed by the flames from a f urest fire I figs. 10 and 11). After a forest 

 fire, the .-eeds fall from the cones to the soil where competing vegetation 

 and much of the dry litter has been destroyed. 



A large quantity of seed is stored in the serotinous cones of black 

 spruce. Collections made in stands near Ely. Minn., over a period 

 of 4 years showed that usually half or more of the viable seeds still 

 remained in the cones 1 year after the cones have ripened (table 2). 

 It lias been found in Ontario that about 40 percent of the seeds were 



