16 



CIRCULAR 791, U. S. DEPARTMENT OF AGRICULTURE 



seed stored on the trees. Observations extending over a period of 12 

 years indicate that total seed crop failures are infrequent, and failures 

 for as many as 2 or 3 successive years are likely to occur only rarely. 

 It has been observed that by striking recently fire-killed trees with 

 an ax large numbers of seeds can be shaken from the scorched and 

 dried cones. Recent instances of the regeneration of black spruce 

 stands following fires are numerous throughout northern Minnesota. 



Table 2. — Viability of seed and number of viable seeds per acre in 

 newly ripened and 1-year-old black spruce cones 



Swamp Stand 





Viable seeds per acre 



Viability 2 



Year of collection l 



New cones 



1-year-old 

 cones 



New 

 cones 



1-year-old 

 cones 



1936 



1937 



1938 



1939 



Number 



194, 648 



292, 909 



51, 583 



181, 521 



Number 

 125, 548 

 238, 097 



91, 094 



92, 794 



Percent 

 52 

 76 

 63 

 69 



Percent 



38 

 76 

 62 

 90 



Average 



180, 165 



136, 883 



65 



66 



Upland Stand 



1936 



1937 



1938 



1939 



1, 651, 284 



281, 542 



595, 132 



95, 999 



384, 253 

 392,311 

 371, 750 

 183, 330 



64 

 75 

 81 

 78 



50 

 84 

 73 



89 



Average 



655, 989 



332,911 



74 



74 



1 Cones gathered in September or October. Each collection included the cones 

 from 25 trees selected to represent all crown and size classes in the stand. Since 

 it was necessary to cut the trees to gather the cones, a new sample was taken each 

 year. 



2 Germination in 16 to 32 days. 



Black spruce has regenerated extensively following fires on both 

 uplands and swamps. Although fire is not necessary for the repro- 

 duction of spruce in swamps, the exposed moist peat surfaces and the 

 temporary absence of competing vegetation are conditions especially 

 favorable for reseeding. Fires account for the large areas of even- 

 aged black spruce swamp forests, including some areas where other- 

 wise it appears that white-cedar or tamarack will replace the spruce. 

 The presence of black spruce in even-aged upland stands, either pure 

 or in association with other species, is explained by its specialized 

 method of reseeding after forest fires. 



It has been stated that the best stands of black spruce in Quebec 

 and Ontario have arisen after forest fires (<?, &6) and the same seems 

 to be true in Minnesota. Old stands in swamps that have not been 

 rejuvenated by fire usually support less timber than do somewhat 

 younger stands. The ground is covered by a dense growth of Labra- 

 dor tea which hinders reproduction. Furthermore, there is often 



