ROOT HABIT IN THE FAR NORTH 233 



GENERAL CONCLUSIONS 



The foregoing- discussion may be summed briefly. Root systems 

 may be classified as deep when the habit is centered about a main, 

 deeply penetrating tap root ; shallow when this tap root is absent, 

 and the roots remain near the surface of the soil. Various degrees 

 of transition may be recognized but the important point, if true, 

 is that some trees have a very rigid root habit, while with others 

 it is more flexible. Deep root systems of an inflexible nature 

 can not produce large trees in shallow^ soils, whether the shallow- 

 ness is caused by rock or ice. Trees whose root systems are 

 flexible and are not too deep rooted in deep soils may endure 

 shallow soils. The degree of flexibihty of habit and the degree 

 of penetration in deep soils may determine the northward dis- 

 tribution of many plants regardless of relations between the 

 plant and its environment that may exclude other species from 

 those regions. 



Of the species examined, Black Spruce, Tamarack and Canoe 

 Birch may be classed as having a rigid shallow root habit ; White 

 Spruce a flexible shallow root habit; Balsam Poplar a deep, 

 flexible root habit; Jack Pine and White Pine a deep, rigid root 

 habit. 



Other differences between the root habits that are evident 

 from the figures are omitted from discussion as having no ap- 

 parent bearing on forest composition in the far north. 



