SILVICULTURAL MANAGEMENT OF BLACK SPRUCE IN MINNESOTA 23 



area on torn-up duff surfaces shaded with sticks to simulate light 

 logging slash. The results were as follows : 



Main period of 

 Time of sowing : germination 



May 1 June. 



May 15 June- July. 



June 1 June. 



June 15 July. 



July 1 July. 



July 15 July-August. 



August 1 - August. 



August 15 October and May. 



September 1 May. 



October 1 May. 



November 15 May. 



Germination and early survival under natural conditions are 

 strongly influenced by the kind of soil surface material. On a recently 

 cleared" upland forest in northeastern Minnesota, mineral soil, from 

 which vegetation and organic materials had been stripped, was found 

 to be the best of four kinds of surfaces that were tested, and natural 

 undisturbed duff the poorest (table 5) {20). 



Table 5. — Germination and early survival of black spruce in relation 

 to soil surface on a loamy upland soil, northeastern Minnesota 





Germi- 

 nation 



First -year survival 

 in terms of — 



Soil surface 



Seedlings 

 germi- 

 nated 



Seed 

 sown 



Mineral soil 



Scarified and shaded duff 



Percent 



47 



30 



30 



9 



Percent 

 66 



19 

 15 



8 



Percent 

 31 

 6 



Burned duff 



4 



Undisturbed duff 



1 







The same principles apply in swamps although the surface mate- 

 rials are quite different. Peat that has been exposed either mechani- 

 cally or by burning makes a very favorable seedbed if its surface is 

 not subject to flooding. The effect of the removal in various ways of 

 a heavy cover of Labrador tea and sphagnum moss in a swamp having 

 only a scattered overstory of trees is shown below. The seedlings 

 originated from natural seed fall. 



Seedlings 



per acre 



after 6 



itears, 1 



Treatment: number 



None 



Shrubs cut with brush hook 544 



Shrubs uprooted by pulling 3, 049 



Shrubs, litter, and mosses stripped off with hoe 8, 385 



1 Trees present when plots were established are not included. Basis, 16 plots 

 each 10 by 10 feet. 



Rotten wood is a good medium for seedling establishment and in 

 some swamps is sufficiently abundant to be a considerable aid (fig. 16). 



