no 



Conservation Reader 



II. W . hairbanh 



An a\'alanchc has passerl through this forest. 



ing trees and partly to the less frequent occurrence of forest 

 fires to burn off the humus on the ground. We know that 

 the seeds of certain trees find difficulty in sending their 

 roots down through the humus to the soil beneath. 



The narrow-leaved or cone-bearing trees, which are the 

 main source of our lumber, also have other enemies. The 

 most destructive of these are the little pine beetles which 

 lay their eggs in the bark of the yellow pine, sugar pine, 

 and tamarack pine. From these eggs there hatch worms 

 which burrow under the bark until they cut off the flow 

 of the sap. This kills the trees. The trees that are young 

 and strong are sometimes able to pour out enough sap into 

 the wounds to drown the insects, but many thousands of 

 trees in the Western mountains are destroyed every year 

 by these insects. 



Wind and lightning are both enemies of tht forests. 



