54 



ECOLOGICAL RELATIONS OF THE FLORA. 



Pinus resinosa, on the other hand, is a greater humus producer and 

 very soon beneath this tree appear mesophytic species which lead to 

 the deciduous forest. It should be stated that Pinus strohus appears 

 ■with the Norway pine only as scattering growths and these are generally 

 replaced by the hard woods; 



Summary of Ecological Relations. 



The ultimate forest formation will be a mixed deciduous one with 

 a siDrinkling of Pinus strobus. Carya microcarpa has been found at 

 North Island, five miles from Sand Point and Ulmus americana and 

 Tilia americana are making strong growths in the bottom land of Sand 

 Point. 



Judging from the progressions under similar conditions in other 

 regions about the Great Lakes, the beech-maple type is the climax asso- 

 ciation. There is every indication here that the mesophytic trees — 

 maples, elms, hickories, basswoods, oaks, etc., are taking possession of 

 the humus covered ridges of the pine association, and probably only the 

 Pinus strohus can persist in the mesophytic forest. The older helophytic 

 and mesophytic associations will persist in their lowest situations and 

 the pines will hold the ridges. But the valleys and hollows between 

 are so shallow and the agents of filling and denuding so rapid in this 

 loose soil, that it is but a question of decades until the area will be 

 levelled. With this, of course, comes the uniformity of association. 

 However, the nature of the soil ■\^^ll shut out for a long time those 

 trees that are common in calcareous areas. 



Scheme of Ecological Succession on Sand Point. 



