Tliat is the heart of this question of the changes in the type 

 of trees in the woods. The trees fit conditions. When conditions 

 change, the tree crop changes. To produce the right conditions, 

 there is often need for the association of various plants together, 

 ^en those conditions are upset by a fire or a flood which destroys 

 rich -plant food or washes it awa;^'- in the top soil, the conditions 

 are so changed tl \t they are not longer suited to growing the same 

 kinds of trees. The same is true after destructive logging, 



TJhen such a catastrophe happens, a crop of weed trees comes in 

 and tal':Bs possession of the ground. Those weed trees, such as aspen, 

 and paper birch, scrub oak and other inferior or scrubby species, take 

 the place of the more valuable species which predominated in the 

 original forest. 



Those weed trees act as a sort of nurse crop, for the better 

 species which grew there before the catastrophe. 



Those weed trees, you see, help stop the erosion or washing away 

 of the soil. Their leaves gradually build up a new leaf mould on the 

 forest floor. Their shade protects the land from baking. In other 

 words, they gradually build up . better conditions for the better, 

 stronger trees which require better conditions. 



Then the valuable pine or oak or spruce, as the case may be, in 

 different "localities, begin working into the sides of the land rfnere 

 those trees had been replaced by the weaker weed trees. They get in 

 possession of part of the ground covered "iy the nurse crop. They 

 force their way up. They overshadow the scrub or weed trees. They 

 crowd out the weed trees, and regain the ground which their kind once 

 occupied. 



That tal?es tine. In any case, Mr. Duthie says, it will take 

 fifty to two hundred years for a valuable species to begin to take 

 over the ground again. Th-^t is wliy he speaks of floods and fires, 

 and short-sighted timber cutting as catastrophes. 



As a rule, fires cover much greater area than floods. But since 

 the forests began there have probably been fires and floods at times, 

 but not nearly so many as now when man has added his destructive work 

 to that of nature, by clearing - the forests and setting fire to them 

 in one way or another, 



THhen the white settlers first hit this country, Mr. Duthie thinks 

 that most of the forests they found here were of the ultimate types of 

 the best species of trees. Of course, here and there there were un- 

 doubtedly some burned-over lands on which weed trees were predominant, 

 B'ut, taken by and large, the forests were at their best. 



In cutting, the tendency, Mr. Duthie says, has been to take the 

 most valuable trees, regardless of conse^qaences. As a result of such 



