A NATIONAL PLAN FOE AMERICAN FORESTRY 



371 



tural development. So far has the removal of the old-growth timber 

 progressed that almost any tree that will saw out a board is market- 

 able. 



Cutting has not been solely responsible for the change in the forest 

 cover; fires have been common and extensive. On the cut-over areas 

 fires destroyed what timber was left after logging. Fires have occurred 

 repeatedly on many of the cut-over areas, making conditions even 

 more unfavorable to future forest growth. 



RELATIVE INFLUENCE OF FORESTS 

 ON WATERSHEDS 



MAJOR INFLUENCE 

 MODERATE INFLUENCE 

 SLIGHT INFLUENCE 



FIGURE 7. Upper Mississippi River Basin and upper portion of St. Lawrence River Basin. 



The conifer forest, destroyed by fire and cutting, has been replaced 

 by such cover types as sweet fern, brush, aspen, fire cherry, or birch. 

 On some areas an oak woodland type has developed, and on others with 

 sandier soil a jack pine woodland has appeared. 



Because the soils at the headwaters of the Mississippi are for the 

 most part very porous, it is possible that even the destruction of the 

 humus has not materially changed their capacity to absorb and hold 

 water. 



