REPRODUCTION OF BLACK SPRUCE 447 



seedling spruce could be found in the swamp. Seedling spruce were 

 quite plentiful on the edge of the swamp where the seed fell on 

 mineral soil. 



The next step in the study of the spruce habitat was to dig down 

 to mineral soil and find out the depth of the peat, the differences in 

 its composition at the different depths, and the nature of the root 

 system of the spruce. The pea was found in this instance to be 8 

 feet deep and underlaid with sand. The roots of the spruce were very 

 superficial and did not extend below the surface more than 2 feet. 

 The soil or peat samples were examined at intervals of 6 inches. 

 This particular swamp supported a stand of 550 spruce trees to the 

 acre, averaging 6 inches d. b. h. and 60 feet tajl. The samples 

 taken consecutively from the mineral soil to the top of the moss showed 

 a transition from a grass peat in the lower samples, to a peat com- 

 posed of grass and shrubs in the next section above, and to a peat 

 almost wholly composed of sphagnum moss in the upper 4 feet. Inter- 

 mingled in the samples of the upper two-thirds of the peat were 

 found well-preserved branches of shrubs and black spruce. These 

 layers of peat show the stages of succession which have taken place 

 from the time the open pond filled up with grass to the present forest 

 type characterized primarily by black spruce. A contemporaneous 

 study of the formation of muskegs from the different stages present 

 in northern Minnesota, which space will not permit a discussion of, 

 substantiated the record of succession preserved in the peat. In many 

 regions of Minnesota may be found today, in close proximity to each 

 other, swamps in which every stage from the open water to the ultimate 

 forest are present. 



To get back more pointedly to the subject at hand, the foregoing 

 has been stated to bring out the fact that black spruce is the ultimate 

 or dominant type in the muskeg formations, and in the swamps studied 

 no seedling reproduction could be found on the floor of moss. The 

 reasons for the lack of seedlings may be briefly summarized — the 

 soil was nearly always saturated, the temperature was below the germi- 

 nation point except at a few times in the latter part of the season, any 

 seed which might possibly germinate would make little growth the 

 first year, due to the lack of mineral soil and lack of adequate sunlight 

 and unfavorable temperature. On the other hand the moss surround- 

 ing any seedling piles up its loose uncompacted layers at the rate of 

 several inches a year. As a consequence any young seedling would 



