Bcological Studies on a Sand Plain. 



159 



Loss of weight in burning due to organic matter amounts to 3 

 per cent, and the moisture content is 1.4 per cent. The humus is 

 2 inches in depth and in excellent condition. 



One other association may perhaps be distinguished, namely 

 the Hemlock and Hardwood Mixture. This, however, simply 

 forms a transition between the Hardwoods and the Hemlock and 

 is unimportant. A large part of this Sand Plain has been burned 

 after logging. On these areas the Aspen and White Birch have 

 come up rather thickly. 



In summing up the results it would appear that only two of 

 these four associations are permanent and form the climax type 

 on their respective sites. These two are the Hemlock and the 

 Hardwoods. Beneath both their own seedling growth is dense 

 and in good condition, while other species appear to make no 

 headway. The Red Pine on the other hand, casts a shade too 

 dense for its intolerant seedlings with the result that the White 

 Pine will eventually replace it if undisturbed. Although not 

 permanent the Red Pine is very likely recurrent on these coarse 

 soils whenever fire or logging opens them up. 



The variance in the composition of the associations is illus- 

 trated in the subjoined table. When considered in relation to the 

 soil the response to the physical conditions is striking. 



Comparison of the Associations. 



