tope of thrifty saplings 'in the natural forest 

 and girdling the bark completely around the stera 

 and limbs of $ to 5 foot seedlings that grow in 

 the open. Out of 70 seedlings counted that were 

 at a distance ranging from one-quarter to one 

 mile from the natural forest "boundary south of 

 Silver Lake r Oregon, 42 seedlings had been com- 

 plete^y girdled so that death was inevitable, and 

 13 others were partially girdled. Only lp had not 

 been molested. This work had been done during the 

 winter of 1911-1912. From this it can be readily 

 seen that the porcupine is a serious pest in the 

 Yellow Pine forest and since they usuall3* remain 

 on the edge of the forest in the winter time, they 

 are a very important agent in retarding the exten- 

 sion of the present limits of the forest. Stock 

 grazing assists very material3y in the extension 

 of the present limits of the Western Yellow Pine 

 forest by keeping the bunch grass in check and thus 

 removing one of the most active competitors for 

 soil moisture - and in this way preventing the es- 

 tablishment of seedlings. 



Bark beetles do some damage throughout 

 the entire Western Yellow Pine forest, but since 

 the percentage of insect-killed trees are not 



-16- 



